I used to work in a machine shop and we would do them in a lathe. The only reason being that we would turn down the original weld, cut them to lenght, slide the end back in and weld, checking for run-out. There isn't anything wrong doing it this way and saves some bread. A friend of mine just get's his 4 1/2 grinder out and grinds the original weld away, cut's it with a chop saw and slides them back together and welds. Simple.
I have a friend that has a muffler shop. His pipe bender machine has a pipe expander that he expanded the end of the tube enough that I could tap the yoke in.
***************************************************** While I agree with you, there is a situation that I found myself in that does qualify for just such a blatant "error". Building an O/T drag car, and butt-welded a metric tube to an SAE tube in order to fab a "dummy" shaft. It did work for moving the car under it's own power, (in the driveway and at low speeds), but I did take it to a shaft shop to have a custom one built. The biggest benefit of this is that you prove you've made one the correct length, and can take it in as a sample for the shop to follow. BTW.....I did try to have a local muffler shop expand the SAE tube so that the metric tube would slip inside.......can't be done cold. That sucker sure made a loud "POP" as it split during the exercise.. Apparently drive shaft tubes are hardened. Roger
I don't trust myself enough. I'd be the asshole posting a reply about ripping the floors out of my car on the freeway after trying it. Great tech though.
hi guys, two things to add here; 1) after marking the yoke position and cutting the tube, use a level to make the clocking correct, make the factory end level and then match the cut end to it, then check runout before welding. 2) mark the position of the weights to be moved, the yoke is most or all of the misbalance thats why the yoke and weights need to be back to thier original positions. gary
Driveshafts are made to have torsional strength, or twist to over come hard shocks. The bigger diameter the better. I seen somewhere that they are riveting the ends on some.
You need to make sure that the two flats of each weld yoke are in phase with each other, and a level will work, but a flat surface is even better..
In laymans terms, 'Phasing' of the uni's, as described above, is to assist with balancing, and more importantly removing vibration due to the uni's being out of sync as they go through their revolutions. The motion of the uni's as they go through their curves as it rotates 36o degrees is like a sine curve, and if your front and rear uni's are 'fighting' each other due to not following the same relationship as the shaft rotates, you will have a very notable vibration, and short uni life.....amongst other bad things....
I actually amazed myself earlier this year. I needed to shorten one of those wacky GM driveshafts (to use as a "mock up") so that I could verify exactly what length I needed to have my "real" shaft cut down to (by "real" I mean that I already had a custom shaft made up by a real shop, but since I was changing from TH350-T5 I would need to get the "real" shaft cut a bit). Due to the strange ends I decided to cut mine about 1 1/2 feet from the back end (keep in mind, the intention is just to use it as a mock-up with no real intent to drive this way). I clamped it in a piece of angle iron and welded her back together. Not only would this allow me to positively verify the length I need, it would also allow me to move the car around. Next thing I know I run out of time to get the "real" shaft cut and I decide to run the "mock up" out to a show about 15-20 miles from my house. I ended up taking the highway 65mph and didn't even get a wiggle out of it. I couldn't believe it. I left it in for another couple weeks before I got around to getting the custom shaft recut. I didn't really trust my homemade one (not that I didn't trust it really, I was not happy with having to weld it together in the middle of the tube) seeing as I also just built a trailer hitch and have every intention of doing quite a bit of towing with it. Bottom line is this, If I had a regular shaft (one that can be shortened the way the original poster did) and not the wacky GM "swedged" ones I would have done it all myself. Just make sure you keep the ends in phase (as has already been mentioned).
Nice tech - clear, great pics, etc!! Had an old fella around the corner from my father's house that built and repaired heavy equipment and had nice old WWII era lathes. He had done our last several drive shafts for $25 a piece. He also cut the centers out of a pair of wheels and pushed the out to add a little back spacing for the same price. Heard he passed - haven't been by in a while. I'm sure the son has taken over (he was actually the welder)...gonna have to see if the prices still stand. If not, I'll be trying this pretty soon. As for the question several posts back: I've also heard of pumping grease into drive shafts to balance. Anyone ever do this? Results?
Done the same thing her a few times .If you don,t have a tubing cutter you can wrap a bit of A4 paper around the shaft and over lap it and use this as a straight edge to cut along.
I started tossing up the idea of going from a turbo 350 to a 700r trans the other day and one of the expenses I was considering is having to buy another drive shaft, thanks for the tech help buddy this one is great. Cheers Sam navarro
What y'all don't realize is the most simple part of the job of shortening a driveshaft is cutting the weld and saving the possible good weld yoke, shorten the tubing, getting it straight as first pics in thread--good science based on non-machine shop tools. How do you correct runout at the center of the tubing of a shaft that can be saved for a non-performance application? I'm not saying it can't be done at home, I started with basically the same science as the thread starter. I had basic tools, no balancer. Then I learned more after the first three years. I learned more after that too. Want a comparison? Do you get your tires balanced for your late model daily driver? Why? Fenders and wiring harnesses don't give a care about constant shake? Wheel bearings? The driveshafts is lighter but out of balance weight squares by double of rpm and driveshaft parts manufactures DO NOT produce balanced parts to be pulled out a box. They have production tolerances and QA lets shitty parts and fitment fly out. Dodge dealers told to fill shafts with spray urethane foam to deaden rearend noise. Shaft filled and can't get needed air to set foam. Looks like bullsnot when ends are cut out of the tubing. 1993. Lay a factory GM aluminum shaft on the floor while taking delivery from dealer driver. Shaft rolls to place IT wants to be. 2003. Customer across the salt in front of me at 263 mph, my driveshaft. 1995. Customer through beams at Centerville Arkansas strip at 188 mph in 1/8 mile. 2007. Showed me a ticket in 1992 for having pulled a wheelie in his street car--358 sbc 4 spd car. Pay now or pay later more. Home built is close, so are horseshoes-hand grenades- atomic bombs.
Great tech article! This is essentially how I do mine too. I mark the yoke and tube so it goes back on the same way. Once I get the yoke out, I clean it up on a lathe using a 3-jaw chuck and tailstock center. I do the pipe cutter thing as well. In lieu of the indicator, I've had good success with a good machinist's square and v-block set to get the yoke on as straight as possible. The next one, I will use an indicator. Bob
Been doin this since 1967,,,a good friend showed me how with a hacksaw and a piece of thick paper to wrap around the tube for a straight cut and a tape measure for length and don't forget to align the joints....never had a vibration....
as stated previously, most of a shaft's factory imbalance is produced when the front yolk is forged and there is a thickness variation between one ear and the other after machining. take a look at your yolk and check the ears thickness left to rh sides just below each cap hole with a vernier. some are even visible just by eyeballing. I have found if you lay the yolk on a flat surface and slowly roll it ... it will show the heavy side every time. i just use a hand grinder to take off some metal of the ear until it rolls smoothly. Another thing to look for in front yolk selection is to look for any heavy groove marks on the seal diameter. these grooves will cause oil leaks!
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