The Jalopy Journal
Discussion in 'The Hokey Ass Message Board' started by TINGLER, Mar 8, 2006.
hey tingler, i think the only way you could do this safley is if you have a lath in your shop. the profesionals do it for a fairly cheap price. im not saying you cant do it at home. but if your gonna be flyin down the strip at 90 i wouldnt want something i dont trust that close to me. cory
I don't think you'll ever get it right without a lathe and some jigs. I've tried several ways and while they have been useable, they weren't perfect. There is a driveline shop in Wichita that charges less than $50 to shorten a regular shaft.
If you have dial indicator, grinder, and welder, you could probably figure out a way to do it without a lathe.
Sill, the preferred method involves a case of beer or two, and a buddy who works at or owns a driveline shop.
Have you ever watched a driveshaft being shortened? They take a diegrinder with a 3" cutoff wheel (or a hacksaw) and cut thru the weld at the cast end of the driveshaft. Knock out the cast end. Then a cut is made for the correct length of the shaft (hollow tube). It is good if this cut is straight, but not critical. The cast end is inserted into the driveshaft witn a BFH. Use an angle finder to keep the ujoints in phase. Weld the driveshaft, roll it as you weld, try to do it in one pass to keep the weight of the weld the same all the way around.
A large lathe is nice but you can do this on your work bench.
I have done a half dozen. When I used to pay to have it done, I asked about balancing the finished driveshaft. No one does it. (Well maybe in California)
I would think another reason to have it done at a shop is to have it balanced properly.
Why not just have all the HAMB add their take on this task Tingly?
MY two cents.....
NOTE-I have done this -but preferrably it should be done on a lathe.....
BUT......if there is a need to drive and a shop to do it AINT THERE-
Grind the weld on the rear of the shaft till it is flat with the tube itself....
Try to not let the grinder touch the cast edges of the flange cap-as it can help in aligning later.
Mark a straight line around the weld at 90* about 1/4" from the cast flange.
Next take one of the thin cut off discs on your air cutoff and cut on your line around the shaft....it will turn "blue" when you actually cut thru the thin tube and into the "cap".......
once cut you can peck it off the tube/seperate it...
next figure the distance from center of the Ujoint cap on the pinion to the rear seal on the tranny.
using this measurement- start measuring at the "seal MARK" on your yoke to determine the new shafts size.
CAREFULLY mark a [square]90* cut line at the appropriate place on the tube.
Cut this with the thin cut off instead of a chop saw as the saw will tend to angle the cut worse than a hand cut will.....
Now the cap you cut off will have a clean area about 1/4" long to insert into the tube....
Align the U-joints till correctly "phased"[in line with the front ones].
Next get a good tape measure and measure the length of each side of shaft [measure at outside of Ujoint caps].
It will soo be apparent how close or far off you are in length/square....
Keep tapping and measuring till it is as close as you can get to a match on sides.....
Tack in 3 places with the Mig on high setting..... then roll the shaft on a table as you weld it all the way around.
This should net you a useable driveshaft that will run 70-80 MPH,May not be 110 % perfect but a useable shaft done at home!
The one in my roadster is done this method and was adequate to break an axle at the drags-Ha!
It's hillbilly, but folks have used a piece of angle iron and laid the shaft parts in it. Tack, turn, straighten, repeat til it spins nice and even in the saddle of the angle iron. 'Necky but it's been done. Seen it.
glad you posted it,after all if we all took our parts to have "professionals" do the job all of ours rods would be the same, really expensive.Most of us do our own brakes,and that's gotta be fairly important while cruising at 90mph
The guy I have do mine (Ray) uses the lathe to cut the old weld, but you can do it with a grinder. The end fits into the tube pretty tightly, but it could be cocked a bit, so setting up the yoke in a trans and some type of roller under the shaft and using a dial indicator on it and tweaking as necessary could get it pretty darn straight without the need for the lathe. Ray doesn't balance but he does put the indicator on the shaft and does some magic with the torch to get the indicated runout near the end down to an acceptable level. They usually run smooth.
I could probably do them in my little old south bend since I have a rest for it, but I still farm them out....
What he said. Take a piece of paper and wrap it around the tube where you are going to cut it, mark with chalk, a perfectly straighe line magically happens. To balance? If there are any balance weights on the shaft now. leave them. To tweak the balance after shortening, put a large worm clamp around the freshly installed drive shaft, leave it just loose enough for vibration to move it, it'll find the balance point for you. If you think its vibrating after that, tighten that clamp where it is, install another.
I have done it pretty much the way choprods describes but I use my chopsaw to cut the tube to size.
I forgat to say the reason for cutting it on the REAR of shaft is that if you install a little vibe it is less noticeable there rather than under your ass!
I never grind the finish weld either but I'm a slob so that is why.....
round here there ALOT more than 50.00.. I havent done one this way, but am ready to try..
too bad all the cars I am doing require the shaft to be LONGER!
tingler, pay your local guy to do one, watch closely and do the next one yourself.
