dihiesel

hey yall thanks for the tech on the speed sensor on the diff. it made the abs/brake light go out. but unfortunatly the over drive still does not work and the OD off switch still does nothing. no the light does not come on. yes the tc lock up is engaging. and some times it acts like it wants to shift but it just don't. its a 98.5 with 47re4x4dually please help

prattman

There is another speed sensor on the tailshaft of the transmission. I just ordered one from Rockauto.com. It was about $21.00 shipped. I just lost overdrive on my '98 12 valve 2500 last week also a 47RE. It shifted through all the gears then down shifted into 3rd and now won't upshift to overdrive. It shifts through 1-2-3 fine. I haven't had time to dig into yet. I'm going to check my TPS and then change the speed sensor. I saw on the T.D.R. that worked for a few people. The tranny also my be in limp mode. I have no codes. If that doesn't work I'll be dropping the pan and changing out the governor pressure solenoid and the governor pressure sensor. They both control the electric ECM input for the overdrive shift according to my service manual. I figured I would start with the speed sensor since it's the cheapest sensor and the easiest to change. My truck has about 130,000 miles on it. Stock tranny with a DTT torque converter and valve body. I've changed the fluid at regular intervals. I'll try these before I hit the tranny shop. Let me know how you make out. -Glen

dihiesel

thanks glenn for the info. also when I bought this truck the guy told me he had 4 sensors changed in the trans.I'm wondering if there is a relay switch or something . does your OD off button work or show a light at all? mine does nothing.

dozer12216

OD button also turns light on/off. It is a temp close switch and can check with v meter. The speed sensor on tailhousing is for tranny operation only. There could be issue with solenoids or press transducer or wiring in tranny.

prattman

Yeah my overdrive switch and light work. That's what I would check first. I missed that in your post about the light. I don't know that much about automatic transmissions. I've been perusing my service manual looking for things to check before I take my truck to the tranny shop. You could also try calling D.T.T. in Canada and asking Bill Kondolay for advise. Nice people to deal with. www.dieseltrans.com . -Glen