I Have a 94 c3500 6.5 liter
the trans kicks out of o.d randomly and i have codes 68, 78, 81, 82, 83, and 87. any advise? I have heard that the tps can cause this also the input speed sensor, but seems like its torque converter problem. sometimes it will reset with computer sometimes not. when it happens, usually its hot and it sticks in second gear. please help!? I want to set the son of a bitch on fire. btw i have no speedo issues i.e output sensor, and it is fine until it heats up. also i have a small coolant leak i need to fix at t-stat housing that causes a low coolant light. also the glow plugs seem to work like congress...they dont. hard to start and dies sometimes requiring extensive cranking to get running again. ive put new batteries in it, new pmd and relocated, new 4" turbo back exhaust, and new coolant temp switch. shortly before it f...s up it usually sputters and runs like sh.t right before.

 

For your transmission problem.... I had a similiar issue, kick out of OD when warm. The computer kicks it out because it reads a large enough difference in rpms between the engine rpm speed sensor and the input shaft speed sensor. This can be due to one (or maybe more) of the following:

Bad Torque Converter
Bad, weak, or leaking TCC solenoid (or possibly worn sealing area around TCC seal)
Fluid too hot (blocked trans cooler) or simply
Fluid in need of a change

 

For your glow plug problem.... FIX THEM!!!
It is very hard on your starter to crank on the engine for long periods. "

How long is too long?", you ask? 15 SECONDS

Crank for 15 secs, let cool for a minute.

Does the glow plug light come on when the key goes to "run" position? If so, how long? If not, glow plug inhibitor switch, or wiring.

There are only a few components in the glowplug circuit. It mainly consists of a glow plug inhibitor switch (under IIRC 135 degrees, glow plugs fire), a glow plug relay, glowplugs and the associated wiring.
Using a screwdriver, jump across the large posts on the glow plug relay. Using an assistant, have them watch the dash light for it to come on. If it does, it is either inhibitor switch or relay (or associated wiring). Check for power on all 8 plug wires (unhooked from plugs) while jumping the relay posts.
I never thought I'd say "plug wires" when talking about a diesel, .

Remove all 8 plugs and check condition with a short length of wire and pliers on your truck battery's terminals. IIRC, If less than 5 plugs work, the relay fires for about 1 sec.

This should help you get on track to fixing your glow plug problem, unfortunately, this procedure will not fix Congress.

 

thanks for the info! ill try trans service first on trans issues and do glow plugs
test asap. what about shift solenoids as called for by codes i guess if you are in there might as well change them i just dont want to throw parts at it, as i have done so before and usually regret it. i dont have tons of cash and have three vehicles f...d up one with a thrown rod, one with a blown head gasket and my truck... baby jesus have mercy! I need a beer!:assh at::asshat :

 

Does it shift fine until it kicks out overdrive? Or does it slip in 1st, 2nd, or 3rd? Does it shift too early? If you have a volt meter, you can check the TPS to make sure it is set correctly. IIRC, check voltage between two or the wires and set it to 0.48 volts. I don't remember which wires, tho.

 

heres what usually happens. It starts to run rough, sputters etc then kicks out of o.d. into second and will not shift out of second. at a stop light it will take off in second and not shiftup or down.

 

until it acts up its fine. almost seems like a intermittent fuel supply problem putting it into limp mode. sometimes though it will kick out of overdrive into neutral, and if you romp on it it kicks back in. this seems like t.c. failing to me. there is no code related to fuel issue also.

 

Limp mode kicks the transmission into second gear. The trans will not shift from 2nd gear until conditions are met that tells the computer to leave limp mode. I'm gonna bet that your TPS is bad. Have you checked the voltage on the TPS?

 

ok cool. that would be sweet. ill try testing tps and hope thats it.....