Ok going to try and explain what is going on and i hope it will trigger something that someone knows what it is...

i get a thump...not so loud that i can hear it by its self..its more felt in the floor board, i guess best way to explain it is like a low backfire sound when you let off the gas in a older car(we have all had those in some car at one point) but...its not all the time..

so when does it happen...

only at speed...past 50 mph...low speed i can not "feel it" but when i get over 50 i can...RPMs dont change it...on the gas vrs. coasting doesn't change it (as in worse or less). I would have said i had bad timing and a back fire issue but it happens when i am on the gas also...and not at low speeds...

I cant tell much of a change due to road..bumps vrs flat road doesn't change it....so ruling out spring issue..


I cant tell that speed changes it more or less..just kinda thumpin non rhythmically as i roll at HWY speeds...

i got it up on a lift yesterday and looked over Drive line for rub marks on shafts or lift components...nothing...

so...i cant find out what makes it worse (to id it) other then it shows up at HWY speed only...on the gas vrs off doesn't change it...HI RPMs vrs normal on HWY doesn't make it worse or less... 50 or 80 mph doenst make a huge difference...just a gurggle type thing in the floor board...is it a eng issue? or am i missing something in the Drive line?...ugg..

 

I have looked at your profile and do not see aftermarket drive shafts or gears. I have had problems with both and each has caused this erratic problem. Angle of the aftermarket drive shafts unloading from torque cause them to bind until I adjusted them to the correct angle. Driveshaft angles under torque is not the same as angles at rest. In my rear housing (ring & pinion), I actually had loose bolts on the ring gear to locker install, the bolts were too long a very small amount and back out. The "thump" from this was a bolt hitting the housing. For a starter, take a close look at you drive shafts for binding marks or looseness...

 

ah ok, will do...

For more info on DS, i have TF adj CAs up front, with a 5deg on driver side and 5.5ish on the pass side. I have not installed the rear yet..but i have all 4 and spring wedges to install..

I will check out Rear DS for any issues again but havent see anything on it..will post up later today on that train of thought...

Any other thoughts out there to check?!?

 

probably wouldn't hurt to check all u-joints

 

did that yesterday, that was my first thought..cant see any issues with them all around the truck...

 

If you think it may be an engine issue, rev the motor to a steady rpm in neutral (at the rpm you'd be at going about 50mph) and listen for the sound. Worth a try.

 

Are you running stock driveshafts...I think so. One shaft could be binding/loosening on torque unloading (freewheeling). It may be prudent to unbolt each driveshaft at one end and manually turn them with the wheels off the ground. This means you can feel the bearings in your hands with only the front/rear axel connection and sence anything in the shaft or axles. Heck it may be good to remove the front drive shaft and drive it some to troubleshoot. You will not have it (front driveshaft) in the equation and can isolate problem to the front or rear of driveline. This helped me out a lot on troubleshooting my vibration problems. I know it involves some work...

 

Great advice bro! I like it...going to do it sat...

But Friday is RC run...i guess if anything is going to break it will be then and i will know then what it is.. if i make it back without any big issues I will give this a try

 

I have done this at lower speeds and no issues...RPMs dont change it. So if i was going 30 MPH in second at 3k rpms then nothing...but if i am in 6th doing 65-70 around 2.8k rmp its there..so its the speed that brings out the beast...or it might be there at lower speeds but just not as pronounced...

i am going to play around with the drive shafts and joints i guess has to be something in there....or like i said..something will bust tomorrow...and then i will know..