How to shorten your driveshaft

[406 Q-ship]

I will always leave driveshaft modifications to the professionals. I have paid between $60 to $100 to get one shortened, balanced, and new u-joints. No chance of having a vibrations, or a phasing issue. Even at $150 like one shop wanted, if a backyard driveshaft takes out a trans, rear axle, or causes an accident, then that $150 will be chump change. Just not worth the risk unless you have the knowledge and the right equipment.

[brad_man_72]

me and 2 other guys where I work built 150 driveshafts last week alone using every proper piece of equipment, new trans yokes, new ujoints, new weld yokes, new DOM tubing. All machine welded, all straightend before welding and at least checked for straght after welding. All built better than oem tolerances. Every single driveshaft was ballanced and every single one of those new perfect condition driveshafts took at least some weight.

we also made several shafts for our walk in customers but those 150 were for one customer.

[pumpkin]

I've been building my own driveshafts for 30 years. I've yet to have a problem. One is is my sons 3/4 ton 72 pu with a 535 hp small block that he is realy hard on. Funny thing the original unbent, ballanced shaft actualy had a vibration that I had been trying to find for years. Short of getting the driveshaft checked for balance I had done most everything else. Well after building a driveshaft at home,,,,,,,,,, vibration gone.

[brad_man_72]

Originally Posted by pumpkin

I've been building my own driveshafts for 30 years. I've yet to have a problem. One is is my sons 3/4 ton 72 pu with a 535 hp small block that he is realy hard on. Funny thing the original unbent, ballanced shaft actualy had a vibration that I had been trying to find for years. Short of getting the driveshaft checked for balance I had done most everything else. Well after building a driveshaft at home,,,,,,,,,, vibration gone.

unbent, ballanced. Did it have factory ujoints in it? When changing ujoints it's very common for people to not mark things like trans yokes and replace them 180° from how the shaft was originally ballanced. How straight was the shaft, how did you check it, did you take a baseline measurement when the shaft was ballanced? .010" is enough to disturb the ballance of a driveshaft. That's less than the thickness of a fingernail.

[smitty62]

I think you all should give the guy a break instead of criticizing him--he showed a little ingenuity and saved himself a few $. Will it give him trouble in the future? Possibly, although I doubt it. It doesn't sound as if he's building a 12 second quarter mile truck. Even so, the conseqences won't be any where near as severe as some has suggested. I have gotten by with jury rigging many times over the years and I for one admire it when well done. Is there jealousy here because some paid $200 for this job??? I wonder.

Just because something costs more does NOT make it better!

[brad_man_72]

sorry if I'm coming across as a bit of a jerk but even professionals build driveshafts that get people killed.

[Jacfourteen]

Originally Posted by smitty62

I think you all should give the guy a break instead of criticizing him--he showed a little ingenuity and saved himself a few $. Will it give him trouble in the future? Possibly, although I doubt it. It doesn't sound as if he's building a 12 second quarter mile truck. Even so, the conseqences won't be any where near as severe as some has suggested. I have gotten by with jury rigging many times over the years and I for one admire it when well done. Is there jealousy here because some paid $200 for this job??? I wonder.

Just because something costs more does NOT make it better!

Originally Posted by brad_man_72

sorry if I'm coming across as a bit of a jerk but even professionals build driveshafts that get people killed.

Don't sweat it guys, I'm not taking offense. I meant to give a disclaimer when I wrote this but forgot to add it, now everyone has been warned of the possibility of failure from guys like bradman that know alot more about this than me. I knew that there would be people that would give me a hard time with this mod, and with good reason there is alot riding on your drive shaft. I mainly wrote this because it was in my build thread and someone found it useful so I figured I'd share with others. Like stated above I'm not building huge power or going to the track with slicks so I think this shaft will serve me well until I do my tranny swap and change it to a one piece shaft. I have learned a lot with the comments on here, and because of bradman's advice I am thinking about taking it to a shop to have it checked out and I would suggest that others do the same.

