Thump and bump
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New User
Joined: Mar 2004
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From: arizona
Thump and bump
Hello All,
Have a problem that I have researched on FTE But to no avail..
When accelerating from a stop a thump is herd and "Felt" towards the rear of the truck.
95 F-150 4X4 Rancho Lift 97,000 miles.
I replaced the trans mount and the engine mounts and the thump still is there.
Took it to a Four wheel shop today and the Tech had no idea what was causing it.
He recommended a trans shop. I have read quite a few Fixes but nothing definative. All bushings, mounts, and springs are intact. Trans has 30,000 on it and no leaks.
So far I have a list for the Trans shop to consider;
Slip yoke Lube
Trans Modulator
Vacume lines on trans
Drive shaft
U-joints
Trans not Dropping into 1st gear when coming to a stop.
Filter and fluid change
Trans tailshaft bushings loose
Carrier bearing on driveshaft.
Suggestions welcome!!
J.
Have a problem that I have researched on FTE But to no avail..
When accelerating from a stop a thump is herd and "Felt" towards the rear of the truck.
95 F-150 4X4 Rancho Lift 97,000 miles.
I replaced the trans mount and the engine mounts and the thump still is there.
Took it to a Four wheel shop today and the Tech had no idea what was causing it.
He recommended a trans shop. I have read quite a few Fixes but nothing definative. All bushings, mounts, and springs are intact. Trans has 30,000 on it and no leaks.
So far I have a list for the Trans shop to consider;
Slip yoke Lube
Trans Modulator
Vacume lines on trans
Drive shaft
U-joints
Trans not Dropping into 1st gear when coming to a stop.
Filter and fluid change
Trans tailshaft bushings loose
Carrier bearing on driveshaft.
Suggestions welcome!!
J.
Freshman User
Joined: Mar 2004
Posts: 37
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I had a 90 F-150 that did something similar. It was an automatic. It ended up having a cracked tailshaft, It did drip fluid though, but it's something to look at. It very well could be the u-joints though. They will also make noise like a squeek or clank when taking off in reverse or forward. Since you mentioned the truck now has a lift the driveshaft is at a different angle. If the joints before were slightly worn, this could be the bullet in the back for them. May sound stupid, but check that the exhaust is not hitting anything or that the spare tire came loose. Maybe it got disturbed in some way when doing the lift. Wish you luck.
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New User
Joined: Mar 2004
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From: arizona
Thanks Svdweb1,
I forgot to mention that it is an automatic.
I'll take a closer look at the U-joints and Tail shaft (no leaks) to see if that could be the culprit.
The lift has been on the truck for quite a while as far as i know.
I purchased the truck a month ago. The spare is in the Bed of the truck and the exhaust is in good shape. It appears to be something in the driveline.
I'll try something new today and start out in 1st (low) and see if i get the thump. perhaps the trans is not downshifting when driving normally.
I'll also try starting in drive "D" then down shift to 2 then 1 and stop. put it in drive and see if it is the tranny as i suspect.
I just pray that whatever it is, It's not costly. lol !!
I forgot to mention that it is an automatic.
I'll take a closer look at the U-joints and Tail shaft (no leaks) to see if that could be the culprit.
The lift has been on the truck for quite a while as far as i know.
I purchased the truck a month ago. The spare is in the Bed of the truck and the exhaust is in good shape. It appears to be something in the driveline.
I'll try something new today and start out in 1st (low) and see if i get the thump. perhaps the trans is not downshifting when driving normally.
I'll also try starting in drive "D" then down shift to 2 then 1 and stop. put it in drive and see if it is the tranny as i suspect.
I just pray that whatever it is, It's not costly. lol !!
Freshman User
Joined: Mar 2004
Posts: 37
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I hope for your sake it is'nt the tranny but there easier to yank out than front wheel drive cars. Another idea to check for the condition of the u-joints is to grab the drive shaft with your hand and try to shake it up and down. It should not have any play, but it is normal to have some play when you twist it because of the drive train and rear-end. U-joints are about 15 bucks. 30 bucks if you need both, but I would do front and back at once because if one is worn the other is getting close too. machine shop or some parts stores will press them on for about 20 bucks a piece give or take 10. I do wish you luck.
