1992 Suburban Shifting Issues

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92 Burban

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Hello I have a 1992 Suburban that I purchased recently that would not shift into overdrive. 152,000 miles on it. Had the transmission rebuilt, still no overdrive. Took it back, said some wiring was bad and they replaced it. Nothing, Said there wasn't enough voltage going to the quad module. Put an alternator on and shifted great for about 10 miles then would drop back into drive. Took it back, they said it was in the distributor... Obviously I don't know what the problem is and neither does the transmission shop. Recently put a throttle position sensor on it. Nothing. Now it doesn't shift at all into OD and also doesn't go into first even when I manual drop it down... I give up! Any suggestions would be greatly appreciated. Thanks
 
did you check the computer for any codes? Did the shop pull the transmission and rebuild it or you pulled the transmission? If they pulled it, didnt they test the transmission after they rebuilt it rather than give you back a vehicle with the same problem? Is this a state licensed shop?
 
The computer didn't show any codes, The transmission was pulled by a local shop and rebuilt by a reputable transmission shop a "box job" is what they call it. Despite several attempts from both parties I am still stuck with it. Does anyone know if that year had a seperate ECU for the transmission? Is it possible that there is something with the speed pickup in the distributor? Thanks for any info.
 
How are you determining the transmission isnt shifting into 4th gear?
 
Well first off knowing the shift pattern on almost the exact same motor tranny combo on a later model suburban. This suburban is running right around 2800 rpm at 60 mph. It has shifted into OD since rebuild rpm around 1200, and all the other work done. When it did it lasted around 5-10 miles then I could feel a slight hesitation around 62mph and it would drop back out. For just a short time frame I could turn the vehicle off for about 10 minutes and it shifted fine again.If I drive in OD mode it will shift in to OD when I let of the accelerator going down hill. If I drive in Drive it will not coast like in OD and RPM stays the same. Before having tranny rebuilt it would start out in second and bump down "hard shift" into first gear to start off. Now it always starts off in second even if I drop it down into first. Basically I have 2nd 3rd and reverse.
 
Does anyone know what electrical componet actually tell the 4L80E to shift?
 
I'm not sure about the 92 but I have an 85 that had a similar problem. I ended up getting a new kick down switch, which is located on the accelerator pedal assembly, it engages when you step on the pedal all the way. Could be the kick down solenoid too, both are reasonably priced. It could also be a speed sensor which is usually mounted on the drivers side of the transmission. I would get a multimeter and check the continuity of all of those. If that fails it would definitely be something in the ECM which controls all the shifting. Governor/Modulator? Pressure control solenoid?
Check Rock Auto for all these parts. New ECM is around $100.
 
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I agree. If not shifting into overdrive is what you took it in for, then why aren't they honoring their work? Sounds like a small claims case if they won't get it right. What does your original shop ticket say the issue is that you brought it in for? Assuming they are trying to fix the OD problem, then obviously what they have charged you for so far wasn't the problem.
 
I really appreciate all leads and all advice. It is my fault that the situation wasn't handled better. I purchased the vehicle knowing it had tranny issues. I asked a local shop to pull the tranny out and send it to a transmission shop. They both did there job. Unfortunately for me the shifting issues are something other than rebuild. The local shop says hey we did what you asked, the tranny shop says hey we rebuilt it and will warranty when it shifts right. The tranny shop is willing to help fix the problem but are simply throwing stones at the giant. It is costing me money to keep sending it to them. The problem is mine, I screwed up not knowing it could be other things. Both shops did what they were paid to do, I just can't keep shelling out money to problem solve. Thanks so much for leads already!
 
Did they replace the torque converter? Maybe that's the issue?
 
Okay, at least they aren't trying to screw you.
We have the same transmission. I took mine in to a shop to discuss an intermittent problem in mine. They referred me to a guy who specializes in electrical and electronic repairs. Well, I talked to this person and he said when it happens again, call him and bring it in. My point is, cars today are very complex and diagnostics can get very involved. This shop acknowledged that the problem was beyond their capability and referred to a 'specialist'. He had the equipment to do a deeper dive into the issue. You may need to find someone like this where you live. Throwing parts at the problem gets expensive as you are finding out.
 
Problem exists before and after the overhaul. Would they have rebuilt the transmission and not replace the TC?? It's possible, but not smart.
 
I'm a member of several different car forums and it's not unusual for a shop to reuse the old TC after a rebuild. It's stupid, as far as I'm concerned, because of contaminated fluid and possible "pieces" inside, but what do I know? I'm just an old shade tree man.
 
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