Hard Knocks

So this may be written out of frustration: I ordered the wheel spacers/adapters to be 4x110mm to 5x114.3mm and I got a call from the company saying their data base says the 81 rx7 has 4x108mm bolt patterns (ezaccessory.com as mentioned in the first post) and that they already shipped this updated item - "if it doesn't fit send it back." Well of course it does not fit, I used the Mazda repair manual specifically to get this bolt pattern as well as four years of researching many other persons posts about bolt pattern size. So the 108's are just so small that I cannot fit a socket into the hole to tighten the wheel bolts. Great. Spend more money to ship them back and wait another week to get the rear axle finished. The moral of the story is stand up for what you know and don't let some person over the phone make a "better judgement" and be proactive about what you know. If you have valid information, get it out there!

1981 Mazda RX-7 Rear Axle

Merry Christmas!

Hope everyone is having a happy holiday.

Now for the rear axle. As mentioned previously, it is good to replace the differential and axle seals if you are restoring the car. The axles are held in by three bolts that hold a plate to the axle, and slide out easily once the bolts are removed. The seals are inside the axle and pop out with a flat head screw driver easily. The differential should be inspected for damage and wear. This is what your axle looks like disassembled and partially cleaned up. When taking the differential apart, remember how it goes together. The order of parts from inside out is as follows: Crush tube (which shouldn't be tampered with unless replacing the ring and pinion), Conical pinion bearing, differential seal, mounting plate, washer, lock bolt (which should be new as well - can get this from racing beat along with your differential seal)


Take everything out of the axle, clean up the rust, wipe it down and put some fresh paint on it. It is good to put a rust-proof primer on the metal, two coats of a base-coat primer, three to four coats of a base coat and two to three coats of the clear. If you are using an enamel, life is much easier. Here is a picture of the primer being put on.


When reassembling the axle, the bolts get tricky. To attach the differential back in place, clean up the edge of the axle and differential where the two mate to ensure proper contact. Re-tap the holes on the axle: the bolts are Grade 8.8 M8x1.25 and should have a length of 20mm to ensure proper attachment. Place black rubber RTV sealant as the directions on the product describe around the inner and outer diameter of the differential hole on the axle, and tighten down the bolts. Allow at least a day for the sealant to cure. Slide in the axles (after lubed up) and use the same bolts but with nuts as mentioned before to attach the seal plates on the ends. The support arm needs reattached as well, using the same bolt thread. For the drain plugs however, you need to use Brass Pipe Fittings (not flare fittings or black iron pipe fittings) with 1/2 thread. Two of these will fit in the drain and fill holes. Next fill this baby with oil, slosh it around, drain that oil and refill it. This ensures that all debris during assembly has been removed. The parts list for this portion requires the use of:

16 -M8x1.25x20mm Grade 8.8 bolts
16 -M8 locking washers
6 -M8 Grade 8.8 nuts
1 -Extra long (length unknown) Grade 8.8 M8x1.25 series bolt (this goes through the differential, if you have the original, save it for reference)
2 -Brass Fittings 1/2 end caps
1- 1/8 threaded nipple (works as a place for a vent tube to be reattached - place RTV on the last few threads and by hand thread it into the top hole where the drain plug was inserted)
1-Tube of RTV sealant

Having a nice, smoothly operating and shiny rear axle for your restomod project is always nice. I suggest using Royal Purple Gear Oil for these applications: the additives work better in high performance applications, whether it be off-roading in 100 degree heat or running your Cobra at 6,750 rpm for hours.

Correction: there is no front axle. It has a wishbone suspension.

Greetings all!

So there is a back story to this car. I purchased it 4 years ago (fall 2004) from a guy in South Dakota for less than my engineering calculator cost. The primary reason to buy this car was for the engine: it runs a 1.1L Wankel 12A. The engine needs completely rebuilt, and there is a side story attached to this, as well as the body, drive-train and electrical components. So a little work needs done. The plan for the engine involves research I am doing at the University of Pittsburgh. A faculty member and I are trying to increase the thermodynamic efficiency of internal combustion engines using alternative fuel sources. Preliminary data suggests the injection of air, hydrogen and water within this particular engine to increase its efficiency. Wankel rotary engines are prime candidates for this use due to large surface areas (prevents pre-detonation of hydrogen) and its particular geometry (great for handling high pressures).

Not to get too far off subject: the car needs a lot of work and has sporadically been getting some much needed attention over the past four years. Everything has been stripped out of the car, as seen by the Webshots link, and we started cleaning up the body. To confront the issue of working on the underside, my father and I made a rotisserie! If you guys want some more photos of how it was made, let me know. Now the car is able to be rotated to do work on the underbody, which isn't in too bad of shape for being 27 years old and spending most of its life in harsh, cold and salty conditions.


The current plans for the month of December are to rebuild the rear axle and front axle, sand blast the underside and fix the metal. Paint will then be applied, the suspension will be mounted and construction of a roll cage will begin. Here are some details:

The rear axle:
The cast iron housing is rather light, but the differential accounts for most of the weight. Rear brake calipers and rotor replacements are easily found, with www.racingbeat.com having many of the supplies you needed (rotors, not calipers). The rear axles are held in by a plate with three bolts on the outside of the axle and once removed, the axles come out easily with a puller. The bearings and seal replacements can be found by the company Beck Arnley and are rather cheap. When rebuilding the axle, if you want to change out the original pinion and ring with a ratio of 4.33, look at racingbeat.com, but the stock one, if not damaged or worn, provides a good ratio. The outer bearings and seals on the axles should be replaced, as well as the crush tube and pinion bearing if you take the differential out. It is advised to clean off the housing (by a means that does not produce much heat so you do not weaken the cast iron) and repaint the housing. It takes a full day's work to clean up the axle and replace the bearings, but it feels a lot smoother. And another important note: the bolt pattern on the axles is 4x110 mm (some sources suggest 4x108 mm) and there are wheel adapters out there to take you from stock to 5x114.3. It is really hard to find any good looking and well-performing wheels to fit these axles, so check out www.ezaccessory.com. I'll put up some pics on how to do all of this soon!