Picking the transmission for the V8Mongrel was actually quite easy.  Unlike those running small block Chevrolet engines, the number of choices is quite small if you don’t want to run a custom bell housing.  Eliminating automatic transmissions further reduces the field.

Please note, I don’t have anything against automatic transmissions, they just aren’t for me.  I like to shift gears.  Heel-and-toe downshifting is something I enjoy.  Rev-matching and slipping the shift lever into gear without using the clutch at all is a joy.  Automatics can be fun too, but I want a manual transmission.

There are some non-factory equipment transmission options available to small block Ford owners that I didn’t consider because of cost.  New, these transmissions are quite expensive and they are difficult to find on the the used market.  Units such as the Tremec TKO and T-56 offer a lot of strength, but are all larger than factory offerings.  Since the SA22C chassis originally came with a four speed transmission designed only to cope with 1.1 liters of rotary fury, size is an important consideration for me.

The factory offerings come in two flavors – four speed and five speed.

The four speed transmissions are:

1. Borg Warner T-10
2. Ford Toploader
3. SROD

The SROD is a development of the Toploader, but since most parts aren’t interchangeable, I list it separately.  It has little to offer, and other than being small and light, I see no reason to use it.  The T-10 was the original manual transmission for the small block Ford.  It was supposed to be replaced by the Toploader, but was never completely phased out.  The Toploader was the Ford transmission of choice during the muscle car era, but it was the versatile T-10 that went on to be the transmission of choice for racing.  There are a huge number of gear choices and aftermarket components for the T-10, and it was my top choice of the four speed group.

There is only one five speed available as factory equipment, the T-5.  Designed by Borg Warner and later manufactured by Tremec, the T-5 is a lightweight five speed that was factory equipment in the famous Mustang 5.0 for most of the 1980s and the early 1990s.  There are a myriad of different versions of the T-5 as it was factory equipment for vehicles like the Nissan 300ZX, the Chevy S-10, some Jeeps and even base model, four cylinder Mustangs.  For a V8 swap, the transmission to get is the “Z spec” T5 that came in the Cobra Mustangs of 1993.  As those are usually rare and expensive, a reasonable alternative is any V8 T-5 built to World Class specs.  Basically, the newer the better as Ford and Tremec continuously update the T-5 over the production run.  Most of these updates can be made during a rebuild, but starting with a newer gearbox is usually a safe choice.

The reputation of the T-5 is mixed.  Some people categorize it as a glass transmission that breaks all too easily.  Others report great success under demanding conditions.  Chevy folks seem to have a much worse view of the T-5, likely because it was used during a time when a 200 hp 305 was the hottest option you could get.  Also, Chevy was much slower to adopt the improvements made to the T-5 than Ford, and ultimately went to the larger, stronger, six speed T-56 which has a reputation for being virtually bulletproof.  The Ford enthusiasts never got that option from the factory, so they learned to deal with the T-5, and most improvements, both factory and aftermarket are for Ford versions.

I ultimately decided that the T-5 would be the best option.  What breaks in a 3200 lbs Mustang running drag slicks is likely to be less prone to breakage in the V8Mongrel.  Furthermore, the T-5 is cheap and easy to rebuild, the overdrive would be nice to have, used units are more plentiful than the older four speeds and the knowledge base is great.

Jeff Diehl found a World Class T-5 in pieces for about $200.  Another $75 got me a bell housing and an engine plate.  All that was left to do was put it back together!

It has been a long time since an update. Partially because of the weather and partially because I have been so tired after working on the car. Yes, a lot has been done and I am very close to being able to fire it up. But more on that later.

One of the joys of building the V8Mongrel has been the opportunities to do all the projects that I have never been afford the chance to do before. One of those things is safety wiring.

The above aluminum casting is the rear cover for the quick change axle. Beneath the two orange plates are the bearings in which the gear shafts ride. The only reason I can figure that they need to be removable is so that the bearings can be pressed in and out. I don’t believe that they perform any function in the changing of gears or fluid. As you can see, each plate is held in place with three small diameter socket-head cap screws. They have been drilled for safety wire, but the wire there is old and has snapped. Thus, the reason for my opportunity.

When I asked my friends, Kendt Eklund seemed to know some about safety wiring. His brother is involved in motorcycle racing where the use of safety wire is widespread. Due to the catastrophic consequences of having errant parts in the path of other riders, it is often mandated that minor items such as body panels and covers have their fasteners safety wired.

