I have to do some suspension work soon and want to do switch posi and gearing at the same time. Can get a nice SLP posi for 100 bucks I see *thanks to someones link on these forums forgot who* and gears for 40-50 on ebay. Really have to go to a shop for this, wondering does anyone know approximately how long a shop will take to do this work? ANd what kind of improvement will I notice in my takeoff? I have crappy stock 2.73 gears on now... This is the first car I've ever started to mod *or was worth moddin'*

 

It should take about 3-4 hours to do with the rear in the car. It would be about 2-3 hours with the rear out of the car; or about 1-1½ hours with the rear out and all the other stuff like axles out of it.

The SLP posi will work with your axles only if your car is 90 or newer. If you have a 89 you might get lucky but probably not, and if your rear is 88 or older, it certainly won't.

As far as how much difference it will make, that would depend on what you put in, and what your motor is. If it's a stock 305 TBI or TPI auto like it sounds like it is, a set of 3.42s would make it like a whole other car. You won't even think you're in your same car the first time you take off out of the driveway of the shop.

Resist the temptation to stand on it for the first few miles; temp-cycle it a couple of times by bringing it all the way up to operating temp at a steady moderate speed cruise (10-15 miles should do it) and letting it cool all the way back down (2 hours wait), then be halfway easy for a few hundred miles.

If your motor doesn't breathe good above 4000 RPM you'll really notice right away how it falls on its face at the top of 1st gear. You'll get that good pushed back in the seat feeling through some RPM range, and the push will just go away once the engine passes through its torque peak. Also resist the temptation to keep it in low gears once you've reached that point; the motor won't suddenly out of the clear blue start pulling at some time after you've reached the induction system's flow limits and the motor has nosed over; the car won't go any faster from just winding it out farther, it will go slower in fact than if you shift at a reasonable RPM, and of course the motor will last alot longer too.

 

Thanks for the info! Yes your right, my car is a 305 TBI automatic. Probably switching to a 350 within the next year or so. Also, it's a 1991 so I should be fine on that front. Couple more questions, with the SLP posi BOTH my rear tires will spin, correct? *which is what I want* Is there any other things I need to replace for that modification? THanks.

 

You'll need a gear install kit, has the pinion and carrier bearings & a shim assortment. I strongly recommend a "crush sleeve eliminator", sometimes called "solid pinion spacer". Kit is about $100, sleeve is about $25.

Give these guys a call, they have everything imaginable at decent prices, even some stuff (like the spacer) that isn't on their page.

http://www.drivetrainspecialists.com...=28&cat=GM+7.5

Here's the spacer part #.
http://www.ratechmfg.com/gmsolidspacers.htm

 

you will love posi

 

Holy $#!* a posi for $100 where at. I need one and a set of gears also.

 

Ok I'm getting worried now,


I've just ordered the SLP posi and received it, you think my car may still have 26 spline axle ???

1989 RS ?

 

I'd say the odds are about 3 to 1 that your 89 has 26-spline axles, higher if it's one of the typical V8 RS gears (2.73 or 3.08). But you never know until you look. That's why I tell people over and over again to take off the cover and look at what they've got before they order parts, and don't depend on the codes or what their buddy's car has or anything else.

 

By open the cover, I will probably not see the axles until I remove one. is there something that will tell me without starting to tear it down ???

 

Couple more questions here.... if I get the work done at a shop will they be able to recalibrate so the speedometer reads correctly? Donno how that works.......also are used gears usually ok or are they much worse worn? Can get 3.42's off ebay in decent shape for 50 bucks or so vs 200 new....Thanks. Btw posi for 100 bucks does look like an awesome deal