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94 Plymouth Voyager transmission

94 Plymouth Voyager 3.3L

When coasting downhill at 50 MPH or so in overdrive the engine speed drops below 1000 RPM and then the transmission jerks into 3rd gear. Shop replaced transmission with a used one but it started doing the same thing in a few days. Seems like there must be an external cause such as bad info going into transmission computer. Does this transmission have any vacuum control at all?

Otherwise it is fairly smooth, accelerates fine, no worn out disc symptoms. Problem virtually goes away in sub-freezing weather even driving 40+ miles.

Your thoughts please.

Thanks,

john

When coasting downhill at 50 MPH or so in overdrive the engine speed drops below 1000 RPM and then the transmission jerks into 3rd gear. Shop replaced transmission with a used one but it started doing the same thing in a few days. Seems like there must be an external cause such as bad info going into transmission computer. Does this transmission have any vacuum control at all?

Otherwise it is fairly smooth, accelerates fine, no worn out disc symptoms. Problem virtually goes away in sub-freezing weather even driving 40+ miles.

Your thoughts please.

Thanks,

john

Reply to
gtb
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Are you using the Cruise Control when this happens?

Reply to
Leviathan

Sounds like the transmission may be going into "limp home" mode. Your description of it "jerking into third gear" could well be when it actually reverts to second gear in the limp home mode (not third). The transmission controller is programmed to revert to second when it is either not working properly, or (more likely, especially in this case) when it is not receiving one of several signals it needs to determine the proper gear ratio. Two of the signals used are the engine and axle speeds measured in instantaneous revolutions per minute in order to calculate the appropriate gear ratio to be used. If the input speed sensor (measure engine speed) or output speed sensor (measures wheel speed) are failing, then it will go into second gear. The clue here is that you do not mention if the speedometer goes to zero or stays at the correct speed. The speedometer receives its signal from the output speed sensor, so if it is reading correctly, it could be the input sensor that is failing.

The bottom line here is that it would appear that the shop you used may have replaced the transmission prematurely when all that was needed is a $30 speed sensor. Take the vehicle to a shop that can read Chrysler transmission codes and has real experience working with Chrysler electronic transmissions.

Good luck.

Bob

Reply to
Bob Shuman

Thanks Bob!

jh

Reply to
goodTweetieBird

Sorry, didn't see your post at first. Cruise control was on but not engaged.

jh

Reply to
jh

Reply to
Leviathan

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