Kednt’s first suggestion was that I don’t even think about trying to safety wire without the proper pliers. It is possible to twist the wire without the designated safety wire pliers, but it is also much harder to do. Kendt followed that up by suggesting that I look at motorcycle supply places for a good safety wire setup.

And that is exactly what I did. Through the magic of Google, I was able to find Airborn Racing Industries. I placed an order for their budget safety wire pliers and one pound safety wire container. I am usually reluctant to buy a budget tool, but the amount of safety wiring I know I need to do is minimal. Plus, at just thirteen dollars, the investment is minor enough that I won’t worry about it should they need to be replaced with a better unit.

Airborn shipped the pliers and wire out, and were in my hands in less than 48 hours. While this wasn’t a hard order, it is good to know that there are places that can still get the basics right. So if you need safety wire supplies, give Airborn a shot. Next step, a visit from Kendt and learning how to safety wire.

The clutch hydraulics on the Mongrel is an example of unintended consequences. A classic case of one thing leading to another and making something else more complicated that originally intended.

In order to provide greater brake fluid volume and then the consequent greater assist required to handle its delivery, online sources showed that an easy upgrade for the SA22C brake master and booster were the units from an Isuzu VehiCross. Actually, most of Isuzu’s SUVs share the same setup, I just like being able to say that I am using VehiCross parts since they are such bizarre vehicles. The larger booster covered the holes required to mount the clutch master cylinder. In the picture above, you can see the replacement in place. This post shows how I got it there.

First, the OE Mazda clutch master will not work with the commonly available downstream clutch hydraulics. The Ford Mustang from which the transmission came provides no help either as it uses a cable clutch. The cable clutch is considered inferior in every regard, so I decided to figure out the hydraulics. I found a used Howe master cylinder in the required 7/8″ diameter from a local used parts seller, and came up with plan to put it on.

Above is the master cylinder after a fresh coat of epoxy paint and the first stages of a mounting plate template attached. In retrospect, I would have better served to purchase a master cylinder with a remote reservoir rather than the integral one shown.

Regardless of the booster, the pushrod on the clutch master still has to connect to the clutch pedal. While this is easier said than done, when find where to put the master, my default answer was always as close to the factory location as possible, without contacting the booster.

Just to the right of the booster, and, logically, to the right of the factory clutch master cylinder mount, is a large hole. As delivered from the factory, the hole houses the grommet for the main electrical pass-through. Since I need none of the factory engine wiring and had located all of the engine wiring I need for the V8 to the passenger side, the hole was requisitioned for the mounting of the clutch master cylinder. I will have some wires to pass through to the front of the car, such as horn and lights, but they hardly require such a large hole.

I made a simple cardboard template to fill the hole. I looked at the factory mount and found that it wasn’t anything more than a simple hole in the firewall, so I figured I’d duplicate that. The force on the clutch pedal I hope will be very low. I don’t like a heavy clutch pedal and would hope that I won’t be bending the firewall every time I shift gears.

I found that the rivet I had used to mount the fuel pressure warning light sender (where the bright blue wire in some of the pictures leads to) required a notch. I transfered the notch and general shape to some sheet steel.

I cut the metal using aviation snips. I advise anyone working with sheet metal to get some snips and familiarize themselves with how the left-hand, right-hand setup works. It really makes cutting sheet metal less work if you do.

I then used the bench grinder to open up the notch so that the steel sheet wouldn’t contact the aluminum rivet; a battle the steel would eventually win.

Next, I poked the master cylinder rod through the cardboard template, marked the holes, and then transferred it all to the plate. Above is a test fit before final cleanup of the holes.

The master was affixed to the plate with Grade 8 fasteners. Much to my dismay, I found that one of the bolts would only go in one way so any difficulty in threading the fasteners wouldn’t be able to be done from the other side. Squeezing my body into the pedal box to was something I want to avoid, so I decided to attach the master cylinder to the plate before I mounted it to the car. The bad news was that doing so wouldn’t allow me to attach the plate to the car. This is where the remote reservoir unit would have be greatly appreciated. Pedal box work really isn’t fun, particularly when there is a roll cage in the car.

Mounting was actually a challenge. I could have had VK weld the plate in place for me when he was around to do the other welding. However, I wasn’t 100% confident that this arrangement would be correct.  As a result, I wanted a less permanent solution. So I went to my old standby – rivets.

