lately I've been working on adapting a 3.9 Hydratrak diff center from a Holden VU GTS. It looked like a pretty straight forward conversion when I started but it's proven to be a fair bit of work.
My original researched showed me that the Holden and ford housings were similar as were the internals. the back cover has the same bolt patern and the exles have the same spline. So I figured swap the Ford back cover onto the Holden housing, weld a new front mount onto the chassis and pop the Ford axles into the Holden center.
Nothing is ever so simple....
It turns out the Hydratrack runs a different axle so I couldn't use my Ford drive shafts as their axles are part of the CV joint. I almost gave up at this point.
After much thinking and measuring I found that I could adapt up some Holden drive shafts and get the whole thing working. The Holden IRS have used the same style of CV joint for the last 10 years but they have used a few different drive shaft lengths. I found drive shafts from 2 different models that matched close for length the long and short drive shafts in the ford rear end. The CVs on the Ford rear are combined into wheel hub spline as well as the diff axle spline. I machined off the Ford CV at the Hub and machined up some flanges to suit the Holden CVs and welded them on. There's no suspension loads on these flanges only drive loads so I wasn't woried about the strength of the weld.
I had to recess the cross member in front of the diff to make clearance for the front mount. The new mount is made from 8mm plate and provides ample reinforcement for the slimmed down cross member. I cut down some nolothan suspension bushes for the front mount in much the same way as I did my gearbox cross members.
the last headache was the fill plug for the diff. the Holden diff housing has the fill plug in the back cover but the Ford has the fill plug down near the pinion. I machined the ford back cover and fitted a fill plug. I then had to drill and sleeve the rear cross member so I could get at it with a socket wrench.
It's all done now, I just have to pull it appart clean, paint and reassemble it.
There's some pics in my gallery:
Diff conversion 1
Diff conversion 2
Diff conversion 3
The next job is the fuel system.