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Rachet

Rachet

Active Member
Messages
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Location
Camano Island, WA
Hello all, I'm new here and have a 1996 GMC C3500 Dually 6.5l 116,000 miles. Trying to get more info on 4l80E trans stuck in first gear any help would be appreciated. The truck is a former ambulance from a small town in Mass. I drove it across the country to NW Washington State where I live. I had no problems on the trip. So far I've changed the corroded battery cables, fuel filter, and the PMD w/#9 resistor.
 
Hello Ratchet. Welcome to the forum.
Back of right side(passenger side) cylinder head, should be some ground wires. Check those wires to see if maybe one or so have broke at the terminal, remove the nut holding them down and sand and scrub them until they are bright and shiny. Wire brush the stud and nut until they are the same, then install them back onto the stud.
Might be some grounds at the bell housing and transmission too.
 
MrMarty51 said:
Hello Ratchet. Welcome to the forum.
Back of right side(passenger side) cylinder head, should be some ground wires. Check those wires to see if maybe one or so have broke at the terminal, remove the nut holding them down and sand and scrub them until they are bright and shiny. Wire brush the stud and nut until they are the same, then install them back onto the stud.
Might be some grounds at the bell housing and transmission too.
Click to expand...
Thank you! I will try that and let you know.
 
Welcome.
Stuck in first gear, but would like clarification.
Is the shifting mechanism stuck in one position? Or
You can shift into park, and all positions but only goes foreword? Or
You have park, neutral, reverse, and only 1 foreword gear which you think is first gear?

Way different scenarios there.
 
You need to check it for codes. Stuck in 1st means the PCM ic controlling it as limp mode is 2nd gear. And does your speedometer work? The most common issue for stuck in 1st is a bad output speed sensor not telling it the correct speed.
 
Will L. said:
Welcome.
Stuck in first gear, but would like clarification.
Is the shifting mechanism stuck in one position? Or
You can shift into park, and all positions but only goes foreword? Or
You have park, neutral, reverse, and only 1 foreword gear which you think is first gear?

Way different scenarios there.
Click to expand...
Shifts into all gears and moves in reverse and forward but will not upshift out of first when in drive.
 
MrMarty51 said:
Is there any codes set to the SES lamp. Need a scanner to check that. Parts store scanner should be able to read and clear codes.
Leroy Diesel has a nice package for these trucks if You need to buy one.
Click to expand...
Yes, the SES light is on. I will be picking up a loaner OBD2 code reader from the parts store. Thanks for everyone's input.
 
Rachet said:
Also, read the SES and came up with P0758.
Click to expand...

I just did a quick search on your DTC code. check all your grounds. remove them and clean the connections well, then clear the codes and re-check. I attached a bit of text that I copied from a site online for troubleshooting that code and a photo of the trans shift solenoids. I hope this helps. but do clean the grounds, that could be the source of the problem. their may be more ground connections on or around the transmission and the bell housing. you may need to remove the dog house to get to them.
 

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  • DTC P0758.txt
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    24cc3520-a729-4587-a12d-6ef2f96d40b5_65.JPG
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I know that there is back-and-forth about the #9 resistor. My vote is to remove it and make adjustments with the programming so that the system stays in balance. Put another way, if you want more power, have the computer do it in a harmonic manner. Related, don't drink the Kool-aid on marine injectors, stick with OE. I ran marines for a while and found that the only 'benefit' was that they belched an embarrassingly black cloud on start-up. Went back to OE and the system made less smoke, the throttle was more responsive, and there was no difference in observable power.

FWIW, might consider getting some form of software driven code reader and not one of the less expensive handhelds. Edge makes the Insight which is able to read codes, clear codes, display real-time data as the PCM sees it, and calibrate the speed display based on changes to tire size. Actually, the speedometer is known to have some inaccuracy to it and I found that after calibration the Edge tracked with GPS, so in time I completely ignored the dash and relied on the Edge for all performance information. I also used AutoEngenuity for more in-depth troubleshooting and found it useful to isolate an injector failure as it had the ability to turn off one injector at a time.

A good thing to know is that the dash gauge for coolant temperature is near worthless and feeds from a sending unit above the #1 cylinder. Better way to go for reading ECT is from the PCM which displays actual temperature and this sending unit is at the thermostat crossover pipe.
 
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