Hey folks I haven't posted in a while. I went and did an impulse buy on a stock rear end from a '84 or '85 (can't remember which) f-body with stock 3.73s and disk for a conversion onto my '87 trans am auto with 2.73s and drum. The posi in the old '84 carrier is totally shot but my posi is great so I figured it could be swapped over. The cars not in the shop yet but my mechanic told me, sight unseen, that they're not interchangeable and the 3 series gears (is this '84 a 3 series?) are a different thickness than my carrier (how do I tell if its a 2 series?). So does that mean the posi can't be swapped over too? Again he hasn't seen the car yet hes giving it an educated guess. I suppose I can pick up a 3 series posi at a junk yard. Can someone tell me if I'll be okay with what I have as I have put a bunch of time and effort into this swap and I want to have everything I need once that cars in the shop. Will the aluminum driveshaft and aftermarket traction bars swap over without issues? And yes I've read all I can about axles, gears, and carriers from this site and others but I'm not a mechanic so it really doesn't make sense to me. And I'm on a poor mans budget

p.s. I do have the '84s proportioning valve for the disk at least

 

There is a difference in thickness of the carrier's where the ring gear bolts up between a 2 series and a 3. Why not just rebuild the posi on the 3.73? From what i can tell your carrier might be a 3 series, Summit used to have and still may have a ring gear spacer for the 2 series. The best way to tell is to remove the covers and compare the thickness of the carriers where the ring gear bolts up to.

 

How do I rebuild a posi? Assuming my mechanic knows how, is it cost effective or should I look for a used one?

 

If you end up swapping carriers, you should replace the bearings also, which then will need to be reshimed. I would look at the 3.73 and rebuild it if possible. Is your mechanic a good rear end guy?

 

I think hes a decent rear end guy as hes got a snazzy camaro that he races on the track. Honestly, I don't have a lot of options on mechanics as I'm up in east bum screw maine and the only known f-body guys are down in MA. Its just not an option. I will have him do the bearings while its apart. Question: Can he rebuild the 3.73 posi with the guts from the 2.73 posi???

 

What's your goal? Do you want the disc brakes or do you want the gears?

The early disc brakes are garbage. Even if you can get all the parts for free, there's a pretty good chance the car will stop worse with 82-88 discs then it did with drums. Even the argument that disc brakes make for easier pad changes doesn't fly with the early Delco rear discs. They look cool, but that's about it. A better option would be to find the 89-up PBR rear discs or another similar alternative and convert your rear brakes to something that'll actually work. If you really want the brakes, you need to research that topic on the brake forum.

Gears are cheap. Gear setup is not. It'd be downright stupid to pay someone to setup used gears. You'd be further ahead to get a 3 series limited slip carrier (new) and a set of new gears, along with bearings, etc and have the entire rear in your car rebuilt to be what you want. That way you're working with a known quantity and when it's all done you know exactly what you have and you shouldn't have to mess with it for another 100k miles.

 

The posi in these cars is the Auburn, and it can't be rebuilt. Your rear end with 2.73 gear in it has a 2 series posi and the 3.73 requires a 3 series. Your mechanic doesn't need to see your car to know this. Ring gear spacers are nothing but trouble and will likely cause gear failure or noise if you try to use one. The very best thing that you can do for yourself is to get a new Eaton Posi or a Duragrip and install it in the 3.73 rear end. Use new bearings on it and be sure to get the shims that will be needed to set the backlash and bearing preload. Read this. http://www.nastyz28.com/forum/showthread.php?t=19773

 

Look guys I'm with you on the do it right the first time buisiness. If I had the cash I'd just crack open a Summit catalog and go nuts. Heck, if anyone really wants to follow thru on the do it right the first time around routine, just go down to the local dealer and drop 30k on a new camaro. Unfortunately for me I'm a poor limo driver and can barely afford the $75 I paid for this rear end , the other goodies, and the labor to install. I think the gist of what everyone is saying is I'll need a 3 series posi and with a little luck and a good mechanic to replace shims and bearings I should be road worthy. And I've read up on the brakes but figure its a decent place to start, again on a budget, and i can fairly easily up grade rotors after this in the future though I'm pretty sure 4 disk brakes can stop my somewhat stock 305 as needed. Thanks for all the help!

 

Summit is too high on their price on the Eaton Posi, and the Duragrip is about $$80 less than a good price on the Eaton. Don't butcher it just because the Summit price on the Eaton is over $500.

 

Good point big gear head. I think I did make a valid point about budget though. Almost every single upgrade question on this board could be answered with "hey, go buy this new high dollar part..." and if money weren't a factor it'd be the right answer just about every time. Anyway I'll search around and see if I can find a duragrip for less than a weeks paycheck

 

There is no cheap way to do what you're suggesting. If money is really as tight as you're suggesting, you'd be better off to find a used rear that doesn't need anything. Rebuilding your 84 rear will cost about the same as having gears installed in your 87 rear. The only advantage of the 84 rear is disc brakes that don't work.

 

You need to cut the attitude. You've obviously already jumped into this without researching it and understanding what you're getting into. It's probably not a good idea to mouth off to the people trying to help you. I'm not suggesting you spend money you don't have on something you don't need. I'm suggesting you spend your money smart so you'll actually have something to show for it.

 

Um Drew I don't really think there was any 'attitude' from me here. Notice the multiple thank yous and smileys? And I already admitted I made a mistake in buying the rear end (note the title of the thread) with the shot posi. About all I got from you was a comment about being 'stupid' and a jab about not reading up on what I was doing though I'm not sure y since anyone will tell you rear ends are tough and I just needed clarification. Relax bud, I appreciate all the advice from everyone and thanks again for your time.

 

The 'attitude' is comparing the advice you were given, to advice to just buy a new Camaro. Then criticizing its accuracy because it doesn't fit your budget.

Don't worry about it, I'm not going to waste any more of my time trying to help you.

 

Good call Drew. I used to help guys on car audio in a similar site and it gets frustrating to say the least. We newbies are a tough crowd! Thanks again for the advice guys.