Shorten a driveline

[DRIVEN]

Disclaimer first: This is a demonstration of what I did to shorten a driveline on a budget. I used tips from "old timers" and info from other sites. This may not work for everyone and should not be attempted without necessary skills or tools. You might do it different. This is presented as an alternative to a custom driveline at a higher cost. If you have done something similar please feel free to add tips about thing that work or warnings about things that don't.

 

I replaced the 4-speed with a 5-speed in my 510 wagon. Since the new transmission was longer, the driveline needed to be shortened. My initial thought was that 5" would be the right amount but later found that 6" was better for my application. In an ideal situation it would have been nice if the shaft was one diameter from end to end but this is not the case. It was necessary to cut the tube in the "fat" part of the shaft. I chose to cut the rear part because, in the event of a failure, it wouldn't pole-vault the car.

Step 1. Located a section to remove without losing any existing balance weights. By wrapping the shaft with a piece of paper and spray painting the edges I was left with a clean cut line.

Step 2. Before cutting the shaft, I scribed a reference line to keep the U-joints in phase after the cut. It's hard to see but I'm pointing to it with a screw driver. I'm fortunate enough to have a band saw but a hack saw or cut-off wheel would work fine.

Step 3. With the two pieces cradled in a piece of angle iron and the reference lines reunited, I placed another piece of angle iron in top and tack welded both sides. Then I rotated it 90 degrees and tacked it again.

Step 4. Once tacked, I welded about 3/4" at a time while alternating from side to side. Concentrated heat causes distortion and warpage. When I was researching this it was suggested that the tube be pre-heated to get better weld penetration but I didn't do that. After it was welded all the way around I ground the weld down. This was more to keep an even weight than for aesthetics.

Step 5. Checking for balance. This picture is tough to see. Once I had the driveline installed I spun it in place to see if it looked straight. It had visible run-out. I held a piece of scrap close to the tube (near the weld) and spun it while moving the scrap closer and closer until it just touched. The resulting mark established the high (heavy) spot. If, by chance, yours has no visible run-out you can run the car on jackstands and do the same thing. At high speed the heavy side will throw out as if the shaft were bent. You can use a piece of scrap to mark it the same way.

Step 6. Install 2 hose clamps with the screw opposite of the high/heavy spot. At this point you can test drive the car. If there is no vibration - you're done. If there is - add 2 more clamps. Repeat until the vibration starts to get worse again. At that point rotate 2 of the clamps in opposite directions a little at a time until the vibration goes away. In my case 3 clamps yielded no vibration at any speed up to 90mph. It's actually smoother now than before it was shortened. 200 miles and counting with no problems.

Hope this helps. Good luck!

[fo0manchu]

oooohhh, that scares me. :unsure:

I would be likely to do something similar, but just seeing it done scares me.. ahaha.. :D

[78kingcab]

well i guess its one way to save 75.00...

[DISLEXICDIME]

And once you have the hose clamps in the right spot you can weld washers where the larg part of the clamp is and then take the clamps off

[Duke]

Or you could cut it at the u joint and put it back together like it should be, instead of a butt weld in the middle of the drive shaft. I second the whole this scares me thing...but it scares me more that you would show it off on the forum.

[DRIVEN]

I think some of you guys might be missing the point here. I'm not "showing off" anything. Obviously this isn't comparable to having a shaft built or shortened by Drive Line Service or 6 States and yes, it would be better to cut and weld at the end. The shape of the shaft won't allow it. Ideally the entire tube would be replaced. This was mainly presented as a temporary and basically free alternative that would allow you to keep a project mobile -- perhaps while having a real shaft built by a real shop. It took me about 45 minutes and cost nothing. It is what it is :rolleyes: . Thanks for the constructive input.

[freekwonder]

Plenty of old timers around here talk about doing the exact same thing on different vehicles over the years and never having any problems. Sure they weren't race cars, but they were driven.

[Duke]

This isn't the way the 'old timers' did it though. They remove the tube from the u-joint by cutting though the weld and then shorten the tube and reinstall the u-joint. That is how drive line shops do it as well. It can be done at home. Hell, I bet it wouldn't take much longer than what was done here.

[freekwonder]

Sorry, I forgot you know ALL the old timers and their exact ways of doing things through out the country. My apologies.

[Duke]

Good, I'm glad you realized your mistake. ;)

 

I'm not saying that people didn't do it this way, however all of the research that I did and the drive-line shops that I spoke to suggested to do it the way I described. I just wouldn't trust a drive shaft with a butt weld in the middle, especially one that looks porous in the photo's. :blink:

[DRIVEN]

Duke - I know the grownup thing to do is ignore the fact that you haven't actually added any useful tips or photos of all the shafts you've shortened. Life is full of compromises and temporary situations. This thread was meant to illustrate how to the average guy could "get by for a while" on a budget. Sometimes payday isn't for another week, your other car is broken and the driveline shop isn't open on weekends. I really don't want to make this personal. For the third and final time, the driveline shape did not allow me to remove enough material from the ends. I wish I was fortunate enough to have a tube that was the same diameter from end to end. If it were, I would have taken it off the end. I had originally planned to take this shaft to a shop and have the tube replaced and get the assembly balanced. Now I'm tempted to drive it forever just to prove you wrong. Thanks for all the inspiration :thumbup: .

