Mechanics

WON'T GO INTO DRIVE

2002 Chrysler Town and Country • 163,615 miles

I was driving and suddenly my 2002 Town and Country stopped moving forward. When I put it into drive it makes and noise and won't move. The tow truck driver says is a transmission issue. I called a mechanic, without seeing it he says I need a rebuilt transmission. Is that true? There were no warning signs, the transmission never slipped and there is no leaking fluid.
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Ray Malibu
March 30, 2012.




The mechanic should at least make an effort to perform some diagnostic tests first but one somewhat common problem has been the large pin coming loose in the differential part of the transmission. That typically tears a hole in the rear cover and is pretty obvious.

As for a computer or other electrical failure, the solenoids are spring-loaded to default to second gear. You can also hydraulically select park, reverse, and neutral. It just won't shift automatically to the other forward gears.

You must also consider the possibility of a broken cv joint. While that is rare, it will result in no movement and will make noise in gear that won't stop when you press the brake pedal. That is a very inexpensive repair. You can find that yourself by crawling underneath and looking at them. A rebuilt or used half shaft can be found for as little as 80 bucks for some vehicles, but $150.00 is more typical.

Caradiodoc
Mar 30, 2012.
What is the transmission oil filter is clogged? Would that stop it from going into gear?
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Tiny
Ray Malibu
Mar 30, 2012.
What if the transmission oil filter is clogged? Would that stop it from going into gear?

Tiny
Ray Malibu
Mar 30, 2012.
That isn't going to happen suddenly. Also, if the filter gets plugged, you have more severe problems because something is coming apart internally. The typical symptom from a plugged filter is a delay dropping into gear, but it usually shifts fine after that. Applying a clutch pack takes the most fluid volume, and once that occurs, not much additional fluid volume is needed until an up-shift occurs and a different clutch pack has to be applied. There won't be any noise with a plugged filter either.

Have you looked underneath to see if a cv joint came apart?

Caradiodoc
Mar 31, 2012.
The cv joint hasn't come apart. How would you hydraulically select park, reverse, and neutral?

Tiny
Ray Malibu
Apr 1, 2012.
What I mean is you can still select park, reverse, neutral and drive with the shift lever, but the computer will not switch to first, third, or overdrive when it has detected a problem. Staying in second gear is called "limp mode" that allows you to drive slowly to a repair shop without needing a tow truck.

All automatic transmissions were hydraulically controlled in the past. Two main pressures in the system varied to cause valves to move to different positions. One pressure was related to gas pedal position. The other one was related to road speed. When one overcame the other, a valve moved and opened a port to apply a clutch pack for a different gear. THAT'S what is meant by hydraulically-controlled.

Chrysler was the first company to develop a computer-controlled transmission. It was used in many 1989 models. There were some advantages that I won't go into, but to me they did not outweigh the disadvantages, most notably, that intermittent defaulting to limp mode. Anytime you add a computer to anything in a car, you add problems and high repair costs. That's why I refuse to give up my rusty trusty '88 Grand Caravan.

Instead of those two pressures determining when a shift should occur, the computer looks at two speed sensors, engine load, and throttle position to determine when a shift is needed, then it does that by electrically turning on or off a series of solenoid-controlled valves. That's computer-controlled, or electrically-controlled vs. Hydraulically-controlled.

When the system goes to limp mode, those solenoids are not activated by the computer. Instead, they are spring-loaded to default to the positions necessary to put it in second gear. You can still switch to park, reverse, and neutral with the shift lever. If the vehicle doesn't move when you shift to reverse or drive, besides a broken cv joint, the most likely cause is something came apart in the differential. A small bolt breaks and lets a very large pin slide out of place. Normally that pin catches on the housing and cracks it. There's lots of noise associated with that.

Caradiodoc
Apr 1, 2012.

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