[gtobird]

Can you use 1969 differential gears in a 1968 rear end? These are 3:36 gears. I would be be using them with a newer Auburn posi.

Thanks
OJ

[RAJ7395]

Yes 67-69 ring and pinion sets interchange just make sure you order a carrier that matches your gear ratio.

FWIW- I don't like the Auburn and recommend the Eaton instead.

[gtobird]

Okay, so I have to ask why you don't like the Auburn's? This is actually a slightly used unit I bought from a friend for a song. Only issue he had with it was he first used the GM differential additive and it then bit too hard turning corners. Changed to the recommended Auburn lube and ran perfect. It is the right unit for the 3:36 gear set. He still had the box it came in with all of the info that came with it so I know it's a match.

Originally Posted by RAJ7395

Yes 67-69 ring and pinion sets interchange just make sure you order a carrier that matches your gear ratio.

FWIW- I don't like the Auburn and recommend the Eaton instead.

[68 Firebird]

Upgraded to the Auburn HP posi a few years ago and have no issue, even with my factory
3:08 gearing. Had an open factory carrier up to 72,000 miles. swapped to auburn posi and have been happy with it for 5,000 miles. yes I do not race or see any track time.
I have used factory auburn additive and Valvoline gear lube.

Gerry

[RAJ7395]

I like the Eatons because the clutch packs are easily serviceable when worn and the performance stays more consistent across the units life. Even when completely worn, the Eaton still works. Also you can change the friction material and spring force to adjust the torque bias to match your application.

Once the Auburn is worn out and the cones hit bottom, the unit no longer provides any torque bias, you need to replace it as it is not rebuildable, and pay to have the new unit installed and reshimed.

[AG]

Check the ring gear bolt size of the '69 gears. It was either sometime in '69 or '70 they changed the ring gear bolt size from 3/8" rh to 7/16" lh.

[1969GTO]

I have owned my Auburn posi 12 years now, I have had 3.55 and 3.90 gears with it.
Some strip time, mostly street.
I use 80/90wt oil and 2 bottles of the GM additive.
I have never had a problem of any kind.
The car is a 69GTO with 8.2 BOP rear.

[TedRamAirII]

Originally Posted by 1969GTO

I have owned my Auburn posi 12 years now, I have had 3.55 and 3.90 gears with it.
Some strip time, mostly street.
I use 80/90wt oil and 2 bottles of the GM additive.
I have never had a problem of any kind.
The car is a 69GTO with 8.2 BOP rear.

You wont have a problem until one day, its not going to work like it used too. When that happens, its worth its weight in scrap.

[1969GTO]

Originally Posted by TedRamAirII

You wont have a problem until one day, its not going to work like it used too. When that happens, its worth its weight in scrap.

aren't they all

[TedRamAirII]

Originally Posted by 1969GTO

aren't they all

At least you can replace the plates in a Eaton type. Can you do that with a Auburn? I dont think so. Not "rebuildable". After your Auburn goes bad, you can upgrade to a Eaton, or get a New Auburn Unit. Which do you think is cheaper to operate?

[1969GTO]

well I just can't answer your questions or remarks about you Auburns lack of quality or rebuild ability.
That is due to the FACT that after 12 years of service, my Auburn Gear posi unit is Still Going Strong.
You must have a lot of experience having to rebuild your Eaton posi, I have none.
So I guess while your car is up on jack stands waiting for parts, I'm driving mine. ;o)

[gtobird]

Thanks for all of the comments. Exactly what I was looking for. In this car it's not likely to matter whether I have an Eaton or an Auburn as long as it is set up correctly and I have the right fluid and additive. Doubtful that I will ever drive more than 2000 miles a year and with only an occasional burnout (sometimes I just can't resist).

Good input though for when I buy a new posi carrier for another car. Also, I appreciate the comment about the ring bolts. I validated the information provided against some other things I read. Evidently the larger 7/16" LH bolts were for the 70 rearend ring gears, but those of course started being produced in the middle of the 1969 calendar year. Looks like the 1970 gear set would still work in a 68 rearend, but then I would need a carrier that accepts the larger bolts or would have to drill out the holes. Not something I want to do.

Regards,
OJ

[TedRamAirII]

Originally Posted by 1969GTO

well I just can't answer your questions or remarks about you Auburns lack of quality or rebuild ability.
That is due to the FACT that after 12 years of service, my Auburn Gear posi unit is Still Going Strong.
You must have a lot of experience having to rebuild your Eaton posi, I have none.
So I guess while your car is up on jack stands waiting for parts, I'm driving mine. ;o)

I have replaced Posi plates in 2 Eatons, the 3 Auburns got thrown in the scrap pile and replaced by Eatons. Once it turns into a 1 wheel peel, its done. If you drive like a normal person, they should both last. If you do any kind of drags or road racing where 1 wheel goes faster that the other, well, Auburn? Good luck.

[1969GTO]