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sunny 07-27-2012 04:25 PM

Hello, I'm new and need help
compliments to us all, I have a yr 2000 Grand Cherokee 4x4 thats been jerking when the transmission changes. it got me to lose some nuts in the steering coloum that almost caused an accident. The error codes on my instrument panels are: P0731- Gear 1 ratio incorrect and P0443- Evap control system purse valve circuit fault. My mechanic has advised that I look for a new Transmission Valve Body but I am afraid it might be a wild goose chase; Pls what are your suggestions. Sunny

Frango100 07-28-2012 01:43 PM

Re: Hello, I'm new and need help
Welcome to the garage. Which engine do you have?
Is there only strange behaviour of the transmission in 1st gear?
The P0731, gear 1 incorrect ratio, means that there is a slippage detected by the TCM in 1st gear. This can mean several things and just changing something could, but not necessarily will, solve the problem. It can be that there is really a clutch slipping( what the jerking at least seems to indicate) , due to wear on the discs or due to too low pressure at the clutch pack. First have a look at the transmission fluid, is it still red with a sweet smell, or is it dark with a burnt smell? The color itself is not a good way to check the fluid state, but could give you a clue. If this seems to be ok, then there can be a problem with:
1) Transmission solenoid pack
2) A seal breakage between the transmission solenoid pack and the valve body ( happened on mine and caused the OD clutch to wear prematurely)
3) Some other leak inside the tranny, which reduces the pressure to a clutch pack.
4) Worn clutch pack.

Don't know for which reason your mechanic told you to look for an other valve body without even opening up the transmission.
Sometimes also a faulty speed sensor could cause strange transmission behaviour.
I would do a transmission service with fresh fluid and filters and remove the valve body for inspection, evenhow there is not too much to see to it. But then you could remove the solenoid block and change the seal plate in between valve body and solenoid block, just to be sure that there are no leaks there.
I also would change both speed sensors ( input and output speed sensors).
I'm not a transmission expert, but i'm having some transmission issues myself and i have my transmission completely open at the moment for a rebuild.

The P0433 message is probably due to an inoperative purge solenoid or broken/disconnected wiring. Also have a look at fuse 21 on the junction block, under the steering wheel, could be blown.

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