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Discussion Starter #1
Well I got a deal on a truck of my dreams that needs some TLC. Its a 1993 Chevy 3500 4X4 crew cab dually. Got it cause they said 4th gear was out of it. I test drove it, and figured out it has to be something electrical as it has 4th gear/OD COLD, when it gets hot, notta. Had a SES on and would run a constate 199 degree's

Well for starters I did my in general 'new car' stuff

New thermostat and coolant, which glad I did as there wasn't much coolant in it, and the old thermostat looked like hell. I installed a 180 degree thermostat and Be Cool HD Coolant and water wetter.

I then did a ignition tune up, cap, rotor, plugs, wire, module.
Ran better.

Oil and filter change, just to make sure it was good.

I also put on a new TPS and Brake Switch, as I have seen a few trucks have hundred of dollars sunk into them for just these fixes.

So I then hooked up my old school Actron SCAN TOOL. I got a code 15, a code 43, and a code 73.

15 being a coolant temperature sensor (For ECM) Malfunction. Got a new one, and replaced the old pig tail. Code vanished.

43 came up on my tool as a ESC Module or component fail... Odd as I just put in a new module, not saying things can't be bad from the get go, but I highly doubt it. I looked up the code at work and it said Knock Sensor. Well sure as day, knock sensor was unplugged. New pig tail for it and code vanished.

Now there was no SES but a code 73...Then I noticed my brake warning light was on. So I learned that the brake light will come on as the kind of CEL for the transmission.

Well code 73 comes up as Transmission Force Motor Current Error on my scan tool. But at work it comes up as 'Pressure Control Solenoid.'

Well I ordered one, and am waiting on it so I kept doing some diagnosing. I noticed my brake light in the dash would trip, when I was going to loose OD. I then noticed my volt gauge would drop a bunch.

So when I got home I hooked up my DMM up to the alternator and battery (+ on alt output - on battery negative) and I was getting a steady 13.8 but as I let it set and get hot, it would drop all the way down to 11.2 and shoot up to 12.6 then 13.4, and it was a wash, rinse, repeat.

So I put a new alternator on it, truck acts better but again once warm no 4th/OD.

I am going to check the VSS wires, and I am also going to pull the trans plug and clean it out and put some dielectric grease on it. I have seen the old VSS wires with the insulation rotted off shorting out. So gonna try that.

But I was wondering if anyone had any ideas of something I could be missing. Fluid level is correct and has good color. Hoping to get the bugs worked out. I am having the senior tech of 25 years help me with this as much as possible.

Any help will be appreciated.
 

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I got a deal on my '91 3/4 ton suburban because the 4L80e would not go into OD and shifted hard. the problem was the throttle position sensor (TPS), and it cost me ~$120 to fix
 

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Discussion Starter #3
375 H&H (Built one of those not to long ago) I have a code 73, which has to do with the PCS (Pressure control solenoid) and defaulting line pressure, which answers why I lose 4th/OD. I will try the TPS, and hope for the best again, as I already replaced it once, Iw ill see what it reads on my Scan Tool.

I doubt it will fix it but you never know.

I pulled the rear mounted VSS and cleaned it and the plug in up, I also pulled the transmission connector cleaned it up and used some dielectric grease on it. Still the same. I was wondering, was my harness updated? As its a snap (I guess thats the word) style plug instead of a bolt in design? I ask as I know nothing about these transmissions or there connections.
 

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Discussion Starter #5
Autostoners trying to act like they know more then a GM technician, used my scan tool to read the voltage from the TPS at idle and it was reading .72 volts, so I took it back since it has a life time warranty. Dumbass tried using a multi-meter and read the sweep, then when I explained it to him he said 'Does it effect the performance of the vehicle' my respond was 'Yeah keeps my truck out of OD' but they only had a valuecraft one so I figure try it since I will get some cash back and if it doesnt work then, well... on to other trials and errors.

I plan on trying to get a set of solenoids so when I drop the pan I can change them all out, along with hopefully an internal wiring harness. But I gotta figure out if mine is the new up to date style.
 

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Discussion Starter #7
Thats what my scan tool calls it to 375, but at work on SI, it states it as 'Pressure Control Solenoid' which from what the master tech told me, is the same thing, just a different name.

Cause mine reads exactly like this

73 'Force Motor' current error

And it has a picture of a bell next to it.

I ordered both shift solenoids, and the TCC solenoid as well so I will replace all the solenoids in it. Hoping to get a inner harness as well.
 

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I could scan the code 73 troubleshooting flowchart from the service manual if you need, but it looks like you've already done most of it.
 

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I printed the flow chart off of SI, and I had the master tech simplify it for me, but I appreciate all your help 375.

Fun story, I cleaned up the original TPS that was on the truck and took it back to autozone as the one I got from them was reading .72 V at idle, so I took the old one back, and knew I could BS my way threw this, but I never thought I would meet a genius.

I told him that I had specced the TPS out at work (I work at the local GM dealership) and that it was reading .72 volts at idle, when it should read no more then .5 well he goes and gets a multimeter and starts trying to check it, I asked what he was doing he said 'Im checking continuity' I told him, that it sweeps fine but at idle it reads .72, he then finally asks 'Does it effect the performance of the vehicle?' my reply was simply 'Uhh yeah I dont have OD' So anyways I got a Valuecraft TPS and some money back. I'll try it and if it helps I will get a AC Delco unit so I know the quality is good.

Anyways more tinkering to be done.
 
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