Drive shaft angle tolerable?

I've been corresponding with a fellow who has a 79 CJ-5 with T-18 and D20 t/c. The fellow he bought the Jeep from swapped in a 44 from what I believe is a 72-75 CJ-5 or Commando. Is the drive shaft side angle as pictured tolerable? Because he is planning to install a lift, he will be installing a CV drive shaft (single /CV joint at t/c).

 

Here is what you do.
1st. It is kind've hard to tell, but it looks like the driveshaft is assembled wrong. Make sure the yokes on the ends of the driveshaft are matching. It looks like they may be opposite. If they are opposite, it will shake you out of your Jeep.

2nd. The left to right angle is tolerable as long as you do not run a double cardan (CV). When you run a single double-cardan up by the transfer case, you need to have the differential pinion pointed directly at the transfer case output. That is impossible if the diff is not directly behind the t-case.

3rd. You really do not know for sure what you need to do untill you have installed the lift springs or whatever you are going to install to lift it. Most people just lift it first, and then see what needs to be done to make it work. You have to install the springs, then mount the tires you intend to run, then lift the jeep by the frame so that the axle /tires are suspended in the air, then you will be able to see how bad your u-joint angles are at full droop. Got it?

 

That's what I was thinking. As pictured with the left/right angle, the CV would cancel out vibrations caused by angles in both planes at the T/C but the pinion would still be generating vibration even if he had the pinion pointed directly at the T/C because of the left/right angle.

If his lift was not so high as to require a CV shaft, and running a conventional 2 U joint shaft, having equal angles at the U joint in both the up/down and left/right planes should result in a smooth running shaft.


This is the way I understand how it should work but both he (Scott) and I spoke to a drive shaft people and were told that a single CV shaft should work. I have my doubts.

 

That does not look right. Is the pumpkin not centered? Is the transfercase not centered?

It might be the picture but if you imagine a line down the center of the transfercase it looks like it's cantered off to the side a bit, not parallel with the frame. The pinion appears to be pointed a bit the other direction. Kinda like they are parallel to each other, not in line with each other.

I'd check the set up. Something is wrong.............I think..........

 

Ask dummy, i think he had something like that.


Anyhoo, as the suspension cycles, you will get vibration. To run that angle smoothly, you need to rund a Double-Double cardan shaft. (one with CV joints at both ends) This would require to switch from a pinion yoke to a drive flange. Check out the knowledge base at www.4xshaft.com Or give them a call, the are extremely helpful, and I highly reccomend them. I am 99% certian that a single CV will not work for that. I ran a single CV without the pinion pointed up at the t-case, and i tore a drivesahft to pieces. I would think that the incorrect left/right angle of your pinion would cause similar forces as the incorrect up down on mine.

 

Correct, because there is really only one angle at both ends. It just happens to be "at an angle".

 

There is definitely more tolerance on that CV offset than theory indicates. My rear shaft is 22 inches long with the engine offset 1.75 inches to the driver's side and about 5-6 inches above the pinion. With the pinion turned up to face the tcase, I don't feel any driveline vibration. I don't know what the actual limits are for these offsets with the CV shaft, but they're definitely better than dead on +/- a degree or two.

 

I just got off the phone with a gentleman named Troy at Tom Woods Drive shafts. What he said concurrs with what has been said here. The best solution would be for the Jeep owner to locate a stock AMC 20 rearend to get rid of the compund U joint angles. Theoretically, if the Jeep had more a bit more drive shaft length, a shaft with a CV joint on both ends would solve the problem. On the other hand, if he had more drive shaft length (depending on how much, of course) the angularity might not be so severe and perhaps a conventional 2 U joint shaft could be used.

 

From looking at the picture, it appears that the offset is about the width of the yoke plus some. So probably about 4 inches. The shaft can't be much more than 16 inches long.
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It looks like you've run this to ground...so I'd like to ask a question...are you saying that a Dana 44 will not work with a T-18/Dana 20 combo due to the offset as well as angle?

I ask because that is exactly what I am trying to accomplish with my '74. I noticed the offset, but didn't that that it would be a huge issue. I'll be lifting the suspension about 2"-2.5"

 

Silly question, if the 72-75 dana 44 was slightly offset did it not line up with the dana 20 of those yrs? Was the driveline offset also.

 

Run single u-joints on each end and you will not have to worry.

No, the alignment was a littie off.

 

The owner of the Jeep concerned purchased it from a fellow who kind of slapped things together. I gave him measurements off my Jeep and he will make comparisons. I kinda suspect a problem with the motor mounts but we won't know for sure until he takes his measurments.