My best guess based on what I have read here is that I have the factory rear end mentioned above. The gearing is 2.73 and I'm looking for maybe a junkyard swap with something in the 3.55-3.73 range that would hopefully drop right in. It sounds like a Chevelle, Cutlass, Grand Prix unit would work? Not sure of the years though,,,any advice is appreciated...
If it is a 71 Buick 8.5, the 2.73 gears will work with 3-series gears. Anything from 2.73 up with fit it. At least 3.73 and I believe 4.10 - 5.13 also works. If you don't already have a posi, you'll want to do that at the same time as changing gears. Get inside of it one time to fix both gears and posi.
I was little scared off by all the precise clearances, backlash parameters, pressing of bearings etc. involved with purchasing and installing a new ring and pinion...Thus the hunt for a junkyard rear with the better gearing. Budget prevents the addition of posi also,,,
You can get a posi for $270. https://www.ebay.com/itm/MONKEY-GRI...480914?hash=item3aafdb3112:g:A~MAAOSwySVaN-hH Ring and pinion for $50. https://www.ebay.com/itm/3-73-RING-...577171?hash=item23a295bb53:g:FZEAAOSwnvVbF8vt We put that model posi and a set of used gears in a buddy's truck two weeks ago.
Wow, good find. How much do you estimate a shop with the right tooling (and experience?) would charge to install? I have never done a swap and am a bit unsure about getting everything correct---
We did it in his home garage. Are you mechanically inclined? You'll need a 1 1/4" socket for the pinion nut, magnetic mount depth gauge and an inch pound lever arm torque wrench. Other than that, it was pretty straight forward. To me, a used set of gears is a lot easier to setup since they already have a pattern you are trying to match. We got lucky. Everything worked with the factory parts. We didn't have to futz around with the pinion shim, the side shims or anything else. We got lucky. I'd say a shop would charge about 2-4 hours of labor so if the labor rate is $80/hr that would be between $160-320. They should be able to give you an estimate. With what I posted, you will also need side bearings for the posi. The place you get the posi from should be able to sell you the proper bearings. The shop you use will have to press them on. You will also need the GM positrac lubricant additive and I'd recommend putting in a new pinion seal as cheap insurance. A new rear cover gasket as well.
Ok, when you say futz around w the pinion shim and side shims, what are the potential issues that you might have had to deal with there? Could I bring the posi unit and bearings to a shop to press on, or will they need the car (entire axle)?
We had a machine shop press the bearings on the sides of the posi unit. It isn't a very hard job but most people don't have a press capable of doing it. As for the pinion and side adjustments, we got lucky and the pinion bearing and shim were already good. The factory side shims worked nearly perfectly. The gears had a good pattern, the right back lash and are quiet when running. If you've never done it before, you could probably do it but it takes a few tools most people don't have, as mentioned before. I'm no expert but when it works, I can do it. If there's a problem, I don't have the tools to change the pinion shim. I'd probably pay someone to do it if you can't get help from someone local that has done it before.
You sold me, that sounds like the way I'll go vs finding a compatible junkyard rear. Thanks for the advice!
You buy something out of a junkyard,you are buying a chance. Even if you did find a posi rear,I would highly suggest servicing it before putting it under your car. I would add a posi & gears to your existing rear. The one under your 71 is a desirable one to build.
likely hood you find a a-body rear in any junk yard with 3.73 3.55 etc is HIGHLY UNLIKELY...lol. They just did not get that gearing from the factory. #3 for installing the NEW parts. I do not know ABOUT those new parts...lol. But it is your rear... you ill know if you spent your money wrong when you hammer down. If you do not have the money to do it correct best to wait and gather your money from life's bad habits. Drinking, smoking, sex etc...,. lol What ever you pay for that is not a necessity Jim J D
Hmmm, so better to spend a couple extra bucks on new gears versus used? If so, is there any downside to getting the most inexpensive new gears I can find versus a big name?
AGAIN Y/N I am not saying there are not deals out there. Used gears are great if your wanting quite gears and cruising... BUT do remember there is always a chance you get a terd gear that will not set-up...WE JUST had one on this site and I fixed his issue.... Even I can not always tell which gear set will have set-up problems just by looking...There are some sneaky stinkers out there. Posi unit ... that is the key to making the rear hold up and good place to spend the money. Bearings stay with name brand Timkin or Koyo That is what most of the world uses. Gears... NEW there are a lot out there. I have really not had issues with to many... Some are definitely more finicky than others... I like the Nitro Gear and Yukon Purple box gears. Yukon has gone to China... BUT it still sets up fine and i have not had any noise issues...??? It is all quality control and the company selling needs to keep the quality control tight or you get a mess. Jim J D Race
Pinion depth might be wrong and needs the pinion bearing pressed off and different one used. You might have different different backlash with stock side shims and require additional ones to get the backlash set properly. I'd think those are pretty common issues.
Ok, if I see a used unit with bearings already pressed on, they will not necessarily be correct bearings for my needed pinion depth, correct? https://www.ebay.com/itm/GMC-Chevy-...027773?hash=item2ca94e153d:g:5SIAAOSwmmxW5CDw
