I have a 68 GS 400 with an open differential. I'd like to put in a posi and have recently come across an opportunity to pick up a 10 bolt posi out of a chevelle. I am unsure of the year of it. But I was wondering if there is anything I should look for. I.e certain years won't swap out without heavy mods, etc...I'd like the conversion to be as painless as possible. Thanks!
I had a 69' Skylark the axle bearing went south and ruined the housing. I bought a 8.5 10blt from a 72 4-door skylark. It bolted right in no headachs.
The Chevelle 10-bolt,if original,is an 8.2" 10-bolt Chevy. It is not as stout as your existing rear,but would be fine in a stock application. The Chevy 10-bolt has a 1310 u-joint,whereas the Buick rear has a 3R u-joint,so you would need an adapter U-joint,and possibly need to shorten your driveshaft a hair.
Yep when you are messin with Buick Power you at least go with 8.5 and the best is 12 bolt. Don't go 9" or you will lose 2 tenth in the 1/4 because of the pinion to gear angle.
Well first I'm not racing the car. Strictly a street application. Obviously I want the car to run good, but wouldn't a posi with say 3:55 or 3:73 run much better than my current 3:08 open differential? Not smart remarks here, I'm new to this so all of your info is important to me. I am learning!
Thanks for the image that will be helpful. I have yet to even see this rearend just was told it was out of a chevelle. The guy that has it is a ford guy through and through. He just knows it a 10 bolt and said its out of a chevelle. He has no desire for GM stuff so just wants to get rid of it. Thanks again
See, you need to ask yourself some basic questions. What do you want out of the car, and what are you willing to put up with? Why do you need a posi? The main reason for a posi is so you can launch with both wheels, but any healthy BBB will easily overpower street tires, both of them, so to really get the best out of the posi, you need sticky tires so the car actually launches. When you actually hook that torque, that puts maximum stress on the rear end. The Chevy rear is definitely weaker, it is a C clip rear, and as mentioned, uses a different u-joint. Buick rears are bolt in axle, which is stronger. If you just want to be able to do 2 wheel burnouts and leave 2 marks, go for it. Burnouts actually stress the rear less than hooking it up solid. As far as gears go, the higher numerical gearing increases your RPM at highway speeds. What can you live with? 3.73's will have you close to 3000 RPM at 60 MPH. Yes, you'll have better acceleration with higher numerical gears, but gas mileage will suffer as well. 3.08 is a good all around ratio.
Good input and much appreciated. Car will not see a lot of highway miles. More cruising speeds at typically 40mph. That's not to say I won't get in it because that's the fun part. Burn outs are fun but not something I'm looking to do a ton of. Looking at more get up at go. 3:08 is a decent ratio for running the car on trips and it does run well, I agree. I had a 5.0 with 4:10 and that was more than I liked especially the times I was on the highway. That's why my max would be 3:73. But that's why I wanted to ask about the chevelle posi. How much weaker is it. I don't want to compromise durability just to go to a posi. And the 400 engine is stock.
The only Chevy style rear I'd consider for a big block Buick is the 12 bolt. Even at that it still has the "C" clips for axle retention. The 12 bolt posi Chevy rear I have in my '71 GS I got for free 20 some years ago, BUT had I known then whats known now about rears, I would have kept the stock '71 8.5 that came with the GS. I liked the 3.08 gear that was stock for the 350 GS in '71 I currently have 3.42 in the 12 bolt, I wouldn't go any deeper than 3.42 if you don't have overdrive and do a lot of highway driving
From what it sounds like your after the chevy unit will serve you fine and Buick 8.2's are extremely robust rears just aren't any aftermarket support. Your not gonna hurt it on street tires I promise you
Thanks guys. I still need to go look at this rear, I'm operating off of all word of mouth. Just wanted a good foundational knowledge of what I'd be getting myself into. It's supposedly in good shape the guy, being a ford man, just wants it gone. $150 for the whole carrier seems like a steal! But I definitely didn't want to do myself a disservice by putting it in my car. Appreciate the advice on the gear ratio too. It doesn't/won't see much highway miles but will see some. And I do not have overdrive.
I am always thinking of this. The Race car has a 4.10. It is getting close to too much RPMs the faster I make it with stock rods. I have a 2004R that I want to put behind a 455 and drive it on the street and drag race it in a Regal. I know it will work with a 3.73 but the way I build 455's I will break it if I don't buy all the high dollar parts for it. I found out a stocker 74 Apollo is running a 200 metric with no problems but he has a 350 engine. Lighter better for stockers!!! I'm buying a 350 and I will max it out if I put it in the Regal but want to drive it on the street so I'm going to use an A body rear with 3.73 and then decide what to use. The 200 in the Regal has TCC now so that will help a little on the street. I am still thinking of what is the best way to do both things. It's a lot easier if you just Drag Racing!!!
Boy isn't that the truth! Getting a car to perform at its best on the track while keeping it "street friendly" sure is a delicate balance!
Well I picked up that rear end. It needs some dressing up on the outside but it's in great shape where it counts. So I took the cover off and to my surprise it already had a very nice set of 3:55 in it. Which made me happy. The peculiar thing I found was that I was told it was out of a chevelle, however everything about it looks like my open diff with the exception that this is posi. The rear cover is even identical to mine. The guy I bought it off is operating off of what he was told about where it came from. Supposedly the original owner bought it to stick under a GTO but passed away before being able to do so. I don't have a measurement for ya on the ring gear size. But I think I did ok for getting everything for $150!
Fortunately for me racing is out. Love to watch and would definitely be hooked if I started running it down the track which really start a snowball effect that my wife would not be thrilled about!! Lol. With that said, I still want the car to be respectable on the street. Which it is, in my opinion, just the way it is. But I think it'll be a little snappier with a posi and 3:55 gears. But hey I am new to this with a lot to learn. Only one way to find out!
If you had the rear open sometimes its staped on the ring gear as to what size. I did a rear swap on my olds. It was 3.73's out of a monti ss, big mistake with a metric 200 3 speed. Car shifts way too fast and can barely do 60 without screaming at 3000 rpms. Went out and found a 2004r for it which will make everything happy just need the coinage to do it. As for my buick rear, it has a factory 12 bolt with c clips. For street use the c clips are fine if you are doing heavy racing and launching you want the bolt in axels for strength. Now as far as ratio i wouldnt go higher then what you have with the 3.55's. You will probably be between 2600 and 2800 when doing 60 and dont forget to change the speedo gear in the trans! I have an eaton posi waiting to go in my 12 bolt and plan on putting in 3.08's or 3.27's wich i believe is enough oomph for the stump puller buick motor. Also remember the power band in most buicks maxes at 5500 rpms and its easy to over gear it. I had a 79 trans am with a 70 lt1 350 that was worked and had 4.11's in it. Let me tell you ive snapped my neck back on that thing a few times launching it at 3000 rpms and was fun at the track, the ride home afterwards at 11 at night, not so much since it screamed at 3200 doing 40 mph and got 5mpg. ou:
