I did the search and the answer looks to be both yes and no depending on the time the question is asked, so I'd like to ask these specific questions to get specific answers for the records. And, of course, to make my life easier when it comes time for the deed.

Both of the cars are GS's.....1983 RX-7 GS and a 1984 RX-7 GS.....

• Question One -- Can the pumpkin from the 1983 car be pulled and then put into the 1984 car's rear housing and then have the 1984 axles just slide back in? They should both be big axle, right?
• Question Two -- Can a LSD differential pumpkin from a 1984 GSL be swapped into the 1983 housing and then have the 1983 axles just slide back in?
• Question Three -- Completely unrelated, but I'm curious. How long can an FB tranny last after you start hearing 1st, 2nd, 3rd and 5th gear start loudly "whirring" like it has straight cut gears?? 4th gear sounds normal...it has Redline synthetic in the case.

Thanks in advance for the answers to these burning questions of mine....

 

1983 is a bastard year, may be big or small axle. As long as the 83 is a big axle like the 84 then the parts will interchange any way you like.

-billy

 

The man know's his FB's... he's right!


As for Question 3:
Try going with some good Redline tranny fluid.
Helps... a LOT!

 

Re-read question 3, he said it already has Redline in it.

As far as 83 being a "bastard" year, does having the larger driveshaft flange generally indicate the larger axles are also used? I am curious, due to having an 83 myself. (03/83)

 

Well, knock me down and call me illiterate...

 

When you say large axle, Do you mean the splines or the actual axle itself? From what i've seen so far is the splines are the same size, Just the axle bearings are different and the axle shaft was thicker. Also, I have noticed that the outer diameter of a 82 lsd flange was smaller than the inner diameter of my 83 housing. What this amounts to is that the mounting holes all line up but there is no support from the flange on the lsd unit. Now if this means the 84 lsd will fit the 83, Then I don't see why the 83 axles wouldn't fit the 84 as I still have 83" axles on my car.

 

It's ok, we all miss things occasionally. Your advice is usually spot on

As for the large and small axles, what are the differences? I know the bearings are different, and the large axles cannot be used in housings for the small ones.
Are the splines all the same? If so, this would mean the pumpkins can be interchanged between the early and late housings, as long as the flange and driveshaft are matched, correct? Or are the splines also larger?

 

Only 114.3 bolt patter cars have the larger splines. So that would be the SE in the states.

 

No. '83 is small axle/small bearing. But it had the nonrebuildable driveshaft and the lightweight rotors/water oilcooler setup. Transitionary year.

See above: No. If you had a small-axle limited slip diff to gut, you could pull the diff from the pumpkin, disassemble the diff, and swap in the small-axle side gears, though, if you really had to.

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I dunno, mine sounds like a blender. If I don't change the fluid right away after a race, all of the metal particles in the fluid circulate around and eat the bearings. My '80 trans sounds like a blender But it still shifts fine, unlike the original trans which sounded like a coffee grinder (had bad/glazed synchros too)

My educated guess is, it depends on the FB. Early coarse-gear trannies (models up to mid-82 I think?) would tolerate more bearing tolerance than the later fine-gear trannies. With smaller teeth, a given amount of gear mismesh makes for a higher *percentage* of gear mismesh. (But the smaller teeth are a little quieter when new so they were better for people who were paying a surprising amount of money for the later cars!)

 

Nope! All Mazda 7" diffs went to the larger spline in 1984. This includes B-series pickups and all of those US market 12A powered cars that still had 110mm bolt circle and even drum brakes back there in most cases.

 

I stand corrected. In that case I would love to get my hands on a US spec Series 3 12A rear end.

 

I have one. It's functionally a lot like a Series 2 rearend, same size brakes, same width, etc, only the housing is weaker and the assembly weighs something like 50lb more. I haven't put it on a scale to verify, but it sure it a lot more pork than a Series 1 assembly!

All you would need, really, would be the axleshafts. The Series 3 housings themselves are the same 12A (110mm) vs. 13B (4 1/2"), the only differences are the axles (12A: standard length relative to prior years, 13B: 15mm longer outboard of bearing, to compensate for higher offset wheels used on that car) and the 12A cars have the old standard drums or solid discs, whereas the 13B cars have the vented discs.

Oh! Also, the 13B cars have a weaker limited slip than the 12A cars (if equipped). Presumably this is so the heavier (fully loaded!) torquier 13B cars are more predictable to drive. My 12A diff might as well be a spool if the road isn't clean and dry, even after some significant wear. Trying to make a tight turn in a snowy lot is an excercise in frustration, the car just crabs sideways...

 

Peejay- It was my understanding that the 13B lsd was smaller than the 12A to make room for the larger pinion gear used. To make it fit, they gave the 13B model one less clutch per side than the 12A model came with. I think that the 12a had 4 per side, and the 13b had three (or something along those lines, sorry for being so vague). Does that sound correct?

 

Not really.

For one thing... the GSL-SE had a *smaller* pinion gear. 4.10ish ratio vs. 3.91ish ratio, and the ring gear stays the same diameter. The pinion stays the same distance from the axle centerline, anyway. (No matter what gear ratio, the pinion and ring gear are in the same relation to each other spatially... the pinion gear changes in diameter and the ring gear changes thickness to compensate)

Even if... the clutch packs load in endwise, so any diametral differences have nothin' to do with it.

 

Thanks man, must have tripped over some garbage someone else was spreading..

 

I've put 9000kms on my s2 box and it is VERY loud. ~6months of daily driving

Its getting rebuilt next week tho

So I'll tell you how it comes up. btw the box was stuffed when I bought the car, so who knows how long, but I do know someone had one after 2 years when he posted it, and it was still going....

 

mine lasted about 800 miles after it started making the same noise you describe. it runed out to be my counter shaft. i lived in houston at the time,all of my spare parts were here in bama. so i decided to make the trip home, drove about 600 of those miles in 4th gear and very gently. by the time i got home i no longer had reverse,1st and second would barely pull.