My 94 LC wont shift to over drive.

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San jose, ca.
Hello all, driving home from work last tuesday and was driving 65mph when my OD went off like i turned off the switch on the shifter. I performed a flush today hoping it will do good but to no avail. The OD light on the turns on but no change on the rpm. Right now if i driving 60-65 on the freeway, the RPM is at 2000-2500 rpm.
Youre help is much appreciated.. Thanks!
 
The 4 speed tranny is right about 2300 rpms in 4th at around 65 mph.
 
It was below 2000 rpm at 65mph before it started acting up

I have 285/75/16 tires (approx. 33" diameter) on my '97 and I am about 2100 rpm at 60 mph in overdrive....if that helps any.
 
20180113_113744.jpg
 
There are all kinds of things wrong with that pic. Why is your check engine light on? How are you in Park? Where's your oil pressure needle?

Otherwise, that looks about right for being in 3rd gear.

Normally when there's an issue with the tranny, the OD light will throw a code. I'm not positive the 94 has that capability.

Also, if the tranny is cold, it won't shift into OD. Your temp sensor may not be sending the correct signal.

I'm sure there are other ways for it not to shift into OD, but I don't know what they'd be, short of a problem with the tranny.
 
Normally when there's an issue with the tranny, the OD light will throw a code. I'm not positive the 94 has that capability.

you can flash the trans codes from the obd connector under the hood.



I would start by finding out why the check engine light is on and start from there, it may be related but it may not be. check your fluid level when the trans is at operating temp and make any needed adjustments. what size tires are you running and do you know what the gearing in the diffs is?
 
I'm betting on corrosion in the NSS barrel connector. Problems with the indicator and transmission can be associated with bad wiring in the barrel connector. If the transmission thinks it may be in P, I'm thinking the overdrive is not going to be working as well. Remove the driver's side tire. Find the barrel connector above the starter. Unplug and inspect the internal connector wiring. Be careful with the wires if heavily corroded, they may break off at the connector ends.

On my son's 94, he had corrosion in the connector. Indicator lights weren't lighting up properly, reverse lights weren't working and the transmission was occasionally starting in 2nd gear. Fixed the wires at the barrel connector. Installed a new inner fender mudflap to cut down on water splash to the connector and all has been good for several years now.
 
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There are all kinds of things wrong with that pic. Why is your check engine light on? How are you in Park? Where's your oil pressure needle?

Otherwise, that looks about right for being in 3rd gear.

Normally when there's an issue with the tranny, the OD light will throw a code. I'm not positive the 94 has that capability.

Also, if the tranny is cold, it won't shift into OD. Your temp sensor may not be sending the correct signal.

I'm sure there are other ways for it not to shift into OD, but I don't know what they'd be, short of a problem with the tranny.


CEL was for an EGR. But i dont know now if theres an cel for the trans not shifting to OD.
As for the Park position, i noticed also that today when i got home.
Oil pressure is good. New oil last week. Temp gauge is also good but i will look into it tomorrow.
 
I'm betting on corrosion in the NSS barrel connector. Problems with the indicator and transmission can be associated with bad wiring in the barrel connector. If the transmission thinks it may be in P, I'm thinking the overdrive is not going to be working as well. Remove the driver's side tire. Find the barrel connector above the starter. Unplug and inspect the internal connector wiring. Be careful with the wires if heavily corroded, they may break off at the connector ends.

On my son's 94, he had corrosion in the connector. Indicator lights weren't lighting up properly, reverse lights weren't working and the transmission was occasionally starting in 2nd gear. Fixed the wires at the barrel connector. Installed a new inner fender mudflap to cut down on water splash to the connector and all has been good for several years now.

I will look on the barrel connector tomorrow. Thank u much for your reply. Cheers!
 
But i dont know now if theres an cel for the trans not shifting to OD
Diagnostic trouble code for 1994 automatic transmission. Codes 41,42,61,62,64,65,66, and 88. Code 64 deals with the torque converter lock up, it reads as follows, severed lock up solenoid, or short circuit, severed wire harness, or short circuit. Note if codes 62,63,64, and 65 appear, there is an electrical malfunction in a solenoid. Causes due to mechanical failure, such as a stuck valve will not appear.
 
Oh, one thing i forgot to add about, if you jumper the connector on the firewall to read your trouble codes for the trans. Those codes will flash on the OD light on the dash, not the check engine light, and the OD switch on the shiftier and ignition switch has to be in the on position. These next codes are trouble codes for the Transmission Control Module 81,83,84 and 85 these you read off the check engine light
 
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If it turns out to be a bad solenoid it's a good idea to replace all 4 at the same time. If you don't want to buy factory solenoids, with a little searching you can find good quality aftermarket ones for less money. The ones listed below list factory part numbers, and are $156 busks each plus shipping.

 
Temp gauge is also good but i will look into it tomorrow.
The temp sensor you are concerned with is not the engine temp, it's the transmission. Not the dash gauge. The truck won't shift into OD until the transmission comes up to a certain temperature. At least I think it's a separate sensor, not the engine temp sensor.
 
The temp sensor you are concerned with is not the engine temp, it's the transmission. Not the dash gauge. The truck won't shift into OD until the transmission comes up to a certain temperature. At least I think it's a separate sensor, not the engine temp sensor.[/QUOTE

Where is this trans temp sensor located a
The temp sensor you are concerned with is not the engine temp, it's the transmission. Not the dash gauge. The truck won't shift into OD until the transmission comes up to a certain temperature. At least I think it's a separate sensor, not the engine temp sensor.

Where is this trans temp sensor located at?
 
I have no idea.
 
If you haven’t already, gain possession of a copy of the factory service manual. Not only will it help you troubleshoot and solve your own 80 problems, it will help you ask the proper questions and provide pertinent info when you come to ask the gang on Mud.
 

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