'94 Grand Cherokee Shifting Problem! Changed Trans still not shifting!
I was having problems in my '93 GC 4.0L. It had no overdrive and intermittently wouldn't shift at all automatically. Changed the trans, the old one was full of metal shavings. We figured the trans was bad. We Put in new transmission and now its doing the same thing. Its the 42re transmission. So I can shift it manually but it doesn't go into first even when you put it in 1. I'm not sure what it can be. The "new" trans is used with about 70k.
I was searching through and saw some things about bad solenoids, but its a diff trans so i ruled that out. Also heard about a bad trans computer, but haven't checked into that yet. Is there a way to check the computer with a meter? I'm stuck and need some help.
I'm having a similar issue. Something else to check for is a check valve on the lower transmission line on the radiator. People say they sometimes get plugged up. The only thing I could find on the computer is to check voltage output on 8 plug pin. http://fseg.net/mopar/downloads/42re.pdf try this link also, if i find out what is wrong with mine i'll post findings, also ther is someone by the name of baxy on this forum that rebuilds transmissions you can try him to see if he'll respond to a PM.
Check the fuses under the hood!!! I drove mine for months having to shift it manually. Finally I replaced the transmission, and the problem still occurred. It was simply a small fuse under the hood. Replaced that, and I haven't had a problem in months. If its not that then I would try another TCM
Fuse is good. The trans and cooler were flushed right before we bought the new trans, to see if that would help the old one. How do you check the TCM? Also I was reading in another thread that a '94 GC doesn't have a trans computer. Thanks for the help so far!
'01 Jeep GC I6 | '01 Jeep GC V8
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i have having the same issue, but for me its somewhat an on-off sort of thing. If its warm outside or if i have been driving for a long time then restart it, it will shift. But if its cold, or just an off day, she doesnt shift. I too replaced my transmission and dont even know where to start to look. And by the way when it does shift, it shifts vary hard and often i have to let off of the gas to allow it to shift.
You guys sure must like to spend money if you're replacing entire transmissions before even checking codes to see if it's a simple solenoid or wiring issue...Yes you can check the codes without a drb. DRB is not an every day code scanner and i doubt you'll ever feel like dropping the coin on one. Go to autozone or advance auto, they'll pull the codes for free. Or pick up a cheap scanner for 20 or 30 bucks from them..orrr i believe it works on zjs..turn the key to on (without starting) then off in this cycle: on,off,on,off,on. On the last on position your check engine light will blink kind of in morse code type blinks.Example: one blink...pause...one blink,one blink. = code 12. I'm not sure but your overdrive light might even blink.
The TCM, transmission control module, will throw codes just like the Power Control Module will. I believe there are only separte TCMs on the years 1993 to 1995. To read the codes you count the number of times the Over Drive lamp lights. The Over Drive lamp is located on the over drive switch.
Extracting Fault Codes:
Without ever starting the engine Turn the ignition switch ON, OFF, ON, OFF, ON and observe the Over Drive lamp. The Over Drive lamp should begin to flash a series of codes. The flashes will be separated by short and long pauses. The long pauses separate the "ones" and "tens" positions, and each code from the next. A code 55 will be displayed at the end of the test.
Tranny codes for 1994 OD button LED
11 Engine RPM input
12 Output shaft sensor input
13 Vehicle speed input
14 Governor pressure sensor input
15 Throttle position sensor input
16 Transmission fluid temperature input
17 Overdrive override (control) switch input
18 System voltage
19 Internal fault in module
21 Governor pressure solenoid output
22 Overdrive solenoid output
23 Converter clutch solenoid output
24 Overdrive override (control switch) lamp output
25 Internal fault in module
26 Governor pressure sensor offset drift
55 End of code transmission
94 Black Laredo 4-Liter with QuadraTrac (42RE trans & NP249 TC) 200,000 + miles purchased new
88 Cherokee 2-door with 5speed manual 139K miles(deceased) purchased new
okay i will try that, but you say the long and short pauses separate the 1's and 10's, think you could explain that a little more? and how i look at the flashes and decipher it into a number that would tell me whats wrong?