OK i have a 91 cummins 2500 4x4 and right now there is nothing rong withit butt the fact that it wont shift into 4th gear i dont know what it is and would love to get some good advise

 

when ya shift into other gears does it slip out sometimes?

 

sounds like a shift fork bind to me

 

sounds like you have the same problem alot of us are having. bad top cover. read the thread getrag woes or shift tower all jacked up

 

I merged both your threads into one here...

I'm gonna guess that its a auto... You didn't say but if it is...

First try this...

https://www.dieselbombers.com/1st-ge...ensor-tps.html

Check the wires going into the side of the tranny, make sure they are connected. On is 12v and teh other is a ground. When the computer calls for OD it grounds the circuit. If the wires are hooked up with teh truck running use a test light to determine which wire is teh 12v hot wire, un hook the OTHER Next wire in a temporary swicth to the tranny that grounds when turned on. Go for a ride, get to 3rd gear and ground teh circuit, see if it hits OD.


Also do you have cruise? Is it working? Is the alternator charging? I ask that because it will help tell if teh computer is shot.

 

No it never slips in any other gears it was slippin in fourth and then it just completely stoped

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my bad yess its an automatic and no my cruise control doesnt work and i dont think my alternator is bad butt i have to buy a new battery cuzz my old one is shot and i cant even jump start my truck butt is that the alternator going out.

 

if you cant even jump it your battery is most likely bad, and acts like sponge when you try and jump it

 

All things considered, there's a big difference between slipping and not shifting at all. Does it pick up OD, but then freewheel? Or just not pick up OD at all? Elecrical probs won't make it slip, but will make it not shift. Your OD is spring apply and pressure release. A weak spring will cause OD to slip, and when bad enough, fail all together, which will also affect reverse. If all gears have failed, there's a chance enough clutch material has your VB plugged. armchair troubleshooting prety much stops there other than the battery of pressure tests you can run. The above applies only to your "slipping" condition however. If you have an electrical situation that is preventing OD from picking up entirely, then move to elctrical troubleshooting as some have stated. BUT, an electrical problem WILL NOT prevent the bottom 3 forward gears and reverse from working. It IS a hydraulic, mechanically governed transmission that requires no ECM input other than for OD, and in later years TC lock-up. Good luck, you'll get it figured.

Chris

 

My truck doesnt go into od butt it does fo into reverse an all the other gears just fine could it be my shift solinoid or what thanks for the input

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NAd i do have cruse and it isnt working butt my alternator is

 

I bet its either a bad TPS do the adjust I showed above or its a bad ECM. IF the TPS adjustment in the link above does not work look at the passenger side of the tranny, There are two wires, i always forget which is which, using a test probe find which one has 12v to it while the truck is running. Now wire a temp switch into the OTHER wire, run this switch into the cab, you want this switch to GROUND when you turn it on. Get up to speed and ground the circuit (flip the switch) it should shift into OD. If that fixes your problem you know its not your tranny its the communication to the tranny.