Help! EXTREME road shudder!
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Senior User
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Help! EXTREME road shudder!
'66 Merc longbox
240 with three-on-the-tree
I'm experiencing some major vibrations from the old girl lately...
Shift and take off in first is just fine, but as soon as I shift into second the shuddering starts. Shifting into third also has the same result up until I get to about 30-40mph. When I get to this speed and release the gas pedal very quickly it stops the vibration and she drives smooth...only to return again when I begin to slow down.
Also, if I downshift from third to second, I get a heavy 'clunk' (sorry for being so technical there).
Any direction of where to start would be helpful. I've checked my u-joints and they seem to be fine. I wondering if it's something in my transmission or perhaps my rear axle??
Chad
240 with three-on-the-tree
I'm experiencing some major vibrations from the old girl lately...
Shift and take off in first is just fine, but as soon as I shift into second the shuddering starts. Shifting into third also has the same result up until I get to about 30-40mph. When I get to this speed and release the gas pedal very quickly it stops the vibration and she drives smooth...only to return again when I begin to slow down.
Also, if I downshift from third to second, I get a heavy 'clunk' (sorry for being so technical there).
Any direction of where to start would be helpful. I've checked my u-joints and they seem to be fine. I wondering if it's something in my transmission or perhaps my rear axle??
Chad
Lead Driver
Joined: Oct 2004
Posts: 8,062
Likes: 35
From: Central Oregon
It sounds like a u-joint, how did you check them? The way I check a u-joint is to jack up the truck, getting both rear wheels off the ground, then check the drive line. Also you may have a bad clutch spring. But with the "clunk" I would look into the u-joints first.
Postmaster
Joined: Apr 2002
Posts: 3,613
Likes: 6
From: Coal country
Check for driveshaft problems, such as bends or dings.
Look for fresh scuff marks or bright metal scrapes indicating you may have hit somthing.
Check your carrier bearing as well, and the slip joint in the driveline.
Check the play in your rear end's input shaft with the truck parked, brakes lock and in gear. There should be only very small amount -if any- of play in the input shaft.
Check your rear wheel bearings. Jack the axle up and attempt to move the wheel up and down. If it does, you'll need to have the bearings replaced.
Hopefully, it is something simple!
Look for fresh scuff marks or bright metal scrapes indicating you may have hit somthing.
Check your carrier bearing as well, and the slip joint in the driveline.
Check the play in your rear end's input shaft with the truck parked, brakes lock and in gear. There should be only very small amount -if any- of play in the input shaft.
Check your rear wheel bearings. Jack the axle up and attempt to move the wheel up and down. If it does, you'll need to have the bearings replaced.
Hopefully, it is something simple!
Fleet Mechanic
Joined: Jan 2004
Posts: 1,465
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From: Southern Alberta
Chad.
Do what Bertha 66 and John da Picker says. My uni's front u-joints were shot, but parked and in gear they seemed tight. You have to get the back wheels off the ground and then check, in fact the way we tested mine was to have the wheels off the ground and solidly on jack stands, then I started the truck and ran it in gear , with my buddy watching the driveshaft flop around like a chicken with it's head cut off. The symptoms are identical to mine for your truck, I'd vote u-joints too.
PS, mine had a single driveshaft, yours, if stock, has 2 -a short one and a long one. could be any or all of those 4 u-joints.
RF
Do what Bertha 66 and John da Picker says. My uni's front u-joints were shot, but parked and in gear they seemed tight. You have to get the back wheels off the ground and then check, in fact the way we tested mine was to have the wheels off the ground and solidly on jack stands, then I started the truck and ran it in gear , with my buddy watching the driveshaft flop around like a chicken with it's head cut off. The symptoms are identical to mine for your truck, I'd vote u-joints too.
PS, mine had a single driveshaft, yours, if stock, has 2 -a short one and a long one. could be any or all of those 4 u-joints.
RF
Last edited by Ringo Fonebone; Aug 25, 2005 at 08:32 PM.
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Thanks for the help so far guys!
I inspected the shaft carefully, and it does not show indication of being struck by something. The carrier bearing is new, but I also inspected that to ensure it was not the issue. Will check the input bearing though!
Also, will jack up the truck as suggested and see if it does in fact 'flop around like a chicken with it's head cut off' as mentioned.
Much thanks to bertha66, banjopicker66, instig8r63 and Ringo for the advice!
Chad
I inspected the shaft carefully, and it does not show indication of being struck by something. The carrier bearing is new, but I also inspected that to ensure it was not the issue. Will check the input bearing though!
Also, will jack up the truck as suggested and see if it does in fact 'flop around like a chicken with it's head cut off' as mentioned.
Much thanks to bertha66, banjopicker66, instig8r63 and Ringo for the advice!
Chad
