potential transmission problems

[Swatland]

Hi guys, this is my first post on this board. I am looking at a 91 dodge ram 4X4 with a cummins and an automatic transmission. I want a standard, but the privce is right on this rig. Heres the problem. The transmission doesn't go into overdrive. This has the overdrive override swith(i suppose you would call it this). Is it possible that the switch or wiring is faulty? How would i find out the source of the problem, short of taking it to a transmission specialist. Thanks

 

[jrjuday]

Welcome to the nuthouse, Swatland. For a newbie you sure ask complicated questions. I just got my overdrive working again, this time it was the vehicle speed sensor. It was fairly easy to diagnose because the OD, speedo, and odometer all quit working at the same time. Overdrive problems are so common on these trucks that some owners have gone to manual overdrive switches, etc. Do a search on this forum and you"ll get quite a bit of good info on the various causes of OD problems. If the transmission shifts good in L, 2, and 3 and their are no signs of internal problems I would not let the OD issue scare me away from a good deal... might even be a good bargaining tool. Most of the electrical issues are more irritating than expensive. Good Luck.

 

[1stgen4evr]

No OD

The PCM controls the OD with a number of inputs from several sensors on the truck. The OD is wired hot and the PCM enables the shift by grounding the circuit. A fault here may be one of the sensors or it may the the early signs of PCM failure. Does the AC and alternator work as they should? These are also under the command of the PCM.



As jrjuday mentioned, don't let these things stop a good deal but be aware that you may spend some money and time to clear the problem. Typically, if the OD 'just isn't there', the OD unit isn't bad but the control inputs/PCM are faulty. The common solution for the OD is to put a switch on the shift lever ( or use a later model shift lever) so that you control the shift rather than the PCM. The transmission itself is right substantial and will take the cummins pretty good. The torque converter will need to be upgraded to get the most from your truck. After market suppliers have done wonders with the Torque converter and valve body.



James

 

[Swatland]

thanks guys, i'll check that check out the alternator/ AC when i go look at the truck. I was hoping that this was the case and that the transmission itself wasn't prone to massive OD failure. thanks again.

 

[KSommer]

my truck came with the same problem, a toggle switch cured it. who do yo guys sugest for transmission upgrades? i would love to beef mine up befor i put more power to it.

kent