They are hard to see, but the picture shows the large head rivets I used to attach the plate. Note that the plate I made is inside the hole. So the rivets aren’t responsible for the load of the pedal pushing into the master cylinder. All they do is position the cylinder vertically and take the release forces from the return spring on the pedal. The main forces are taken by the flange.

In future posts, I’ll detail the attachment to the pedal, the slave hydraulics and other parts in the clutch actuation system.

On Monday afternoon, I came home to the best thing next to a naked wife grilling steaks – boxes of parts!

As you can see, it took four large boxes to ship all the pieces for the axle assembly. As soon as I had the opportunity, I cut the tape and unpacked the contents.

As expected, MR Racing delivered all the parts as I had ordered. Since outside on the driveway wasn’t going to be the storage place of choice due to what has to be the wettest spring I can remember, I quickly moved the parts into the garage for further inspection.

The large casting in the front of the picture is the center section. In spite of being aluminum, it is quite heavy. I will be weighing all the parts later and making a comparison to the Mazda factory axle. I expect that the quick change will be heavier but, am interested in a real amount.

In the above picture, you can see the black driveshaft yoke protruding from the far side of the center. Power comes from the engine, to the transmission, along the driveshaft, and enters the rear axle at this point.

From there, power travels along the shaft, called the jackshaft, seen lower right in the picture above.

The bottom of the two shafts (right in the picture) is the back end of the jackshaft.

Onto the shafts fit the quick change gears. The gears fit on both shafts, so each pair of gears provides two ratios. The pair above provide a 6.09 and 3.89 ratio. My brother, Paul, is working on finding some wheelie bars so I can run the 6.09s!

The gears slide on quite easily, and in the picture above are positioned to provide the 3.89 ratio.

The ends of the gear shafts ride in bearings that are in the large cover that goes over the quick change gears. It appears from my quick inspection, that this chamber has its own oil supply, so when the quick change gears are pulled, the oil drained will be far less than if they were in the main supply.

The cover is then bolted to the back of the center.

The top gear shaft then turns the pinion gear, seen above the jackshaft.

The pinion gear to ring gear (crown wheel) interface is conventional in every way except for the fact that it happens from the back rather than the front. This is how the power is transferred from going along the length of the car to perpendicular to it, and thus able to drive the wheels. The picture above shows the aluminum spool onto which the ring gear is bolted.

The spool is held in place by the bells, and the tubes cover the axle shafts that transmit the power to the wheel hub assemblies. Since the wheel bearings and spool mate to the axle shafts through splined couplings, this makes it a full floating rear axle. This means that the axle shafts are not part of either end (differential or wheel) and therefore their failure will not cause immediate failure of either of those parts.

The ratio of the ring and pinion is 4.86:1. This means that the quick change gears work from that base. In essence, they either overdrive or underdrive that ratio just like the gears in a transmission. Since 4.86 is a low gear for a light car with V8 power, chances are I will be overdriving all the time.

I didn’t get a chance to measure or photograph the wheel hubs. The most critical dimension is the rotor mount, so it is likely that this description will end up in the brakes category. Along with that, I have to determine the camber on the axle tubes, then bolt it all together and take final measurements. Stay tuned!

With the quick change axle on the way from MR Racing, I had to find some information on these axles. I said in my previous entry, I had spent some time learning about the Ford nine inch axle; time that has now left with little more than improved bench racing abilities. I went searching, and one of my favorite magazines, Circle Track, had a very informative look at the insides of a quick change.

Circle Track Magazine Quick Change rebuild article.

After that, I searched for quick change manufacturers so that I could see what they have to offer in the way of tech.

Frankland – My center section is from Frankland. The center holds the pinion, the quick change gears and the jackshaft, which I assume will be Frankland brand as well. I bought extra gears, but I am assuming the axle includes on set.

Winters – My bells are from Winters. They bolt to the center and encapsulate the spool, which itself holds the ring gear. I am guessing that those components will be Winters brand, but I am nost sure.

Tiger – I don’t have any Tiger parts, but they were the main supplier for the Circle Track story, so I took a look at their site as well.

Based on what I know, there are two main issues I will have to confront with this axle immediately.

