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Unread 08-25-2004, 06:18 AM   #1
jeep1703
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Vibration at 45 MPH

Hey guys got a question for yall hope someone can help. Let me start off by telling you what I am running. I have a 90 Model YJ with a 4.2 and automatic transmission. Have the stock gears and running 33" tires. OK when I am running at 45 MPH I get this vibration in the dash, well actually all over. Now if I let off the gas down to about 40 or speed up to about 50 all of the vibration goes away. I though that it might be the transmission lugging from having the bigger tires but I still have power when I give it a little gas. I also had the idea that maybe the driveshaft has gotten out of balance somehow. But that raises another question can a drive shaft just go out of balance, and if it does will it vibrate at just certain speeds. I also think but not for sure it might be in the transmission which has 155,000 miles on it. I don't know any help would be appreciated.

Thanks,

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Unread 08-25-2004, 06:22 AM   #2
CAJUN_YJ
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lift

Are you running any lift?
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Unread 08-25-2004, 07:09 AM   #3
jeep1703
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Ya I have a 3.5" BDS suspension lift.
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Unread 08-25-2004, 08:20 AM   #4
BamaJeeper
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You have a toasted u-joint.
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Unread 08-25-2004, 09:01 AM   #5
jeep1703
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Thanks guys I will check my U-joints and let you know.
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Unread 08-25-2004, 12:40 PM   #6
OlllllllO Jeep1
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Quote:
Originally Posted by jeep1703
Hey guys got a question for yall hope someone can help. Let me start off by telling you what I am running. I have a 90 Model YJ with a 4.2 and automatic transmission. Have the stock gears and running 33" tires. OK when I am running at 45 MPH I get this vibration in the dash, well actually all over. Now if I let off the gas down to about 40 or speed up to about 50 all of the vibration goes away. I though that it might be the transmission lugging from having the bigger tires but I still have power when I give it a little gas. I also had the idea that maybe the driveshaft has gotten out of balance somehow. But that raises another question can a drive shaft just go out of balance, and if it does will it vibrate at just certain speeds. I also think but not for sure it might be in the transmission which has 155,000 miles on it. I don't know any help would be appreciated.

Thanks,
I have this same prob but all my u-joints and axle joints are fairly new, What I dont get is when I downshift into 3rd it goes away, So basically I can go the same speed in the lower gear and not get the vibration. That leads me to believe that the engine is out of its powerband. But then again I am not a mechanic. Let us know what you find. I have a 91 YJ with a 3" lift and a Transfer case drop and 32x11.50 inch Goodyears.
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Unread 08-25-2004, 03:00 PM   #7
GreenReaper93
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I'm not sure where I read it, but after you lift your vehicle your suppose to loosen your tranny from the skid plate, take it around the block then tighten it back up. I'm guessing it settles the tranny for the new angle? Anyone heard this, or an I actually losing it.....
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Unread 08-25-2004, 05:36 PM   #8
BIG KEV
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I have this problem too. My vibration ( more like wobble) seems to be coming from the front. My front wheels seem to wobble side to side moving the front end of the jeep.

I have a 95 yj with a BDS 3.5in lift, tranfer case drop, sye and new tom woods drive shaft, and 33x12.5's.

HELP?????
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Unread 08-25-2004, 05:42 PM   #9
TSEJEEPERS
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If you have had the lift on for a while and did not have any problem when it was installed check to see if your tires are balanced, u joints, and transmission mount. If you still have the stock transmission mount replace it. You will have to adventully anyway. Also check your tie rod ends and alignment. As always start with the cheapest thing and move on.
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Unread 08-26-2004, 04:27 AM   #10
BamaJeeper
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Quote:
Originally Posted by GreenReaper93
I'm not sure where I read it, but after you lift your vehicle your suppose to loosen your tranny from the skid plate, take it around the block then tighten it back up. I'm guessing it settles the tranny for the new angle? Anyone heard this, or an I actually losing it.....
Bad idea! That's a good way to destroy the motor mounts. The only reason to loosen the tranny mount and "settle" it would be if a motor mount lift were installed but you sure a hell would'nt want to drive it with a loose mount.
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Unread 08-26-2004, 04:30 AM   #11
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Quote:
Originally Posted by BIG KEV
I have this problem too. My vibration ( more like wobble) seems to be coming from the front. My front wheels seem to wobble side to side moving the front end of the jeep.

I have a 95 yj with a BDS 3.5in lift, tranfer case drop, sye and new tom woods drive shaft, and 33x12.5's.

HELP?????
Stick your head out and watch the tires while you drive. If the they shimmy then it's time for new tie rod ends.
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Unread 08-26-2004, 04:32 AM   #12
BamaJeeper
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Quote:
Originally Posted by OlllllllO Jeep1
I have this same prob but all my u-joints and axle joints are fairly new, What I dont get is when I downshift into 3rd it goes away, So basically I can go the same speed in the lower gear and not get the vibration. That leads me to believe that the engine is out of its powerband. But then again I am not a mechanic. Let us know what you find. I have a 91 YJ with a 3" lift and a Transfer case drop and 32x11.50 inch Goodyears.
How new is "fairly new"? Get under there and give those u-joints a good shake. Got slop? If you do it's time for new u-joints.
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Unread 08-27-2004, 04:45 PM   #13
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Thanks for the help! I'll check the tie rod ends. By the way how do I do that?
Thanks

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Unread 09-21-2004, 03:38 PM   #14
mbiusa
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Vibration through transmission

" have a 90 Model YJ with a 4.2 and automatic transmission. Have the stock gears and running 33" tires. OK when I am running at 45 MPH I get this vibration in the dash, well actually all over. Now if I let off the gas down to about 40 or speed up to about 50 all of the vibration goes away. I though that it might be the transmission lugging from having the bigger tires but I still have power when I give it a little gas."

I have 90 YJ 4.2 Auto with 4" lift and 33" tires and have exactly the same symptoms. My local 4-wheel drive garage mentioned it was more typical with auto transmission as the auto box is longer and that makes the angle of drive shaft universal joints to rear end more acute. Lifting the vehicle caused the problem in the first place, the fact that its got an auto box makes it worse. Although joints maybe going, they will go again unless you can reduce angle of drive shaft joints by dropping transfer box using spacers (washers) - that is what I was told - hope this helps!
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Unread 09-21-2004, 04:03 PM   #15
tobias94yj
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Quote:
Originally Posted by BamaJeeper
Bad idea! That's a good way to destroy the motor mounts. The only reason to loosen the tranny mount and "settle" it would be if a motor mount lift were installed but you sure a hell would'nt want to drive it with a loose mount.

if you do a tc lowering kit then you will have to loosen those bolts where the tranny mounts the the skid plate. I could not get mine into 2, 4, or reverse until i did that. then i ditched the tc lowering kit and did the sye
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