Trouble is the driveshaft lab will put their new guy on for welding practice, the shafts never get done by a pro, 'cause the pro is usually the boss. Anyhow, $50 equals approximately 3 cases of Lucky Lauger......HAND ME THAT WHIZZ WHEEL!!!
I'm with b29. $50 is a lot of money, plus the time and gas spent to take the driveshaft to a shop. To me, the point of building a hotrod is to do everything possible myself. I dont rebuild automatics but I do everything else that I can. I firmly believe most traditional hotrods were built by individuals, not professional shops. Anyone who pays someone else to build his car---------------- well, thats just wrong. The rich guy misses the entire point of having a hotrod.
Hey choprods, I thank you, maybe there was a 'thank you' in there somewhere, but it sounded kind of like the guy that ask for the proceedure can't read too good, and now he wants pictures?
Ha Ha ....Time to start building some altered wheelbase stuff .
I've done a handful at home - first without a lathe and then with one. It goes something like this:
First find a driveshaft that is either CLOSE in length already OR one that has a constant diameter (so you can cut it anywhere).
Mark the ORIGIONAL orientation of the bearing end - it may potentially save you grief later. Note the relationship of the end to the balance weight if present.
I've ground the weld as mentioned above - carefully watching for the blue colored metal to let me know I am CLOSE to breaking through.
When I got a lathe I simply cut off the end and chucked on the inside of the stub and then "peeled" the weld on the lathe.
Next I measured the driveshaft for the right length. To mark a square cut I just wrap a piece of paper around the driveshaft and mark it with a sharpie. I then CAREFULLY grind to THAT mark. If you're real careful you'll be surprised how close you can make it. A huge tube cutter works as well, but will make it harder to install the end.
Next I reinstall the yoke - if you used a lathe to peel the weld and indicated everything you can pretty much install it to the shoulder you left. If you ground it by hand you will want to make sure it's square. I've done this by slipping a long piece of shaft through the bearing cap holes and used a carpenters square against it- checking both sides (incase the carpenters square ain't perfect). You can also use the shaft to align (phase) the Ujoints.
Then I tack it !!! 4 places - then recheck. If all's well - I weld it - the last one I mig welded with my little 110 MIG - preheat - even though it's held for a dozen years I will TIG my next one!!!
Next install - try it and see if there's any vibration. IF there IS all is not lost!!!
You can balance a driveshaft at home with some patience by the following:
Put car on jack stands - not those crummy ones shown here all folded over - use some GOOD ones!! Start the car and put it in DRIVE. Take the motor up to 3 grand or so. While running steady a sharpie against a block and slide it towards the drive shaft (the side you cut) until it just BARELY touches the drive shaft - the out of balance shaft will "move" towards it's HEAVY side and you will be identifying that - by just BARELY touching the shaft - you will only draw a line on the "HEAVY" side. Now that you know the RELATIVE POSITION of the location of the BALANCE weight (opposite your mark) you now only have to figure out HOW MUCH weight to add. This too is easy enough to do at home. Take 2 IDENTICAL hose clamps - and install them such that the wormscrew sides are on your HEAVY location. Redo the "marker" test - or drive it and see how it is. Continue to add PAIRS of hose clamps until you have added TOO MUCH. Once you have added too much weight you can determine how much LESS you need by doing the following: First MARK the position of the weights - (hose clamps) you will ROTATE them in OPPOSITE DIRECTIONS to make their EFFECTIVE weight less - this method will give you INFINITE adjustment even though you have a fixed amount of weight. First imagine your weights are ate the 6 o'clock postion (as you look down the center line of your drive shaft) you then rotate each clamp to - say - 5 o'clock and 7 o'clock positions - or 4 o'clock and 8 o'clock - once you determine the correct position you can take the easy way out and add weights in these TWO positions OR you can go the next step and use some basic geometry and figure out what the "net effect" a single wieght would have at your origional position. This really IS simpler than it sounds.
Most times you can START with the origional weight installed in the SAME relationship to the end and be very very close.
It's a POTENTIALLY SLOW process but it does work. Now you see why people generally take it to a shop. We're lazy!!!! But when you have more time than money - it will work and work well!!!
These methods have worked for me - your mileage may vary!!!
this is admittedly NOT for the faint of heart - if you have any doubts to your welding skills - or fabrication skills you are far better off paying the money to a shop - any good shop will do this - peice of cake.
The driveshaft in my A truck was shortened before I got it, then I shortened it again alittle, and did it on the lathe and in a very similar way that Hemirambler described...........................and I have drag raced the hell out of it...........it can be done..........just take your time..........Littleman
Nope; Not Unless...........your slam, implying cutting a driveshaft and welding it is a good way to kill yourself was the shit that needed to be stirred.
