[usajdm]

Hello everyone,
First off I'd like to say I hope none of you have had to deal with this, but if you have, please chime in.

Here's the info.
2002 Dodge Ram 4.7 with 102000 miles on it.
About 8 months ago I started noticing what seemed like early/delayed shifting along with rpm fluctuations.
It was random and only once in awhile.
I asked a few friends to drive it, but none felt a problem.
It was one of those things that you know after 12 years of driving your truck that it seems different.
As of recent, the problem has escalated.
The rpms jump up or down on a steady throttle.
Sometimes after a shift, the engine will rev upto 4k and quickly drop back down.
Double shifting has also started to occur.
As in it'll shift, downshift, then shift again.
I'm not experiencing any jerking, except on these double and high rev shifts.
It's not jerking, but produces a single sudden jerk from the shift itself.
No odd noises at all, except every few weeks, a thud that comes from what feels like the mid under section of the truck upon slowing down for a stop.
Also, now and then at a stoplight, the rpms will dance from 400 to 900.
This problem has become constant, but before this when it was "now and then", the truck ran great.
Even with the problem, the truck itself is running fine.
I check the tranny fluid every night upon returning home.
Fluid levels are perfect.
I'm not insisting it's a transmission problem, but the increased/decreased revving and shifting issues are the result of whatever's going on.

Within the past 8 months I've had 3 mechanic shops and 1 transmission shop look at it.
The tranny shop checked all the solenoids and sees no problem there.
Without taking the tranny apart, they said they can't come to a conclusion, but said they don't think the tranny is causing it.
The 3 different mechanics were no help at all.
Basically telling me to drive it til the check engine light comes on, then bring it back.
That they can't tell anything til there's a code.
No help.
It seems mechanics are dwindling away and no they are just parts changers being told what to do by the dreaded ecu.

I'm trying to prevent the check engine light and possibly being stranded on the side of the road.
I work for an airline, so I understand preventative maintenance.
It keeps planes from falling out of the sky.

The truck has been routinely maintained.
Just had new plugs put in.
All new cooling system about a year ago.
Routine oil and fluid changes.

Please advise with any experience or knowledge of this problem.
Open to all suggestions.

Thank you,
Robert

 

[TransEngineer]

So you have no CEL, and no fault codes? Hmmmmm....

Actually, consider yourself lucky that you didn't choose a shop that would just sell you a rebuilt transmission (even if you didn't need one). Sounds like they are at least trying to find the actual problem, before throwing parts at it.

If your trans was actually slipping (in gear), it would set a fault, put you in "logical limp-in" (1st and 4th gears only), and light the CEL. So it sounds to me like your trans is shifting strangely, but not slipping once it's in a particular gear. So the key question is: If the trans is shifting strangely, is it doing that because the PCM (or TCM) is telling it to, or is it doing it on its own? Odds are, the PCM/TCM is commanding it to do the screwy shifts. A tech with a scan tool could ride with you (monitoring Current Gear and Target Gear, as well as TCC Status) to see what the PCM/TCM is commanding. I'd bet that the trans is just doing what it's told to do.

So, if the trans is merely obeying the (somewhat strange) commands from the PCM/TCM, the next question is: Why is the PCM/TCM telling it to do that? The inputs to the shift schedule are output speed and throttle opening, so have your tech with the scan tool watch those readings as you drive. Is the throttle position reading jumping up and down? If so, that would cause the trans to shift erratically (as if you were actually pumping the accelerator back and forth). So my first guess would be a bad TPS signal. Maybe that's also related to your fluctuating idle speed?

So, find a tech with a scan tool that can ride with you to see what's happening. That should point you to where the problem really is.

 

[usajdm]

Thank you so much for the speedy response.
I'll give this a shot on my next day off.
Bad rain ere in the SF Bay Area.
Lots of doubles.

Let me ask you, is it damaging to drive the truck if that's the problem?

 

[TransEngineer]

Yes, it could possibly be damaging to the clutches, depending on how often it's shifting back and forth. Try to drive as gently as possible. You might also try manually downshifting it to hold it in a lower gear, if that helps to limit the number of shifts.

The problem with rapid erratic shifting is that each shift adds heat to the clutch, so over time, with a number of shifts back-to-back, you can overheat and burn the clutch. The amount of heat increases with torque level, so to limit the heat, either limit the amount of shifting (by using a lower gear), limit the torque (by driving gently at light throttle), or both.

 

[usajdm]

Well I'm on week 3 after replacing the TPS and all is well.
Truck seems to be running like a champ.
TransEngineer, if you are reading this, THANK YOU!
If I'm ever in Michigan, I'm treating you and your family to some steak dinners.

Anyone having problems even remotely like this, give the TPS a try.
Cheap and easy to replace.
Again, thank you TransEngineer.

 

[TransEngineer]

Glad to hear that you are apparently fixed up! And blessed to have been able to help. Thanks for the kind words; no other thanks needed. Go take your own family out for dinner and celebrate!