1st Generation Specific (1979-1985) 1979-1985 Discussion including performance modifications and technical support sections

83 GSL rear. big axle or small?

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Old 01-14-17, 12:29 AM
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83 GSL rear. big axle or small?

I have an '83 GSL rear in my gf's '79 LE.

My question is, how do I tell if I have an '83.5 - newer rear OR if I have an '83-83.5 small axle rear?

My I would like to do some LSD unit swapping between my '85 and my gf's 79 with this 83 gsl rear in it, but I don't know if the LSD in my '85 would fit the '83. How can I tell short of pulling them all apart and counting the # ??

MUCH THANKS!
Old 01-14-17, 08:40 AM
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All '83 were small axle. All of 'em. All '84 were big axle, including the rare early-year 3.933 rearends. (My early production '84 came with one. I also has a fine-tooth GSL-SE rearend for a while, too...)

The simple way to tell using just your eyeballs, no fancy measurin' tools, is to look at the bearing retainer bolts' relation to the caliper mounting bolts. Two of the axle retainer bolts are roughly parallel with the caliper bolts. On a large axle rear, those bolts are on the same side as the caliper. On a small axle rear, those bolts are on the opposite side.

So simple even a caveman can do it!

I think the confusion lies with two weirdities: Mazda switched driveshaft flanges in '83 and some people think square flange = large axle (it ain't). The rest of the time, some states assigned titles with the year the car was first titled, so an '83 that was on the lot a long time might be titled as an '84 and an early production '84 might be titled an '83. The underhood emissions sticker ALWAYS will have the correct model year. The VIN will also ALWAYS have the correct model year. These are Federally mandated things, there's no leeway.

Last edited by peejay; 01-14-17 at 08:46 AM.
Old 01-16-17, 04:19 AM
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Originally Posted by Sh00bs
I have an '83 GSL rear in my gf's '79 LE.

My question is, how do I tell if I have an '83.5 - newer rear OR if I have an '83-83.5 small axle rear?

My I would like to do some LSD unit swapping between my '85 and my gf's 79 with this 83 gsl rear in it, but I don't know if the LSD in my '85 would fit the '83. How can I tell short of pulling them all apart and counting the # ??

MUCH THANKS!
The LSD from the 85 will only fit big bearing housings (84-85). The 83 GSL should already have an LSD. So it sounds like you have two cars with two different generation LSDs, I'm confused as to what you're trying to accomplish. Is yours in the 85 worn out?

I'll have two LSDs for big bearing housings (GSL-SEs) tomorrow, for sale.
Old 01-16-17, 12:16 PM
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Bear in mind that GSL-SE had different diffs than GSL. They had only one clutch instead of two, or they had the steels and clutches inverted so it acted like only one clutch... Either way the GSL-SE's diff action was weaker/softer than the 12A cars.

One can be converted to the other, but to be honest I don't remember if the GSL-SE had three steels and one clutch per side or if they were just oriented steel/clutch/clutch/steel.
Old 01-16-17, 02:39 PM
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Correction. I have a complete 82 GSL Small Bearing Setup (Brake Calipers, Axles, Rotors, Housing, and 3rd Member) and a 84-85 3rd Member Differential GSL-SE Setup. Picking up the rest of the parts tonight for sale.
Old 01-16-17, 06:08 PM
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Nice.

There was a guy from Oz who made an account on Ohio Rotaries (plug) asking for any and all Series 2 limited slip/disk rearend parts, to ship back home. We were like, man, we import that stuff from YOU guys, all that stuff has been gone here for a long time
Old 01-16-17, 08:20 PM
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Originally Posted by peejay
Nice.

There was a guy from Oz who made an account on Ohio Rotaries (plug) asking for any and all Series 2 limited slip/disk rearend parts, to ship back home. We were like, man, we import that stuff from YOU guys, all that stuff has been gone here for a long time
Yea, I had a few spares from the previous owner and during my experimenting I picked up a few more. Time to clear the garage out and help another FB get back on the road.
Old 01-17-17, 11:22 PM
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These two will be for sale now.



















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