How do I determine how many splines my axles are?
 

My rear end is making a terrible roaring noise but doesn't do it under load. Anyone know how many slpines are on the axles? Jegs offer axles replacement but there's to diff spline counts 26 and 28.

Pull one out! Simple as that.

Or, check your SPID code for the rear end of your 91 and use that information to order new axles after checking with the dealer to confirm. I am 99% certain that the rear axles in a 91 Z28 with the G92 limited slip rear are 28 spline.

Also: That should have the G92 limited slip as it is a Z28 - make sure the additive for the limited slip is in your rear end housing or it will howl and you will hear a clunking noise when backing up as the rear end binds.

preciate it. I just bought it, was thinkin bout putting a whole nother rear end under it but if I can upgrade it would rather do it that ways. Also you wouldn't happen to know of upgrading the rear brakes would you?

There are lots of upgrades for brakes...yours should have rear disks already. If not, I am curious of what the codes under the center armrest say.

Yeah ive got disk just changed the rear pads and resurfaced the rotors yesterday. Is there a dual piston out there?

89 was the year they started to put 28 spline axels in. If your 91 is original rear, it's a 28 spline. Might want to pull and count anyway. :)