1. The width. At 60″ it is 2″ too wide based on my most recent measurements. While tubes are available or the current ones can be shortened, that will require shorter axles and more money. At this time, I am thinking that the best solution is to make wider fender flares, but I will have to see how close things are when it arrives. Increasing rear track and thus rear grip may not be the worst idea in the world.
2. The camber. That car has a typical circle track camber – negative on the right, positive on the left. While optimal for turning left, it isn’t good for what I need. My hope is that I can either rotate the tube or the bell without ill effect in order to have negative camber on both sides.

Not much else to do concerning the axle other than hurry up and wait!

If you recall from previous entries. I had looked at the OE Mazda rear axle (Assessment), determined it needed replacing (Planning Part I), determined that I would use a Ford nine inch axle (Planning Part II), only to find out that the rear hubs I had prevented me from using the commonly available housings (Planning Part II½). I was thinking that I would be able to find a solution to the problems quickly. This turned out to be untrue.

First, using the 2″ bearing hubs (aka Howe/Vogel) would virtually eliminate my ability to use a reasonably priced axle housing. Second, buying a kit with hubs included would be a $700 or more proposition. Third, cobbling together a bunch of used parts got me into this mess, so lacked appeal. I was actually looking for an easy solution. Simple and easy? Unfamiliar territory for me, to say the least.

I was feeling like I was tied to the nine inch Ford because I had already invested some money in parts for it. I had already bought:

• A TrueTrac® differential
• A 3.89 ring and pinion
• An SCP belt driven gear oil pump
• A 1330 yoke with pulley to drive the pump
• The aforementioned hubs

Not to mention the fact that I had spent a lot of time looking at options and had determined that the Ford nine inch was the way to go.

I was searching eBay, Racing Junk and everywhere I could think. I was rapidly becoming disheartened as the search lagged on. I consulted with my council of trusted advisers, and was convinced it was time to bit the bullet and get one of the complete kits with hubs and all.

I was literally only a day away from pulling the trigger, when I was making a quick look through all the usual suspects. I was on MR Racing, perusing their used parts listings, when something caught my eye.

“The best-laid plans of mice and men often go awry. ” A very appropriate quote for me right now. The plan was that the next installment, Part III of the Planning – Driveline – Axle and Differential series would detail the successful ordering of my nine-inch housing. Well, I cannot do that because I have hit a snag.

As I have written elsewhere, I have been speaking to Doug at Quick Performance. Service has been great and he has been remarkably patient with my never-ending stream of questions. After getting all the measurements need for the axle, we had to confirm the snouts.

While this was supposed to be covered in Part III, in order for this to make any sense, I have to explain what this means. Most axles look like the ones below.

Photo from Quick Performance.

They have a flange on the end to which the wheel mounts. The axle is held into the housing, as in the case of the 9 inch, by the bearings in the axle end or, as in the case of 8.8, by c-clips on the inner end. Problem is, the wheel forces of turning and braking are transmitted to the differential, and vice versa. The largest problem is piston knock-back in the caliper as the pads are contacted by the rotor. This is obviously bad for pedal feel and braking distances.

The solution is what is called a full floater. There is an axle with an identical inner end, but the outer end is splined also. It goes into a matching drive plate, which attaches to a hub and bearing just like on the front. More explanation (with pictures) in Part III, but those bearings have to ride on a surface. That is the snout.

Unfortunately for me, the snout isn’t universal and one cannot swap bearings for one snout into the hub designed for another. So, they need to match.

I managed to score a couple of hubs off eBay for far less than new. Floater hubs are expensive, and I got two used Port City Racing hubs for less than a quarter of the cost of a single new one. Here is the photo from the eBay listing for one of the two hubs.

All was going well until it came time for the snout measurement. Turns out that the Port City hub uses a 2 inch ID bearing, while the more common Grand National hubs that are used by Quick Performance are 2.5 inch ID. As I said before, there is really no way around this.

I am going to be regrouping over the weekend and figuring out my options. I can say that option numero uno is to call back Doug at Quick Performance and see if there is anything he can do. Maybe I can get some snouts sent to him. He has earned my business based on excellent customer service, and I intend to make every effort to give it to him. Hopefully Part III will come soon, but even if it doesn’t, there is always plenty else to do!

The Mazda RX-7 rear axle assembly has the following critical dimensions:

Flange to flange width 56.75″
Pinion offset 1.375″

Matching this proved to be more difficult than I imagined.

