Turbo Diesel Registry
Issue link: http://read.uberflip.com/i/594528
16 www.turbodieselregister.com TDR 90 TRANSMISSION SHIFTING PROBLEM WHEN WARM The transmission in my '98 Turbo Diesel 2500 shifts correctly when cold, but if it is over 210° it won't downshift to first gear and sometimes won't upshift out of second gear. The transmission shop that rebuilt my transmission three years ago has replaced about everything on the transmission and they are at their wits-end. My truck has new batteries and a new accelerator pedal position sensor (APPS). There are no diagnostic trouble codes (DTC). Could it be a failing powertrain control module (PCM) or possibly a faulty engine control module (ECM)? Any suggestions would be appreciated. rotohead, Reno, NV Was the temperature sensor replaced? Were the governor solenoid and transducer replaced? cerberusiam, Minco, OK Yes, all parts in the transmission have been replaced twice with the "new and improved" versions from BD. I'm thinking it is a possibly a failing PCM. rotohead, Reno, NV The temperature sensor should be external on your transmission and it gets overlooked sometimes, which can be the source of bad signals. Have you monitored actual governor pressure and throttle valve pressure when the problem happens? Have you monitored demanded governor pressure? If it demands a certain pressure and it doesn't set to that mechanically, then you have another direction to go. The PCM can definitely throw glitches and it gets worse as it gets warm. You can try replacing the PCM or do a little more research on pressures to narrow it down. cerberusiam, Minco, OK All the pressures seem normal. I can't find that external temperature sensor part anywhere available for purchase. The PCM would be a last resort, but a possibility. Thanks for the tips. rotohead, Reno, NV There should be an external temperature sensor and it should be a simple thermistor you can override by using a jumper wire which will signal the transmission is cold. If the temperature sensor went open when driving, the PCM would determine the transmission was overheating. You might try that and see if it makes any difference. Have you checked actual and demanded governor pressure when the transmission won't upshift from second gear? If that pressure is good (based on wheel speed) and the throttle valve pressure is good, then it has to be a mechanical issue. Either a shift valve is hanging or the direct clutch circuit is losing pressure so it won't apply the direct clutch pack. cerberusiam, Minco, OK We discovered that the problem was in the electrical middle connector on the PCM. Two wires in the middle of the connector had become loose and there were a couple of other suspect connections. The transmission tech connected the Snap-On scanner, and with the key on but without the engine running, he could move the harness around and watch values jump all over the place. After about two hours of clean-and-splice work, I have a smooth, clean shifting transmission again. My cost was less than $200 including new transmission fluid, a governor solenoid and transducer. rotohead, Reno, NV Editor's note: Man, I love this stuff. Just when it seems you've discovered all of the repairs for shifting problems we find another cure. It does us good to keep a running tabulation of the different problems and solutions, so here are the TDR chapter(s) and verse(s). Transmission Noise Issue 70, page 28 Issue 69, page 30 Issue 62, page 25 Issue 54, page 38 Issue 53, page 10 APPS Issue 68, page 29 Issue 66, page 30 Issue 60, page 92 Shift Problems Issue 60, page 28 LOOSE OBD II PORT While trying to pull up and clear some diagnostic trouble codes on my '01 Turbo Diesel 3500, I had a difficult time setting the scanner to work properly. There is play in the receptacle end of the OBD port and I had to constantly apply pressure to get the scanner to work. How do I repair the OBD port? VolsFan, Keedysville, MD I think you need a data link connector repair kit, Mopar part number 05017132AA, is what you need. mwilson, Lincoln, ME Yes, that is the correct part number. Bob Wagner, Fox Island, WA Coverage of the '98.5 to '02 Model Trucks (24-valve engines). Web Site Correspondence Edited by Bill Stockard.