Loud thump from under the truck...Help
 

Was driving the truck yesterday. A 2000 2500 w/ 52,000 miles. Noticied twice when starting from a stop sign there was a loud thumping sound coming from under the truck. It only made this sound one time each, but it felt like I could feel it in the pedals when it happened. Looked under the truck but saw nothing odd. Also do not think I ran over anything. Drove the truck about 10 more miles with several hard accelerations and all appeared fine.<br><br>Just curious if this is any type of problem like those who have had engine stumble or anything associated with a lift pump failure. Engine power seemed fine both times this happened.<br><br>Truck is 100% stock...thanks.

Re:Loud thump from under the truck...Help
 

Two things come to mind immediately. First, how are your universal joints? What happens if you back up a foot or two and then drive forward? Any noises such as a snap or clunk?<br>Second thing is rear tranni mount. Is it loose or broken?<br>After you have eliminated those two possibilities someone else may have an idea.<br>One other remote possibility. Are all your exhaust hangers in place and working correctly?

Re:Loud thump from under the truck...Help
 

Hey reed?<br>just curious...was your fuel tank about 1/2 full?<br><br>i get a thump sometimes ONLY when my fuel tank is 1/2 full...was told its the fuel sloshing back and forth. There are supposed to be baffles in the tank...but?

Re:Loud thump from under the truck...Help
 

Yes my fuel tank is exactly 1/2 full. This is the first time I have heard any strange noises from my truck and it concerened me. Felt just like something slid out from under the front seat and hit the pedals, but nothing did.<br><br>Guess I'm just paranoid with everyone talking about lift pump failures. I don't know what the pump failure symptoms are. I'm at work now and will drive it some tonight and tomorrow and see if I can duplicate it. Thanks for the quick replys so far.

Re:Loud thump from under the truck...Help
 

Lift Pump Failure Symptoms.
NOTE: You may experience any number, or none of these symptoms. When mine failed I experienced none.

1. Truck no longer runs. Especially noticable after changing the fuel filter.
2. Truck gets poor fuel mileage.
3. Lack of power.

The best way to determine if there is a lift pump problem is to test it with a gauge, or better, install a permanent gauge.

Lift pump failure does not cause any thumping anyplace that I know of, except once when the injector pump goes belly up.

Chris

Re:Loud thump from under the truck...Help
 

Check your track bar where it connects to the frame. You are discribing the exact symptoms that mine had when the track bar was worn out.

Re:Loud thump from under the truck...Help
 

[quote author=Stamey link=board=4;threadid=15188;start=0#142732 date=1054081069]1. Truck no longer runs. Especially noticable after changing the fuel filter.<br>[/quote]<br><br>Hehehe....I tend to think this one would be noticable whether you'd just changed the filter or not. ;D

Re:Loud thump from under the truck...Help
 

I once had a similar thump when my drive shaft splines were worn. Everytime I took off they would thump as they slid on eachother because the drive shaft wasnt totaly true under acceleration. The shaft pulls and pushes apart when you stop and accelerate. I would also check those u-joints. If you did any lifting to the suspention you should really check every part of the drive line.