Transmission Drag or Creeping at Idle

[lcashmack]

2002 Wrangler. 4.0l.
Happens while vehicle is still warming up, within 5 miles or so. When stopped at a light, the Auto tranny seems to really want to keep the vehicle moving forward, i believe this is called Creeping. As if the torque converter is not entirely "dis-engaging" as it should. It will cause the engine to stall if you don't have you hand on the gear selector and switch into neutral. After about 10 minutes and 5 or so miles, it doesn't have any trouble with this. I've read that this could be Tranny fluid and filter. I had a trusted Tranny shop look at it, and they said they couldn't find any concern, and didn't feel it was the tranny causing this.

 

[hear]

Wanting to pull at a stop and trying to die if you don't let it, that definitely feels like torque converter. Esp that after you drive for a little bit it stops doing that. There is a check valve in one of the tranny cooler lines that is supposed to prevent the TC from draining out, and also I believe one of the valves plays a role. I know Sonnax makes a modified valve that will also allow the TC to charge while in park, which may also be part of your problem.

Having said all that, I'm a little surprised you can even drive if the TC isn't' charged; that's how the drainback problem normally manifests. So this may be slightly different. The only easy diagnosis steps I can come up with is to check your fluid (while running, in Neutral!), and then unplug your torque converter lockup, just to be certain that isn't part of your issue (I'm confident it isn't). Oh and also let your jeep idle in neutral for 10-15 minutes at initial startup before taking it out, and then report back if it does the same thing or not.

Bottom line, if you have all your gears and it seems to shift at the right times and in a reasonable way, it's almost certainly not in the transmission. Draining the fluid and replacing the filter is never a bad idea though. My money is on torque converter, and possibly bad flow to the TC.

 

[lcashmack]

What you are describing is exactly what i have to do with my 2005 Cummins Ram. start -> Neutral for about 30 seconds -> Runs fine. Otherwise it goes now where until pressure builds up in TQ.
On this Jeep, i think i'm gonna go with tranny fluid and filter and see how it responds. I've seen that recommended a couple times but thought eh Tranny shop would make that suggestion. Cheap box to check off in the process I suppose.

 

[hear]

The only thing surprising here is that a tranny shop didn't tell you that you needed a rebuild.

 

[KennethS]

Sounds like the torque converter lockup clutches to me, assuming this trans has a lockup converter (I know nothing about Jeep automatic transmissions).

 

[ColoJeep]

Sounds like the torque converter lockup clutches to me, assuming this trans has a lockup converter (I know nothing about Jeep automatic transmissions).

On a GM car I would check the brake switch , but I'm like you , no experience on Jeep slush boxes .

 

[hear]

Sounds like the torque converter lockup clutches to me, assuming this trans has a lockup converter (I know nothing about Jeep automatic transmissions).

That's why i said to unplug it, to at least ensure the computer isn't responsible. But that it goes away after some driving is super sus.

On a GM car I would check the brake switch , but I'm like you , no experience on Jeep slush boxes .

Maybe it's the auxillary stall function? I mean, as long as we're just making up components that don't exist on his transmission.

 

[ColoJeep]

That's why i said to unplug it, to at least ensure the computer isn't responsible. But that it goes away after some driving is super sus.




Maybe it's the auxillary stall function? I mean, as long as we're just making up components that don't exist on his transmission.

Interesting . , As I said I don't have Chrysler/Jeep auto experience , but in GM world the brake switch is also signals the T/C lockup clutch to unlock stopping at traffic signals etc.. Faulty brake light switches cause exactly what is happening to the OP. For my edification , what enables the T/C to unlock on a Jeep autobox ?

 

[hear]

Ultimately, the computer looks at a few parameters and then completes the solenoid circuit which then flows the fluid to the TC and applies the lockup clutch.

 

[ColoJeep]

Ultimately, the computer looks at a few parameters and then completes the solenoid circuit which then flows the fluid to the TC and applies the lockup clutch.

Interesting , Thanks .

 

[hear]

I don’t believe there is a brake input on the non-ABS jeeps, so the shut off trigger seems to be either throttle input or probably a drop in governor pressure…but I’ve never actually read up on that.