We doing a 70 frame off restoration, not to original. Want some suggestions on rear end. We have a GM 12 bolt posi and are trying to figure out should we stay with the 12 bolt and beef it up or invest in a ford 9". This car will not be a track car nor will it be raced. Will be putting in a rebuilt 454 with M22 4 speed. From what I found out so far a Ford 9" will cost about $2 to
$3K. To beef up the 12 bolt maybe it will cost a grand.

Any advise will be appricated.

The 12 bolt will hold up to anything that you will throw at it, save the bucks.

I agree with Robert, the 12 bolt is more than capable of taking most abuse a street motor will dish out. The tranny or "U" joints will be the weakest links in the drivetrain.

Don't change anything in the 12 bolt except maybe the bearings if the rear has been idle for a while. Check where the axle rides on the seal and make sure the axles are not pitted. If they are they might leak around the seal, sometimes you can smooth them off or buy some Mark Williams, stock GM axles or some other stock replacement axle that still uses your c-clips. Probably will have a posi unit, so get that rebuilt if necessary.

The 12" will NEVER cause you a problem whith your intended use and even if you decide to race
you'll be good to the 11's.

The 12 bolt is the best choice. And it uses about 7% less power to turn. graemlins/thumbsup.gif

When I build a 12 bolt for performance usage I weld up the tubes with a nickle rod. The factory tubs are pressed and have plug welds. I you see oil on the plugs they have probably cracked. I have had two rear ends where the tubes have broken loose and twisted. When that happens you have to break it down and put a jig in to get it straight. It is simple to lay some beads around the tube before you start the rebuild.
John

Originally posted by ImpBiscuit:
When I build a 12 bolt for performance usage I weld up the tubes with a nickle rod. The factory tubs are pressed and have plug welds. I you see oil on the plugs they have probably cracked. I have had two rear ends where the tubes have broken loose and twisted. When that happens you have to break it down and put a jig in to get it straight. It is simple to lay some beads around the tube before you start the rebuild.
John just wanted to add to do a little bit at a time try not to heat the tubes too much they will distort if you are not careful.

The welded axle tubes thing is a good idea but must be done by someone who knows what they are doing as they do tend to warp. Done properly it works real good.

Anybody have any opinions on the Moser 12 bolts? They come welded, larger bearings and stronger axles, powdercoated and no c-clips anymore for about $1800.