Any transmission techs with a minute to spare??

My friend Bill has a 2001 Caravan 3.3 automatic with a possible trans. issue.

It starts and runs fine but stalls when he puts it in gear, drive or reverse.

It's acting just like the lockup torque converter staying locked.

If in fact it is staying locked, what is the fix??

I've had this problem with older FWD GM's and it was easy to repair.

Unplugging the TCC solenoid allowed one to drive until replacing the part.

I tried searching for a TCC solenoid for this unit but couldn't find any.

There are solenoid assemblies and control units readily available.

Which one if either controls the lockup converter??

Do either normally cause a locked converter.

Is this a normal or unusual problem??

Any education much appreciated!!.

Thanks
Randy

There is no separate stand alone solenoid for the TCC. it is part of the solenoid pack bolted to the front of the case.

Unplug that, start it up and go to reverse. No stall then it is the solenoid, still stalls then it is a bigger internal problem.

OK, so the lockup function is integral to the solenoid pack.

How about the Transmission Control Module by the left tire?

Does it have any connection to the lockup converter??

Thanks
Randy

Quote:

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Originally Posted by 135sohc

There is no separate stand alone solenoid for the TCC. it is part of the solenoid pack bolted to the front of the case.

Unplug that, start it up and go to reverse. No stall then it is the solenoid, still stalls then it is a bigger internal problem.

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Does that actually diagnose the problem?

If the solenoid is stuck open (full or partial) it seems like the problem would continue. To diagnose a stuck solenoid you would need an oscilloscope and current probe. You would look for the pintle bump on the scope wnen the TCC solenoid is powered on. Manually powering the solenoid and listening for it to click should work too.

If the problem goes away by unhooking the solenoid pack, then I would suspect the wiring or controller. Need to probe the signal for the TCC solenoid to see if the controller is trying to power it up. If there is 12v on the for the TCC solenoid I would inspect the harness between the solenoid pack and the controller. Were it rubs or flexes are the most likely places for a problem.

Alternatively, you could try cutting the wiring near the controller to take the controller out of the loop for TCC. If there is still 12v on the TCC pin at the trans, then there is a problem with the wiring harness (assuming you don't move the harness too much and remove the fault.)

Another clue, sitting overnight it must unlock as it goes in reverse/drive.

If he slowly drives about a block, it locks and stays locked all day.

I'm an electronics dumdum, just trying to help out another senior.

Bill lives in the big City so there's no place to work on his van and its cold.

If he gets stuck in an intersection the tow/impound fees would be high.

They would probably cover the cost of a solenoid pack or 2 for sure.

I live in a rural area so we can do more testing without fear of cops.

If something goes wrong I can probably haul it home myself.

He's expected here this afternoon, after the tow truck drops it.

I'm trying to figure out the first plan of attack.

Drive it cold to see if it has all gears??

Or unplug and see if limp mode locks.

Any more input??

Thanks
Randy

Quote:

---

Originally Posted by 135sohc

There is no separate stand alone solenoid for the TCC. it is part of the solenoid pack bolted to the front of the case.

Unplug that, start it up and go to reverse. No stall then it is the solenoid, still stalls then it is a bigger internal problem.

---

Tow truck dropped it off so I went for an extensive road test today.

Naturally, the trans worked fine, smoothly slipping in and out of lockup.

The only thing odd was a couple of times shifting into reverse.

The shift solenoid pack was clicking and buzzing like crazy.

Shifted out of reverse, back in and all was normal.

Thanks
Randy

Intermittent problems are tough to diagnose... If it continues to behave normally, I would inspect the wring harness from the transmission to the transmission controller. Several years back I bought a Lebaron that was stuck in limp home mode. The harness had not been properly secured and rubbed a pulley and wore through one wire and was on it's way on another wire... Two butt connectors and the trans was shifting fine.

Some questions for the car owner:
So is reverse always fine? Or just the first time?

When it was giving problems could he rev the engine up and drop it into drive and keep the engine running? Does it drive "ok" then?

If you are daring, you could block the tires and have somebody with there foot on the brake HARD as you gently touch the wiring harness... You might be able to get it to act up and hopefully only stall. I would probably use a stick to manipulate the harness rather than put any part of my body in front of the vehicle... The risk is it doesn't stall and runs into something or worse someone!!

I am not an expert on these transmissions, but as I understand it the controller pulse width modulates the solenoid during shifts. That would be the buzzing that you are hearing. (FYI. most other transmission have solenoids that turn on or off to shift gears...)

Do you have a test light? If it starts acting up the best way to test the TCC theory would be to back probe the TCC wire at the transmission connector (or pierce the insulation near there and later cover with some liquid electrical tape.)

Intermittent problems are tough, that's for sure!!

I drove it around again today and it's still working fine.

It only happened to him once or twice before towing it to me.

Bills a terrible driver who couldn't master keeping it running.

I'm not qualified to diagnose/repair electronics, trying to help a good friend.

Regular solenoid clicks I'm familiar with, twice it clicked and buzzed angrily

I showed him where the ETX relay is, we removed it and drove around.

As expected, it has reverse, 2nd gear only with no lockup engaged.

Now he can put it in limp mode if he gets in another jam.

Next time we can look for wiring harness issues.

Thanks
Randy