Hi all:

I have a 2002 CC D/A 2WD 2500HD. Have had it around a month and a half. I printed out the maintenence list on this site and have followed it to a T and so far, truck has been great. I bought it with 17k miles on it and I have only put 2k miles on it.

Recently, the truck feels sort of rough, but only when decelerating. It's difficult to describe, but it almost feels like I am on rough pavement when I decelerate with no load or throttle on the engine (this, of course, is when I am on smooth pavement). It only seems to feel this way from about 25 mph, down to about 13 mph, then it's fine. Truck accelerates fine under load, have not had a chance to haul with it yet but other than this weird little glitch, it seems to run great. Also, decelerating from freeway speeds down to street speeds seems fine, it's just when I am at surface street speeds that this sort of rough riding/ almost bucking feeling occurs. Very strange.

I cannot tell if it could be a wheel/break/suspension/tranny issue or an engine issue? Engine seems to not make any strange noises. Seems strange but it only seems to occur when the engine is basically idling as the physical speed of the truck ramps down, for instance, when approaching stop sign or intersection. No roughness in the engine sound, no smoke or anything, just this vibration sort of feel. Engine has never stopped or stalled but it kind of feels like it might, then when you get it down to around 10 mph, it seems to "smooth out" before coming to a complete stop.

Sounds like I need to make a trip to the dealer and have it checked out, I am still under warranty but before I do, do any of these symptoms sound like something I should check out myself? I have inspected tires, air pressure, oil levels, etc. I have not checked the differential fluid levels but the dealer did. Had a fresh fuel filter and oil and filter change about 1500 miles ago.

Have any of you ever experienced this?

Best,

Dan

Hi:

Well, it's been a few days with no response. I drove my truck a few hundred miles today and I am still feeling this vague sort of vibration/shaking. Could this just be the way that the Allison downshifts?

I have read a few posts about the Allison "feel", is that what this could be? As an experiment, I shifted the truck into neutral approaching a low speed/surface street intersection. I did not feel any vibration, so I guess that would point toward the vibrating feel coming from the transmission.

Any words of wisdom? Is this just the way Allison transmissions feel when downshifting? A little vibrating and bumpy?

All the best,

Dan

Dan,


I'll give it a shot here, but you might wait for one of the techs to give you some info.


Mine does the same thing only from 40 down to about 38 mph. Warped rotors in my case. Been livin with it for around 20K and is getting worse so I'll have to bite the bullet at the brake shop soon.


Billy

Hi Billy:

Thanks for your input. I posted a few other places and so far, I have heard it could be U-joint/driveline issues, tire separation, and your brake rotor idea.

I will be taking it to the dealer to check this out, I was really feeling it today and now it's starting to bug me, it just gives me an uneasy feeling when it does it. I suspect transmission or driveline because it seems to go away with I decelerate in neutral.

I will post back as soon as I can make it to the dealer for a check up on it.

Thanks,

Dan

Dan,


I've got a similar problem. Mine happens when the ally is down shifting and most of the time I'm not on the brakes. It feels like the trans is hitting low gear quicker than the suspension is ready to react. It sets up a bounce until the truck slows down sufficiently.


I'm wondering if a re-program of the computer could slow down that dad-blasted down shifting. It's a real pain and I know it's got to be costing me fuel mileage.http://dieselplace.com/forum/smileys/Cry.gif


Doug

Hi Doug:

Well, I took my truck to the dealer this week. They drove it and couldn't find anything out of the ordinary. I must say, since I switched from 245 Firestones to 265 Coopers, the ride has smoothed out and I don't notice or just perhaps borderline notice this shaking now.

Maybe I am just not used to the stiff suspension of the HD truck? I don't know. All the dealer did was an alignment and lubed a steering column joint under warranty. They checked driveline, U-joint, brakes, front and rear suspension, tires, etc.

Not sure what is going on but the truck seems happy now so I am happy as well.

All the best,

Dan