Your car came with another type of 8.2" gear set. Your car came with a 1968-70 Buick only 8.2. They do not interchange. Yukon does not make Buick only 1968-70 8.2 gear sets. They are only reproduced by Fabcraft in 3.42 and 3.64 ratios. Both of these ratios are going to require the purchase of another carrier. https://fabcraftmetalworks.com/product/RAB4-08342/1968-1970-82--Buick-GS-342-Ring--Pinion-Gears/
Yup, you and a lot of Buick guys. Of course this has been covered before, but there are two 8.2 10 bolts for Buicks. There is a 64-67 BOP 8.2 of which aftermarket support is plentiful, and there is the 68-70 Buick only 8.2. They are NOT the same rear, and Sumitt, Jegs, what have you, doesn't know that. There is also a Chevy 8.2 rear.
Start looking for Corp 8.5 . It has bolt in axles and large aftermarket support. Then get yourself a 3 series posi carrier, rebuilt kit and start reading......losta information here, try using search , or check out the "GotGears" section of the forums....Don't get frustrated, your in the right place. Jim
OK, that's what I was waiting for. You already have a clutch pedal and are only swapping to a 4 speed in the floor from a manual 3 speed. If I were you, I'd go with an M20 since that will give you a lower first gear than an M21 if you are set on using a manual. As for gears, you would be better off swapping the rear for a 71-72 8.5 rear. Lots of parts, lots cheaper and easier to find. I agree with what most everyone else has said, you need to decided what you want to do and build the car as a combination to match that. Big cam and big gears (high numerically) go together but gas mileage and hiway driving do not.
I've got the entire Buick 4 speed and new clutch for the car. What I can't find is an 11' flywheel for it. It was used when Buick put the engine in full size jeeps wt Buick 350 and 4 speeds. I guess they are robust and heavy...and apparently hard to find as well...loving the 68 lark!!
That is probably for a Chevy 8.2 or pre 68 BOP 8.2. I am still confused on the difference between pre and post 68 BOP 8.2 rears but I know pre 68 has much more aftermarket support.
Yeah very interesting the aftermarket set up. I'll totally be going 70 rear end already situated wt gears. Seen a few on Craigslist for 500$1800$ or so with drum brakes and such.
70 rears are either 8.2 or Canadian 12 bolt Chevys, look for a Corp 8.5 from a 71-2. Stronger, more aftermarket parts/options....Jim/Rott
Having had a close ratio super T-10, I hated it! It's great for drag racing if you have a low ratio differential, but then the gas mileage will be terrible and you won't drive the car often. I also think that 3.55 is a terrible gear. It's too low for economy, and not low enough for great acceleration. You have to decide what you are going to do with the car - you can't have it all. As Jim said, you can spend a fortune on the 350, but there is no substitute for cubic inches (except cubic money). To get the same horsepower as a big block, you will have a fortune into the 350 and it will be a thrashing machine with no idle vacuum. You will also need to do something about the compression, which means a set of good 10:1 slugs. I may not want what you want, but I'd find a good 455 and THM 400 (you can probably find both together), bolt it in, install a 2.93 posi and be done with it. It will have plenty of acceleration for street use and will be good on gas. In fact (and I don't know if there is such a thing from the factory) but I'd probably use 2.73 gears with posi. I know that this may sound strange, but I had them in our '72 Cutlass 350 4bbl, and we towed a two-horse trailer with it, and on the highway without the trailer it was a 21 mpg car.
More I think about it...sell my 1500 mile rebuilt/ long block 350...two trans and clutch then find. 455 wt trans and rear end. Sad truth but prob end up that location...or sell entire car and buy a 70 GS wt a 455?
That car is sweet, drive it while building a 455/TH400/8.5 Rear with 3 series posi carrier equipped with 3:46/3:73 gears. Do the rear first, then install it, while trans is out to shop, and while 455 is at machine shop. 2-3 years from now, done deal, althou they are never done. Always trying to go faster.....Jim
I dig that Jim. Take time. Runs great now just not tire destroying fast...like I want. Had a 700hp grand national from cottons. Last Buick. Need more power.