Fleet Mechanic
Joined: Nov 2003
Posts: 1,372
Likes: 14
From: West Cornwall, CT
Two possibilities come to mind. The first is drive-away shudder which can feel like a thump or shudder when accelerating from a full stop. This is more evident when accelerating hard from a stop and is less evident when accelerating gently. Drive-away shudder is caused by large differences in the u-joint angles between the u-joint at the slip yoke end of the driveshaft and the u-joint at the rear end. This can be fixed by using tapered rear blocks (or tapered shims) between the rear springs and axle. This is a common problem on lifted trucks.
The second possibility is a thump caused by the transmission to driveshaft slip yoke moving when you take off from a stop. You can feel this thump even when accelerating gently. This problem can sometimes be fixed for a while by lubricating the splines on the slip yoke.
I'll bet that this is not a new problem with the truck and that the former owner just lived with it.
Lou Braun
The second possibility is a thump caused by the transmission to driveshaft slip yoke moving when you take off from a stop. You can feel this thump even when accelerating gently. This problem can sometimes be fixed for a while by lubricating the splines on the slip yoke.
I'll bet that this is not a new problem with the truck and that the former owner just lived with it.
Lou Braun
Junior User
Joined: Dec 2003
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How much is the truck lifted? I believe the driveshaft has some extension built in for suspension travel (...and enough for a lift, 4inches maybe?), and with accelerating, the driveshaft goes from extended position to a shortened position, and with a lift, the driveshaft may be at its end with extension already if you get what i mean, and it hits the maximum extension quickly making a noise. This was a problem in early Bronco's, it is called the "Bronco clunk." I believe a longer driveshaft will solve the problem, one designed for your lift. Maybe I'm wrong, but it's a thought.
Good Luck.
Good Luck.
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New User
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From: arizona
Thanks ALL,
The Truck has a 4" lift with 33" tires.
Going to check the U-joints tomorrow and Start with the least expensive fix first.
I'll lube the Split yoke, look into shims and perhaps it's the Drive shaft.
Once I find a Fix I'll be sure and post it.
Thank you all for the Tech Help.
The Truck has a 4" lift with 33" tires.
Going to check the U-joints tomorrow and Start with the least expensive fix first.
I'll lube the Split yoke, look into shims and perhaps it's the Drive shaft.
Once I find a Fix I'll be sure and post it.
Thank you all for the Tech Help.
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Junior User
Joined: Nov 2003
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From: OKLAHOMA
I had a thump after my lift install x 2. If I took off real easy I didn't get it. With my lift I also added some 35's. This added more stress to everything in the rear. One thump I get which I haven't fixed is I have a trak lok which for some reason let's one tire spin about 1/16" turn before grabbing the other so if I take off a little hard or up a hill the one tire spins enough that when the other grabs it thumps because I'm not on it enough to break it loose, just one.
The other thump I get or got is spring wrap. My stock springs were very soft?! I added add a leafs to help fix this problem. The springs actually deforms out of it's arch and "wraps" or twists just for a second then snaps back into form causing a bump.
Hope this helps...
The other thump I get or got is spring wrap. My stock springs were very soft?! I added add a leafs to help fix this problem. The springs actually deforms out of it's arch and "wraps" or twists just for a second then snaps back into form causing a bump.
Hope this helps...
Thread Starter
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New User
Joined: Mar 2004
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From: arizona
Great News All !!!
Hade the split yoke lubed at Ford for $30 and Presto! No more Thump bump and Jerk on acceleration.
I want to thank everyone wo offered Ideas and Trouble shooting avenues to find a fix.
Thanks again.
Hade the split yoke lubed at Ford for $30 and Presto! No more Thump bump and Jerk on acceleration.
I want to thank everyone wo offered Ideas and Trouble shooting avenues to find a fix.
Thanks again.
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