Hi, I am the owner of 2 1989 Iroc Z28's. I just bought one with the L98. I want to figure out if the previous owner installed a larger rear end gear (lost contact with original owner). My Camaro with the LB9 has a 2.77 rear end gear and runs almost 1700 rpm at 65mph. The Camaro with the L98 says on the parts sheet in the console that it has a 2.77 rear end gear and runs 2400 rpm at 65 mph. Here's an issue with the L98 camaro, the vss doesn't work (mph gauge not working), and I was using my GPS to tell me when it was running at 65 mph when the rpm gauge was at 2400 rpms. I can feel my car shifting into overdrive. So is not having a working vss messing with the rpms, am I running a higher gear, or is it normal for a L98 to run higher rpms than the LB9 at 65 mph with a 2.77 rear end gear?

here ya go grasshoppa' enjoy...

https://www.thirdgen.org/forums/tran...-10-bolts.html

I highly doubt I am running a 3.73 gear, but who knows lol. Thanks for the reply tho.

My next question is, What rpm are you L98 guys running at 65 mph with a 2.73 or 2.77 rear end gear?

The stock tachs are notoriously inaccurate at this point. I wouldnt trust them at all.

you know... I should have mentioned this... but ... you should check your RPM with a timing light and then compare the numbers... ....

Counting the number of times the driveshaft turns in relation to one turn of the wheel will ballpark rear end ratio

Do the maths
http://www.bgsoflex.com/rpmmph.html

I did some messing around, looks like someone did swap in a 3.73 gear. Thanks!

With a 3.73:1 axle, and 245/50R16 tires, and a 700R-4 automatic, you should be doing 2200 rpm at 65 mph if the converter is locking as it should. This calls for a 15 tooth speedo drive gear, and a 44 tooth driven gear.