Bob Brown

Does anyone have a 9" Ford Rear end for sale? Or do you know which Ford car has the best rear end size for the 89 IrocZ?

AlkyIROC

Because of the third gen's torque arm suspension, there is no Ford factory differential that is a direct bolt in. Unless you plan on changing the rear suspension design, your best bet is to buy an aftermarket 9" designed to be a bolt in for a third gen.

My first junkyard 9" was out of a 1970 F100 but I installed ladder bars to eliminate the torque arm.

Bob Brown

Thanks for getting back, I have a welder and was planning on doing a little welding to make it fit, but was unclear on the best ford axle to get. You think a 1970 F100 would be the best fit??. I have a 405 short block with a new 700r4 trans. what gears do you think will work best.

AlkyIROC

The F100 differential is very close to the same width as a third gen but the pinion isn't centered. It's offset to the passenger side about 2" making both axle shafts the same length. A car diff like from an early Cougar or Mustang is a better choice. You'll also need to change the axles or have the wheel studs redrilled to a more common size. Ford truck bolt pattern is very big. I had aftermarket axles with the Ford 5 on 4-1/2 bolt pattern to easily use a Ford drum brake system. At the time, I was using Weld Draglite rims which have Ford and Chev bolt pattern.

With a 700R4 I wouldn't want anything deeper than about 3.55 gears. The 700's low first gear doesn't need a deep gear in the diff.

There's a lot more to using a junkyard diff than the width. You have to change over all the suspension mounting hardware from a third gen diff to the junkyard diff such as shock and spring mounts and the panhard bar mount. As I've already mentioned, there's no easy way to attach a torque arm. When I installed ladder bars, the front ladder bar mount is inside the car so I had to modify the floor. Then there's the brake system that needs to be addressed including park brake cable if you choose to use a park brake. Wheel bolt patterns since you can't put Chev rims on a Ford bolt pattern. You'll need a combination u-joint to hook up the driveshaft and "may" need a different length driveshaft.

By the time you're done fabricating and modifying, it can be cheaper to just buy an aftermarket bolt in diff.

camarokev400

i used the junkyard 9 inch and had all the brackets cut off my 10 bolt and re-welded onto the 9 inch housing. I had it done though so i couldnt really tell you how hard it was, i know the guy that did had a jig built just for doing it, he also narrowed the housing, its slightly shorter than the stock 3rd gen housing. I bought a fully adjustable weld on torque arm mount from some company out of pennyslvania, i would have to look for the name of the place but have pics if you want or need them. I got an adjustable panard bar, and i havent yet ordered my axles thats next on the list. But i am using the ford explorer rear disc brake setup off ebay for 150 bucks.

Bob Brown

Can anyone tell me if a 84 trans. rear end bolt up to my 89 IROCZ and do all the 84 Trans come stock 3,73 and posi.

sofakingdom

iTrader: (1)

Yes. No. No.

camarokev400

there are pictures of that torque arm mount i was talking about on this thread, im selling all my stuff and buying the bolt in housing. I gave up on trying to fab this one up the hard part is done already but i just dont want to mess with welding on the torque arm and trying to get all the angles right.


https://www.thirdgen.org/forums/engi...ing-needs.html