3/4 shift problem

[fysh-guide]

I have a 97 6.5 1500 suburban I recently bought. Since then I've isolasted the PMD/FSD, installed a 4" SS exhaust, downpipe and crossover, new intake, and a shift enhancer. I've also had the rebuilt tranny (14 months 4L80E) flushed and have it filled with Redline high temp ATF. When I'm running under load, up a hill, the tranny goes into limp mode and won't shift into O/D after cresting the hill. When I stop, shutdown for a minute or two, restart and continue down the road, it's fine. If I engage the shift enhancer it enhances the problem. After restarting, the truck seems to miss while cruising but eventually stops after a few minutes. The "missing" got stronger after the tranny flush with the Redline ATF. The trouble codes it gives me are usually P0717 (Input/Turbine Speed Sensor Circuit no signal) or occassionally P0741 (Torque converter clutch circuit performance or stuck off). It is my understanding that there are 2 speed sensors on the driver side of the tranny that could be the problem. I've replaced the sensor forward on the driver side of the tranny and the problem continues. The rear sensor driver side doesn't seem to have a wiring harness attached so I haven't replaced it. Is the forward sensor the input and the rear sensor the output and is it possible the output sensor is elsewhere? If replacement of the sensors doesn't work where would I go next?
Thanks
Fysh Guide

[moondoggie]

Good Day!

From reading on the Page over the years, I think I remember some saying that the reluctor wheels (?) on the shafts and/or the sensors themselves can collect metal shavings, causing them to give such trouble. You might want to search the 6.5L Turbo Diesel forum to see if this is so; if so, removing & cleaning the sensor & wheel doesn't sound very difficult.

You might additionally want to post your question on the 6.5L Turbo Diesel forum. Dr. Lee knows all, but he doesn't own a truck like yours - his is a primo 1984 C10 with probably the nicest 6.2 ever built. If you post in the 6.5L Turbo Diesel forum, there are a few thousand of us who will see your topic, & hopefully help. ;) Dr. Lee will always respond if/when he has time, if he knows anything about your particular problem, but re-posting on the 6.5L Turbo Diesel forum will speed your help. Personally, I usually reserve Dr. Lee's forum for deep technical issues that his tremendous knowledge & experience can help with.

Blessings!

[DmaxMaverick]

Moved to the 6.5L Forum.

Good luck!

[fysh-guide]

It's fixed. The water temp sensor plug wires on the top of the coolant crossover manifold had contacted and melted against the intake manifold. A simple short! A bit of electrical tape and heat shielding and done. The truck hasn't blown a shift since!