First, you asked for a post to describe the procedure. You then made fun of a post, I think in a derogatory comment, asking for pictures of the procedure on “how to kill yourself at home”.
1) This NEW GUY does have a clue, knows how to shorten a drive shaft. I thought that’s what the question was about. Okay, I’ll bite, what IS it about?
2) Jokes about a serious matter can be done with a PM.
3) As for the comments that I’m here “to make trouble”, just because I called you out on the fact that you were berating another person’s post, then to what end? Whether I know that person or not doesn’t make any difference. It’s kind of like making an Ethnic Joke, and the brunt of the joke laughs. That don’t make it right. Attacking the messenger, for the method of the message, is a thumb-sucking tactic.
4) It’s a drive shaft. Suggesting that a mechanic can’t safely shorten a drive-shaft, without a dial indicator, lathe, etc. are by those that can’t comprehend a straight cut and a good weld to begin with. Call a Mechanic.
But would like to add...........I just bought a driveshaft by Denny's........I figured if I was going to put some real power through one, it just made sence to have one done by someone that makes them for severe punishment........Since I plan on stomping on DeathsDoorStep real hard........Littleman
I rebuild automatics, but I don't do driveshafts....yeah, we each do what we're comfortable with, so I try not to give guys too much grief if they have different skills than I do. In fact it comes in handy, I've gotten several driveshafts shortened in payment for doing some engine work! and I sure don't mind doing mechanical work for someone who can and will paint my car.
some things are best left to people who know what their doing.
I've cut a few shafts down and they performed fine at highway speeds. Up to 90+ I've been told by a friend I did a couple for .I cut the trans end but I don't think it realy matters which you cut.use your favorite trick to keep your cut at the end straight.wrap it with paper or use a hose clamp etc. but keep this cut straight! The first ones i did i cut through the tube very carefuly with a hand hacksaw cut into the tube till you feel the forged plug turning the tube as you go once you've cut all around the tube heat it with a torch a little and remove the forged end a small plumbers torch will work here you just want to expand the tube a little it doesent need a lot of heat.I forgot to say that #1thing i do is draw a straight line down both sides of the shaft through the centerline of the u joint caps I also draw a ring on the input yoke tube before removing it from the trans so I can replace it at the same depth on the cut shaft.with the cut shaft yoke slid to the proper depth on the trans I measure between the the front and rear Ujoint for length next I cut the tube for lenght heat the end and drop in the yoke with my side lines lined up so my joints are in fase I leave a very slight gap at the tube and forging joint mabey a 1/16 inch by tacking a few spacer shims to the tube end to but up on the shoulder of the forged end i'll remove these after i tack the pieces in place.now weld around the shaft while rolling it on something.I like to dress the top of the weld flush with the origional yoke shoulder just flatten it a bit so its all even.those straight lines down the shaft sides are a good way to pick up shaft twist later if you abuse the shaft like drag racing.NEVER cut the tube anywhere else and butt the cuts even with an extra backer inside also you'll find a cardboard tube inside the shaft when you shorten it,shorten this as needed and PUT IT BACK!the very first shaft i cut I couldn't understand why there was one in it so i tossed it, well when anything touched that shaft it had the nicest bell ring you could want ! well this is what has worked for me and i havent had one fail but I havent run any in any form of racing either
i have a couple things to add, my landlord has been shortening his own driveshafts forever and taught me a few things as we did mine.
obviously the yokes have to be aligned for runout( we used a piece of angle iron to support both ends and used a dial indicator to align it up .)
the trick to keeping it in balance is to
1) after cutting the tube the end has be put on in the same plane as original (the misbalance is almost always the ends not the tube so if you clock the yoke 180 deg out you will have a misbalance.)
2) the weights have to put back exactly where it was before. (as in clocking, eg. 2 oclock to 4 oclock)
do all your clocking of weights and mark the yoke so its clocked correctly before you cut the tube.
one last thing, the ends are forged not cast, if you could mig a tube to a casting you are an incredible welder.
p.s. hemirambler described the alignment real well.
Pure hilarity. Now go away.
Lots of good info here. I've always shortened my own driveshafts (half a dozen or so) right in the garage and never had any failure or vibration issues.
I've probably shortened 50 driveshafts down through the years with a hack saw (now a sawzall), a hammer, a flat work bench, and my mig welder. The most important part of the whole adventure is keeping the two yolks in line with each other. Vibrations come from the misalignment of the yolks most of the time. Take your time, keep the yolks straight to each other and get a good weld. You should be good. Its just a drive shaft, if its way out of balance, balance it. If the tube is bent, pitch it, and if the welds are that bad... well... you have more to look at then just the drive shaft. Really, how many tubes and yolks have you seen fail unless the ujoint failed first? If your hooking up enough power to be concerned about twisting a tube, your crazy for not dropping big bucks for a special shaft anyway.
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