Drive shaft to long?

[hotrod ford]

I flipped my leafspring pearches to make the rear lower on my f100 now my driveshaft will not fit into the axle. According to the "'65-'79 Truck Suspension Lowering Basics
it says nothing about this issue or having to shorten a drivshaft. Is there somthing I'm missing?

[BobbyFord]

I relocated my diff to above the leafs on my short bed and had to get a new driveshaft made.

[hotrod ford]

Being that the yoke can be removed from the driveshaft which I just did. Would I be able to shave down a abit from the toothed end of the driveshaft that goes into the yoke? Wouldn't this make the yoke sit down further on the drive shaft?

[BobbyFord]

Yes but it would damage the coating on the splines.

[hotrod ford]

What is the coating for? Rust and corrosion?

[BobbyFord]

I believe it is to aid in ease of movement and also anti-wear for the slip joint.
You should really have the driveshaft altered by a reputable driveshaft shop.

[hotrod ford]

Well I ended up taking little less than a 1/4 of an inch off the yoke splines. Reinstalled that back into the yoke and the rear of the driveshaft onto the axle. Fit like a glove.

[BobbyFord]

Depending on the spring pack and the amount of clearance between the axle housing and the frame you could need 2"-4" of travel in the slip joint or driveline bind may occur.

[Bob]

Crawl under another similar ride and remove the drive shaft... but before dropping it take a look at how far the yoke will travel. When fully seated in the rearend yoke the tranny yoke will be a couple / few inches back from all the way in. Just barely getting it in there isn't gonna get it. You need to accomodate for the travel of the rearend. When you load it up or hit a bump it's gonna jam your shaft.

Need to pull the u-joints... turn a cap off of one end... shorten... install cap back in lined up with the other end... weld... balance... slap it back in.

[hotrod ford]

How much should I take out of the shaft, about 2-3 inches?

[Bob]

It depends on what vehicle you're talking about and how much travel the springs will allow.

Like I said... best way is to find similar and remove it. When you shove the tranny yoke all the way forward see how big the gap is from the back u-joint to the rearend yoke. That distance is what you'll need for slop in your new one. So then you put your driveshaft onto the tranny all the way forward and see what the rear distance is.

Say the non-modified vehicle had 3" of space and yours has say 1" of space then you'd want to drop 2" out of your shaft.

Another thing you could consider... typically there will be a weight welded on one end of the shaft for balance. Sometimes both ends but more often than not just one. You could probably get away with not balancing if you do a nice job and caqn remove the cap from the opposite end of where the weight is. Leave the weight on... cut the other end... weld back on.

When you cut the cap out of the end you need to be careful you don't hack into the cap. It'll be inside the shaft end about an inch deep give or take. If you center it up in a lathe and take light passes just behind the brim of the "hat" at the tube section... you'll eventually see the transistion from tube to the inside cap and it''ll fall off. The wall of these driveshafts is only aabout maybe .06 to .08...? So go at it easy.

Find out what length you need to be...
Measure what you have and write it down...
Eyeball up position of the u-joint ears on the shaft... (They should be aligned not 90 degrees apart? I think...)
Cut out cap on non-weighted end...
Cut of whatever you need to off the tube and be careful not to crush it out of round...
Install the cap and line it up to the other one. (You can do this with a precision level... Lay it down on solid surface... level the side that's still attached and othe side should match when in right position.)
Tack at three or four places then run a full weld around it.

If you didn't cut too much off you cap.... and didn't get too far out of alignment... and didn't have big variation in weld size... you will probably be O.K. without balancing. I've done it several times without issue.

[hotrod ford]

Somthing else, this is a two piece driveshaft. Shouldn't it be a one piece being that it is an automatic or does it matter. Why I'm asking is because while loking at it again during lunch I noticed the U joints were not as wide as the transmission yoke. Is this an issue?

[BobbyFord]

Short bed or long bed?
What do you mean "not as wide as the trans yoke"?
Most u joints for these are 1310's but some used a combination u joint that went from 1310 to 1330, meaning one side of the u joint was wider.

[hotrod ford]

Short bed.

[BobbyFord]

Short bed should be a one piece driveshaft like this...

Trans should have a bolt on yoke, not a slip yoke.