If I accelerate in a civil manner, all is fine. If I accelerate in a brisk manner (dipping into maybe 5 psi of boost), I hear and feel a single thump or thud from behind me, almost as if something were rolling around in my bed (which is empty). I am afraid to drive it at WOT until I figure out what's going on. Any ideas? Driveshaft, suspension, exhaust? Transmission?

In case it matters, the truck is a 2003 with 8000 miles, and a FTVB. I have a driveshaft loop, Bassani, 2" shackles, and no traction bars yet (running stock F1's... haven't raced it with slicks). Any insight would be appreciated! Thanks!

 

Is it possible your plenum is hitting the fire wall on a more aggressive throttle. I know I get that sometimes since the install of the KB. Paul (REM) warned me it would happen some times, but it doesn't necessarily sound like it is coming from the rear more mid ship when that happens.????

I noticed the works logo, just a thought? Good Luck getting to the challenge.

D-Day

 

More than just you have described that "thump"...I have heard it myself on a hard stop or start, but I havent heard it for about 6 months now....never did figure it out..only happend about twice to me.

 

What brand DS loop...............it may be touching your exhaust when the motor 'torques' under load.

--Joe

 

Could also be your universals...you can check for play in those.

The Eaton is pretty far from the firewall. The KB shouldn't hit the firewall either since all production models have a modified adapter plate with the notch out of them.

 

Do you have an optima battery using a modified stock hold down?

The battery could be sliding back and forth in the tray and it will feel like its something in the bed. Took me awhile to figure it out and boy did I feel dumb when it turned out to be the battery..


Just tryin to help.

MOUNTAIN MOTOR

 

Spare tire loose? Something rolling around in the back of the cab? Tailgate?

Have someone ride in the bed!

 

I think its time for a new wallpaper. If I remember correctly, you said you would put one up once a week....Put your photoshop talent to use!!!

 

Could it possibly be your Bassaini cat back moving under more aggresive throttle?

I just found mine about to fall off last weekend. I was checking air pressure in the tires and noticed that the tips were hanging low (they used to sit perfectly). Sure enough, all three of the rubber hangers were torn. My entire cat back was being held on by the two exhaust clamps that mate the cat back with the x-pipe. I am very lucky that it didn't fall off while I was driving.

Just a thought....

 

Some more notes I forgot to mention:

- The thump is just a faint or dull thud, and I think I feel it more than I hear it. It's definitely not a loud, metallic bang or clank, etc. Imagine something the weight of a small computer monitor inside a cardboard box, softly rolling over 90 degrees onto it's side.

- Interestingly, I tried to duplicate the phenomenon again and it wouldn't thump for me at all. Maybe it's intermittent. I did have 2 golfbags in the bed so I wonder if the load affects it at all.

Dan_03Lightning, good thought - the plenum clearance is ok - the only time I hear it touching is if I mash the throttle in reverse which makes the engine rock over. The thud is definitely coming from behind/below me.

Joe, I am using Sal's PSP DS loop.

Mr. Freeze, what's a good way to check for play in the u-joints?

Sounds like I have to check lots of things... bed, driveshaft, u-joints, exhaust, spare tire, tailgate.... *sigh*

Thanks for all the ideas, and please post any more if you think of any! I was worried it was something in the driveline... but most of your ideas sound relatively harmless so far.

Oh yeah, more wallpapers coming soon, I am on vacation at the beach this week.

 

I had the same thing happen to me with my 01'. I was pulling out of a parking lot and was giving it some gas to merge with the flow of traffic...and I heard/felt a thump as I was turning (I think it shifted into second when it happened). I had pretty much decided it was my driveshaft. Didn't keep the truck much longer after that so I didn't get to really investigate. Good luck though!

 

OK, I guess I may have to bring her into the dealer then and let them try and diagnose it. Thanks!

 

Three days later :::::

"Unable to reproduce customer complaint"

<grin>

 

EXACTLY what i was thinking. Just jack her up and start checking. Its wont be hard to fine. Your U joints should not move up or down with the pin. If you twist them back and forth there shoud be some play. But it should not ride up and down the pin. Tighten up the DS loop. Check everything else.

Ray

 

I have what sounds like the EXACT SAME THING from my 03'.

However, I'm bone stock, and mine does it mostly when I'm carrying a passenger and always when I have two people with me. It makes the noise, right behind the cab over bumpy pavement, and isn't really a factor of acceleration. It sounds to me like the body is hitting on it's rubber dampners somehow, or the suspension is hititing the bump stops...

I've no clue. I'm going to bring it in, but I know they won't be able to get it to do it's thing.