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Thumper828 01-28-2013 03:47 PM

Erratic Transmission Shifts
Hi all. Hoping for alittle help. I have a 02 WJ with a 4.7. The Tranny keeps shifting back and forth between gears. I thought it may be a TPS issue. I recently replaced the TPS for the same issue. The TPS was under warranty so I got it replaced. I installed it there on the spot. As soon as I get up to speed, No difference. I also noticed my cruise control has stopped working. I don't know if the 2 are related.

Any help would be greatly appreciated.

Frango100 01-28-2013 04:33 PM

Re: Erratic Transmission Shifts
Shifting issues are many times due to the TPS going bad, but could also be due to a bad speed sensor. There are 2 speed sensors, both mounted on the left side of the tranny, the input sensor at the front and the output sensor at the rear.
Sometimes non MOPAR TPS can give strange behaviour as well, but when you changed the original one for a non MOPAR and the problem didnīt change at all, i would go for the speed sensors.
Not sure if due to this shifting, that the cruise control will not work, but try to solve the shifting issue first.

Thumper828 01-28-2013 07:29 PM

Re: Erratic Transmission Shifts
I'll try the speed sensors. Most of my research tends to lead me in that direction as well. I guess the thing to do would be replace both. Sure hate to see the money go.

Frango100 01-28-2013 07:36 PM

Re: Erratic Transmission Shifts
I bought mine on They sell the OEM stuff for reasonable prices. I paid around USD 90 for the 2 speed sensors and the line pressure sensor together.

Thumper828 01-28-2013 08:37 PM

Re: Erratic Transmission Shifts
Thanks for the Link!! Where does the line pressure sensor go?

Frango100 01-29-2013 05:11 AM

Re: Erratic Transmission Shifts
The line pressure sensor sits on the right aft side of the tranny. I think that almost nobody changes this sensor, maybe only when problems arise, but it probably is a good thing to change it once. When the sensor gets bad, it could mean that the line pressure gets too low, which could lead to slipping clutches and premature clutch wear.

Thumper828 01-29-2013 08:49 PM

Re: Erratic Transmission Shifts
I was able to swing the speed sensor, will keep you updated

Thumper828 01-30-2013 08:01 PM

Re: Erratic Transmission Shifts
Ok, so installed speed sensors. Everything was fine for about 10-12. Smooth shifting, nothing erratic, and cruise control worked great. Then back to the same ole thing. Rpms up and down, no cruise control. Needless to say I was on the verge of losing my religion.

Well I kept driving racking my mind. "Self". I say," what controls the cruise and tranny" Then it dawned on me. So i stuck my foot under the brake pedal And pulled up.......

Bam, Cruise engages, tranny smoothes out. Press the pedal, cruise wont engage up and down rpms. Went to autozone, maybe 6-8 miles, kept playing with the pedal to confirm my suspicion, and bought the switch that ataches to the bracket. held the pedal back most of the way home,with no issues. I have the new switch on but havent went anywhere yet.

Could it really be that simple? Any thoughts?

Will keep you updated!!

Hacksaw 01-30-2013 09:55 PM

In my experience...yes the stupidest little thing will be the fix after you have spent hundreds of dollars and tons of hours trying to fix it.

Think Outside !- No Box Required.

Frango100 01-31-2013 02:34 AM

Re: Erratic Transmission Shifts
The brake switch has several contact decks, one for the brake lights, but also others, which are, for example, used to deactivate the cruise control . This switch doesn' t do anything to transmission shifting, but it does cause the torque converter to unlock, giving an rpm increase. So a broken or misadjusted switch could indeed give the problems you described.

Thumper828 01-31-2013 05:06 PM

Re: Erratic Transmission Shifts
I put about about 40+/- miles on it today. So far so good. I'll keep you guys updated.

Thanks for the input and advice.

Thumper828 02-06-2013 09:29 PM

Re: Erratic Transmission Shifts
I am thoroughly convinced the brake switch was the issue.

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