I have a 1983 gsl lsd rear pumpkin im selling but the guy that's buying wants to know if it will fit into an 85 with the big bearings? Please help me.

 

If I remember correctly, 1983 was a funny year. Some had small and others had big bearing shafts. No sure how to tell other then measure them.

 

I thought the bearings were the only thing bigger? The carrier should be the same or so I thought.

 

Rockauto lists the diff bearing for all years (79-85 including SE) as both having these dimensions:
Bore=1.5748", Outer Diameter=2.6772", Width=0.748"

The spline count may possibly be different (don't have one apart to check) but the shaft is the same diameter at the carrier. Only the outer "axle bearings" are bigger. Same on the fronts, the inner bearing is the same for all years and the outer was made bigger partway through 83.

 

83 is a weird year, and it confuses everyone.

79-82 use a small axle, which not only has a smaller axle bearing, but it is smaller at the splined end, so the diff has different side gears, which are small.

the 84-54 use a large axle, so big bearings, and the splined end is larger, so the diff side gears are larger. the 84-85's also got a different driveshaft with a different flange.

the 83 is a mix, it uses the small axle diff, but it has the 84-85 driveshaft flange.

 

Short answer is "it depends".
It depends on what part of the model year your car was made. Mazda switched to the larger axles about mid-production 83.
You will need to pull the pumpkin and count the splines on the LSD unit.
Mazdatrix has kindly provided you all the information that you need to know:
https://www.mazdatrix.com/g5.htm

 

no they did not, see the above, they switched to a larger driveshaft flange in 83, but kept the small axles to the 84 model year switch over.

 

That'd be incorrect. All '83 had small axles and late driveshaft flange.

There's some disinformation out there that some early '84 had small axles. I have a very early '84 (had the 3.933 final drive still in it) and it had the large axles.

Where I suspect the incorrect info comes from is from states that assigned a year to a car based on when it was titled, so an early '84 might have been erroneously registered/titled as an '83, or a '83 that sat on the lot a while may have been called an '84.

 

yeah the parts catalog is very clear, and Mazda isn't GM, they didn't make "mistakes", or have extra stuff "lying around" that they needed to "use up".

 

I still like the '02 Audi that I used to service that had an '00 HVAC system in it. Even ordering parts by VIN would get the wrong bits.

Of course, we discovered this when the heater cores (plural) weren't like the ones we took out.

VWAG was so "good" at the "whatever is closest to the assembly line" method of assembly that the final year or two of Audi Coupes were known as "special builds", they quite literally were made of all of the leftovers so they could clear out inventory.

 

It's all good background and discussion from everyone but OP I think the only way you will be 100% sure to say to your buyer is to pull it out and count the splines or pull one axles shaft out and count the splines on it. Then you will know for sure.

 

yeah i had an 87 sirocco once that was built out of leftovers or something, so finding an alternator was really tough.

 

If it's a disk axle it is really easy to tell just by looking.

Disk cars have three axle retainer nuts. Two of those will be parallel with the caliper bolts. On a small axle rearend, the two that are parallel are on the FRONT of the axle (opposite side). On a large axle rear, the two that are parallel are on the REAR (same side).

Easy-peasy, no need to disassemble anything, just look at it from under the car with a flashlight.

I couldn't find any images of a small-axle housing, but this is a large-axle housing:



The three-bolt pattern is rotated 180 degrees (or 60 degrees ) on a small-axle rear.

 

The other way to know easily; Diffs through 82 had threaded holes in the drive shaft flange. 83 onward had drilled holes, not threaded. The latter used separate nuts and bolts.

 

While true, people swap the flanges back and forth sometimes so you could get caught out by that.