I have a 1979 F150 4x4 short bed with a 460. I swapped it from an automatic to a manual NP435. My driveshaft is too short now. The truck has a 4” suspension lift. Would a stock driveshaft from a 351 or 400 work? I have not been able to find one yet. But I wonder the length so I know if I’m wasting my time even looking for one. I measured from center of ujoint to center of ujoint and it’s 52 1/2 inches.

 

77f150 4x4 shortbox 351/400. Np435/205

My shaft was custom made a little longer than stock, but only due to a vibration problem. I ran the stock shaft with lift installed and it made the vibration a little better moving into some less damaged splines in the slip joint. It worked but had a lot of spline showing when installed with my 2 inch blocks. Always showed some but was noticable more. Its been close to 2 years but I want to say less than half the female side had splines into it. It'll work but should be lengthened to function correctly....***edit added***......
measure your blocks if their 4" or spring lift true 4" in rear then it might be a little too short. But based the ruler it looks to be about the same****

I will also add I never unloaded the suspension with the factory shaft and the lift installed. This may have been enough to pull it too far. Never tried.

Wish I could measure the stock one for you but i just cut it up Saturday to make a shaft for the front until I can get down to the shop that makes new ones. Came out pretty good though.


Old rear spline end and female end made into front shaft.


Lift advertised as 3inch rough country. Was close to 4 up front. 2 inch in back.

Measured from ujoint centerline transfer case side of double cardin cv

To centerline of pinion u joint

 

My driveshaft with the automatic did not have a double cardan. Also my slip yoke was installed on the transfer case not the rear. Is yours what is normal? Nothing on my truck seems to be normal. I’m used to working on Chevys. These Ford trucks seem to have so many different ways of doing the same thing.

 

yea I feel ya my first ford truck.

From what I know yes it was original double cardin CV with slip on axle end. Thats what I took off and what ive seen on here on some other posts etc. I cant say why some have them and some do not. I think its a good idea with the angle to have one. The brand new shaft u joint to u joint including double cardin and slip just bolt on was 275.

 

That’s not too expensive I guess. I will have to call around.

 

My 1977 F150 SWB NP435/married 205 has the double cardan up front, and the slip in the rear.

 

Take the time to closely watch your driveline manners and which direction your slip joint moves when the truck is loaded with 1k lbs weight and also while empty.
The direction of movement may surprise you because of the lift block leverage angle and the spring flattening.

Jack up one side of the rear axle assembly to put the suspension in a twist to check spline engagement !

Against my belief, my rear driveline spline movement opens up as weight is placed in the 8-ft bed. (1k lbs).
I should have my driveline re-tubed about 1-inch longer for more engagement of splines.
I run a double cardan on the front driveline. I scrounged it from a late '70's full size Bronco.
FYI for $$$$ - I recently had a rear driveline re-tubed because of straddling a rock, and the rock won.
The cost of the re-tube and new U-joints was $160 smackers. I was happy to pay it.

 

Mine needs a new spline welded on, and a new slip yoke. Just worn out. Playing hell finding a shop that can do it.

 

PST
Precion shaft technologies

Clearwater florida. I believe you can order and they will ship to you.

 

Your best bet is to measure your shaft and u joints, then hit a junkyard and start measuring shafts and u joints for a longer one, don't just look at Fords, look at any trucks, but you're probably gonna have to have one made.

There's a few good mail order driveshaft shops around, juts need to google it. We got a local place called Mitchell Differential that does great work, but I don't know if they ship.

Mitchell Differential Inc.

 

Thanks for that info. Do you know if they repair as well as build customs? Didn’t see anything on their website about it. Few driveline shops around here quoted me prices just shy of getting two Tom Woods made. Supposedly a shop about 3hrs north of me that was recommended but haven’t talked to them yet. Trying to keep the original, as I had just replaced all the joints/centering yoke when I sheared the pinion.

 

Adding a inch or few should be no problem for a shop experienced in repairs/replacement of driveshafts. I feel that would be the cheapest option. Look around for big truck shops that would work on dumptrucks semi etc. Alot of them install pto drives which alot require custom shafts made..