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Slight jitters on acceleration

X

XJ91

NAXJA Forum User
Location
G'Nagiwanka
I finally got the rear of my RE6025 in (3.5"/full leafs) Neghbours think I'm a hick now, the heep lifted in the rear for now.

I noticed this morning slight shaking on initial acceleration, Is this what is refered to as DW? or should I be looking at droping the TCase or use degree shims in the rear?

Another thing I noticed was going over a bump or turning into my driveway, I hear a thump comming from the passenger side rear. I'm hoping it's just the bar pin, which I'm going to eliminate using the rear sway bar mounts.
 
XJ91 said:
I finally got the rear of my RE6025 in (3.5"/full leafs) Neghbours think I'm a hick now, the heep lifted in the rear for now.

I noticed this morning slight shaking on initial acceleration, Is this what is refered to as DW? or should I be looking at droping the TCase or use degree shims in the rear?

Another thing I noticed was going over a bump or turning into my driveway, I hear a thump comming from the passenger side rear. I'm hoping it's just the bar pin, which I'm going to eliminate using the rear sway bar mounts.
Click to expand...

Do you have an SYE? If so, I'd guess the bolts from the driveshaft to the flange are loose.
Billy
 
JeepFreak21 said:
Do you have an SYE? If so, I'd guess the bolts from the driveshaft to the flange are loose.
Billy
Click to expand...
No SYE, what bolts ya talking about? I'm hoping with my '91XJ & 242 I won't need a SYE.


Okie Terry said:
If you didn't think you were going to die, then it wasn't death wobble.
Click to expand...

Not death wobble by any means..

I took it for a good 2 hr jont on the highway. He's what I noticed:

1) Picking up speed I got the shakes, say 0-25/30 miles
2) Anything above 30 right up to 75, I was fine.
3) on decell (take my foot off the gas) I can almost feel the TC under my
feet vibrating.
4) When I got home my left arm felt like I was holding a cut-off grinder.
 
XJ91 said:
No SYE, what bolts ya talking about? I'm hoping with my '91XJ & 242 I won't need a SYE.

Not death wobble by any means..

I took it for a good 2 hr jont on the highway. He's what I noticed:

1) Picking up speed I got the shakes, say 0-25/30 miles
2) Anything above 30 right up to 75, I was fine.
3) on decell (take my foot off the gas) I can almost feel the TC under my
feet vibrating.
4) When I got home my left arm felt like I was holding a cut-off grinder.
Click to expand...


Make sure all your suspension bolts are tight - otherwise that just sounds like the vibes you get after lifting your rig. Try a t-case drop.
Billy
 
Might be a long shot, but I ran into this installing my homemade t-case drop/crossmember/skidplate. If any part of the drivetrain (well... trans/t-case) isn't securely fastened via intact rubber mount, you could be transmitting vibes into the body of your XJ. One corner of my t-case was hitting the skid upon startup and hard accel, and it sent some shimmies and shakes right into my floorboards. As it turned out, the t-case mount was worn and replacing it fixed it for me. So, while you are checking all the bolts down there, see if anything is touching a skid or crossmember.

-Rich
 
If you have a vibration on low speed acceleration, it is very likely a driveline vibe, caused by the pinion rotating up slightly from the torque of acceleration. Use some small degree shims to lower the pinion a little and see how it does.
 
Goatman said:
If you have a vibration on low speed acceleration, it is very likely a driveline vibe, caused by the pinion rotating up slightly from the torque of acceleration. Use some small degree shims to lower the pinion a little and see how it does.
Click to expand...

I'm not that much of a techie, you need to enlighten me.
Where would I put the * shims? Where would I find this "pinion"?

ThanX
 
XJ91 said:
I'm not that much of a techie, you need to enlighten me.
Where would I put the * shims? Where would I find this "pinion"?

ThanX
Click to expand...
The pinion is the pinion shaft that is in your rear end (or any differential housing for that matter). It is the part of the axle assembly that has the u-joint yoke on it. It has gears on it and transfers the energy given by the driveshaft to the ring gear which then is sent to the axles and wheels.

The shims are flat tapered pieces of metal that mount between the leaf spring pack and the spring perch on your rear axle. depending on the orientation of the shims, the pinion shaft will be rotated up or down.
 
OKay, I understand now...

Do I get these at any 4x4 supply shop? And do I ask for certain degree's?

I have read post where people have used 4* or 6*, can I assume this is true for mysefl?
 
Since it's only on acceleration, the overall u-joint angle must be close to what it needs to be. Start with a 2* shim. Do a search of various 4x4 supply vendors to find one who sells various degree shims. Install the shim backwards, big end facing forward, beneath the leaf spring pack.
 
In the mean time while I hunt down * SHIMS, Will harm be done to my Heep driving with the vibes? I'm luck if I put 10/20 miles a day on it.
 
did i read your initial post correctly? did you lift the rear only??? and not the front? the vibes are most likey from the pinion angle needing to be adjusted a lil, but a t/case drop might be all you need... i have 3.5" springs and an extended shackle in the rrear and i have no vibe issues at all, it seems the new arch in the leaves combines with the shackle seem to have matched the t/case output pretty closely...
 
sidriptide said:
did i read your initial post correctly? did you lift the rear only??? and not the front? the vibes are most likey from the pinion angle needing to be adjusted a lil, but a t/case drop might be all you need... i have 3.5" springs and an extended shackle in the rrear and i have no vibe issues at all, it seems the new arch in the leaves combines with the shackle seem to have matched the t/case output pretty closely...
Click to expand...

Yes, rear only for now as time permits I'll do the front.
I believe around here it's called, Yucca-Man Lift LOL

Would it not be easier to add degree shims? As I've read and heard horror stories of people running into problems with a T-Case Drop.

With problems I've had over the last 10 days or so, I'd rather put shims in.
 
XJ91 said:
Yes, rear only for now as time permits I'll do the front.
I believe around here it's called, Yucca-Man Lift LOL
Click to expand...
happyfinger.gif


Since you don't have an SYE you need to make sure the face of the rear-axle pinion is parallel to the face of the t-case output. That ensures the operating angles of the u-joints are the same, which should stop your vibrations. However, if you have an old set of u-joints in there already, they may vibrate even if the angles are correct - simply because they're old and 'set' in their ways. If the u-joints are old or you question them I'd say replace them just to get that variable out of the way.
 
Yucca-Man said:
happyfinger.gif


Since you don't have an SYE you need to make sure the face of the rear-axle pinion is parallel to the face of the t-case output. That ensures the operating angles of the u-joints are the same, which should stop your vibrations. However, if you have an old set of u-joints in there already, they may vibrate even if the angles are correct - simply because they're old and 'set' in their ways. If the u-joints are old or you question them I'd say replace them just to get that variable out of the way.
Click to expand...

Just play'n with ya. :thumbup:

I read some where that I should replace my u-joints cuz "there set in there ways"

I just found an install instruction sheet for T-Case Drop.... :doh: I thought that would have been more work than putting * shims in.

I have 1/4" thick washers, I think I'll give that a try first. The Jeep funds (wife) :D are getting pretty tight.
 
You may also be about ready to lose your output yoke. If you can see a whole lot of shiny silver on the yoke, it may not have much spline engagement left in which case it can get cock-eyed and wobble. This would explain some low speed vibration and noise. The stock yoke doesn't have much clearance available for the driveshaft yoke at +3" of lift either.

If this is part of your problem, it's not a good thing to be driving.
 
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