Advice - Conversion to slip diff rear end

[jpdog357]

Guys:

My 400 72 Lemans is about to get a bit of a makeover with your feedback. Will be dropping on a new manifold and 4 barrel.

The only issue is the one-legged-wonder rear end.

Can you guys give me some advice on getting a limited slip? I have been told its easier to find a whole new rear-end in a junkyard from a GTO but I haven't had much luck. Also, an aftermarket Curtis or whatever looks to be an expensive alternative.

Any ideas?

Thanks,

Jason

[Larry]

The change of the entire third member is usually the easier way to go. Now finding a 3.55 posi is a different story. Back about 15 years ago when we decided to get rid of the 2.90s(?) in my '69 Lemans wagon we figured we would just run to a local salvage yard or two and get something from a GTO... no way, best we had to settle for was a 3.23 non-posi rear end. But, I have noticed a 3.55 or two at swap meets for a few hundred dolars instead of the near grand they were up to some years ago. So, first choice is locating what you want at a reasonable price.

Here are some Hollander Interchange ideas for you too. If you have 10-bolt axle cover in your '72 Lemans now, it only shows a direct interchange with an axle assembly from a '69 Tempest or a '70-'72 Tempest with 10-bolt covers.

If you have a 12-bolt axle cover now, you can change out as follows:
- Use a 10-bolt axle cover assembly from a '68-'72 Chevelle; a '71-72 GMC Sprint (fat chance of finding one of those!); or a '70-'72 Monte Carlo. (It notes that the ones above require a pinion flange interchange- probably using your old one.)
- Or use a 12-bolt axle cover assembly from a '70 Buick Special; a '68-'72 Chevelle; a '71-72 GMC Sprint; 'a 70-'72 Grand prix; a '70-'72 Monte Carlo; a '70-'72 Tempest. (It too notes a pinion flange interchange required.)

There are others that will also work, but they would be using drums different than yours (non-Pontiac) as well as the pinion flange interchange.

Chew on some of these and let's see what some of the others would recommend. I'm sure that some of our racing members can give you chart and verse on which assembly to use and how to accomplish it the easiest.

Keep us all posted on what and how you do.

Thanks,
Larry

[super]

If you have difficulty locating a reasonable priced limited-slip differential for your Pontiac, you might consider using a Richmond Powertraxs system. These units are generally available through speed shops such as Summit and Doug Herbert performance. You might give Herbert's tech line a call and get some info on the Powertrax. They run about $430. You could choose what gear you want to run and set it up fairly easy.

My friend owns a 1971 GT-37. It came equipped with a 3:55 open rearend. He is going to set his rearend up with one of the powertraxs.

There are other companies that offer similar set ups. Summit has some systems that are even more reasonable.

Herbert - 704-732-2400

Summit - 800-230-3030

[jpdog357]

Thanks for the recommendations.

How difficult are these Richmond Powertrax to install?

Thanks,

Jason

[AlsCustomS]

so how is the powertraxs
working after all these years worth it