Cutting a drive shaft?

I have a drive shaft from a 81' Chevy truck I want to cut about 20" out of to fit my 31'. Is it safe to cut the center section of the shaft? I will take it to someone to do this but thought I would check here first. Anyone in the Portland/Beaverton area do this?

 

What we do is machine one cap off the end of the tube. Cut tube down to width needed. put the cap back on the end making sure it is correctly phased.. I would not take it out of the center. Jason.

 

What he said.

 

I agree with Termites.......

If you cut it out of the middle and weld the two ends together, you'll be very hard pressed to weld them back together without creating runout and have a bitch of a time truing / balancing it. Do it the 'easy' way - from the end.

 

Call the Dutchman in Portland. He can steer you in the right direction.

 

make sure the shaft is 'timed' right. U-joints in sync when welded back together.

on my 34 pickup someone (previous owner) cut & welded my driveshaft -right in the middle in the late 60s. AND ITS PERFECT! ----- its a fluke - dont try it. although it looks pretty neat with a big old arc weld around the center.

 

Don't take it out of the middle.

The best way to do it is to take it to a driveshaft or 4x4 shop & have them do it.

I've shortened a few driveshafts at home though. Cut one end off close to one yoke - maybe 1/2-3/4" or so. Then carefully, and patiently grind away the original weld until you get to the yoke itself. Shorten the tube the correct amount & reinstall the yoke into the tube. Be sure the yokes are in phase & perfectly square. A lot of careful measuring here will save money for a new driveshaft later. I like to make four small, equi-distant tacks at 90* to each other on the yoke. Then, recheck your measurements to be sure it's still in phase & square. Once I'm happy with that, I set the driveshaft in some V-blocks and have a helper turn it slowly while I weld the thing.

Last one I did didn't even need to be balance!

Home balancing can be done with some large hose clamps...

 

I've done it like Flat Ernie says,

I ground the weld flush on the end opposite the weights
put a hose clamp around the freshly ground end
and using the hose clamp as a guide cut with a hack saw just through the tube right at the center of the weld
knock the end loose

then pretty much like said,
cut the tube to length
reinstal the tube on the severed end
align carefully
and weld it up.

 

I've done several the way Paul and Ernie said to do. You can cut next to the weld but take care to just cut through the tube and not cut into the end. I usually work my way around so that I am deepening a shallow cut as I go.

Years ago JD Fikes out of Waco showed me how to use a ring compressor (the one you tighten up with the band) as a guide to get a straight cut on the shaft. You run the saw blade right next to it.
I've usually had pretty good luck doing this with only one out of about a dozen that was out of balance and just wouldn't work. I did the one that is in my 71 GMC now and missed the mark a bit and it is a bit longer than I wanted so measure closely.
Other than that call Dutchman and see if they do the work or "who" they say to have do it. http://www.dutchmanms.com/contact.html

 

flat ernie, the man. all I can add is, recheck recheck recheck recheck recheck.
off the end.
never try to make a drive shaft longer. Don't ask me why I know that.
trust me
Daye

 

Being lazy and on vacation instead of doing mine at the shop in a lathe i ground the weld down as flush as i could get it then i cut thru the rest of the weld with my sawsall working carefully all the way around the shaft .. then i knocked the end out with a hammer and cleaned it up a bit. Next i cut the shaft to length with my hack saw trying to get it as straight as possible then i lined the yokes up and hammered it together. I then put it in the car and rotated it and checked it with an indicator and tapping the shaft with my plastic hammer till it was within a couple thousands run out. then i tack welded it and pulled it out and finished welded it .. Works fine.. They can be cut in the middle but only if you sleeve them then weld em together.. Not worth the trouble....
Dave

 

have someone who knows what their doing do it, because it needs to be balanced so it don't vibrate the fillings out of your head!

 

The few I've done have never been badly out of balance. In fact, the last one I did, I ended up taking off the factory weights - required zero weight to balance!!

To balance, I get the rear wheels off the ground using jackstands, with front wheels well chocked. I start the engine, put the car in a high gear (Drive for auto, 1:1 gear for a manual) & let it idle. Then I hold a piece of chalk close to the driveshaft until it just barely touches. Stop the wheels with the brakes & turn off the car - you should have a small chalk mark somewhere on the driveshaft. Then I use a large hoseclamp with the screw end opposite the chalk mark. Then I try it again. You can get it pretty close doing this. Of course, taking the driveshaft to a shop is better, but.

I can't emphasize being careful enough doing this - I chock the front wheels, make sure to use good jackstands, & never do it alone...

 

What the other DIY guys did is fine,I've done it probly 20 times in my life and only did two bad ones. Being in a hurry and not paying attention.

For shorening the shaft, the easyist way to get the first cut in the tube nice and square is to use a pipe cutter. Then procede to removing that stub from the yoke as above^^^^. And replace the yoke back on the shortend tube.

Frank

 

I only have 18 years of doing jobs like this to make a living. Step away from that driveshaft and find another donor. If that is an original shaft, the weld yokes (your u-joints press into these) are not machined to fit, rough cast finish. NEVER EVER EVER cut a shaft in the middle, UNLESS it is TEMPORARY, no road use at all.
Find a shaft from a Maverick, Granada, short bed pre-75 Chevy or Ford truck, no Chrysler product stuff.
If you plan to spend your money once, take it to a pro driveline shop and have it shortened and balance correctly. If you want to spend money on transmission and floorboard damage, go ahead and do it yourself.
I've looked through holes made by simple things as u-joint neglect and failure from what was a good driveshaft. U-joints and more will fail from less than quality work.

