THUMP!

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LFD2037

LFD2037

TEXAS LEXUS!
10 Year
Joined
Oct 22, 2013
Threads
183
Messages
3,889
Location
Wax., TEXAS
If I'm steadily driving down the highway, @ say 1/3 throttle (not specific), & quickly let off the gas I get a mild 'thump'. If I'm coasting down the highway giving it no throttle & I push on the accelerator quickly I get a hard 'THUMP'! Not a downshift issue. It's a hard enough thump that it sends a shock-wave thru the whole truck. Steering wheel, dash, everything 'bounces' from the THUMP. I'd think this would be u-joints but mine are Toyota & only 20K miles on them. I'll check tomorrow to see if it does it @ city driving speeds as well. I also get a 'wave' thump when quickly taking off from a complete stop but it feels a bit different. That particular thump seems to start @ the rear & load up with force as it works itself forward then it thumps the whole truck once I hit about 10-15mph.
What the hell could this be?
Think they are related?

***ETA*** Just realized this goes away when it rains ie. when undercarriage is wet. Is that a tell-tale sign it's control arm bushings?
 
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Your drive flanges are worn down would be my guess. Pop your cap off the front wheel hub and bend down close while someone gently gives gas and brake. You should be able to clearly hear the clank/thump. It's very misleading until you do this.

ACC in ATL swapped in new drive flanges for me a couple of years ago on a rig I used to own; not too much $.
 
Drive flanges look great. Not pointed or tidal-waved.
 
Struts? Wha choo talkin' bout, Willis?
 
Dragos80 said:
Bad cup holders, or a loose suspension component.
Check all the bolts that attach the struts and shocks to the body.
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The only strut an 80 series has is its pimp strut as its goin down the road.
 
Ummm...motor mount, transmission isolator, control arm bushing...body (human) rolling around in the back? Jack loose in the rear quarter panel, spare tire loose underneath, bicyclist caught under vehicle. Those are my guesses. Oh, sway bars...bushings, mounts, ball joints if they're that type, and one I know personally pan hard bar fasteners coming out.
 
It's definitely not something rolling around. It feels like the truck is getting lightly hit in the rear by another car. I can literally see the dash bounce up/down, feel the wheel thump, the seat bump, everything! Motor mounts, tranny isolator & tranny mount all look good. I have no vibrations or any other odd things happening. Truck drives straight & doesn't pull. I could try replacing all the control arm bushings but that's a rather large undertaking financially & physically to just hope it fixes the problem. Bushings are, what, $40 each & need 10. There's $400 plus the price to pay someone to press out the old ones/press in new & the hours of labor I'd endure. I'm hoping someone has had this issue before. In my normal everyday driving I don't notice it because I never quickly do from 1/2 throttle to no throttle or quickly go from no throttle to 1/2 throttle. For the most part it takes a conscious effort for me to make it happen.
 
LFD2037 said:
It's definitely not something rolling around. It feels like the truck is getting lightly hit in the rear by another car. I can literally see the dash bounce up/down, feel the wheel thump, the seat bump, everything! Motor mounts, tranny isolator & tranny mount all look good. I have no vibrations or any other odd things happening. Truck drives straight & doesn't pull. I could try replacing all the control arm bushings but that's a rather large undertaking financially & physically to just hope it fixes the problem. Bushings are, what, $40 each & need 10. There's $400 plus the price to pay someone to press out the old ones/press in new & the hours of labor I'd endure. I'm hoping someone has had this issue before. In my normal everyday driving I don't notice it because I never quickly do from 1/2 throttle to no throttle or quickly go from no throttle to 1/2 throttle. For the most part it takes a conscious effort for me to make it happen.
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Transmission isolator a often look great until you put a jack under the tail housing or transfer case and raise them a little. As far as replacing bushings, you don't have to replace them if they're not torn or rotted out, just remove the links, one link, one link end, inspect, Reinstall and move to the other end. But seriously, underneath spare tire? Seen them slide back and forth and make the driver believe someone love tapped em on the road...that was me... I just about decapitated a little old lady with my knife hand until I realized it happened again and she wasn't behind me lol.
 
You won't really be able to tell the condition of any bushing or mount without fully removing it. Chased issues many times when bushings 'looked' okay. These bushings are old, replacing will only be good. Get a Go-Pro or something if you want to dig into where it may be originating from.
 
No spare tire on truck. My truck has 183,646 miles. There's no corrosion under it anywhere from living in Texas all its life. Driven like a beauty queen most it's life. How long do these bushing and mounts usually last in these type conditions?
 
If the motor mounts are bad you can frequently see the whole motor move when you step on the gas pedal, easy way to diagnose.
 
Sounds like your rear axle is clocking, bad bushing on one of the rear links.
 
I vote U joints
 
Some of the newer Toyotas exhibit a similar condition. On those it was the driveshaft slip joint running out of grease and then loading, binding and unbinding. You may need to "lube your shaft" so to speak.
 
DWHeigher said:
Some of the newer Toyotas exhibit a similar condition. On those it was the driveshaft slip joint running out of grease and then loading, binding and unbinding. You may need to "lube your shaft" so to speak.
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Did that, properly, about a week ago thinking it was a problem. No difference.
 
Well I'll be a monkey's uncle. All I did was jack up the front to check wheel/trunnion bearing play, they were good. Greased u-joints, which I do about every ~7K miles and the thump is gone. Ujoints have ~20K miles on them, Toyota brand. Can't believe they were that dry that fast. I can still make it do it at juuuuuuuuust the right RPM's but if you know what you're doing you can pretty much get any vehicle to do it at just the right time.
 
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