[fo0manchu]

yah, the shafts taper in at the ends. When I got mine done they had to replace the whole tube. Cost a around 200 buckaroo's with new u-joints. I take it that you won't be racing with that driveshaft. :D I did something similar on an old bmw, but sleeved it with another tube on the outside to over lap the joint.

[freekwonder]

Good, I'm glad you realized your mistake. ;)

 

I'm not saying that people didn't do it this way, however all of the research that I did and the drive-line shops that I spoke to suggested to do it the way I described. I just wouldn't trust a drive shaft with a butt weld in the middle, especially one that looks porous in the photo's. :blink:

 

 

Oh me too, but when my next door neighbor that works at a machine shop offered to shorten mine and told me they have done a few at the shop no problem, I let him do it. He did it the same way.

[808DA6]

I did almost the same thing to the temp driveline thats in the SR521. The only difference was I used a split section of the material that was cut out as an inner sleeve. It helped keep the shaft straight and also kept me from blowing holes during welding.

 

-Brian

[Farmer Joe]

hmmm,

 

well it looks okay to me...

 

just get rid of those clamps... weld some washers on there in there place and youd be super golden!

[jrock4224]

the way i shortened my drive shaft was i setioned the center like that put it back in the truck still in two pieces while the truck was on jackstands... start a brand new roll of duct tape on the junction... start truck, put in a higher gear and let clutch out...simultanously diving under truck to grab the roll of duct tape...and begin re attaching two pieces of drive shaft... i like to move up and down the shaft cover at least six inches of the junction for strength... once you have applied the full roll you now are ready to run...road test on nearest highway at high speeds to verify you duct tape is properly balanced...

 

Im not sure what and if at all the purpose of the hose clamps are in your repair, but if your welding requires reinforcing my hose clamp might wanna research getting a new drive shaft made... this might be fine for a field repair to limp a truck home to fix or load on a trailer but as for taking it to a show unless that show is in your back yard I would take heed...no one wants to experience sticking half a driveshaft in the asphalt at high way speed can you say dangerous...

[Charlie69]

Call Mountain Driveline Dick Brown 928 532-8452. They Ship Anywhere! Great prices. I have been using Dick Brown Drivelines since the early 1970s.

[DRIVEN]

Im not sure what and if at all the purpose of the hose clamps are in your repair, but if your welding requires reinforcing my hose clamp might wanna research getting a new drive shaft made... this might be fine for a field repair to limp a truck home to fix or load on a trailer but as for taking it to a show unless that show is in your back yard I would take heed...no one wants to experience sticking half a driveshaft in the asphalt at high way speed can you say dangerous...

It's for balance -- definitely not weld reinforcement. Google it, man. I know it sounds hokey if you've never heard it before but it is actually an acceptable means of balancing and considered a permanent fix for an unbalanced shaft - kind of like a wheel weight. It's going to the driveline shop next week to be re-tubed and balanced. For the record though, I have well over 1000 miles on it and it's still smoother now than it was with the factory welds and weights.

[VintageRice]

I like it.

 

Whats the worst that could happen.....

 

 

:D

[DRIVEN]

Update: After putting 2000+ trouble-free miles on it, I decided to have it professionally done. I was planning a 750 mile weekend trip and figured it might be good insurance. Twelve business days, one "do-over" (because they made it an inch too short), and $165 later I had my retubed and balanced driveline installed. I'm sure it's safer and certainly prettier. It isn't noticeably any smoother, vibration wise.

[78kingcab]

holly molly 165.00.....i just paid 75.00 and not only was it balanced he sanded it and repainted it...looks brand new...he just did one for my retarded cousin and redid it 3 times cause my cousin didnt understand what to measure from, and he didnt charge him xtra but the dude was hella pissy

[ggzilla]

Driveline Services cannot shorten many/most driveshafts for $75. Most have a tapered shaft which has to be replaced. And of course most businesses will recommend their services, rather than a less profitable method at another shop -- so their warning need not be take as the last word unless you always trust authorities.

 

DRIVEN, thanks for an informative technical account, with appropriate disclaimers. To be safe, one only needs to add a driveline loop -- which is safe enough for racing, so it should be safe enough to the street. Or if a competent proffesional technical welder does the job, it will be as strong as the original tube.

[fastdadd]

thats what i payed to have mine made into a one piece

[Charlie69]

Dick Brown, Shorten (even tapered), balance, instal 2 new spicer u-joints, sand & paint $65.00. But then I have been doing busines with him since the early seventies, and he does not make mistakes and have to redo a job and pass the redo expense on to the customer. :angry:

[I'm BLUE]

DRIVEN --- Thankyou ! It's nice to see some of the old school methods come through. Even better when someone reports 750-2000 miles of trouble free cruising after this procedure :cool:

 

You made PERFECT and concise sense at each point through.

 

This is what Ratsun is/was/should be

Nice job man !