I'm swapping a NP435 into my '89 F250. I know some other people have done this and I have a question for them. Did the drive shafts have to be changed? What I mean is, did the length need to be changed?

Roger Lane
Test Analyst
Sr. Automated Test Engineer
IBP, Inc.

 

Roger, the length I used was 57.75", but that is immaterial as I also used a 7.5" OD box in front of the 435, and a NP205 transfer case behind it, for an additional 8" of gearbox length, which altogether shortened the driveshaft(s) quite a bit, in fact I was able to go from a two-shaft, 3 U-joint carrier bearing driveshaft setup to a single shaft, two U-joint setup; the shorter shaft makes shaft balancing both easier and possible.

There is a further complication, which I think is relevant to your swap: Transmission output yoke type. My M50D had a slip-yoke, 1330-series output; I think the NP435 uses a Spicer style fixed yoke, with the slip spline in the driveshaft itself.

Go www.tomwoodscustomdriveshafts. Tom has an extensive, step-by-step, fill in the numbers and match the drawings data sheet that makes it real hard to screw up. Here's a plug for Tom--he built exactly what I wanted, and mailed it to my office, for cheaper than I could get locally (and it was exactly correct)!

Beware that final U-joint at the rear axle--apparently Ford randomly used a weirdo piece there, that has the 1330 size cross and a mix of 1-1/16" and 1-1/8" caps.

Eddie

 

Thanks Eddie,
All I'm replaceing is the trans itself. The NP435 bolts to my BW1345 w/o a problem. So, the output is still the factory original. I'm going to start pieceing this thing together tonight. I will check out the web site you posted and see what it comes up with.
My main concern is that my drive shafts have slip yokes incorporated into them and I don't know if they will work or if I will need to have them resized.

Roger Lane
Test Analyst
Sr. Automated Test Engineer
IBP, Inc.

 

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1. What is your overall new gearbox combination length, front of bellhousing to rear output (@U-Joint cap centerline {measured a face of cap])?

2. What is your overall old gearbox combination length, front of bellhousing to rear output (@U-joint centerline [measured at face of cap])?

Subtract one measurement from the other, which will tell you the difference you'll have to adjust in the driveshaft.

Shortening, or retubing to add length, then rebalancing, are fairly common occurences.

How about crossmember location--is that going to move forward on the frame rails, or can you adjust through the slots for the trans mount?

Eddie