74SpiT

Hey guys,
I have a 1989 IROC-Z L98 with a 9 bolt Borg Warner Posi. I was under the impression from the owner that it was a 3.27 ratio, but my car doesn't have an engine oil cooler so I don't think it's a G92 code. He said he thought it was original, but just to be sure I was under the car checking for codes on the passenger axle tube. I couldn't seem to find them-I was mostly trying to uncover them from years of grime next to the gear set, but is this the right location or am I missing something? It just doesn't seem like I could have anything but 2.77s. Thank you very much!

sofakingdom

iTrader: (1)

Since you mentioned that you were about to change the rear end fluid, as any sensible purchaser of a used car would automatically do, just look at the gears while you have the cover off.

RS Chris

I don't think GM marked the gear ratios on the diff for third gens, but I could be wrong. Your list of RPO codes can tell you what the car came with originally. It is found in the trunk in the passenger side compartment. You could also just jack up the rear end, put the car in neutral, and count how many times the driveshaft turns per one revolution of the tires. It will either be under two or over.

74SpiT

Thanks for the feedback guys. To be honest, I actually changed the rear end fluid right after I bought the car, but I hadn't thought about this issue and didn't think to check the ratio at the time. Oh well. Thanks for the helpful suggestions!

74SpiT

Oh and I'll definitely check the driveshaft rotations, thanks good idea

jmd

iTrader: (4)

In 1:1 gear at 70mph with tires close to 26" should have about 2800 on the tach, or 3300 on the tach.

cosmick

Go buy 2 quarts of 75W90 synthetic, $5 per quart, and a new cover gasket for another $5, and change the rearaxle lube. Noone ever does it, let alone as often as they should, and it'll give you a good chance to confirm what's in there.
If you buy one of these cars used, then you need to change the gear lube right away, since it's probably never been done since the car was built.

RS Chris

I am definitely guilty of that. Car has 250,000 plus and as far as I know it was never changed before I had it.