The Yj has a Cherokee engine, trans, and tcase. I have replace the driveshaft u-joints, the driver side engine mount, the passenger side has been inspected no excessive movement, and the transmission mount has inspected for separation. When I took the skidplate off to inspect the trans mount, the mount moved away from the bolt holes, needing a ratchet strap to make them lineup again to put the nuts back on (I would say that is do to it being rolled three times by the previous owner).
Takeoff shudder causing transferase to move side to side.
- Thread starter BADJOOP
- Start date
Take a picture of the rear driveshaft from the side, capturing both u-joint angles. Stuff like that usually happens when the angles are not correct (parallel) and they start fighting each other.
Any lift?
The part about needing a ratchet strap to get the transmission mount into the skid slots is interesting, though I doubt that would make a difference in this case, although maybe if the frame is tweaked so badly that it has added a horizontal element to screwing up the driveshaft angles.
Any lift?
The part about needing a ratchet strap to get the transmission mount into the skid slots is interesting, though I doubt that would make a difference in this case, although maybe if the frame is tweaked so badly that it has added a horizontal element to screwing up the driveshaft angles.
Well there’s the problem. On a straight 2-joint driveshaft like that you can’t have 7° angle at one end and 18° at the other.
Show how you're measuring 18 degrees on the rear axle. Stock angle is like 6 degrees.....something aint right if you're getting 18 with no shims. Maybe somebody rewelded the perches to run an SYE and double cardan shaft.
The leaf springs do have a shim from the lift. Also The Joop did have a SYE with a old Transferase made for a manual but PO told me that it had a vibration a 45 mph. I don't know if I can open both the transfer cases to swap input shafts to be able to use the old one with the auto trans.
Shims are not correct if you're using a factory driveshaft. Especially not a shim that large. The PO could have had vibrations with the SYE for a number of reasons. It's possible that huge shim on the springs wasn't correct for that setup.
You can take the SYE out of your old transfer case and put it in the new XJ transfer case. I would do that, reevaluate the angles and change the shim if needed (likely), and then lastly try a new driveshaft.
You could try to ditch the shim and run the stock driveshaft, but the stock driveshaft does not like much added angle. I would drop the suspension to stock height or close to it if I were going to do something like that.
If the pinion is 6* factory would you recommend taking out these in theory 12* shims and running 1* of driveshaft slope. Or If I can find 2* shims and install them backwards to remove 2* of pinion and have 3* of driveshaft slope?
The pinion angle from factory is with the perches welded as they are....not with 6 degree shims.
Don't worry about the driveshaft slope for now. You need to get the angles of the joints themselves right. Your transfer case is at 7 degrees as you mentioned earlier, and that isn't changing. to run a stock driveshaft, you need your axle pinion angle to be around 6 degrees. the 1 degree difference in angles is to account for torque under load. This is how the factory set it up.
The problem is that you have lift, and lift makes the angles on that super short driveshaft problematic...you could install a transfer case drop kit which lowers the transfer case and also angles it down....if you did that, you would need to add probably about 2 degree of shim to the springs (after removing the 12) , to account for lowering the transfer case and matching its new angle.
for lifted Jeeps, the stock driveshaft is not a fantastic solution due to the angle restrictions. In stock form, the stock driveshaft is great and has no need for any improvement.
Flyer58
YJ Enthusiast
I think I've posted this before and the video shows a good example of what happens when the angles are not correct and not properly phased..
I’m not sure you’re understanding how all this works. A 3 degree shim backwards will not be proper at all for a slip yoke eliminator and double cardan. A slip yoke eliminator and double cardan needs the pinion pointed up at the transfer case. But not up as high as it was pointed.
You also don’t need to keep measuring the driveshaft angle, that doesn’t really tell you anything useful except for the angle the joints are operating at. The important thing is angles need to be parallel if running a stock shaft, or you need to get the pinion straight to the driveshaft if using a double cardan shaft.
As I said, stock shaft won’t work very well and so you should use the slip yoke eliminator and double cardan, like you’re planning to. In that case, you need to install the SYE and DC shaft, and evaluate your pinion angle at that point. Installing a 3 degree shim backwards is not the right move for SYE and DC.
No, that will be too high. A SYE changes the length of the rear driveshaft. You need to get the SYE installed first before you can do any planning for angles.
I don’t know what lift or transmission and engine you have but typically 6° shims for SYE and 2.5” lift is about right. But you need to get converted to SYE before planning anything. The stock driveshaft doesn’t give you the ability measure anything.