U-joint angles, what's too much?

[b3uhbp]

I have a slight vibration when drive train is under a load. The DS is new and the working angles of the front and rear ujoints are within .5-1.0 degrees of each other but I still have the vibe. The angles are about 13-13.5 degrees. Is that just too much? Am I going to be forced to a DC shaft?

 

[Torxhead]

You could try to add a angle shim under the rear spring pads. I am not sure what angle to recommend, whatever is in the kits that they come with. A dc driveshaft does require that the pinion angle be the same as the driveshaft.

 

[Peanut Butter]

Tom Wood's Drive Shafts has a Tech site. Really good stuff. Here's the link: Tom Wood's Custom Drive Shafts - Tom Woods Custom Drive Shafts Custom Driveshafts Specialist

 

[b3uhbp]

I have viewed the Rom Woods site. Excellent! I spoke with an expert shaft guy yesterday. He advised me to continue to experiment but that 13* is pushing the envelope and may be hard to find the sweet spot. The only alternative is a double card on shaft. $450.

 

[Torxhead]

I am surprised that a CJ7 would require that type of driveshaft with only a 2 1/2" lift. I once had a Rancho 2 1/2" lift and it was fine even w/o any shims or lowering the Transfer Case .

 

[Belizean]

I've had the 2 1/2 Rancho for maybe 28 years w/o shims and no problems

 

[b3uhbp]

I am surprised that a CJ7 would require that type of driveshaft with only a 2 1/2" lift. I once had a Rancho 2 1/2" lift and it was fine even w/o any shims or lowering the Transfer Case .

Mine is also a Rancho lift. I guess the vibration could be caused by something else but I doubt it.

 

[b3uhbp]

Mine is also a Rancho lift. I guess the vibration could be caused by something else but I doubt it.

To put things in context, when I bought the jeep it had the Rancho 2.5" lift and the rear diff had 4* shims to point the diff toward the tfer case. The center lines of the diff and tfer were off by 6.5* but I had no noticable vibration. After I replaced the clutch and tranny mount I noticed the vibration. I removed the 4* shims from the rear and the vib improved greatly but the u joint angles were still 2.5* off so I added 2* shims to tilt the diff down 2* and the vib improved more. The diff and tfer case are now within .5* and I only have a vib when drive train is under load.

 

[Lumpy Grits]

With my lift to clear 33's. Along with the my 9" rear. I still run 2 U-joint rear DS with no 'vibes' at all. I did have the pinion rotated up 4* when the axle was built by Currie.
Has the d'shaft been balanced?
May need to remove this shaft, and check it on a surface plane for run-out and twist.

LG

 

[b3uhbp]

With my lift to clear 33's. Along with the my 9" rear. I still run 2 U-joint rear DS with no 'vibes' at all. I did have the pinion rotated up 4* when the axle was built by Currie.
Has the d'shaft been balanced?
May need to remove this shaft, and check it on a surface plane for run-out and twist.

LG

Well this update has good news and bad news. First the good news. I decided to do the cheap thing and replace the motor mounts since it's cheap and not too big is a pain. As far as I can tell it fixed the vibration problem. The bad news is I'm stupid. Should have done this long ago. Just goes to show you, you can't tell if mounts are good by sight.

 

[Lumpy Grits]

BTDT-Part of the learn'n curve.
Let me suggest you also replace the tranny mount with one of the polymer mounts.
If also been using the M.O.R.E. made engine mounts. Pricey-But a one time buy.
https://www.mountainoffroad.com/jeep-cj/cj-motor-mounts.html
LG

 

[b3uhbp]

BTDT-Part of the learn'n curve.
Let me suggest you also replace the tranny mount with one of the polymer mounts.
If also been using the M.O.R.E. made engine mounts. Pricey-But a one time buy.
https://www.mountainoffroad.com/jeep-cj/cj-motor-mounts.html
LG

Did it.