I understand that the SLP unit will not go into my rearend unless I buy new axles casue it's an '88. I've talked to some people and they said it would be better to just buy a used rearend w/ disc brakes and 3.42 or 3.73 gears. What else would I need to look for to find a used rearend that can be used for posi? How do I know if it's 26 spline or 28 spline?

 

any rear end from a 3rd or 4th gen f body could be used for a posi or have a posi in it. it'd be about as easy to use your rear and buy a set of axles.

 

Powertrax.

 

What kind of axles would I need, and where would I get the SLP unit?

 

28 Spline....here some stuff you could consider:

The magical SLP take off unit can be found here (super cheap):



Thier in limited supply but I called the other day after taking my order she said they had plenty.

 

I'd get a PowerTrax, $330 bux or so I believe but you can install it yourself. Install cost on a posi upgrade would likely be pretty high, and you've already got good pretty good gears so it doesn't make sense to buy a whole new rear. Of course if you can find a whole posi rear with decent gears for cheap enough that is easy enough to swap in too.

I actually bought a 3.42 open rear from a V6 and threw a Powertrax in it and chucked it under my 87Z (instead of a 2.73 open rear). Cheaper than the gear and posi upgrade +install cost I did in the 86 IROC.

 

How do you like the Powertrax. Is power equally distributed to both tires even through turns just like posi? And you said it's about $330? Is the upgrade to Powertrax worth it?

 

I like it alot actually. The only thing that is noticeably different from a standard "posi" is that at low speeds, like under 5mph in a parking lot, you can hear it clicking slightly in near full lock turns. I've never heard it under any other circumstances. (the powertrax has teeth that disengage around turns and thus click enough to hear if you're barely moving, vs a "posi" ie limited slip unit that is quiet as clutchs slip during turns basically). Not sure on what the longevity of it compared to a posi is supposed to be though. The posi in my old 86 IROC is starting to wear out (it wasn't new when I put it in though), but zero problems with my Powertrax so far...

I only paid around $310-$320 from Summit when I got mine (about 2-3 years ago I guess), but looking at Summit's page now it seems the price has gone up significantly to $400, which eats into their price/performance ratio. Makes them about equal to buying a bargain posi and getting it installed then. Sorry about that, I thought for sure I'd seen them for $330ish just recently, don't know whats up with such a price hike on them...

Try to find out what you can get a standard posi installed for at some shops near you so you'll know what you're working with, a local shop here charged me $300 for install labor alone when I had one put in my 86... Maybe you can find someone willing to do it for cheaper.