i have an 89 RS 305 TBI and i dont know what size gear set to get-7.625"? 7.5"? other? im going from the stock 2.73 to 3.42. also, i am looking to get a posi unit, and im assuming i have 26 spline axles since ive heard those are more common in 89s but what kind of posi units are good for a 26 spline. i know about the $99 SLP one for 28 spline but id rather not change my axles if at all possible. thanks for any help/advice
CJ

 

sorry, i forgot to mention it has the 700R4 if that matters

 

Gears are the same from 77-03 in this model of rear end, doesn't matter what the "size" is said to be, they're all the same.

Look here for parts http://www.drivetrainspecialists.com...=28&cat=GM+7.5

As far as advice... take the cover off and pop an axle out and count the splines before you buy anything. Beats the crap out of buying the $99 posi and discovering you need a $250 set of axles to use it; or buying a $375 posi and discovering it doesn't fit your axles, that you should have bought the $99 one instead.

 

Hey i just want to know what the difference is between say the SLP posi unit and any other one thats more than double the price? and are the gears that Jegs makes good? or should i spend more and get a real brand? i was cosidering 3.42- also for a 89 RS LO3- i would have to get the gears for the 3.08 & lower carrier right? i was thinking PN 555-60008 @ this page

 

The SLP one is a "used" stock one out of a late-model Z28 that they were putting the SS package on, which includes a heavier-duty posi. It has a few miles on it, usually less than 50. But since it's not new, they sell it cheap.

Jeg's doesn't "make" gears, they just sell them. Without knowing who made those I wouldn't buy them.

Look at the page in my link. AFAIK by the time you buy everything you need, it's the cheapest place around, and has every brand of gear (out of the high-quality ones) that there is to choose from. For the same or less than Jeg's.

I would not get the "special" thick gears in that link, even if I was keeping the 2-series carrier you now have. The SLP posi (assuming you can still get it) is a 3-series anyway, so if you get that, you'd need the regular gears. But even if you stick with the existing carrier you have, use a spacer instead; that way if you ever do get the right carrier, you won't have to replace your gears, you can still use them.

Take your rear end apart and count the splines on your axles before you buy anything. You have the changeover year, so you could have either of the possible spline counts, no way to know for sure although about 80% of the people on this board with 89s have found 26-spline setups.