I'm using a shortened Ford 9" rear for my current project. For once in my life, I decided to farm something out to a real profesional race shop. I found one, had them shorten it, and get the matching length axles from Moser. When I picked it up I commented on how big the difference in the length between the 2 axles was, but the owner guy told me that was normal for ford 9's. Him being the pro and me having never had a 9" apart, I took his word for it.

I went to welding the brackets on it, and I noticed that the housing was off center by about 1.5". Again, never having done a 9" and seeing the difference in the axles..I thought this must be normal and got everything on equadistant from the backing plates.

I go to put it all together, and one axle is too short. it won't even engage the splines. The other seemed to be fine. The shorter of the two is 4 3/8" shorter than the other. how off is it?

 

Because of how the pinion and carrier are setup inside a 9" housing the proper way to shorten the diff is to center the pinion under the car inline with the tranny. A 9" pinion is offset when compared to a GM diff. Since the pinion is offset, the driver side axle is shorter. When they shortened it they probably measured from the end to the pinion on each side. This will put the pinion in the center.

Measure twice, cut once. Looks like you need a longer axle to make it work.

You order axles after the diff has been shortened.

My diff is out of a 1970 F100. Both axles are the same length but the pinion is offset 2" to the passenger side.

 

i just got done looking through jr motorsports and they have the whole 9 inch swap kit for a gm in 60" and 58" so i am assuming that each side would have to be 29" but dont hold me to that. and that assupmtion is figuring that thirdgens need 58". hope that helps. just some quick logic i figured through use of jr motorsports. so if u got the cash like 1200 just for the housing talkt to them. then u need the axles.

 

 

Hmm.

I'm trying to remember off the top of my head. I think my axles had an approximately 2" difference in them. No way was it almost 5".

 

JR Motorsport sounds expensive-All of our drag racin buddies go through Quick Performance (Quickperformance.com I believe) Ford 9" to fit in 3rd gen with 31 spline Strange axles $875.00 A complete 9" with 31 spline, choice of gear, and posi is about $1200-$1600 depending on frills-I've never seen one go out at the drag or the oval. Plus he gotta nice shop full of high dollar race cars. Located in Gilbert IA. Close to Ames and Des Moines