Engine/Transmission (1998.5 - 2002) Drvietrain "Thump"

[rogerblind]

Drivetrain "Thump"

I recently traded my 2000 on a 2002. I have also recently purchased another 2002 as a work vehicle. Both the 2002's have a similar characteristic that I never experienced with the 2000. As you come to a stop, you can feel a definite "thump" in the drivetrain (or somewhere) just before coming to a complete stop. Likewise, when pulling out from a stop, a similar thing occurs. Does anyone have any idea what is going on and whether it is something to worry about. Since both trucks do the same thing, maybe it is somehow related to the 4-wheel disc brakes??

 

[JCyrbok]

fuel tank

My 2001. 5 2500 does the same thing occasionally. I had read an articale or a TSB about fuel sloshing forward and rearward in the tank when it is between 7/8 and 3/4 full. This is the only times that it occurs in my truck. Kinda feels my someone rearends you lightly. U can actually feel the thump instead of just hear it.



Mine does not do it all the time, or I may just be used to it. I spoke with the Stealer about it and they advised that they could not find any TSB or anything else on it "so it must be fine. " It does not affect driveability but can be annoying. I checked my tank mounts and they are fine. Must just be one of those annoying qirks in life, Kinda like a wife, you just get used to it. LOL



Just my . 02cents on what I had found.



J-

 

[rogerblind]

Never thought about the fuel possibility, but I think it occurs at all tank levels in my trucks. I'll keep an eye on it to see. Like you say, you can feel it, but not hear it, and it is annoying. Glad to know dealers are still using the "it's normal" excuse, but the "No TSB" is a new one to me. Maybe they eliminated some internal tank baffles ... along with the hood insulation, assist handle and wheel well liners, etc. What can you expect for only $40K?

 

[rogerblind]

Checked last night, and it definitely doesn't feel/act like a fuel slosh. Almost seems to be brake related, but I'm not sure. Has no one else noticed this? Both my trucks do exactly the same thing. It is really obvious. Even the wife noticed it.

 

[CFAR]

My WAG



Too much play in the Rear Drive shaft?





Woody

 

[Lsfarm]

Drive shaft splines

I've had a similar 'thump' , it was the sliding splines on the driveshaft to the rear axle.

What happens is when we stop, the rear axle is pulled to the rear, kind rotates around the spring attachment point. If the driveshaft splines are sticky, they stay extended in this position when you stop.

When you accelerate away from the stop, the axle tries to push forward, and the stuck splines let go with a 'thump. '

Try greasing the splines, or take it back to the dealer and let them do it.



I hope this helps, Greg L, the Noise Nazi

 

[rogerblind]

Greg, That sounds right to me. Exactly where are the suspect splines located, and what is involved in lubricating them? I would like to avoid a dealer visit, for all the normal reasons.

 

[Gary - K7GLD]

As I recall, a couple of fellas here mentioned something similar, and it turned out to be loose U-bolts at the rear axle, allowing the axle to slide fore and aft on the springs? Might be worth a look...

 

[emjay]

I can't resist, so I'll apologize in advance....

Put some carpet in the back so the old lady can get some traction!!!:-laf :-laf

 

[LSMITH]

The other possibility is it is a VB that more correctly operates, and it is shifting down into first as you come to a stop. To check this either manually downshift to 1st as you stop or kick it into nuetral as you begin to slow down. My bet is it will not happen if you do either. When taking off pull it down to first when driving off, I would bet the thump you feel is it shifting to second. Bear in mind unless you have heavy throttle applied it will shift to second at less than 7 MPH if left to decide on its own.



emjay, I like your answer LOL!!!!!!!!

 

[rogerblind]

Emjay. No carpet, but Linex should acheive the same result.

 

[RFerguson]

Originally posted by rogerblind

Greg, That sounds right to me. Exactly where are the suspect splines located, and what is involved in lubricating them? I would like to avoid a dealer visit, for all the normal reasons. [If you haven't done it all ready, check the tightness of the rearend u-bolts. I changed the blocks on mine to lower it for fifth wheel towing and found all 4 u-bolts loose. But like you said, what do you expect for 40k. /QUOTE]

 

[Rattler]

Mine does the same thing sometimes. Not always though.

 

[JAS]

Thump, SLIP

I too have noticed a "thump" from the drivetrain at times. It usually happens when I come to a stop. Then when I hit the go pedal, the transmission appears to slip and the engine has to work hard (RPMs) to get the thing moving again.



This happened around 25,000 miles. I took it in to a dealer twice to have them look at it and after changing the ATF fliud and filter, they never found anything. (I don't know if they put it on a dyno or not?)



I've only noticed it a 'few' times since then. I now have 65,000 miles on it and I'm always looking out for the problem to show up again.



Anyone experience anything like this?