1967 rear diff

Seeing if the factory rear differential in the 67 I have in the shop. Not sure if it has been swapped but feels like the gears have might have been. If original other gears available? Parts available? Or if it has been swapped what rear is it and what’s available.

 

That is the more common Buick 8.2”. You can get posi units and gears for that.

 

Ditto - 8.2 Pontiac gears
with aftermarket Auburn or Yukon will fit right in.
MAke sure you match up the correct carrier with the correct ratio.
2.56- 2.78 (2)
2.93 - 3.23 (3 - or mid series)
3.36 - 4.33 and beyond (4 series Steepest)

 

Don’t want to hijack this thread but I was just going to post a question on the same rear end. I have a 1967 skylark that originally came with a 340-4 combination and automatic transmission. What would the factory gear ratio be in the 8.2 rear end that I have now? It is the original rear end and hasn’t been changed. It seems like there were multiple options, I’m just wondering if the different ratios I am seeing was based off motor option.

 

Thanks! I’ll have to clean years worth of crud and see if I can find the marking. I am related to the original owner so know that it is the original. I had the cover off years ago so I know it’s not posi but didn’t check gearing at the time.

 

Cover off is ALWAYS the best way. it will be on the outside ring gear diameter stamped in...Take a pic and post the numbers will get you the answers.

 

Brian/ Monza where is a good place to purchase new gears and a Posi unit. Unless I car re use the posi. What would be a good rear gear. 3.36? Might be best as would be around the same series. I’ll have to scrap off and look for stamping to see what’s in there currently unless it’s been changed out sometime in the past.

 

I would see what you have for sure,first. If I were to choose between the Auburn or the Yukon,I would choose the Yukon. As far as gearing goes,what are you looking to do with the car? I have a set of GM 3:08’s,if you want a nice cruising gear. There are new 3:42’s available,and a few other ratios.

 

I'm not the owner of the car-
But he would like different gear. He will be doing some highway cruising with a little in town driving. But don't want anything to low or to high. Car is a 4 speed if that makes a difference. Not sure what these came with from the factory. My knowledge is the 70 cars.

 

Do you know if it is a wide ratio M20 or a close ratio M21?

 

Yes, that makes a difference. That's why Brian is asking.
A wide ratio M-20 with a 2.54 first ratio can work ok with a 3.08, whereas M-21 with a 2.20 first gear would need at least a 3.55 to get the same off-the line performance. Combining a M-21 with a 3.08 rear would mean lots of clutch pedal/clutch slipping to get the car going from a stop.

 

Looks to be an M20 out of a 68 Buick. Found the axle code today. Was originally an LX code so 3.36 Posi. But someone changed it out and man did they. 1 tire rotation is 4.5 rotations on the driveshaft. So would like to go back to the 3.36 that was originally in there.

 

If it does have an M20,a 3:08 or 3:36 would work well with that and give you a nice cruising rpm. What is the cruising rpm now at 70mph?

 

Take a few minutes and remove the cover and check the numbers on the ring gear so that you know what you really have now. I'll bet that the gear ratio nowhere near a 4.5 ratio. I wouldn't be surprised if the 3.36 gears are still in it.

 

Well when cruising to town. Going 50 mph the rpm was at 3500. I feels like a pretty low gear in it and not the factory 3.36

 

Car was drag raced in the late 60s early 70s near St Paul MN before going out to AZ in the mid 80s according to 2nd owner

 

3500 rpm at 50 mph? WOW, that would require a really deep set of gears. Hopefully you can find the time to remove the cover and solve the mystery. I'm really curious to read about what you find.

 

That much gear also makes me think it has an M21,but if it originally had 3:36’s,it could have the M20. It all depends on if it was swapped out. Regardless,I think 1st gear would be non-existent with 4:56 or any steep gear like that.

 

Yah, could have anything... I would assume if they are drag racing it has a 4 series carrier posi at the very least...so 3.36 3.55 3.90 4.33 4.56 4.88 5.13 were available.
If it is posi you can do the spin test (m again assuming they are racing with a 2 wheel lock up...of coarse... ) lol.
so if the wheel spins one turn the yoke would spin 4 full turns it is likely a 4 to 1 gear.
You have to mark the wheel and the yoke with reference points on NON moving casting or backing plate etc. you have to watch the yoke carefully so you do not get mixed up.