1999 Dodge Caravan tranny problem

Tiny
JAY55
  • MEMBER
  • 1999 DODGE CARAVAN
  • 3.3L
  • V6
  • 2WD
  • AUTOMATIC
  • 196,000 MILES
I am having a problem with the tranny not shifting. Replaced the input speed selector and was told a bad diode in the alternator can cause the transmission control module to cause a shifting problem. The alternator is new so wondering if the diode in it is bad. It sets codes 700, 733, 734. Any help would be great. Thanks!
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Thursday, January 23rd, 2014 AT 1:37 PM

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Tiny
CARADIODOC
  • EXPERT
There's actually six diodes in an alternator. One bad one will cause a loss of two thirds of the unit's output current capacity but I never heard of that causing a shifting problem. GM generators are well-known for developing huge voltage spikes, and those can interfere with computer sensor signals, but that just results in elusive engine running problems.

P0733 - Gear 3 Incorrect ratio
P0734 - Gear 4 Incorrect ratio

Code 700 just means there's codes in the Transmission Computer. 733 and 734 mean the input speed sensor and output speed sensor are working, but based on engine speed, the wheel speed is incorrect. That typically means there's slippage taking place in one or more clutch packs and the transmission needs to be rebuilt. That's not surprising at the mileage you listed. An experienced transmission specialist can use Chrysler's DRB3 scanner to read the "clutch volume index", (CVI). That is a set of four numbers indicating how much fluid volume it takes to apply each clutch pack. Those numbers go up as the linings on the fiber clutch plates wears down.

Clutch plate wear always starts out causing intermittent slippage. As soon as that happens, the computer goes to "limp" mode where it stays in second gear to allow you to drive slowly to a repair shop. To get it out of limp mode, you must turn the ignition switch off, then restart the engine. As a temporary measure, you may be able to keep it out of limp mode by accelerating a little harder than normal to keep it in the current gear, then let off the gas while it up-shifts to the next gear. Once it's solidly locked up in that gear, you can accelerate again. Doing that can reduce the slippage in the clutch packs, and may get you a few more weeks before the transmission must be rebuilt.
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Friday, January 24th, 2014 AT 5:48 AM

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