1975 F100 Longbed, 302, FMX, 9" rear

I recently got my truck running and found out the carrier bearing is completely seized up and trashed... I removed both the driveshafts today and they're seized/rusted together, the slip yoke between the two wont come undone... I'm wondering if I could find a one-piece driveshaft that will fit with the FMX transmission in my truck, or if all the longbeds use the one piece...

thanks in advance

 

Usually they build them two-piece due to harmonics and weight savings. I wanted to have a one piece built for my truck, but the shop didn't suggest it.

The tubing would have been huge and thick! It makes sense because all trucks, light-medium-heavy OTR trucks all go to 2 peice shafts after a certain length.

 

Some had two-piece, some had one-piece. It depended on the GVWR of the truck, the transmission, 4x4 vs: 4x2, driveline angle, among several other things, including length.

So if it came with a two-piece, then I'd replace it with a two-piece.

And that's my two-cents...

 

For what it's worth my '79 F250 4x4 (regular cab, same WB as your's, but I have a C6)has a one piece rear d-shaft, it works and I'm lifted 6"s (even longer stretch for the driveline).

I see no reason why you couldn't use a one piece d-shaft, unless that FMX is REALLY, REALLY short, but I doubt it.

 

A 2wd driveshaft is longer than a 4wd driveshaft with the same wheelbase because the 4wd has the transfer case which makes the driveshaft length shorter. I think this is why the 2wd LWB's usually have 2-piece shafts, while the 4wd LWB's usually have one piece shafts (I'm talking F-100's and F-150's, don't know about 250s and 350s.)

I had to have a longer driveshaft made for my 78 (3" lift, stock driveshaft came apart at the splines on a episode of hard braking after my hood flew up while going about 45.) A couple of places told me they couldn't make the shaft any longer because it would be too long for a one-piece driveshaft, but a local guy made one for me and it's been working for for years.

 

My '79 F250 2wd LWB (6200 GVW) has an one-piece driveshaft.

 

No F100 or F150 ever used an FMX transmission.

From 1969 thru 1977, the only A/T available with the 302 was the C4.

With a 302, either the C4 or C6 was available in 1978/79.

The only F Series truck that used an FMX were 1973/77 F350's with the 300 I-6.

You can still buy from Ford. the complete driveshaft center support kit, which includes the bearing, rubber support, brackets and shims.

D9TZ4800A .. Drive Shaft Center Support Kit (aka carrier bearing kit)

Fits: 1957/83 F100 / 1975/96 F150 / Most 1953/79 F250's.

MSRP: $53.00 // FTEpartsguy.com price: $38.16

 

I found a center support kit, but I can't get the two halves to separate at the slip yoke...

Also I'm positive the transmission is not a c4, as it has no servo cover. It's possible this was swapped out as I don't really have a history on the truck

It does have a 14 bolt pan, and according to what I've looked up, this is an FMX (C4 11 bolt, C6 17 bolt)

 

14 transmission pan bolt holes: 1958/67 FX & MX Cruise-O-Matic / 1969/79 FMX.

Since the trans has been swapped, the engine may also be swapped.

Cars with FMX's came with 302's, 351C 2V's and 351W's.

What is the 4th digit of the VIN?

 

G, which is a 302

But I agree, it could have been swapped for another engine, although i'm almost certain it's one from the windsor family. This is just my get-it-running stage of the resto but I believe the FMX is a different length than a c4 or c6, which means i'd have to get a driveshaft made

 

i have a question im putting an I6 with a 4 speed into my 2wd long bed it came with a 400 c6 and two piece drive shaft now i have to use the 80's driveshaft that came with it cause that is the one that fits in the four speed but it is too long do i need a one piece or two piece drive shaft for this set up

 

Im wanting to put a 6in lift in my truck, and was wondering did you put the blocks in or new leaf springs in the rear?? would i have to get a longer driveshaft or will mine be fine? thanks

 

I had an 87 D***e van with a single piece driveshaft that was about 8 feet long. The man I bought it from bought it new and said that he'd had to replace the u-joints every 10000 miles, so I might want to have them checked. I did, and there was A LOT of slop in the rear u-joint, so I had both replaced.

When I asked the mechanic what would cause that, he immediately pointed to the driveshaft and said "That. Long single shafts always eat up u-joints."

I put about 3000 miles on that van after that (for a grand total of 305,000 miles BTW), and when I got under it to prepare it for sale, LO AND BEHOLD the rear u-joint had a good amount of slack in it!

 

IMO, you just gotta go to a drive line specialty shop for work like that.

I'm all for a farmer welding in a hunk of exhaust pipe but for a reliable highway
going vehicle the drive line shop can't be replaced. Sad but true, some things
a guy just can't do himself. :/

Alvin in AZ

 

For years and years heard about certain brands having that problem on
newsgroups. :)

My '75 F150's got a two piece drive shaft and it never-ever has had a
loose or bad U-joint in it, ever!

Carrier bearing went out once and after taking the caps off of one of the
original U joints (over 150K miles) there was a slight amount of "wear".
I made a comment and he said the carrier bearing did that otherwise they
would look almost like new. Hey, they looked almost like new anyway.
No kidding on that. :)

Alvin in AZ