Shifting problem

[Philbob56]

I have a 1990 Comanche with 4.0 automatic tens (2wheel drive) I pressure washed the undercarriage ( major oil gunk) I drove it and it quit shifting. It will shift into 2nd if I nail the gas, but it won’t shift any further. I’ve checked the solenoids with a ohmmeter and changed fluid and filter. I haven’t checked the VSS , but all wiring and connections check out. 

[gogmorgo]

https://www.bc4x4.com/tech/2010/jeep-neutral-safety-switch-nss/

 

There's a chance you pushed some gunk into the NSS and its acting up, although I don't know that would cause shifting issues... usually that turns into a no-start or no reverse lights.

 

Have you tried adjusting the throttle valve cable?

https://www.allpar.com/SUVs/jeep/cherokee-transmission.html

 

The other thing to check is if you blew the trans fuse. I think cruiser54.com will have a thing about it?

[cruiser54]

CRUISER'S MOSTLY RENIX TIPS

TRANSMISSION CONNECTOR REFRESHING

OCTOBER 30, 2015 SALAD 13 COMMENTS

 

Over near the transmission dipstick tube are 2 rather large connectors. One is black and goes to the NSS and the gray connector goes to the transmission itself

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. These 2 connectors carry all the info between TPS, TCU, NSS, speed sensor, and transmission solenoids.

Unplug each one, visually inspect for corrosion or bent pins, spray them out with electrical contact cleaner and plug them back in.

Additionally, if your Jeep is an ’87 to ’90 Renix, it’s always a good idea to reach up under the glovebox area and unplug the connector to the TCU and spray it out along with the receptacle of the TCU. While you’re there, find the fuse right in that area for the TCU. Remove it and spray out it’s receptacle and clean any corrosion from the fuse.

[Dando]

Is it possible you got the TPS wet? I’ve had issues with shifting from a bad sensor. 

[cruiser54]

17 hours ago, Dando said:

Is it possible you got the TPS wet? I’ve had issues with shifting from a bad sensor. 

that's also a possibility.