 

absolutely.

more is the key word here, as in every part of a hand fabricated car
if you have any doubt about your ability to build a safe roadworthy vehicle then please by all means have a profesional build one for you.

 

Here is what you do to get it cut and welded. Besides getting all the measurements and then getting them again, find a "machine" shop that specializes in Semi Trucks. Walk in and say, "I don't know if y'all do this, but can y'all shorten a driveshaft? If not, do you know anyone who can?" Did that to a shop down the road and the fella said, "Oh, it's for a regular car? Yeah, that's nothin." An hour later I picked up a newly shortened driveshaft that wasn't just "dead nuts", it was balanced perfectly, painted, and they even threw in u-joints. Price = $50. Put something in front of a man who knows his job and he'll do more. Only thing I'm disappointed about is I don't have anything else they can do.

Brian

 

So this is what I found at the Tigard U-Pull it, didn't think it would be that big of a deal to take a section out. What some people are missing are the keys to the problem: the shaft is a CO2 bottle shape on both ends, and I need to take more out than the sum of each bottle neck. Solution: Take it back, get a shorter shaft and try to make the tranny slip yoke length work with the shorter shaft. (There is a 65' Wildcat at the yard, 2 piece shaft, 1st piece may be long enough).

 

Driveshafts are another of one of those things that unless you know what you doing, dont do it, just pay to have it done right. I used to pay $27.00 to have them shortend by a pro drive shaft shop up to about 5 years or so ago. Now I just do them myself.

I've done it a several times, with great sucess, including two of the trucks that I drive now, and never had to balanc one yet.

I grind the welds down at the rear of the shaft, nock out the end, shorten the shaft, and slide it back in, clock it correctly, then tack it good in 4 places where i want it then weld it carefully.

Or,... you can always do what a frind of mine did.......................................
make one out of muffler pipe for his 454 crewcab longbed dully!!!!!!!!!!!

 

I paid $40 to have my driveshaft shortened and balanced with a 1 day turn around. Is it really worth the hassle of doing the work yourself and the crapshoot of getting it right to save $40 measly bucks? Think of how much it'll suck as an out of balance driveshaft wipes out the rear seal in your trans, or comes completely apart at speed and takes out your entire rear end....then answer the question.

There is a difference between being frugal and cheap

 

Why balance a driveshaft? Or get it within .003" of being straight at each end before welding? Depending on gear ratio, the driveshaft only turns over 2000 rpms or faster when at highway speed. I made an observation 15 years ago, a simple dirt car shaft (almost interchanges with short wheelbase hotrod stuff) will let the balancer come up to rpm faster than a shaft that's not fine tuned.
Did you balance your tires? They only spin around 700 to 900 rpms at highway speed. Why balance something that spins faster?
The shaft out of the Wildcat won't be a lot of help either. Odd tubing size, can't buy weld yokes to fit. If you're on inside snap ring GM u-joints, look for a shaft from a 78 up mid-size GM car (Malibu, Monte, Regal, etc). They're made of 2 1/2" tubing, but most have non-reusable rough cast weld yokes.
If you want something pretty, have your driveline shop build a shaft from new tubing, weld yokes, u-joints. Have them polish it up while they have it in the balancer.
PM me if my shop can help. Closer to you, Six States is in the family of companies I work for.

 

HEY... I cut a 89 chevy truck driveshaft yesterday...

Figured my length by sliding the yoke up into the trans (63 C10) then used a pipe wrap to get a straight line around the 2" tube.. cut with port-a-band saw by rotating and staying on line.. Scribed a index line up tube to retime it with yokes.

Put in lathe, cut weld from end plug yoke.. yoke plug slid up into the cut tube with a few taps of hammer.. squared itself, then I spot tigged it, then went 180, then 90, then 180.. then tigged it up solid all way around.

Fits, looks good. Now need to raise the $400 to complete this one..

One problem?? the plastic crap GM used to set the universal melted out.. will have to replace rear u-joint. Crawled out of hole like a blue worm.. Replacements have c-clips.

 

I've done a few, mostly on stock cars and odd ball combinations. I use a Rigid pipe cutter with the big rollers to get it square. First thing, I scribe a line on the tube to flange so it goes back in phase. I grind the old tube off the yoke end, used a lathe once which took a little set up to get it to run true. Gotta love a 4-jaw chuck and live center.

The tube has to be beveled to accept the yoke plug, a big rat tail file works well, an air grinder would be better.

I get the plug back in, hold the shaft on the bench in v-blocks and check for squareness, it'll have to be rotated around to make sure you got it in a couple of planes.

From there, tack it in a couple of places, check squareness again, alternate the welds to minimize distortion.

For balancing, I take it for a ride. I've had some good as is. If not, I save the tack-welded weight from the donor shaft and attach it towards the rear of the shaft with a hose clamp and go for a ride. I'll rotate it 90 degrees at a time until I have no vibration. Tack the weight in place and remove the clamp. Done!

Bob