The truck I just bought has only ONE weird problem that I have never seen before. Here goes, and ANY suggestions or comments are accepted...

The Wife and I took the kids to the mall today in the new rig, the '02 3500 dually and we went via the highway. Well, here is what has me baffled, everything rides and runs good until I get to 78 MPH, then I get a vibration in the seat of the pants/ through the seat but not through the steering or suspension. However, it goes away when I reach 85 MPH. Also, it has the 5spd Allison, but the tranny temp never gets above 150* and the fluid level is fine...
I was thinking u-joints, but I was thinking that if it was the u-joints or the drive shaft being out of balance then the vibration would be all of thee time regardless of speed?...

There are absolutely NO other problems at all. I don't get it???
Anybody ever had this???
Thanks
Chris

 

Few things here:
#1- If you wanted a Cadillac you should of bought a Cadillac.
#2- Speed limit is 70.......
#3- I think that's a 2 piece drive shaft, check the carrier bearing for play.


Tranny temp is more than fine. 150 is great, when you start to work it, it should not get over 200* At least mine doesn't, anymore.

 

ok, here goes, I do not expect a caddy, I have owned them and they are not all they are said to be...

Also, it was the first test of how the truck would run and ride on the interstate, I have had 12 4x4 gmc and chevy trucks in the last ten years so I know what to expect from them as far as ride quality, however, I plan to haul close to 43,000lbs regularly with Christmas trees so if something is to go wrong I do not want it to happen when I am under a load and it is for business. I only drive that fast when testing a vehicle to find problems that may or may not exist, this kind of problem, (which could very well be a Bad wheel or tire could cause major problems under a load and if I did not test it I would be in REAL trouble later.

The drive shaft in my truck is NOT two piece, I checked that..

After some serious deliberation I have come to the conclusion that it is a problem with the rims or tires and I need to have them checked out if not replaced.

the only reason I mentioned the tranny temp was because I was trying to rule out tranny fluid levels being low, or levels of fluids in other systems of the truck, and if the fluids were low in the tranny then it would have heated up more than 150...

but thanks for the reply anyway...

 

pissy pissy pissy..

Simple balance of the wheels/tires could take care of it. There is a lot of rotating mass there, it ALL has to be balanced to be good.

Ally will be fine. She can take a hard, hot beating and still come out smelling like your girlfriend in high school.

 

2nd the tire theory, I've have to do mine regularly on the POS Chev 2500 I drive everyday to avoid the same problem.

 

We're good,
I just wanted to clarify why I was driving like that, etc. I do not condone driving like an idiot, but to truly test these things you sometimes have to go fast.
But I also understand how some people will buy a 7500lb 4x4 and expect it to ride like a caddy so I know where you were coming from there too, I am just not one of those people, GM trucks are all I have ever owned, or would own. I love them!

It's all good....

 

When you've worked at the dealer for so long and every soccer mom that walks in the door bitches about how rough their truck rides, you start to go insane.

 

I heard that, I have heard the same crap from other so called truck guys too, so I do understand where you are coming from...

 

i would have to back the tires sence there isnt a 2 piece drive shaft in it. My dmax work truck is bad for the center hanger bearing like 1 a quarter 7" if lift and 35" tires pulling a gooseneck all the time