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93 C3500 4l80 w/ trans problems

tanman_2006

tanman_2006

Just a farm kid...
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Seiling, Oklahoma
Found it for sale, its a clean low mile 93 single cab 2wd 3500 Drw turbo 6.5. The owner said it lost OD, could it be a bad tps or is this a common 4l80 issue not an engine sensor issue? Says it has all other gears and runs great with 140k on it

Thanks.
 
Shifting hard? Codes in ECM? - trans does NOT trip SES light. IMO the SES light is bulb check only on 1993. Or Engine stall/no engine RPM sensed indicator.

Mechanical would be failure of a sprag clutch. Could be a slipping TCC clutch as well. Rebuilds here are $1100.00.
 
Seems to shift fine just keeps reving, I didn't go look personally a guy I know in the area checked it out. Said it didn't feel like it ever tried to shift to him
 
If it shifts through 1st to 3rd just fine, but not 4th, then thats normally a CTS or trans fluid temp sensor. The TPS normally causes all of the shifts to be higher, and 4th won't shift.
 
Like I said, I haven't personally driven it but my friend said it wasn't shifting hard and just acted like it was "hung" in 3rd.

Didn't ask about the shift rpms, I figured that typically depends on your foot too.
 
Ok if the truck is still there I will be checking it out Thursday.

What tests can I do to narrow it down.

I don't want to buy it if the trans is toast but if I can narrow it down to a sensor then I'm good with that.
 
Pull codes with a paperclip. Inspect wiring for speed sensors. Look for cracked engine RPM sensor/oil pump drive. Manually shift and see if the TCC lockup is missing or just 4th. Again auto trans rebuilds are cheap. IF you find a good place that is cheap...
 
I'm pretty sure I know a couple places that will do a decent job on a rebuild but the asking price will have to be adjusted accordingly.

He is asking 3700 and my buddy offered 3k and he was ok with that, said he would run and get the cash but called me to tell me what he knew. I figure I can get lower if I show up and act like I know what I'm talking about.

A rebuilt trans and, higher stall, and ATT wouldn't hurt my feelings at all lol
 
Where are each of the sensors located, I've never had a 93 w/ 4l80.

My only 4l80 was on my 95 and it never had a problem in 300k miles
 
THEFERMANATOR said:
If it shifts through 1st to 3rd just fine, but not 4th, then thats normally a CTS or trans fluid temp sensor. The TPS normally causes all of the shifts to be higher, and 4th won't shift.
Click to expand...

CTS in in the coolant crossover, where is the trans temp sensor? Honestly never knew the trans temp was monitored by the truck, just thought it just referenced engine temps.
 
tanman_2006 said:
CTS in in the coolant crossover, where is the trans temp sensor? Honestly never knew the trans temp was monitored by the truck, just thought it just referenced engine temps.
Click to expand...
It's part of the internal wiring harness in a 4L80E. If the trans fluid is cold, the TCM will change the shift speeds and timing accordingly, as well as locking out lockup and OD to help make the fluid warm up quicker.
 
tanman_2006 said:
I guess I should have said trans controlling sensors.
Click to expand...

Every sensor, unless it drives a gauge, is for the ECM and transmission. Only the cold advance, a dumb fail prone switch, on the coolant crossover has squat to do with the 1993 engine. Glow plugs are a self contained stand alone controller. The ECM has zero idea or care about engine temps.

Engine RPM (Oil pump drive RPM sensor), Engine load (TPS), Input shaft RPM (Converter slippage), output RPM (Correct gear and trans slippage), internal temp (Hot/Cold Converter lockup)

TPS on IP Needs to be in adjustment and working or weird shifting results. RPM on oil pump drive prone to cracking and failing (Seal crack on housing with silicone RTV if the sensor still works), Input speed and output speed sensors on transmission are prone to the insulation falling off the wires going to them. The main transmission connector is prone to oil leaks and bad connections due to being full of oil - an updated connector is available.

Word about idle and fast idle adjustments required every 6 months by the book: The TPS needs to be checked and adjusted after idle adjustments. It's idle voltage range is very limited and will code (limp mode) if it's much over or under 0.5v with the cold fast idle solenoid disconnected.
 
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