• Welcome to the new NAXJA Forum! If your password does not work, please use "Forgot your password?" link on the log-in page. Please feel free to reach out to [email protected] if we can provide any assistance.

Driveline vibes after new gears

DMS3XJ

DMS3XJ

NAXJA Forum User
Location
Monterey Bay
I got new gears put in today, 4.88 on newish 32's, I already know that its low for my tire size, but hey I drive slow anyways. On the way home I experienced significant drive-line vibes for the first time. I was driving (what I'm guessing was around 60) on the highway and feeling vibrations through the floor.

I know I should expect to notice vibrations with lower gears at the same speeds, but what I don't understand is why I did not have them before when I was turning the same RPMs in the same gear with stock gearing ratios?

My question is could this be just a re-balancing issue for the rear drive shaft or am I just going to hear that I need an SYE. An SYE is in the future when money permits, but I will be happy if I can tame the vibrations in the mean time.

BTW I have an 89xj with NP242 rear-D44 and 4.5" rough country lift with transfer case drop.
 
The operating angles haven't changed but the driveshaft spins faster at the same vehicle speed. The higher speed will stress parts operating at questionable angles more. There is always the possibility that the gear install is the problem. The simplest things to do are try rotating the driveshaft 180 in the rear yoke, remove the driveshaft, and then check balance.
 
Also, condition of your u-joints and associated hardware can have a factor in this. Maybe check and make sure yoke and pinion bolt is tight.
 
md21722 said:
The operating angles haven't changed but the driveshaft spins faster at the same vehicle speed. The higher speed will stress parts operating at questionable angles more. There is always the possibility that the gear install is the problem. The simplest things to do are try rotating the driveshaft 180 in the rear yoke, remove the driveshaft, and then check balance.
Click to expand...


How do you check the balance on the drive-shaft?
 
You can run the vehicle with the vehicles off the ground and look; take it to a driveshaft shop if it looks questionable or is out of balance. It shouldn't move around much at all.
 
md21722 said:
You can run the vehicle with the vehicles off the ground and look; take it to a driveshaft shop if it looks questionable or is out of balance. It shouldn't move around much at all.
Click to expand...

And just to clarify those last instructions, by rotate diveshaft 180 in rear yoke, remove driveshaft, check balance you mean to disconnect from rear u-joint, rotate rear yoke 180 degrees, reattach to u-joint and then run on jack stands looking for any motion outside the plane of rotation?

Sorry if this is obvious to most.
 
I would put jack stands under there rear axle and put the transmission in neutral and confirm there is no play in the u-joints.
Then I would start the engine and let it idle in drive and look at the driveshaft for imbalance. Then I would use the brakes to stop the wheels from turning, put the vehicle in park, shut off the engine.
Then I would turn the rear u-joint 180 degrees in the yoke and repeat the idle in drive test.

The driveshaft should not be moving around very much, but it may not appear smooth as glass. Make sure the yokes and output shaft of the transfer case are not moving around. When changing gears, the most likely thing is that the driveshaft and yoke position was put out 180 degrees. It is also possible that there was a problem with the gear install, such as a pinion seal spring that came dislodged and the pinion yoke isn't sitting against the outer pinion bearing correctly, or worse, such as a cup/cone not seated correctly on install.
 
md21722 said:
I would put jack stands under there rear axle and put the transmission in neutral and confirm there is no play in the u-joints.
Then I would start the engine and let it idle in drive and look at the driveshaft for imbalance. Then I would use the brakes to stop the wheels from turning, put the vehicle in park, shut off the engine.
Then I would turn the rear u-joint 180 degrees in the yoke and repeat the idle in drive test.

The driveshaft should not be moving around very much, but it may not appear smooth as glass. Make sure the yokes and output shaft of the transfer case are not moving around. When changing gears, the most likely thing is that the driveshaft and yoke position was put out 180 degrees. It is also possible that there was a problem with the gear install, such as a pinion seal spring that came dislodged and the pinion yoke isn't sitting against the outer pinion bearing correctly, or worse, such as a cup/cone not seated correctly on install.
Click to expand...


Thank you for going into detail. I will try to get around to this this week and put up what I find on the thread for anyone else who may come across this later.
 
You must log in or register to reply here.

Similar threads

S
Work in what order to fix driveline vibes?
Replies
15
Views
5K
denverd1
denverd1
I
Bought Son 2000 XJ, Need Help with RC Lift
2 3
Replies
45
Views
6K
Tim_MN
Tim_MN
R
thinking about getting an XJ again
Replies
9
Views
281
XJI6191
X
2
Dana 44 front axle question
Replies
12
Views
3K
2T2-Crash
2
U
Drive Line Vibration Driving Me Crazy
2
Replies
22
Views
6K
RCP Phx
R
Back
Top