I'm wanting to buy a 9" and i was wondering what our rear end width was and what vehicles would be closest to that width? How is the width measured? What driveshaft mods do i have to do for the u-joints to work? are baer and wilwood my only choices for disc brakes on 9's? Can i get gears smaller than 3.50? i looked through jegs and that was the smallest one. Is there much if any difference between truck and car rears?

thanks in advance guys, i know these questions have been answered, but search is dead atm...

 

width is 53 or 55 inches i beleive, it's been a while. get under your car and measure backing plate to backing plate. to make u joint work most likely all you'll need is one with differant sized trunnions. i believe 9" rear are the same for trucks and cars, unlike 12 bolts. by smaller than 3:50 gears you mean higher ratio? either way there are a lot of gear sets made for 9" rears.

 

From axle to axle, third gens are around 63".

Most of the trucks are too wide. Trucks also have a huge bolt pattern. Some cars to look for are late 60's to very early 70's Mustangs and Cougars.

I found my diff in a 1970 F100. All I wanted was the housing. I already had a complete center section and I ordered some aftermarket axles. I used ladder bars to install the diff. I use the large 11" Ford drum brakes. My u-joints are large 1350 series.

The only downside to using the truck diff is that the pinion isn't in the center. It's offset 2" to the passenger side.

By the time you find a diff, do all the conversions to make it fit, buy new axles so you can use your GM bolt pattern etc, it would be cheaper to just buy an aftermarket bolt-in diff.

You can pick up the bolt-in housing with axles for around $900. Find a center section with the gears and carrier(posi) that you want and bolt it in.

9" gear ratios vary from 2.xx to 6.xx

 

Just get the bare housing & axles from Moser for around $900 as stated above. It's cheaper in the long run & alot less headaches than modifying one your self.