Originally Posted by wackyracer

Since you have an 83, the in-between years, I dont know exactly what you have: small or large axle. I ran 4.10 for many years with no problem. Better launcher than a 3.90 and good for cruising as well.

If you want a 4.10, find a GSL-SE, early miata and front diffy out of MPV van 4x4. Grab the ring and pinion.

Originally Posted by wackyracer

Since you have an 83, the in-between years, I dont know exactly what you have: small or large axle.

Originally Posted by Blake

'83 is a "small" axle (ironically stronger, due to the housing) with a large companion flange (like 84/85). Axle size is irrelevant for gears, presuming you are installing them in your existing pumpkin. You only have to worry about it if you are grabbing a whole pumpkin from another vehicle.

I have tens of thousands of miles on 4.88 (aka 4.875) gears, as well as many more in 3.909s and 4.08s and 4.30s. My favorite is the 4.88, but it does make driving seem a little like work when you aren't flogging it. The mid-4s (4.3, 4.44, etc.) are really nice compromises. 4.1 is okay, but it doesn't get me all excited. Don't forget that the only important thing is the overal gear ratio, which is determined by the transmission gear ratios, the rear end ratio and the tire diameter.

Many years ago, I did an RPM/Gear calculator in Excel that I still use today. You can insert four "cases" for side-to-side comparison. All the reference data is there for copying and pasting, too. Here is a screen shot of it. If y ou want a copy, shoot me an email. It is over the upload limit here.


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Originally Posted by No_Rotor_RX7

you guys are crazy hahaha. i'm trying to fab up a 3.08 rear so i can have MORE gear :D

Originally Posted by Midwest 7's

actually 83 could have large or small axle, something like 7-83 and later build date
have the large axle, im pretty sure there is a vin # around here somewhere where it tells the date/#. it should be in the 1st gen archives if it is not already. this question comes up all the time.

Originally Posted by Blake

I would very much like to know how you came by this information. Every single *stock* '83 I have every owned or seen had the small axles with the large companion flange (which confuses people who equate the large companion flange to the large axle size). I have never seen a reference to a large axle '83 in any reliable material and cannot imagine them doing that. It certainly is not in the Mazda Electronic Parts Catalog (EPC) and I confirmed this with Rob Golden, who was a Mazda dealer shop foreman. I've owned both early and late '83s and worked on many more. The usual confusion is that people hear that it was an "inbetween" year or similar phrase...and they are right: Mazda changed from the small companion flange to the large companion flange while keeping the small axle for one more year. But I am quite certain, from my own experience, that there were no large axle '83 cars, other than those that have been changed by a previous owner. This usually happens because the later cars are the only ones with the proper sized companion flange, so it was the easier swap.

Originally Posted by Midwest 7's

perhaps it is because the later built 83 cars are titled as 84's?
i know for fact a 10-83 car i found in a junkyard had the large axle because i swapped it in my 84.

Originally Posted by David Dewhurst

Now, I'm going to share a couple facts with ya all.

FACT # 1: The small axle rearends have a bearing outside housing diameter just behind the backing plate of 2 7/8 inch.

FACT # 2: The large axle rearends have a bearing outside houising diameter just behind the backing plate of 3 1/4 inch.

FACT # 3: Now please quit :wallbash: your going to get sore.

Originally Posted by David Dewhurst

***or you can swap flanges, if you are capable of it.***

This ^ would sound likea slam from a PROFESSIONAL.