Ford 8.8

The Ford 8.8 is the current high torque spec axle found in V8 Mustangs, F-150s and 4.0 V6 Rangers. This makes it easy to find and, because of the Mustang and growing popularity amongst offroaders, is supported by a huge aftermarket that allows it to be a good candidate for swaps. It has been around since the early ’80s, and therehave been very few changes, so matching parts is no problem. Also, there is even an IRS version.

Pros:

• Current production
• Strong aftermarket
• Massive numbers in junkyards
• Affordable limited slips, including Torsen T2R from Ranger FX4

Cons:

• Differential unit built into housing makes servicing harder
• C-clips require replacement for use with fixed calipers
• Lack of needed factory pinion offset and width combination would require custom work

Here is some info I gathered from multiple sources (listed whenever possible):

http://members.tripod.com/~grannys/TASAconversion.html
86-’93 Ford Mustang 8.8
59-1/2″ flange/flange width (exact same as the ‘86-’91 RX-7)
4 on 4-1/4″ lug pattern, easily re-drilled to RX-7 4 or 5 on 4-1/2″ pattern
came std w/tracloc clutch style diff
Both L&R axles are 29-1/8″ long 28 spline axles
V8’s came with 2.73 or 3.08 ratios

‘87-’88 Thunderbird Turbo Coupe
61-1/2″ flange/flange width
same housing width as ‘86-’93 Mustangs, but 1″ longer axles to make room for ABS sensors
4 on 4-1/2″ lug pattern (same as the RX-7), easily re-drilled to RX-7 5 on 4-1/2″
came std w/tracloc clutch style diff
Both L&R axles are 30-1/8″ long 28 spline axles
5spd cars came with 3.55 gears, automatic cars came with 3.73
standard w/ disc brakes

‘95-’01 Explorer
59-1/2″ flange/flange width
5 on 4-1/2″ lug pattern
unequal length 31 spline axles (2-3/16″ pinion offset)
std disc brakes w/ 7/16″ x 11.25 rotors

http://www.therangerstation.com/tech_library/Axles.html
Ranger 4.0 1990-1992
Width is same as other pre-93 axles, 28 spline
3.08 (4×2), 3.55, 3.73 and 4.10 (4×4) factory ratios
Either limited slip or open differential
10″ drum brakes

Ranger 4.0 1993+ and B4000 1994+
Width is same as other 93+ axles (1.5″ wider than pre 93), 28 spline
Ratios and differential options as noted above

Ranger FX4 2002+
Width is same as other 93+ axles, 31 spline
4.10’s and Torsen limited slip from factory

Explorer & Navaho 90-94
Width is 1.5″ wider than 93+ Ranger, 3″ wider than pre-93, 31 spline
Spring perches must be fabricated and welded on top
Stock spring perches can be used to lower the truck (like a flip kit)
Shock mounts must be fabricated and welded on
Very common to find ltd. Slip, usually 3.73 or 4.10 (4×4) gears

Explorer & Mountaineer 95-01
Same as above, also has rear discs

All axles listed above have a 5 on 4.5 bolt circle.

OK, so quick math shows
Exploder = 59.5″
Late Ranger < 1.5 = 58″
Early Ranger 1.5 < 56.5″

http://jeepsunlimited.com/forums/showpost.php?p=5508606&postcount=1  (Link now broken)
Explorer 8.8 Measurements
Weight (complete assembly w/ brakes etc.): 174 lb.
O.D. of tubes: 3.250″.
Tube thickness: .250″ (some are .188”!)
Ring gear diameter: 8.800″.
Ring gear bolts: 7/16″ dia. (qty. 10).
Pinion diameter/splines: 1.625 / 30.
Axle shaft/splines: 1.320 / 31.
Rotor thickness (where it mounts to axle is .250″).
Overall width 59.625″ (the F8.8 is .950″ narrower then a TJ Dana 35).
(The F-150 8.8 is drum brake and width WMS to WMS is 65.5”.)
Hole diameter for ABS sensor in top of housing: .811″.
Bolt size (U-joint flange to yoke) is: 12 x 1.75 x 30 mm
Centerline of housing to C/L of pinion difference is 3.875″ toward the P/S.
Pinion offset: P/S to C/L of Pinion, 27-3/4″ (no rotor on axle), D/S to C/L of Pinion, 31-5/8″ (no rotor on axle).

