I have a 91 Firebird that I am swapping over to a 3.73 posi. Is there a way to ID the axle splne count without popping off a axle and counting them? I know since its a 91 it should have a 28 spline rear axle but the car is 20 years old there is no saying over the years the rear blew up and someone threw a junk yard rear in there from a 87...


thanks

 

Not that I'm aware of.

JamesC

 

You need to pull the axles and count the splines. Nothing visual can tell you if it's 26 or 28 splines.

 

Yes, there is a way to ID the rearend housing. It will only tell you what gears and differential were ORIGINAL to the assembly. And you can find the codes specific to the year which would also tell if it has the 28 splines or 26 splines. e.g. '89 on up

http://sethirdgen.org/reardata.htm

Here's where you can look for the code. Depending how rusty the rearend is, you might have to wire brush it.

It's really just best to pull off the pan and look for the ratio stamped on the ring gear or pinion and inspect the differential to see what one it is. If the ring ratio matches the one stamped on the tubes, most likely its the same one.

 

Though worth a peek, rust usually makes deciphering the code difficult, if not impossible. IIRC, Rockety, you yourself experienced that in another thread.

Insomnaic,

If you're going to swap gears, you'll have to yank the axles anyway, so....

JamesC

 

Yes...i did. But it was still fun figuring out the gears that were original to the rearend and even when and where it was made.

 

But technically, the axle code still means nothing if you're unsure it's even original. If the axle code says it's for a 91, that still doesn't mean someone didn't trash the posi and swapped in a 26 spline posi and axles into a 91 housing because they couldn't find another 90-92 donor car. I had an 86 diff housing with aftermarket 28 spline axles in it at one time. Axle code wouldn't have helped at all.

 

is there another list somewhere?mines not on that list.mines clearly 6HN.

 

Umm..there might be. You can try looking in the Hanes manual for 3rd gens.