Uncommanded 4-3 downshift

[fredjacksonsan]

No joy in the Grand Cherokee forum, so thought I'd try here since it's the same drivetrain.

2000 4.0 114K miles. Trans filter change w/pan drop and fresh fluid was done over 15K ago, problem just started about 5K ago so don't think it's fluid.

On the highway and at any speed (has happened at 45, 75, and in between), it will occasionally downshift from 4th to 3rd; it will then stay in 3rd. Sometimes downshifting with throttle or selecting 2nd manually with gearshift momentarily will get it to shift back to 4th. Sometimes that won't work and have to pull over, turn off then restart per owner's manual which resets and puts it back to normal.

Based on the intermittent problem and the "reset" when turning it off, I'm thinking it's a sensor that is going bad.

Any ideas?

[AlohaBra]

Here is a couple of things that I found on a search:

http://autorepair.about.com/library/a/1f/bl922f.htm

http://autorepair.about.com/library/a/1h/bl596h.htm

http://autorepair.about.com/library/faqs/bl654e.htm

Here is another one...about the output and input speed sensor:

#2475 of 3562 Re: 95 Grand Cherokee auto transmission [spy_007] by bernr1 Jan 11, 2006 (8:03 am)

Replying to: spy_007 (Jan 09, 2006 10:05 pm)

I don't know if anyone responded to you in regards to this. I have a 2000 JGC, two years in a row I had a similar problem but the check engine light came on. I took it to Autozone. The first year the output speed sensor went bad and the second year the input speed sensor blew. It didn't cost much to replace them (maybe $20-$30 per sensor)but at the time I had no idea where they were located and paid twice as much to have a transmission shop do the work.

[fredjacksonsan]

Mahalo, Alohabra --

I'll have a look at it soon (like the next time it does it)

[citizen@large]

From a post over on naxja's forum I read just before reading this one...

AW4 Overdrive / Tourqe Convertor Issues Solved!
I had placed a post in this forum a few weeks back, about some trouble I was having with my AW4 jumping in and out of overdrive at 45mph & above. I thank everyone who took time to suggest possible fixes. It sounded like the TPS was the culprit, however I replaced the TPS, no luck.

I was lucky enough to take the DRB III home from work ever the weekend, and trace the problem down. The computer in the jeep was getting a signal that the brakes were being applied, and released due to a loose/faulty/old! OEM harness connector under the dash. When I was driving, this "short" would tell the computer that I was pressing brakes, and kick out the lock up tourqe convertor, causing my problem.(The truck jumping in and out of overdrive.) I am so releaved to have figured this out, and save some major $$$$ in repair & dealer troubleshooting!

I ended up simply using a few tie straps to hold the connector together tighter. If the problem continues, I'll eliminate the connector, and solder the wires.

So far...So Good!

Hope this may help anyone else who mat be expierencing the same issues.

XJ_Lars

I've also read recently that the TPS or NSS are suspectable sesors...
Another 'quick fix' that worked for for someone was to unplug/replug both the TPS and TCU harnesses...

~Good Luck

[fredjacksonsan]

Thanks Citizen, seems like there are a lot of parts that may cause it.

[citizen@large]

Originally Posted by fredjacksonsan

Thanks Citizen, seems like there are a lot of parts that may cause it.

Really, I dunno... .

But, I do poke around quite a bit.(hobby?) And if I recall something, I like to try and help out- Lord knows I've had enough myself! 'Specially around here!

Thanks to you guys.. I'm just trying to 'pay it forward'...

~Good Luck
~Ken

[jeeper186]

My wifes 99 GC did the same thing. only to find it was a solonoid. There are alot that can cause the trouble. It could even be a bad tourque converter.