Yep, seen that before. Sure explains a lot of torn up drivetrains on lifted trucks doesn't it?

Inland Empire has some good diagrams, but seeing it in motion is even better.

that was a good basic informative video . it elightened me on the fact that you want the ujoints IN PHASE in addition to the angles being equal as I had forgotten about the in phase part . They did neglect to mention why you dont want the whole setup in a straight line which in real life might be hard to accomplish anyway and that you want minimal angles. Thank you for posting it!

Believe it or not, a few guys, especially on the race forum, continually argue a parallel relationship between the transmission and pinion is not important when the vehicle is under power.

I have mounted and installed shaft driven fuel pumps on tanker trucks and this is basic knowledge for body builders. Always match the angle of the pto out put shaft.

I had a brand new aluminum tanker truck built by Hutch Tanks in Toronto Canada. This was dual pump truck with 2 PTO driven pumps with short drive shafts just like in the video above and the angles were off a lot, brand new. I already had another Hutch equipped truck and it's angles matched and we had been using it for near 10 years. The PTO u joints on the new truck wore out in a month of use when they last years with proper grease.

They came down and got the truck and took it back to Toronto and re engineer the whole cross member that held the pumps and redo the plumbing. Took them like a month.
There was new management and workers since they built my first truck from them and I could see it in the build quality in other places as well. Never bought another one from them. They did get the angles matched and the U joints last now since 2004.

What do they mean by u joints in phase? How do you adjust for that?

You want the ujoints installed so that the zerk is under compression visualized with the shaft rotating CW, viewed from the front as if you were standing in front of the car looking rearward. Also you want the (2) end welded yokes on the main driveshaft parallel but that would not have changed from (OE correct) unless an inexperienced tech at the driveshaft shop welded one on 1/4 turn away from parallel when the shaft was in for shortening. EDIT when done with the ujoint install move the front yoke thru both planes of travel and the rear ujoint thru it's 1 plane of travel if it it ain't smooth (& it wont be) then set the shaft on your bench with the ends hanging over the edge & whack an "ear" several times with a BFH then rotate the shaft 180 & whack the other ear several times then check for smooth movement & repeat as needed. The "ear is the connector piece of flat metal between the main shaft and the "holes" (ears are opposite each other). grab a helper to hold the shaft & you use a drift along with the BFH to guarantee an accurate strike(s) if need be

Check out Thompson Coupling. Looks like the future is here

Excellent information, I learned something today.

We've had Wrangler transfer cases explode while on the highway when people have driveline problems. High speeds and low axle ratios [around 5.13]...those driveshafts hit warp speed.

That vid is BS and doctored. Everybody whoever races,...

Knows the pinion Angle Must be set between the Pinion angle and the Driveshaft. Period.

Don't trust the Film,

Sport I saw where they jacked up the pinion. What ain't right in the demo? I dont wanna miss anything

no sarcasm bro. this is a legitimate Q. I dont know it all and I dont want to miss anything and I am always wanting to further my knowledge

The Vid is correct.

Background:
What we call a universal joint is named a Cardan joint. What many of you do not know is that when the Cardan joint is transmitting power at an angle, the output is not a constant angular velocity even though the input is.

That is why Cardan joints are used in pairs.

The input to the first joint is at a constant angular velocity (rpm) while the output is not. It changes from faster to slower to faster to slower with every revolution of the shaft. The second Cardan joint takes this varying angular velocity and turns it back into the original constant velocity that was at the input shaft.

Even though the driveshaft itself looks like it is spinning at a constant angular velocity it is not.

Another thing to consider with driveshafts is their harmonic frequency. When the rpm approaches the harmonic frequency or an even multiple of it, the shaft becomes unstable. So one either wants to travel through the first or second or whatever harmonic at a rapid speed so the shaft doesn't disassemble itself, or make the shaft harmonic frequency be above the fastest the driveshaft will ever spin.

One of the problems with adding overdrives is that the driveshaft is spinning much faster than the designer of the driveshaft had intended. Say the car came with 3.23s, but you change to 4.11s and add an overdrive. The driveshaft will be spinning 27% faster at any speed, so at 75mph the driveshaft will be spinning as if the original car was traveling 95mph. This will put the driveshaft speed much closer to a harmonic frequency.

To counter this, the driveshaft must be made stiffer in some way. The easiest way to make it stiffer is by adding diameter.

End of lecture.

R.

that's good info Dog

That is why most late model high performance cars have 2 piece driveshafts. You can easily exceed the safe speed of a 1 piece, especially on a top end run with 2 overdrive gears and 3.92's in the rear.