Cherokee tranny problems

[jose solorio]

I have an 87 Cherokee with a 4.0L engine that began giving me transmission problems about a month ago, and has gotten worse and worse. The first symptom was that a was driving down the Highway and all of the sudden the transmission felt like I had put it in neutral. so I pulled over to see what was wrong. But when I stepped on the pedal everything seemed to be normal again. About a week after that the car started sifting erratically between 2nd and third gear. it was like it didn't know what gear to be in. Then a few days later it began slipping between those gears also. Finally it got to the point that the only gear that did not slip was 1st.
I found an article on checking the TCU (Transmission Control Unit), so I performed all the checks that the article mentioned Everything seemed to be o.k. except for the TPS which I am not sure about because the manual that I have is clear as to what the voltage output on an 87 Cherokee should be. I am also not sure that the TPS can affect the up shifting of gears that much. The other thing I did was disconnect the TCU altogether and to my surprise Now I can drive it by manually shifting the gears. There is no slipping, so that leads me to believe that at least the bands and clutches are o.k. I have taken the car to mechanics but they all want to charge me an arm and a leg by telling me that I need the whole transmission rebuilt. But by the tests that I have done I think they are trying to take me for a ride. In fact I’m almost willing to bet that it is something electrical. Well if anybody out there knows or has any Ideas on what may be the problem and how to solve it please let me know.

[Dale Aeppli]

Originally Posted by jose solorio

I have an 87 Cherokee with a 4.0L engine that began giving me transmission problems about a month ago, and has gotten worse and worse. The first symptom was that a was driving down the Highway and all of the sudden the transmission felt like I had put it in neutral. so I pulled over to see what was wrong. But when I stepped on the pedal everything seemed to be normal again. About a week after that the car started sifting erratically between 2nd and third gear. it was like it didn't know what gear to be in. Then a few days later it began slipping between those gears also. Finally it got to the point that the only gear that did not slip was 1st.
I found an article on checking the TCU (Transmission Control Unit), so I performed all the checks that the article mentioned Everything seemed to be o.k. except for the TPS which I am not sure about because the manual that I have is clear as to what the voltage output on an 87 Cherokee should be. I am also not sure that the TPS can affect the up shifting of gears that much. The other thing I did was disconnect the TCU altogether and to my surprise Now I can drive it by manually shifting the gears. There is no slipping, so that leads me to believe that at least the bands and clutches are o.k. I have taken the car to mechanics but they all want to charge me an arm and a leg by telling me that I need the whole transmission rebuilt. But by the tests that I have done I think they are trying to take me for a ride. In fact I’m almost willing to bet that it is something electrical. Well if anybody out there knows or has any Ideas on what may be the problem and how to solve it please let me know.

HI ITS POSSIBLE THAT YOUR TPS. SENSOR IS CAUSING THE ERRATIC SHIFFTING IT ALSO SEND THROTTLE POSITION TO THE TCU. CHECK OTHER POST ON THE FORUM UNDER THROTTLE POSITION SENSOR THERE IS ANOTHER CHECK WITH CAPT. HIS NAME IS ON THE POST UNDER THROTTLE SENSOR DALE [email protected]

[jose solorio]

Thanks dale, I checked the post that you recomended but unfortunately the values that it mentions are for an 89' and mine is an 87'. I don't know if they are different but I am still trying to find out for sure. My son is is bringing me some really good shop manual that he's got, I hope that this manual can give the proper voltage output, If it does I will post it. I also checked another post (What causes auto tranny shift? Computer?) posted by "scramblet", And this post has a really good response that further convinced me that THe tps may be my problem. Thanks again, I will keep you posted. Jose

[Dale Aeppli]

Originally Posted by jose solorio

Thanks dale, I checked the post that you recomended but unfortunately the values that it mentions are for an 89' and mine is an 87'. I don't know if they are different but I am still trying to find out for sure. My son is is bringing me some really good shop manual that he's got, I hope that this manual can give the proper voltage output, If it does I will post it. I also checked another post (What causes auto tranny shift? Computer?) posted by "scramblet", And this post has a really good response that further convinced me that THe tps may be my problem. Thanks again, I will keep you posted. Jose

HI I GOT OUT THE OLD MANUAL TO GET THIS SETTING 1--UNPLUG THE CONNECTOR AT TPS. 2--- CHECK VOLTAGE BETWEEN THE BLACK AND GRAY WIRES WITH THE KEY ON. VOLTAGE SHOULD BE APPROXIMATELY 5 VOLTS. IF THE PROPER VOLTAGE IS NOT PRESENT CHECKTHE HARNESS FOR SHORTS OR OPENS. 3--ENGAGE THE WIRE CONNECTOR TO THE TPS. WITH THE KEY ON AND THE THROTTLE PLATE CLOSED CHECK THE VOLTAGE BETWEENTHE BLUE AND THE BLACK WIRES VOLTAGE SHOULD BE APPROXIMATELY 0.8 VOLTS. 4-- IF THE VOLTAGE IS NOT CORRECT,LOOSEN THE SCREWS SECURING THE TPS AND ADJUST UNTIL 0.8VOLTS IS PRESENT. 5-- IF ADJUSTING DOES NOT BRING SENSOR VOLTAGE TO SPECIFICATIONS, REPLACE THE TPS.
HOPE THIS IS OF HELP. DALE [email protected]