ZJ Not shifting into Overdrive - JeepForum.com
Sign Up   Today's Posts
User: Pass: Remember?
Advertise Here
Jeep Home Jeep Forum Jeep Classifieds Jeep Registry JeepSpace Jeep Reviews Jeep Gallery Jeep Clubs Jeep Groups Jeep Videos Jeep Events Jeep Articles
Go Back JeepForum.com > Models > Jeep Grand Cherokee & Commander Forums > ZJ Grand Cherokee Forum > ZJ Not shifting into Overdrive

Ruffstuff Axle Simple Swap Kit!Introducing MONSTALINER™ UV Permanent DIY Roll On Bed LineThe Original 3/8" Ruffstuff Diff Cover!

Unread 07-18-2013, 05:39 PM   #1
Registered User
1995 ZJ 
Join Date: Jul 2013
Location: garfield, nj
Posts: 2
ZJ Not shifting into Overdrive

Recently bought a 1995 grand cherokee, 112k on the odometer. I drove today about 85 miles and the truck wasn't going in over drive . The light above the OD off button turned on too. Once the truck cooled down, light came off and went into overdrive. Ps. The truck was sitting for about 10 months from the previous owner. From reading on the forums, i have comprehended that is cause from the trans overheating

1. The trans fluid level is fine
2. The fluid does not look dirty
3. I am thinking that my trans cooler is clogged or one the lines

Any suggestions, things to check and test would be appreciated, Thanks!

ediaz590 is offline   Reply With Quote Quick reply to this message
Unread 07-18-2013, 06:59 PM   #2
Registered User
1997 ZJ 
Join Date: Dec 2008
Location: , Alabama
Posts: 7,509
The OD doesnt work when the PCM thinks the transmission is overheated.

Could be clogged cooler, or the thermistor in the gov pressure sender could sending a wrong signal to the PCM.

Based on the symptoms going away after a cool down period, I would flush the cooler.

(1) Disconnect the cooler lines at the transmission.
(2) Using a hand suction gun filled with mineral
spirits, reverse flush the cooler. Force mineral spirits
into the From Cooler line of the cooler and catch
the exiting spirits from the To Cooler line. Observe
for the presence of debris in the exiting fluid. Continue
until fluid exiting is clear and free from debris.
(3) Using compressed air (under 40 psi.) in intermittent
spurts, blow any remaining mineral spirits
from the cooler, again in the reverse direction.
(4) Pump one (1) quart of automatic transmission
fluid through the cooler before reconnecting.
(5) If at any stage of the cleaning process, the
cooler does not freely pass fluid, the cooler must be

You can check the thermistor by disconnecting battery and pulling the two connectors closest to the engine. Use an ohmmeter to check between pin 4 of white connector and pin 1 of black connector for approximately 1000 ohms at room temperature.
ZeeJay1997 is online now   Reply With Quote Quick reply to this message

Quick Reply

Register Now

In order to be able to post messages on the JeepForum.com forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.
Confirm Password:
Email Address
Please enter a valid e-mail address for yourself.
Note: All free e-mails have been banned due to mis-use. (Yahoo, Gmail, Hotmail, etc.)
Don't have a non-free e-mail address? Click here for a solution: Manual Account Creation
Email Address:


Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.

Thread Tools

Jeep, Wrangler, Cherokee, Grand Cherokee, and other models are copyrighted and trademarked to Jeep/Chrysler Corporation. JeepForum.com is not in any way associated with Jeep or the Chrysler Corp.