Have a lot of vibration at 60+. I removed the rear driveshaft and the vibration was gone. Replaced u-joints in the rear driveshaft but vibration persisted. Replaced with a new rear driveshaft and the vibration is still there. What’s next to check?
Driveline vibration
- Thread starter BamaJeep
- Start date
Even with a 2" lift, it can change pinion angle and cause vibes with the rear shaft. If the previous owner didn't correct it after the lift install, you'll have to correct on your own. Some ignore vibes, but they should always be corrected when possible. Does it have a transfer case drop? Take a pic of the belly between the wheels and post here for us to see. If there are spacers dropping the transfer case skid plate in the middle down further than stock, then that is what is going on. If it doesn't have this or it is lowered excessively, then I am not surprised that you may have rear DS vibes from the pinion angle being off. There are several ways to correct the pinion angle, if that is what you find indeed is wrong.
A little transfer case drop is the easiest/cheapest/fastest way, but is not recommended as the "best" choice since you'll lose clearance offroad at the "tummy". It only needs to dropped about 3/4" or so typically. On newer TJ's it seems to be more like an 1", but it all depends on the lift and how much height it yielded to throw things off.
Other things that can be done to correct pinion angle are:
1) motor mount lift (MML)
or
2) SYE, double cardan rear driveshaft, and adjustable rear control arms (most proper but most expensive way).
or
3) Remove the lift and go back to stock.
If you search a bit on these items and read up, you'll start to learn what happens when you lift a Jeep, even if only 2".
A little transfer case drop is the easiest/cheapest/fastest way, but is not recommended as the "best" choice since you'll lose clearance offroad at the "tummy". It only needs to dropped about 3/4" or so typically. On newer TJ's it seems to be more like an 1", but it all depends on the lift and how much height it yielded to throw things off.
Other things that can be done to correct pinion angle are:
1) motor mount lift (MML)
or
2) SYE, double cardan rear driveshaft, and adjustable rear control arms (most proper but most expensive way).
or
3) Remove the lift and go back to stock.
If you search a bit on these items and read up, you'll start to learn what happens when you lift a Jeep, even if only 2".
Yeah, she's definitely dropped. The transfer case should be up against the frame. It's hard to tell from the picture how far it is dropped, but it seems a bit excessive to me. Is it 1" or more in the gap? If you drop it too far, it can also cause vibes (i.e. lowered past the sweet spot). Perhaps some of the experts here can chime in on what they see.
It would also be good to measure your current spring height. If you measure the length of the front and back coil springs, we'll see how much lift you actually have currently. There are several threads around that address how to measure etc. , so I won't go into details. You just compare to stock spring lengths to get your lift height.
It would also be good to measure your current spring height. If you measure the length of the front and back coil springs, we'll see how much lift you actually have currently. There are several threads around that address how to measure etc. , so I won't go into details. You just compare to stock spring lengths to get your lift height.
It’s a 1 1/2 inch drop so you think I might try to decrease that and see if it improves? Is the mount or bushing that I took a pic of above that mounts the transmission to the skid plate supposed to be there?
Yeah, if that coil is 14”, then your lift would be 2” in the front as you suspected. Rear coil would be 10” for a 2” lift, so I’d double check that as well (sometime different spring lengths in front and rear are used to correct “rake”). Changing the transfer case drop to 7/8” to 1” would be much closer to what should needed to correct for a 2” lift.
You can also look at your rear pinion angle, learn about what is correct (there are pics and some guides for this), and then envision what will happen when you raise the t-case skid plate back up a bit. If all still makes sense to correct the angle, I would definitely recommend raising the t-case to do so.
The one pic you asked about looks normal to me the way it mounts, but it is kind of dark for me to see really well on my monitor.
P.S. it looks like it has been POR15’ed, i.e. painted over frame rust etc. Hopefully everything is solid underneath the coating?
You can also look at your rear pinion angle, learn about what is correct (there are pics and some guides for this), and then envision what will happen when you raise the t-case skid plate back up a bit. If all still makes sense to correct the angle, I would definitely recommend raising the t-case to do so.
The one pic you asked about looks normal to me the way it mounts, but it is kind of dark for me to see really well on my monitor.
P.S. it looks like it has been POR15’ed, i.e. painted over frame rust etc. Hopefully everything is solid underneath the coating?
Thank you, mots, for so much information. I now know what to read up on and what to look for. As for the undercoating, the frame is solid as far as I can tell. There are a few spots I have found where they didn’t clean the loose rust off prior but I plan to scrape and then recoat those areas.
Thanks again. You are appreciated.
Thanks again. You are appreciated.
Hit those spots with a hammer and see what mind of noise they make. A nice, solid, ting is good. A dull sounding thud means the metals less likely to be in good shape.
Pinion angle sounds like the culprit. Maybe just like the camera making a person look fatter, it sure does look like there is more than a few spots of corrosion. Be wary.
Is it me or does the transfer mount look crooked? Haveent had my coffee yet but it seems like the mou t is pinched over on an angle.
Thanks guys for the advice. I’m planning to go over the frame really well as soon as I get this vibration issue resolved.
Goatman, that’s why I posted the pics. I want to make sure everything is how it should be and since I’m new to Jeeps, I’m counting on the skilled eyes of those here for help.
Thanks all for your help so far with this issue. Gonna decrease the transfer case drop tonight and see what happens.
Goatman, that’s why I posted the pics. I want to make sure everything is how it should be and since I’m new to Jeeps, I’m counting on the skilled eyes of those here for help.
Thanks all for your help so far with this issue. Gonna decrease the transfer case drop tonight and see what happens.
Somewhat off topic, but either you drove through some really wet weather, or you have a pretty serious fluid leak
Had a pretty good transmission fluid leak. Got it resolved earlier this week
Glad you got that resolved! Where was it leaking from?
