94 88 transmission swap OBDII OBDI

Ok, here's what I did. I know this was stupid, but I did it. My tranny went out last week. I had a 4t60e from a 92 bonneville that was good. I put it in my 88 and everything bolted and plugged in fine. When I started the car, it ran high idle and overheated. I unplugged the 7-pin connector from the tranny and the car ran fine, but the check engine light came on. After driving the car a short distance, I realized that it wasn't shifting right. Looking at wiring diagrams for both vehicles tells me that the wiring is slightly different on these two trannies. So tell me, can I rewire the connector, or am I screwed? I don't have the money to go buy another trans right now.

Welcome to AF. Why did you do this, the pcm commands all the shifts in the 60e trans, the harness and pcm are required for this swap!

First.... Your car is not OBD2.... Its a Full on OBD1 Compliant car.... But being that you are a 94 GM was in a transitional stage and used the OBD2 Connector and OBD2 codes.. Still keep in mind you are OBD1...

Your next problem is that the 1994 PCM monitors the Transmission Temps where as the 1992 Trans does not, in some cases it may have a temp switch if the car had Traction Control...

If I remember right you may be able to rewire, but I am not sure how the PCM will act without the Trans Temp function... I have read that if the sensor fails the PCM would substitute tranny temp with engine coolant temp...

What you have is a Trans that is wired different, and does not have the Temp sensor...

Do your homework and see if you can rewire it... It may be better than pulling the trans again..

Misread the post, I thought it said you used an 1988 trans, both units are electronic controlled, Jrs3800's advice is correct.

I used both wiring diagrams and through various tries, cannot get it to shift correctly, I'm only getting the 2-3 shift. I know for a fact this is a good tranny, I drove the car I pulled it out of. My car does have the wiring for the trans. temp sensor/switch, but I just left it out. I have another tranny coming today from a friend, but would still rather not pull this one again. Any more ideas before tomorrow would be helpful.....Thanks guys.

You should check with a salvage yard as to what trans actually interchanges, particularly regarding the electronics and pcm compatability.

I don't want to come off sounding bad here or bashful in any manner..

But, this is where its good to come to a place such as the forums that are here and other forums I frequent... There is a lot of good information out there that can help avoid these problems..

Ok lets get a little deeper here... On the 1992 Trans you will have an A & B Shift Solenoid, you will also have a TCC Apply Solenoid.... Now don't quote me on the 92 trans, but it may use the PWM( Pulse Width Modulated ) solenoid that can vary its value from 0%-100% as opposed to on off allowing for a softer apply of the TCC clutch..

Using the 1992 Trans may have been as simple as a $14 side pan gasket set and transferring the complete wiring harness from the 94 trans to the 92 trans..

For the 1994-1995 Models if it has a temp sensor, it will be part of the harness and sit near a fluid flow path for trans temp.. If it was say a 1996 Trans the sensor will be in the valve body measuring the trans temp via a fluid passage in the valve body... The readings for these sensors are very different and are interpreted differently by the PCM...

When I did the rebuild on my 1995 4T60-E I used a 1996 Valve Body complete with Pump... And I attached the 1995 Harness to it so that My PCM would be happy with its readings and control, I simply left the Temp sensor from the 96 in the valve body as I could not have an open passage there.. The 1995 Temp sensor sits at the low point of the valve body...

I know its a confusing mess..

Do me a favor, as I would like to look at the wiring for this trans, But I would like to know what the Trans ID Tags say... The Original to the car and the replacement you used..

Ok, now you just threw me into a whole other barrel of monkeys.....the trans I just got today is from a 96. So you're saying that the temp sensor could be inside the valve body? I haven't pulled the 92 trans out yet, but that's planned for tomorrow. What exactly does the temp sensor control and would it cause any major harm to disconnect it? Other than the check engine light, which I can live with, and the possibility of overheating. What was gm thinking when they changed these trannies a thousand times? GRRRRRRR, this is driving me nuts. I just want to get this thing back on the road. If this car was made before 1988 I could have stuck any gm tranny in it and it would DRIVE. Sorry, had to vent. I didn't grab the numbers off the trannies yet, is there anything that will tell me if the 96 won't work? Thanks a lot.

I'd have to have the Tag Numbers to be able to look up the Wiring of the transmissions... GM had the same trans but set up a tad different for the varying car lines/ PCM's.... Some of these transmissions used Temp sensors, some used Temp switches, some used neither... Some had the PWM TCC Apply others did not..

