Something is clunking/slamming every time I let off the gas. ***?

[basilbowman]

I noticed a couple of days ago that when I shifted from Park to Reverse, Reverse to Drive, or Drive to Park something (presumably the tranny) would slam hard forwards - like hard enough you can feel which direction it's moving. I took it in and had it looked at, it wasn't acting up for them, but they did drain (not flush) the tranny and change the filter and pan gasket. Now, I bring it home, and when I let up off the gas it does something similar. If I ease off of it it'll just grumble at me, but if I have it even at a very moderate acceleration and and come entirely off it'll clunk. Hard. Any thoughts? The brake light comes on too, but I don't know that that's related, I think I've got a bad RABS valve that comes on anytime the truck bounces a certain way. Any thoughts are appreciated

-N

 

[sle2115]

Motor mounts come to mind...engine/trans movement can cause a lot of strange noises and things to happen. Is it 4WD? Could be transfer case issues if it is, or could be torque converter, low tranny pressure, etc.

 

[basilbowman]

2WD - I should check the motor mounts. They had it up on the lift today, I wonder if they would have thought to look for that?

 

[sle2115]

2WD - I should check the motor mounts. They had it up on the lift today, I wonder if they would have thought to look for that?

Good question!

 

[basilbowman]

I'll go shake on it in the morning, see if I can feel anything give. It doesn't feel like it's in the motor though, it feels like it's under the seat, which is why I'm thinking tranny problems.

 

[sle2115]

Be sure to check the transmission mount as well. They can fail and cause weird issues, driveline binding, etc.

 

[basilbowman]

It doesn't do anything in 1st or 2nd, but in 3rd & 4th, when I let it coast in gear it rumbles a bit, which is all new, it wasn't a gradual thing.

 

[sle2115]

It could well be transmission related...they don't have the best track record, but just suggesting simple less expensive things to look at. Would suck to go through a tranny R&R to find something simple still existed. Good luck and let us know what you find.

 

[basilbowman]

I really appreciate the simple things first approach - last time I asked here, I kind of ignored the simple thing people (much more experienced than I) were suggesting and spent a week tearing apart my fuel delivery system to work out that it was, in fact, a bad fuel takeup in the tank. This time, I'll listen to you first, rather than deciding I know best

 

[rhkcommander]

mine was motor mounts when it slammed and clunked. Try getting on 'er. if it stil ldoesnt do it in 1st and 2nd it might well be something else

 

[redneckaggie]

Since yall are mentioning motor mounts, my truck keeps eating pilot bearings, like the last one we took out of there was completely trashed and a month later the brand new one is starting to squeel when I let off the gas and engine brake. could that be motor mounts i wouldnt think so since the motor and trans are bolted together and should move as one but im at a loss to explain it

 

[Shadetreemechanic]

Check the carrier bearing as well. It will clunk, and then grind and make a general nuisance of itself. But it usually does it for a long time before it becomes a real problem.

 

[IDIDieselJohn]

I've never heard of motor mount problems on these engines before.


You sure your rear end is nice and tight? Differential could have to much backlash...

 

[FordGuy100]

I have it to. Mine seems like there is a little play in the driveline somewhere, to if I let off the throttle and coast, then give it some throttle, there is a slight hesitation and a clunk. I always thought it was the play between the transfer case and read diff (truck sitting you can turn the drivline a little bit each way when parking brake is engaged.

 

[ih8minimumwage]

Check your U-Joints as well.