4WD F100 NP435 change to C6

[Jasonlfeaster]

My truck is a 70 F100 4WD, LWB with a NP435 and Dana 21. I had a 420 HP 390 built and just got it in and can call it finished and now the synchronizers are jingling and sounds like the input shaft bearing is going out, making a rotating, squeaking noise when I'm accelerating in 1st 2nd and a little bit of 3rd. Could be all the time but by the time I'm in 3rd, the engine and road noise could be too loud to hear it. If right about the noise and it doesn't turn out to be something else, it's going to be a pretty big job getting the transmission out because of the headers, exhaust pipes, transfer case and crossmember. I used to have a 71 with a T18 and I liked it, but I don't like this 435. If I go through the trouble of getting it out, I want to replace it with a C6. My question is how much am I going to have to change to make it work and if I get a C6 out of a 2wd, what do I need to do to make the transfer case fit it? I'm sure I'll have to figure out driveshafts and all that but main thing is getting it all in there right. The crossmember is between the radius arm mounts and they'll have to come off to get the transmission and transfer case out. I won't really have any problems getting them out, it's just time and work. If anyone has done this before, I'd really appreciate your help and pictures of how it's put together if you have any. Thanks.

[fordman]

U will need the short tailshaft bolt on yoke transmission. Or just the housing tailshaft and bolt on yoke. To pit in and on a long tailshaft c6.

I would guess u may need the proper crossmember too.


Or get a t18.

[Jasonlfeaster]

Yeah, the T18 that was in that 71 went in my dad's 67 in about 96 and he won't let me at it. But he likes 435's so maybe I can work on him and get him to trade with me.

[Tpdaniels]

I switched my 72 F250 4WD to a C-6, It's not all that hard but you do need a C-6 with a short tailshaft. There are two main reasons that you use the short tailshaft, #1 is if you use long tailshaft your center driveshaft won't be but a few inches long, not a good idea. #2 is you need the short tailshaft to be able to mount your 4WD lever to. The hard part is you need a special short tailshaft with the mounting holes for the 4WD lever. I added a picture below for you to see. You might find one right off but it took me a year of looking and searching to find one.

[hfdco4]

I thought the F100 4x4 had a "Married" transfer case. The F250 has a "Divorced" transfer case. This would make using the a C6 out of anything other than an a 1977 to 1979 F250 or possibly out of an F150 in the 1973 to 1977 vintage.

[hazelnut]

In order to change to a C6 trans for a married transfer case you have find a 4x4 C6 or change the C6 tail shaft/main shaft to one for a 4x4, Basically rebuild the trans. And get a tail shaft housing that's made to go between a C6 and the transfer case.

1976 was the last year of production for FEs if that helps.