Hard shift1st to 2cd and no overdrive 1991 3500 4l80e

[orrum]

Ok I am new 2 diesel trucks. The truck is a 1991 3500 6.2l dually with a 4l80e tranny. It has run great and shifted perfect since I bought it, 1000 miles and suddenly it shifts hard from 1st to 2cd and has no overdrive and no passing gear. This happened after I noticed the cruise control cable was broken and the previous owner had duck taped it and I decided 2 cable tie it. Then I test drove it and had the shift problem. I have been checking threads plus I posted a thread on the 6.2 forum and they have helped a lot but suggested I try the trans forum. I have checked the grounds and found one hanging loose behind the passenger front fender, it belonged on the block so I attached it with a screw hose clamp to a exhaust bolt and got rid of the code 22 and test drove it and no help so I ran a ground from the fender to the alternator mount bolt and got rid of the code 22 and test drove it and no help. So I borrowed a test gauge and figured out the tps ground wire and 5 volt wire and the variable volt wire, I tested the throttle opening and got a nice even constant increase so I figure the tps is good. So I adjusted the tps slightly 4ward and did the paper clip thing and the code 22 was gone and then I messed up and started without taking the paper clip out, I snatched it out real quick and test drove it and it shifted hard and no overdrive so I pulled over and shut it off and restarted and drove off and it shifted perfect, I stopped and started again and did great, I even turned the motor off and restarted and it shifted great so I turned and headed 4 home and @ 55 mph I set the cruise control and it sorta hunched but then settled down and the cruise worked great so I pulled over and started out and the hard shift no overdrive was back! Next I checked and got code 12 and 22 as usual but could not get 22 to clear by unhooking battery and no voltage on tps wires. Gave up and went to house for ac and water. Then tackled it again and I must of not been useing the tester right cause I had proper working tps and I could reset the codes and eliminate the code 22. Went for test drive and it shifted perfect but when I stopped @ a stop sign and pulled out it was back to hard shift and no overdrive. So I put tools up and am hoping u here @ the trans forum can help me. Thanks and sorry the post is so long.

 

[HMF]

I have been fighting the same problem. The only difference is my TCM has code 85 when it does this. My truck is a 96 with a 4L80E that has a mechanical pump and a TCM (part number 16196390). The TCM randomly goes into a mode where it does the same hard shifting. The hard shifting is because when the TCM gets into this mode it commands constant full line pressure and that causes the hard shifts. When my TCM gets into this mode it has a code 85, which is "undefined gear ratio". If I shut the engine off, and restart it the TCM will go back to normal. I have tried adjusting the TPS and I have changed the front speed sensor on the transmission. I will change the rear speed sensor in the next few days when I get some time.

What is the description for code 22?

Does anyone have any ideas as to what could cause code 85 other than speed sensors?

 

[orrum]

Code 22 is a TPS code. I dont get a code 85 and mine is pretty much never shifting correctly. What is TCM? How did u adjust the TPS? Let me know how u do.

 

[orrum]

Yee Haw, did i fail 2 mention I am THE words greatest one legged cowboy!!!!!! LOL I fixed it!!!!! Lets just hope it stays fixed!!!! Read on another forum that 2 set the TPS u have 2 unplug the fast idle solenoid before taking and setting the volt readings. Well yall remember this all started when I messed with the cruise control cable and it affects the fast idle solenoid 2! Then I got it to shift correctly again and when I used the cruise control it quit working so I figured they are working together somehow. Looked up setting the fast idle solenoid and found out about the little wire inside it under the rubber boot, took boot off and wiggled little very fine fragil looking wire and put back 2gether and the fast idle solenoid went back 2 working so I unplugged the thing again and used meter 2 set the TPS and it was 2 low a voltage so moved it up to more than .5 volts, its a needle type and not very easy to read such a low voltage but its somewhere between .5 and .75 and test drove it and tyed stopping shut off and everything and my beautiful 4l80e tranny is back! Not brave enough to try cruise control yet! LOL Also now that the fast idle solenoid is working it idles about 1200rpm n then when warm it falls back to 800-900, I can live with this, one day when I am ready to tavkle it I will set it lower but for now its working and I aint gonna mess with it! Thanks all of u, I think it was actually several problems and we solved one but another had to be found etc. Now back to installing the fuel pressure gauge and converting to wvo! More adventures to follow I am sure.

 

[WarWagon]

If the cruise control cable has no slack it can open the throttle or hold it open and set this code. Use a digital volt meter to set the TPS voltage. 0.5 or slightly over like 0.55.
Every time you adjust the idle you get to set the TPS.

Undefined ratio is usually major mechanical in the transmission like unable to shift into overdrive from a blown sprag clutch etc. Of course check wiring first including speed sensor wires that have insulation fall off them.

 

[orrum]

Hey thanks war wagon. To clarify if I change the high idle by adjusting the solenoid do I have to adjust the TPS or only if I change the after it warms up idle? Hmm or both? Bet thats why my tps messes up when I cable tied it I got it too tight and now if I use it it doesnt let the thing idle back down to the right spot? So now how to set the cruise cable slack would be a good questio? U guys r awesome! Thanks!

 

[HMF]

Code 22 is a TPS code. I dont get a code 85 and mine is pretty much never shifting correctly. What is TCM? How did u adjust the TPS? Let me know how u do.

The TCM is the Transmission Control Module. It is used on vehicles like ours that have a mechanical injection pump. 1994 and up that have the electronic injection pump use a PCM (Powertrain Control Module) that controls both the engine and transmission.

I adjust my TPS pretty much the same way you wound up doing it - with a voltmeter. I also have a scan tool, so I can use that to adjust it, but it is pretty much the same.

I think when the TPS is too far out of adjustment the TCM goes into the "limp" mode that you experienced. Mine is going into that mode, but for a different reason.

Thanks

 

[just a number]

one other thing that has been known to cause wierd issues with the 91-92 4l80e is the wiring connector. it has a bolt in the middle. the connector fills with fluid (usually find it weeping on the outside) and messes up the connections. there is an updated(93-) version which corrects this but you have to cut and splice all the wiring. inside and out. the code 22 is TPS low voltage. it should be 5V(feed from the TCM)