Its a different ball game to go from year to year and different car lines..

Imagine this... There is a shift kit that I could install in a 4T60-E, more or less its a shift improver correction kit... But for example say the 1997 Model year... You have to be careful as to what parts you apply due to the possibility of the trans having a different Torque converter due to the TCC apply strategy..

But if you can get the Tag information I may be of more help to you and may be able to drop you some info that could help you..

Tried to edit, but the edit function still does not work for me..

Forgot to add...

On the 1996 Trans you may be able to simply use your 1995 wiring harness on the 96 trans... You will leave the temp sensor on the 96 trans alone( unplugged ) and simply install your 95's sensor, you'll see the sensor at the low point of the trans when you take the side cover off the 95's trans... I really wish I had a good pic for you

Ok, I got the tag numbers off the trannies. I took the 92 one out yesterday. I plan on putting the 96 in tomorrow, so any info before then will be helpful. I'm going to grab a side cover gasket today just in case. The first one is my original:
1994
614YMWWCMGZ
4 YM

1992
61ZBYNW2F4Y
2 BY

1996
616BXWW13JZ

Thank you

Ok there is a problem here already...

Your original trans is a 2.84 Overall Ratio, with a 30 Count Vehicle Speed Sensor reluctor wheel.. And you have the 1420 Stall Torque Converter

The 1996 Trans you want to use is a 3.06 Overall Ratio( Performance Ratio for the 3800 ) it also uses the 30 Count Vehicle Speed Sensor reluctor wheel.... This trans has the 1897 Stall converter

I am not sure how well the cars PCM will handle a 3.06 ratio being that its programed for a 2.84 ratio... I am just uncertain of how quirky it may be... With a higher ratio like that if you were to floor it the car may bounce off the fuel cutoff before the PCM forces the shift due to speed.... They both have similar shift points and TCC lock points... But I think it will be quirky...


Now with the 1996 Trans you have you will be able to use your 1994 harness inside the tranny behind the side pan... With this harness the trans should function fine.. From what I can see in the ATSG manual the 1994 and 1996 Transmissions you have are wired the same, but that temp sensor is different which is why you will use your original 1994 wiring harness..

Hope this helps... If you have any more questions please ask:)

Here is my update. I got the 96 trans into the car. I've got a few bolts left, just got tired and had to stop last night. I just had to say this. When I removed the side cover to switch out the wiring harnesses, I noticed two things. First, the two harnesses were identical, even the temp sensor. I switched them anyway. Second, my original trans seemed immaculate inside. Everything was super clean. I took a look and found a crack in one of the shift solenoids. I could have changed it out and put my original back in, but decided to go ahead and install the 96 trans. I can't be certain that that was my problem. My whole reason for taking it out was that I had 1st and reverse, but it wouldn't shift by itself. It would run through the gears manually and shift as long as it was moving. Please don't tell me a cracked solenoid is what has caused me all these headaches.

Here is my update. I got the 96 trans into the car. I've got a few bolts left, just got tired and had to stop last night. I just had to say this. When I removed the side cover to switch out the wiring harnesses, I noticed two things. First, the two harnesses were identical, even the temp sensor. I switched them anyway. Second, my original trans seemed immaculate inside. Everything was super clean. I took a look and found a crack in one of the shift solenoids. I could have changed it out and put my original back in, but decided to go ahead and install the 96 trans. I can't be certain that that was my problem. My whole reason for taking it out was that I had 1st and reverse, but it wouldn't shift by itself. It would run through the gears manually and shift as long as it was moving. Please don't tell me a cracked solenoid is what has caused me all these headaches.

See that goes to show that you can learn something new everyday... 96 may have been a mixed year depending on the car and car line... But just the same I am glad you swapped out the wiring harness...

A cracked solenoid could be an issue... But I am wondering if the Pump in your trans may have been getting weak.. It may have been a good thing you swapped the trans out...

I hope the 96 Trans will function and serve you well..

Also you may want to flush out the trans cooler in the radiator to make sure there is no garbage in the heat exchanger..

Let us know how this went..

:) It works!! I finished everything up this morning and got her running again. Everything works as it should. LOTS OF POWER!! I have a shaft seal leak issue, I think I'm going to buy a seal from a trans shop instead of the junk ones I've been getting at the parts store. That's an easy enough fix, though. I just wanted to thank maxwedge and especially jrs3800 for getting me through this and now I know where to go next time. On to my next project on the list......

Anytime... Glad to be of help..:)