[brad_man_72]

i didnt mean to criticize. im all for doing alot of things yourself. i built my boat engine, done suspension work on my truck, ls swap on my truck, painted cars ect. a driveshaft is deceptivley simple, after being in the buisness for a few years and learning alot from people who have been building drivelines for decades i know this isnt a project for the diy guy. it doesnt mean you cant build something that will work or get you by. i build alot of multi-piece drivelines for limos, alot can go wrong and the builders notice any vibration. old trucks arent as sensitive most owners wouldnt notice a little vibration, no worse than having your exhaust mounted pretty solid, and a drag car you can forget about noticing any kind of driveline vibration w solid motor mounts, open headers, short ammounts of time at specific speeds ect.

[brad_man_72]

backstory. this guy didnt feel any vibration until the rear shaft left the truck going down the highway.
him: oh it only bent the rear shaft make me a new one
us: we need the front shaft in order to ballance the driveline
he kinda threw a bit of a fit, didnt understand why we need the front shaft we finally got him to bring in the front shaft, it looks great until we put it in the ballancer, we were able to use everything but the tube on the front shaft.
heres video of his "good" front shaft with new rear shaft, the rear shaft only looks bent because it is attached to the bent front shaft.

YouTube - Apr 1, 2011 1:32 PM

[jhwkns]

There's no substitute for a well balanced driveline.

[406 Q-ship]

I was not criticizing if someone is comfortable doing modifiying a driveshaft in their backyard then good for you. There is alot of risks for the pluses in my opinion, they need to pointed out. I would not want to see a novice (welding skills is critical) try this and send a driveshaft throught the windshield of the vehicle behind them......a very real possibility. This is just not a job to be taken lightly. I am the same about brakes, if you don't understand them, learn or get help before the damage is done. I have been a mechanic on and off for 30 years and have seen stuff that would make your blood curdle done by the untrained in the name of saving money (most times it cost more in the end).

[infinite-foamies]

I think I am going to give this a ****. Though I think a pipe cutter is a better way of cutting the tube.

Question: What about changing yokes from one improper length shaft that came with a tcase to a proper length shaft? (if I am lucky enough to have this situation?)

[dirtyjim]

I've been doing stuff that's best left to professionals for years because the professional hacked the job in the first place. the last driveshaft I welded was to fix I brand spankin new professionally built shaft that the professional didn't understand weld penetration, I had to re-weld both yokes because the welds broke within minutes of installation.

[Keith Seymore]

Originally Posted by brad_man_72

me and 2 other guys where I work built 150 driveshafts last week alone using every proper piece of equipment, new trans yokes, new ujoints, new weld yokes, new DOM tubing.

Brad - what does DOM stand for?

K

[brad_man_72]

Originally Posted by Keith Seymore

Brad - what does DOM stand for?

K

It means the tubing isn't seamed like oem tubing. The tubing is Drawn Over a Mandrel making the tubing uniform in thickness and shape. Without a seam its much easier to center a weld yoke in the tube. It takes less weight to ballance a tube that is not egg shaped from a seam. The seam also forms a weak spot in the tubing.

So dom is easier to work with and stronger.

The only reason to modify a driveshaft at home is for an emergency fix. Anybody who thinks they can build a good driveshaft at home is only fooling themselfs.

Like many of you know, I was a professional driveshaft builder, there's no way id attempt to modify/build a driveshaft at home. Then again some of you may have a lathe, welder, dial indicators, ujoint-lathe setups, torches, a $50k driveshaft ballancer, spare pinion yoke, and the know how to operate all of those things.

[brad_man_72]

Originally Posted by infinite-foamies

I think I am going to give this a ****. Though I think a pipe cutter is a better way of cutting the tube.

Question: What about changing yokes from one improper length shaft that came with a tcase to a proper length shaft? (if I am lucky enough to have this situation?)

It doesn't really matter what you use to cut the tubing as long as its pretty straight and smooth. Hot saw, cold saw, band saw, or lathe would probably be the easiest. Cutting the weld yokes out is a little harder, definetly best to use a lathe to cut out the weld, but can be done with an angle grinder. Its still not an easy task without some experience.

The yokes don't care what length the tubing is as long as both tubes have the same inside diameter. 3x.083" and 3x.065" have different inside diameters, not something you can see before you start cutting.

[infinite-foamies]

Thanks, not sure why sh_ot (w/o the underscore) is censored?

I think I can probably set it up on the lathe to cut the weld with a parting tool.

I am aware of how wall thickness works, thanks.