CC Pocock

Hi All I hope someone assist here.

My overdrive does not work. The vehicle has been in the workshop for 2 months and NO ONE can find the problem!! Various mechanics have looked at it and apparently the transmission has been stripped and reassembled and they say there is nothing wrong with it. In addition to all this the Jeep has been back to this same company 11 times over the past year and a half under warrantee after the original rebuild.

I am looking for someone who is a specialist on this vehicles transmission in South Africa.

I have tried to extract the error code for the transmission but the overdrive light will not flash any codes.

Can I apply 12v directly to the overdrive solenoid to get it to work bypassing the TCM circuit?

Also any other advise will be appreciated!

dave1123

Welcome to CF!

Okay, here's what I know. The O/D solenoid is powered by 12v and grounded thru the TCM. Therefore, you should be able to run a wire from the harness terminal #6 (at 9 o'clock looking at the vehicle harness connector) to a switch on your dash and then to ground. Just remember the trans won't downshift with this wire grounded. It would be a good test to see if the solenoid functions or not. It's also possible this wire in the harness is broken.

All the solenoids in the transmission operate by grounding them thru the TCM.

There is also a thermistor (temperature controlled resistor) in the trans that won't allow O/D to engage if the trans isn't above 30*F or below 260*F. It's on the bottom of the valve body and submerged in fluid at all times. the open circuit resistance value should be 1000 ohms at 70*F. If this isn't working, it could also be the problem.

This is all for the 42re and 46re transmissions. I'm assuming that's what you have.

I have a service manual for the 42re transmission that I could send you, but it's 23MB (100 pages) and most servers won't accept that large a file. Send me a private massage if you'd like me to try. I'll need an e-mail address to send it to.

CC Pocock

Thankyou for your reply, very useful info.

I think it is the 46re as its a 1994 5.2L with the quadrive transmission
I do have the PDF manual. and have already studied it.
Do you know if the thermistor is in series with the solenoid or is it connected to the TCM?

This what I plan to do:
1. I want to attach a panel light to the wire going to the solenoid from the TCM
2. I will connect a wire on pin 6 and through a toggle sw on dash to ground.
3. drive the jeep and once it has changed in to3rd in cruise I will check if the light comes on. If not then its not been activated by the TCM, then I will turn on the switch and hopefully the overdrive engages.

I will report back here with results. Im sure this may be a of interest to many others with similar problem in future.


cheers
CC

dave1123

I don't think that's going to work. The solenoids are all powered up all the time with 12V; O/D, TCC, and Governor Pressure. They only function when grounded thru the TCM, so your light will be on all the time. Plus you'd be putting the resistance of the lamp into the mix.

The thermistor is wired into the governor pressure SENSOR, not the solenoid. That's supplied with 5V.

CC Pocock

I understand that, The lamp (LED) will be connected between the ground (control) wire and +12vdc.
I should be done testing by tomorrow.

CC Pocock

New problem.... This transmission does not match the aervice manual I have . It does not look like a 46re. I dont know what it is. The solenoid plug above the Park-neutral-reverse switch only has 3 pins! the color of the 3 wires are: Purple -yellow, dark green, brown- green.

Which one is the OD solenoid? I now need to find the correct service manual for this transmission. The transmission ID number is: PK52118327 1854 0195

blackjack12982

It's not a 46RE transmission, that's why it won't match. 93-95 V8's have the 46RH, which is a hydraulically controlled transmissions. The only ZJ that the 46RE came in was a '98 5.9, the 96-98 5.2's have the 44RE. You must find a service manual for the 46RH's instead of the RE's. Simply fire up Google, I remember I found the manual for it within a few minutes.

CC Pocock

OK will look for it right now. My Chrysler 1994 GC service manual claims that the 94 GC 5.2l only has a 46re!? and they don't mention any other transmission. Anyway I' off to google...

CC Pocock

Ok I see in the manual that it is actually 46RH not "RE" however this still does not solve my problem. It appears that this manual does not show the wiring diagrams for the 46RH

I have just bought another Grand Cherokee manual on the internet and its exactly the same as the one I already have!

I only have the wiring diagram for the PCM but I can work with this for now. At least I can trace the wiring.

blackjack12982

You need the ATSG guide, it'll be under the A518, that's the official designation for the 46RH.

http://www.scribd.com/doc/65625826/A500-A518

dave1123

I guess I'll hand this off to you, Blackjack. It looks like I was beating the wrong horse.

CC Pocock

Report back...

I installed a toggle switch and lamp on the instrument panel to override the PCM and it works well, I can now activate the Overdrive manually.

I removed the Transmission output shaft speed sensor and cleaned the socket and plug and now the OD works again automatically!

I'm going to install another toggle switch to override the TCC in case of that circuit failing too. Both switches will have red aircraft type protector covers. What I really like about the panel lights is that you can see instantly when a solenoid is activated by the PCM.

One more thing... the error codes for the transmission are not flashed by the OD off light as this transmission is controlled by the engine PCM. There is no Transmission control module (TCM). All error codes are flashed by the "check engine" light. One of the codes I got was in fact "Output shaft speed" so there you go! and no shop mechanic could figure this out ?!

Thanks guys for the assistance I hope this thread will be of value to others with similar problems in future!

cheers
CC

cc@bushair.co

Paul Green

​​​​​​​Which wires did you tap into at the transmission. I also have a 94 grand Cherokee and it won't engage the overdrive. I'd like to find a way to manually engage it. I just bought mine a few days ago. It has a 408 stroker and has a b&m shift kit. The overdrive off button has been removed. There was a nest of wires and switches coming out of the dash. I went through and cleaned them up. What I found was there was an alternator bypass switch put in. And 2 others were for lights. And 2 other switches seemed to be useless. I just wanna know what you did to make it work. Or if you have pics that would be awesome and greatly appreciated.

dave1123

You DO realize O/D is 4th gear, don't you? Are you getting 3 shifts or only 2? I'm assuming the shift kit automatically shifts it to 4th gear. 3rd gear is 1:1 anyhow.

Paul Green

yea. I know it's a 4th gear. I get up to 3rd no problem. But someone took out the od off button. What I'm asking is, is there a way I can hook up a toggle switch to put it in overdrive manually. I have no idea what else may have been taken out. Not real familiar with these jeeps.