Specs:
Code Capacity Ratio
43 Open 3200 3.08
41 Open 3200 3.27
42 Open 4.10
46 Open 3.73
45 Open 3200 3.55
D4 Limited Slip 3200 3.73
D2 Limited Slip 4.10
L73 Limited Slip 3.73
L – Limited Slip Differential
C – Conventional Differential

From the above, it appeared that the Ford 8.8 from an early Ranger would have been the perfect width. The problem is the pinion offset is huge compared to the Mazda. The Ford 8.8 I’d need would thus be a custom axle. I found out very quickly that he cost of custom Ford 8.8 axles was much higher than the same work on a 9 inch. So that was what I looked at next.

I just got off the phone with Doug at QuickPerformance (515 232-0126) and he was very helpful. He told me how to measure for my custom rear axle. Previously, I have alluded to the reported strength of the Mazda axle, yet have been unable to reliably confirm just how much power it will take. Going on the theory that an axle failure isn’t something that one can fix easily at the track, I have decided to go with the old standby of the live axle world – the Ford nine inch.

Here is how my decision process went. I found some good info that I think will benefit both those working with an SA22C platform and anyone else doing a conversion on a live axle car.

When looking at axles, there were three choices.

1. OE Mazda
2. Ford 8.8 inch
3. Ford 9 inch

There are other options, but these are the ones that were readily available to me, that, in the case of those that would represent a change, I felt like the available knowledge base would allow me to successfully put one in the car.

OE Mazda

This is the assembly in the car, which, lucky for me, has a nice 4.875:1 ratio and, I think, the larger Mazda Motorsport clutch type differential. Problem is, while the differential is good, the assembly is let down by the housing. I have a rear drum housing and research has lead me to believe that it is not a trivial matter to change this to discs. I wish I had more info to share, but most of my research was answered by the refrain of “just get a GSL-SE axle”.

While I am not 100% sure what unit I have, I do know that the center is not the same as a Miata unit that is shared with the 84-85 13B powered GSL-SE, so many of the upgrades are more difficult to come by.

Pros:

• I have one
• I know it fits
• I know the Granny’s kit driveshaft will bolt up to it

Cons:

• I don’t know how much power it can take without failure
• The oddball size of the tubes mean custom suspension brackets
• Limited selection of ratios compared to domestics
• Very expensive to modify and rebuild compared to domestics

This is the center chunk that came with the car. It does look a lot like a Miata unit, but I have been told it will not interchange.

Here you can see the ring gear and limited slip carrier. If you have info on this unit, please post a comment and let me know!

Ultimately, I decided to not use the Mazda axle because the cost of rebuild is high and there were just too many unknowns. Furthermore, while the brutish nature of a 4.875:1 ratio holds a certain appeal, it would likely compromise reliability and be far from optimal.

I will cover the Ford axles I considered in upcoming posts.

The plan was originally to use the stock RX-7 rear axle with whatever needed to make it work how I want. As stated in Assessment – Driveline – Rear Axle Location, the factory Watts linkage leaves something to be desired. Add in the fact that the upper arms are not a good idea and the rear brakes are nothing but scrap metal and the rear axle housing quickly become little more than a shell to be used as a blank canvas.

The suspension parts will be covered in their respective sections, this entry will cover the differential and the axles. The live axle of the SA22C gets the following glowing review from Granny’s

“Mazda planned accordingly, and designed plenty of strength into the RX-7’s rear differential/axles/and hubs. Experience has shown that the stock NA RX-7 components are strong enough to withstand low 10sec 1/4mi passes, a feat that requires around 500hp.”*

It should take me more than a couple of years to feel the need for 500 hp, so I thought I would be OK. However, a little more digging lead me to Mazspeed and specifically, their piece on the rear axle.

Since I have a 1979 car, if I have the original axle, the Mazspeed axle link says “the axle assembly used in 79-80 models cannot be altered to add a limited slip differential. Treat these units as really big paperweights or one more thing to clutter up your garage.” Great. Of course, upon disassembly, I found out that I have a 4.875:1 ratio and limited slip. If it is a later axle, someone put a lot of money into a drum brake rear end which makes no sense.

The parts are in good condition, the question is what to do? Axle swaps aren’t exactly rocket science, and while the 4.875:1 ratio with certain pin me back in the seat, it isn’t really an optimal gear for track use. Plus, in the Miata, the same differential isn’t considered hardy enough for a V8 swap. How much difference does IRS make to durability? I don’t know and I haven’t yet found anyone who does.

*Please note that I have since found the information regarding this axle to be contradicted by the experiences of some people. Rich, May 2008.