Hi
I have a 86TA that is now a 305 carb and I am going to put a 305Throttle body from a 91 Firebird and 5 speed.

But my question here lies in the rear end gears. Right now the TA has a stock rear end (273s?) limited slip and I want to put in a 3.73 posi. I can use either the rear out of the 91 or 86. How do I go about getting the car to have a 3.73 posi? Can I use the stock rear carrier or do I need a new carrier?

Both cars are running and driving and I may put the rear into the Firebird to test it out and see if I like it then put it into the TA when I do the engine swap.

Also both cars are drum brakes, can I convert to disc or not?

Any info would be helpfull.

Thanks

 

Your car right now has a series 2 rearend, meaning that it came with 3.08 and numerically lower rearend gears. You can buy aftermarket 3.73 gears for this rearend and have them installed. That is one option. I believe that the only rearend housing that came with 3.73's in our cars from the factory is the 9 bolt borg warner rearend. Someone please correct me if I'm wrong.
As far as converting to disc in the rear, I would do a search on this site to find that answer. I hope this helps.

 

if you have limited slip you already have posi so you can save a few dollars there. all you need is a set of 3:73 to fit a 2 series carrier. you won't find any gears from gm that will work for you. i know richmond has them so i'd look there first. you can convert to disk.

 

Use the later model rear, because it will have 28 spline axels, which are stronger than the earlier 26s.

You can use either 2 series 3.73s from aftermarket suppliers, or a gear spacer and a 3 series gearset. Or, you can get a 3 series posi and 3 series gears.

Disk brakes may not work with your stock axels. I would check this out, because I have heard about problems related to this swap. I can't say for sure, but this is what I've read on these boards.

 

i have a question also why are you going with the tbi 305 over the carb. 305 just wondering. and which years came with 28 spline and which came with the 26?

 

I can never get the carbs right and prefer the TBI, they seem to run better, and less work. I've had good luck with TBI.

So I can put a 3.73 in the stock carrier?

Where could I get the gears and who can put them in?

 

Plus I only have ever spun one tire. Does that mean my limited slip is bad?

Sorry the rear end is the only part of the car im not good at and dont know much about.

 

I believe that the '90 up cars are the ones that had 28 spline axels. If I'm wrong I'm sure someone will post in and jump down my throat for lying to you. All I know is that my '86 had 26s, but I upgraded it to 28s.

Provided you get the right gears (for 2 or 3 series carrier dependign on what you have), then you can run 3.73s on the stock carrier. I buy most of my gears and rearend parts from Randy's Ring & Pinion. I have been very satisfied with their Yukon Gear line. The quality is right on par with Richmond, but thankfully the price isn't. Check them out at ringpinion.com. Summit & Jegs also stock the more popular ratios and applications.

For gear setup look for a 4X4 shop. They usually have the cheapest installation rates, since they do a lot of them. A friend of mine runs such a place here, and charges $250 to do a setup plus parts. Usually, if you buy the tools you need you can do the setup yourself, but that's up to you. I already walked one member through this job, so PM me if you're interested in trying your hand at it.

As far as the one wheel tire spin goes it probably means that your posi is starting to go. Under some circumstances though a functioning posi will only leave one mark, or one dark mark and one light mark. If you're in doubt just rebuild it. The parts for the GM posis are very reasonable.

 

89 was the transition year, 89s could go either way, 90 and up are 28 spline, 88 and down are 26. you have to pull abnd axle and count on 89s.

 

See, that was the way to post a follow up telling me that I was mistaken, or only partly right. Thanks for the tact ede!

 

damn i ought to save this thread, first time i've even been accused of using tact