[Alvy]

Hello everyone. I'm a member of a few forums and feel that this one will help me solve my problem. My 94 Sierra crew dually with 6.5 TD has no overdrive until it reaches around 200 degrees on the temperature gauge and then it will engage O/D. After that I have O/D all day as long as the operating temp stays warm, works flawless. Have it sit for a few hours or get cold, back to no O/D until warm. I have been told that it should do this and also that its torque converter lock up that I'm not getting and not O/D. I know the difference between the two and also know that this is a problem and NOT what it SHOULD do. I've read that I should have O/D between 130 and 170 degrees which is normal but mine won't engage until around 200 and sometimes I have to turn truck off and then back on to get it. I have changed the coolant temp sensor for the ECM, T-stat, and coolant with no change. I've also been told that there is a TTS (transmission temp sensor ) in 96 and later models that would do this also but mine is a 94. Is it possible that a 96 or later trans was installed in my truck before I bought it or does mine have this sensor? I've heard of other possibilities being the speed sensors, shift solenoids, or TPS. I don't have any stored DTC's. If anyone could help me here it would be great. I've had no luck with any other forums and I don't want to throw parts at my truck. If anyone has resistance specs for the sensors I've mentioned that would be great too. Thank you, Mike

 

[THEFERMANATOR]

All of the 4L80E's had a temp sensor inside the trans. Sounds to me like you have a CTS problem. You said you've changed the CTS, did you use chevy parts or aftermarket? Friend of mine had a similar problem with his FIREBIRD before, he replaced his CTS as well with a WELLS. Problem was still there. Replaced the CTS with O.E. and still wasn't right. ended up being a bad connector. Check all of your connection, espescially the grounds and the mystery spacer on the passenger side battery. Try asking this question in the 6.5 section as it gets alot more traffic.

 

[Alvy]

Fermanator,
Thanks for responding so fast. Can you elaborate on the mystery spacer that you're talking about? To answer your question, yes, I purchased the CTS from Advanced Auto and not OEM, I'll look into that. I'll try to change this over to the other category too. Mike