Small thud during acceleration after coasting (1 Viewer)

[BnvS]

Team,

I am experiencing a small thud on acceleration after coasting. I greased all my driveshafts with good grease.. I only noticed it after greasing the driveshaft around 2-3 months ago. I have not been riding the truck for a bit but noticed this just now.

Also I do get a a big clunk/thud while putting the car into drive and then back to reverse. I know this is also normal likely for higher mileage trucks. I dont think its a big issue but wanted to check if this is normal.

Let me know.

Thanks

 

[GatorBait1551]

The OFFICIAL clunk/thunk driveshaft thread

My thunk has gotten to the point where I will spare no expense and go to the ends of the earth to fix. Re-greasing was making it better, but not completely solving it. However the rear was re-greased about two months ago and now it is thunking worse than ever. About 18 months ago I had the...

forum.ih8mud.com

30 pages of people trying to diagnose

If you greased your driveshaft and its still happening, many report that replacing the front diff bushing helps

 

[MongooseGA]

Front diff bushings would be my guess. I settled down a nice clunk when mine were replaced.

 

[alwaysbored786]

Front diff bushing removed 90% of my thud, this thud occurred when coasting then getting back on the gas, or sometimes from a stop.

I'll be throwing in all new u-joints (OEM Toyota) here in the next week or so, will report back to see if this cures the other thud)

 

[gregnash]

Same... R&R the front diff bushing removed 90% of mine as well. Outside of that I still have one on coming to a stop on occasion and feels/sounds like it comes from the rear. I have gone through and tightened to spec all the U/LCAs and cross bar, shocks, and other items back there to no avail so seeing as when I got the truck and greased my shafts they seemed like they had never been done before I am wondering if I now have play in my diffs or driveshafts.

 

[alwaysbored786]

Same... R&R the front diff bushing removed 90% of mine as well. Outside of that I still have one on coming to a stop on occasion and feels/sounds like it comes from the rear. I have gone through and tightened to spec all the U/LCAs and cross bar, shocks, and other items back there to no avail so seeing as when I got the truck and greased my shafts they seemed like they had never been done before I am wondering if I now have play in my diffs or driveshafts.

Its definitely driveline related ORRRR very slight chance could be engine mount/trans mount bushings. Source: i've changed every single suspension bushing on this truck in the last 500 miles, thud still exist.

 

[TheForger]

I had the same thud. It would occur when I got on the gas after coasting, accelerating from a dead stop, or going from park-drive-reverse. Replacing the hub flanges almost completely eliminated it.

 

[firefightermtn]

Same boat. Everything is greased and nothing changed. I figure I'll just not let off the gas while driving.
However, I have found that when going from reverse to drive, stopping or going to neutral for a couple seconds definitely lessens the clunk!!

 

[thebeedeegee]

Same boat. Everything is greased and nothing changed. I figure I'll just not let off the gas while driving.
However, I have found that when going from reverse to drive, stopping or going to neutral for a couple seconds definitely lessens the clunk!!

This is my exact clunk. If I give her a second in N before going to D it won't clunk half as bad. I'm almost certain it's my front differential bushings. It doesn't clunk at all if the center diff is locked.

 

[firefightermtn]

This is my exact clunk. If I give her a second in N before going to D it won't clunk half as bad. I'm almost certain it's my front differential bushings. It doesn't clunk at all if the center diff is locked.

Ah! Haven't tried locking the center diff and listening. Will do here in a bit.

 

[Mike NXP]

So I may be wrong but I've convinced myself that if the noise clears up when the center diff is locked, that eliminates any possibility of it being Drive hub / flange / diff bushing related. The same movement ( more or less ) is happening in the front end ( bushing, CVS, etc ) whether the front end if locked or unlocked , so if it goes away wouldn't that point to internal gearing wear ? I would think if front diff bushing were shot, it would clunk if locked as well.

After following the official thread it seems like the logic remains true based on others experiences.

