87 LT with a 2.8L, open rear end, 342 gears. How many spline axles?

 

Welcome to TGO! They should be 26. They didn't go to the 28 spline axles until 89-90.

 

Thanks Ozz, great site. Next question 7.5 diameter Ring Gear?

 

Only if it's a 10-bolt. I don't remember the 9" ring gear size off the top of my head. I think I remember reading that it's a 8.85" or so but don't quote me on that.

 

Count the bolts on the cover. 10 bolts = 7.5/7.625 10 bolt. Around 1986 the 7-1/2" ring gear was upgraded to 7-5/8". Parts are all interchangeable but it's still called a 7.5" diff.

If your rear cover has 9 bolts and a rubber plug in the cover then you have a 7-3/4" Borg Warner 9 bolt. Stronger than the 10 bolt but only available from 87-89 and parts are from Australia.

With a 2.8L, it's very unlikely you have a 9 bolt unless a previous owner swapped it in. The 9 bolt was a performance option to the Z28 cars.

 

It is a 10 Bolt. Question, I plan on changing the carrier to a posi using the same existing ring gear, will the 7-1/2 or 7-5/8 342 ring gear fit on any 10 bolt 3 series carrier or do I need to order a 7.5 or 7-5/8 carrier.

 

Yes, the ring gear will fit. Just make sure your axle shaft spline count is the same as the new carrier.

 

Thanks to all who shared some answers!