Napoleon1991

I have a 69 cutlass with a 2.73 open diff and im gettin pretty tired of roasting the hell out of only one tire. Ive heard that you can convert an open diff. to a posi. How easy is it and where would I find the parts? I really dont know much at all about diffs so unless its easy, I would probably get someone to do it for me.

Allan R

I did mine last year. If all you want is posi, just change the carrier. How easy? Well for me it was as easy as paying a machine shop to install, shim and set backlash because I changed from 2.73 to 3.42.

There are how to vids on this, but you'll also need to get a special dial indicator IIRC. Jim is doing his right now and had quotes of 375.00 for the work. Mine cost more because I also needed all the bearings and axle seals replaced.

If you want to try it yourself, I'd suggest getting in touch with Brian Trick (507OLDS) or Jim Mitchske (monzaz). They are both first rate techs for differentials and could address your concerns quite easily.

JCMC64

http://www.frequency.com/video/insta...tacey/31716779

I was looking to possibly do the same thing.

Here is another guy who did it.

I was talked out of it by several folks.
Go right to Richmond Gears to get all the info, that is what I did first.
Check out the videos here- http://www.richmondgear.com/02powertrax.html

joe_padavano

Be aware that your 69 likely has a Type O axle. Posi (er, Anti Spin) carriers are difficult but not impossible to find.

Run to Rund

The O carrier changes between 3.23 and 3.42 ratios.

boese1978

[QUOTE=Allan R;497978]I did mine last year. If all you want is posi, just change the carrier. How easy? Well for me it was as easy as paying a machine shop to install, shim and set backlash because I changed from 2.73 to 3.42.

Sorry for the slight hi-jack here.....Allan, I am getting close to doing the same to my 68 and have the carrier and gears thanks to Monzaz......I am just wondering what the difference is like when you drive it....very noticable? Any other pros or cons?
Thanks!

Rickman48

The difference will be like you've been starting out in 2nd, and you found 1st gear!
Went from a 2:48 to a 3:42 in the 80's - quite the difference in acceleration, but on the hwgy, seems you're in 2nd.

Octania

HAH, that's exactly what the wife said when I secretly changed the 3.08 open to a 4.33 psi.... "It won't shift out of second gear!"

Oh sure it will- shift manually... screeeeeeech hitting 2nd, then 3rd...

"WTH did you do to this thing? You put gears in it, didn't you?!"

Napoleon1991

I was also thinking about changing my gear ratio up from 2.73. What gear ratio would be recommended? I mostly drive around town but i do take highway trips so I want to be able to drive on the highway without the engine screaming.

Allan R

Hard to drive that sucker with no fuel tank in it yet. Plans for in the spring...

IMO, Best compromise gear would be 3.08

Bob Kelso

I have all the parts to build your rearend into a 3:23 posi . Give me a pm and i will go over the costs and options . I am located in Hebron Illinois , just south of Lake Geneva . Thanks BOB