Posi vs non-posi

[am4blue]

I have an 84 Regal with a plain (for the time being) sbc 350, th350 trans.
It has the GU1 7.5" rear end, which I believe is the 2.43 ratio. I found a GU1 G80 rear end and was wondering if it was worth it to grab it and have it swapped into my vehicle? It is the same ratio... unfortunately.

If it was a lower ratio, it would be a no brainer. Would the diff gears in the posi 7.5" fit and work in my non-posi rear diff case?

I'm probably not going to get it due to the high gear ratio (as this is a street car and not a highway car) and the rear diff I have now has 65,000 miles on it. But I'm curious if I could swap a posi diff into a non-posi diff case? Are the cases and axles identical?

D

 

[beermonkey9417]

if its the same size rear it should fit. the only difference between posi and non is the locking part in the carrier.

 

[Doober]

What type of posi is it? Gov-loc carriers aren't known for their strength, more for just getting out of slippery situations. If it's the same series carrier it should be a bolt-in, just be sure to use the races that came with the new carrier if you can and double check backlash of the gears. Also make sure it's not a 7.625" rear... those will bolt into a 7.5" housing but use a different gear, and some are also built for 28-spline axles.

 

[am4blue]

Good info guys, thanks.

I would assume it's a 7.5" rear end. It's a G80 rear end on a 86 Monte so it should be a 7.5". And the GU1 is more of a highway gear ratio which would not be an upgrade to me. I'm going to take a closer look tomorrow to double check the ratio, but if it's the same ratio as the one I currently have I'm going to pass and wait to find one with a lower gear ratio. Or save my pennies for an 8.5" or even a 9".

Thanks again,
D

 

[Doober]

Well if it's posi and you get everything for the right price, you can still swap different gears onto it. If it's a 2-series you can run 2- or 3-series gears, but if it's a 3-series carrier you can only run anything over 3.08s on it.

 

[FE3X CLONE]

If the other rearend is in good shape, then why tear apart your 65,000 mile rear to swap parts? Just pull the entire rear out of the car and replace it with the other.