thump-thump-thump at stop... tranny?

[LanceW]

Or maybe it's "Buh-buh-buh-buh-buh-buh-buh". When I am stopped at a light in drive, I get the above noise and a vibration. It's not a real healthy sound- low frequency and you can feel it through the whole truck. The noise continues if I let off the truck brakes but hold myself stopped with the trailer brakes, but it stops if I shift into neutral. The sound seems to be coming from under the front, but it just started tonight in the middle of a 600 mile trip and I haven't really investigated much other than that.

I will say that I am due for a tranny flush and an aux tranny cooler- the fluid is pretty stinky. I have my own suspicions but would like to hear from those of you (most) who know more than I do.. thanks,

Lance

(by the way- truck went over 199,000 miles on the way home tonight. Love this thing!)

[turbovair]

Mine went Buh, Buh, Buh, then it changed to a metallic tank, tank, tank and then I discovered my crank pulley rubber was torn and the whole thing was getting ready to fail. Changed the pulley out and both noises disappeared. Even if I am wrong, do yourself a favor and check your crank pulley. Get uder the truck and look carefully. You may see the rubber torn.

[n3qik]

My vote is for the TCC sticking.

[LanceW]

further update- did not do it with engine cold this morning, pulling trailer back to the barn. As the truck warmed up it started to do it again. Will Check the pully tomorrow while I am changing the oil, and will do a tranny flush this weekend to see if that helps. Thanks for the input

[patrick m.]

sounds to me like maybe exhaust or something hitting under the truck, when you take it out of gear, the eng relaxes and the exhaust no longer hits.
just a thought

[Uncle Wally]

Our dually does the same thing. But only when loaded, not light. I narrowed it down to the the downpipe hitting the welded flange on the leading edge of the cab bottom. Clearance that and it should go away. If not, I would not suspect a trans problem. I would look more at drive shaft u-joints, cv joints and the such. Especially if it seems to change linearly with vehivle speed only - not engine speed.

Waldo

[kowsoc]

I don't know how loud the sound is but I had one that wasn't too loud but definitely noticable when sitting in the cab. It sounded just like a knocking main bearing. Hard to believe but I found the transmission dipstick tube touching the firewall and it would transfer low frequency vibes trough the firewall. In neutral the engine would relax on the motor mounts and noise would go away! Simple fix for me by just carefully bending tube by hand to allow clearance. Check to see for anything making contact. Good luck....keep posting....someone will help you nail it! ;)