 

[vishmuzty]

You are experiencing same symptoms that I solved by replacing the front diff bushing. As the rubber degrades and compresses, the aluminum bushing bracket / diff cover is able to contact the crossmember producing a "thud" noise whenever the drivetrain transitions during torque load reversal (ex: off-throttle coast -> on throttle, D->R). Locking the center diff must smooth out the torque transfer so the diff doesn't load as abruptly... I also observed this.

Either use a video camera or a helper in the driver's seat to watch the front diff bushing during P->R->N->D shifts. You will be able to stop the noise by wedging a piece of rubber between the bracket & crossmember or holding the diff with a prybar.

 

[Mike NXP]

You are experiencing same symptoms that I solved by replacing the front diff bushing. As the rubber degrades and compresses, the aluminum bushing bracket / diff cover is able to contact the crossmember producing a "thud" noise whenever the drivetrain transitions during torque load reversal (ex: off-throttle coast -> on throttle, D->R). Locking the center diff must smooth out the torque transfer so the diff doesn't load as abruptly... I also observed this.

Either use a video camera or a helper in the driver's seat to watch the front diff bushing during P->R->N->D shifts. You will be able to stop the noise by wedging a piece of rubber between the bracket & crossmember or holding the diff with a prybar.

My new OEM bushings have just as much movement in it as the "worn out" bushing that I replaced. Few videos on mud showing that, so it's not a solid way to diagnose. May fix some peoples issues but not others.

Back to my concept of, if the center diff is locked, and the noise goes away, shouldn't that tell you the front diff bushing is not the issue? If the bushing was worn it would be clunking whether center diff is locked or unlocked.....right?

 

[vishmuzty]

My new OEM bushings have just as much movement in it as the "worn out" bushing that I replaced. Few videos on mud showing that, so it's not a solid way to diagnose. May fix some peoples issues but not others.

Back to my concept of, if the center diff is locked, and the noise goes away, shouldn't that tell you the front diff bushing is not the issue? If the bushing was worn it would be clunking whether center diff is locked or unlocked.....right?

In my case it was fairly clear that the sound of the diff bracket contacting the crossmember was the same "thud" noise I was hearing during P-D-R shifting and during on-throttle applications. If new bushings allow enough movement for the diff bracket to contact the crossmember, there's something incorrect in the parts or reassembly process. Metal-on-metal contact is not an allowable design condition.

As the the CDL theory: my hypothesis is that if the front diff bushings are worn and free to move, whatever torque reversal input through the transfer case will go to the path of least resistance = front diff. Locking the diff forces a 50/50 torque split so less torque goes the the front diff for a comparable input (P-D-R shift or throttle input).

 

[Mike NXP]

In my case it was fairly clear that the sound of the diff bracket contacting the crossmember was the same "thud" noise I was hearing during P-D-R shifting and during on-throttle applications. If new bushings allow enough movement for the diff bracket to contact the crossmember, there's something incorrect in the parts or reassembly process. Metal-on-metal contact is not an allowable design condition.

As the the CDL theory: my hypothesis is that if the front diff bushings are worn and free to move, whatever torque reversal input through the transfer case will go to the path of least resistance = front diff. Locking the diff forces a 50/50 torque split so less torque goes the the front diff for a comparable input (P-D-R shift or throttle input).

Interesting, just trying to make sense of the various thud symptoms and fixes. New bushing still shows movement but your right, it's not hitting the frame.

 

[vishmuzty]

Interesting, just trying to make sense of the various thud symptoms and fixes. New bushing still shows movement but your right, it's not hitting the frame.

This is a good application for an upgrade option, something like a mid-durometer urethane bushing. If the Febest replacement bushing I installed didn't work or doesn't last (so far 2 years no issues), I was going to machine or mold something in 80~90 duro urethane. Anything too stiff would transmit to cabin. I'm surprised none of the Cruiser vendors have taken this on.