Transfer case drop??

All right guys I'm getting the post lift drive line, tooth filling removal, can't see what's in the mirror behind you vibrations. My drive shaft is at 26 degrees, t case u joint at 4 degrees down and axle u joint at 5 degrees up. So I'm at the 1 degree I thought I should be looking for.
The info I need is have you lowered your t case??? If so how much did you drop it IN INCHES not number of nuts you put in there lol? Did you DIY or buy a kit? What did you end up with on angles????
I'm rocking a 74 I6 CJ5, About 4" of lift, 32" tires, Dana 20, Dana 44, stock drive shafts and re-grease re-packed u joints.
Thanks for the help.
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No I didn't when I installed the supposed rebuilt Tranny/t case I just re-packed the u joints and left the drive shaft alone. Is that something I should look at???

 

According to the measurements you posted the propeller shaft is at 26 degrees, transfer case is at 4 degrees? That's 22 degrees of u-joint angle! Waaayyyyy too much. Typically 7 degrees is max. The rear according to your post is at 21 degrees, again, waaaayyy too much u-joint angle. If this is accurate that is your issue. The u-joints are binding as they rotate. You may not feel it by rotating by hand but under load I guarantee it's happening. It's good that you are at 1 degree difference front to rear but until the rest is fixed you won't fix the vibration issue.

 

Wouldn't the angles be half of that???? I guess the way i'm looking at it is ya I have 22 degrees but that is being split between both u joints IDk I'm probably wrong hopefully these pictures help. I did just make a 5/8" drop spacer and now I'm getting 21 degrees on the drive shaft... I don't know if these pics will help to visually describe what I got going on but I'm trying. I only get REAL bad vibration while shifting into 3rd with heavy acceleration. While under normal cruising or 1st or 2nd gear it's very minimal.





Well so much for pics of the angles but I tried

 

I think what you need to do for one thing is, as Patrick suggested, separate the two shaft sections and slip them together again with the U joint caps aligned. That would be the two caps that are pressed into the shaft yokes. They are almost aligned in the pictures, but they should be in alignment exactly. If you remove the U clamps from the rear axle you can separate the two shaft sections and align the rear half with the front half, then put it together again.

 

When I do that should I or do any repairs while in there grease some stuff up replace seals etc. ???

Well drive shaft out, new U joints installed, all old oil/grease sanded off and a fresh coat of paint drying right now!!! We'll see what happens in an hour or so!!!

 

Well, that's good...at least now you know you're starting out with good U joints.

 

When I look at the pictures of your driveline and read your discription I see multiple problems which will create the vibration you noted.

1. As Nick pointed out, you have way to much driveline angle. Seven degrees as Nick pointed is the maximum angle fractory engineers like to see although others say you can stretch this to 15* but will get some vibration at that angle.

2. You say your transfer case is down 4* and pinion angle is up 5*. This will actually add to your problem when you accelerate from a stop. The pinion angle should be pointed slightly down say 3* in your case. As the pinion rotates up under torque it's centerline should aligns with the centerline of the transfercase shaft.

3. As Rick noted and Patrick questioned, your driveshaft u-joint yokes are out of phase. Follow Ricks direction and phase the u-joint yokes.

With the angle you have created, you really should consider a double cardan front u-joint for your drive shaft and align the rear axle pinion accordingly.

Here is a link worth reading that discusses driveline angle.

http://www.4xshaft.com/driveline101.html

 

No driveshaft at 26 degrees, yoke at 5 degrees. Subtract the two equals 21'degrees joint angle. Donthe same with the other joint will give you the angle for that joint. If you have a doble cardan joint you divide the diveshaft to yoke angle by 2 because there are two impinge dividing the angle. You don't have that.
As was said, put the impinge back into phase and fix the joint angle issue and your vi rations should go away
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Dang spell check on the I phone.......
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To reduce the angle between the axle and the driveshaft, install some degree shims between the spring plate and the spring, thick side of shim to the front. These are usually included with lift springs to correct the increased pinion angle by tilting the pinion up. There are different thicknesses available that I've used to change my front castor angle. Definetly should have had some for a 4 inch spring lift.

 

Well I got some 3 degree shims put in the axle perches today and lowered the T case 5/8". So now my angles are 11 upward in the rear, 19 on the drive shaft, and 4 downward at the T case. I took it for a few trips around the block and all vibrations were gone!!!! Hopefully when the 40 degree days break and I can get out for 30/40 miles and it will be all good...
Thanks everyone for the info!!!

 

8'degrees'and 15 degrees is too much difference. Try and get them within 3 degrees of each other or you're going to eat u-joints...
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Phasers at "stun"

Yep, sure do look to be out of phase to me.



Axis of "U" joint crosses MUST be in the same plane.

 

Okay I think I'm getting the concept of all this drive line stuff....... maybe... I have the drive shaft phase part fixed. I've got rear u joint in decent shape but now I need to get the t case closer... I guess I'm kind of up against a wall right now!! I've already dropped it 5/8" on top of the factory t case shims and when I used my floor jack as a temporary "shim" it looked as if I would need to drop around 3" total. Well here lies the problem... If I do that 1: Isn't my engine way to far off the correct 5 degree angle?? 2: 1st and 3rd gear shifting hit my center counsel. 3: Radiator and fan are thinking about getting close to each other. 4 that's a huge spacier!!!! 5: ground clearance if that really maters for the few off road trips I take. So I guess the way I look at it; spend $200 plus on a new drive shat, or drop the t case more, or deal with what I got and replace u joints as they go out..... And when I tired of doing that order the drive shaft lol. What would you guys do on a rig that sees maybe 2k miles a year????? Live in Iowa doesn't fit in the garage with the top on so it's getting sold, oh and no heater. Took it out, it was leaking.....chainsawguy

 

I may be setting myself up for a lot of criticism, but I think this dropping the transfer case is the wrong approach for your problem. You don't have to get the driveshaft straight in line with the Xfer case output, you just need the angle between the case/shaft to be the same as the angle of the diff/shaft. As long as the angles on either end aren't excessive, you should be fine. On the other hand, if both angles are the same but excessive, then you'll go through U joints at a quicker pace. I'm thinking you put the xfer case back where it started, measure the case/shaft angle, then put in rear spring shims, as I mentioned before, to get the diff/shaft angle the same, or close to, the case/shaft angle. If the angles are excessive, dropping the transfer case a little then shimming the rear springs to get the same angle on both ends, would help reduce the problem.
I hope I'm not misunderstanding your situation, but from how I understand it, this seems the way I would go.

 

:iagree: