Looking to replace my existing 3:08 posi currently in the car. I'm looking for something drum to drum ready to go for a swap. I currently have a 200R4 trans in the car which stays, so a 1979 2:73 H/O axle would be great. Not picky about a posi but I would prefer it. As this has a rebuilt 260 with tons of life left in it and I'm looking to keep that motor in the car, I can't really go for anything too tall for fear of blowing it up. I'm looking to preserve that 65 mph/1,850 rpm/20 mpg pure highway I currently get. This motor hates high RPMS, as in anything over 2800 it starts to get uncomfortable.

I'd be interested in a swap with the 3:08 but I will say this rear is tired and needs to be gone through. I'd like to get something that can be sent directly to the shop I use so they can perform the job and replace my exhaust at the same time.

Thx.

 

FOUND - one of our CO group gave one out of his 79 Calais (2:29 open) to a good friend of mine who advises I can have it. I will be looking to swap out the 2:29 ring & pinion with my NOS GM 2:73 set up and away I go.

Thanks for the look, I will now be able to make this happen.

 

Seems like you could rebuild your current rear a lot easier than a complete swap.

 

Excellent call, but at this point I'd rather ditch the one in it and start fresh. The 2:29 I will be getting has just 39,000 miles on it (info provided by a prior owner of the car it was in). Granted I will still have to go through it, of course. I don't know the history about the one I put in the car 24 years ago, and I have to say it's never been right from day one, IMHO. I was always suspicious I got ripped off on buying a "rebuilt" rear way back then. I'd rather be done with it.

 

I'm thinking that the 260 might not have enough nuts to be happy with a 2.29 gear, and overdrive. I'd think the 3.08 ratio would be ideal.

 

Assuming a 26" tire 65 will be 1285 rpm. This may only work if you live in Indiana.

 

It seemed to me that a 260 Olds would idle down the highway like a Cummins Diesel. A Cummins Diesel has 800 lbs/ft of torque. The OP would need to hold the transmission in 1st and 2nd gear to reach highway speeds. On hills the transmission could downshift til it found a good power range to sustain speed.
.........Just my two cents worth.

 

I doubt there is enough HP at 1200 rpm to go 65. the go pedal will be depressed to far for the trans to shift into OD or stay there for any meaningful time.

 

This may have gotten lost in the posts above:

The difference between the original 3.08 and new 2.73 isn't dramatic, and will be much better than the 2.29 gears.

 

Yep, I missed that completely. But, this only reinforces the idea of using the existing housing. Even with only 39k the shop will likely replace all the bearings and seals. So what is the op gaining with buying a complete rear?

 

Hello 66, I'll be getting that 2:29 rear for free, what I like about it is that it's out of another 1979 Cutlass Calais. The NOS GM 2:73 ring and pinion I bought on E-Bay early last year for $75. Were it not for this I'd probably would have opted to go with the existing stuff. With the 3:08's I am at 1850 rpms at 65 mph with the O/D so I'm thinking a 2:73 is going to place me somewhere in the mid to upper 1600's at 65, something the 260 would be ok with. Around town I'd probably leave it in 3rd, though. On the highway I doubt I'd see much difference between the 3:08 and the 2:73 performance wise.