This overdrive nonsense is starting really stress me out

No overdrive at all. Worked fine till last weekend. All I did was a valve adjustment and then washed down the motor. Thought it was something wet, but it's been a week now and I have drivin the truck a few times and it still doesn't work. It's been in the 70-80's here..so it should be dry by now.

I've got the manual and the supplement manual for 91.

I've checked with a meter:

Fuse.
TPS.
Neutral Safety switch.
Cleaned and inspected overdrive solenoid connector on top of trans.
Disconnected the computer and checked the harness from SBEC to grey engine connector.
Loop through sensors ( trans thermal and coolant thermal) working as they should be. Both being closed and completing circuit. Checked the loop through the overdrive soleniod in the trans.
Checked all connections


Manual mentions a "Overdrive Module (right side on support bracket)"
I can't seem to find it. Anybody ever seen it? Has a black straight 8 pin connector on it.
Dash switch supposedly connects to this module. The light on the switch changes. Doesn't do anything though.

Has anybody battled this problem?

mystery module? SBEC? overdrive lockout soleniod?
It's starting to look like a dealer/DRBII tester deal....which i'm not to happy about

Help!

As a side note..I installed my sensor for the KSB and it's working now
Also put on new front rotor and new pads both sides today

Den

 

Found the mystery overdrive module.It's behind glove box on right side of the opening on a small bracket. Ordered a new one to test with.


Den

 

90% of everyone problems seem to be after washing down the engine, lol. i think ill shy away from that... jiMMy

 

It must like that road grime

I need to print out the wiring diagram and check everything and color it in with a highlighter to make sure I get everything.

Have to read some more...while relaxing and not cursing, throwing wrenches and scaring the neighbors

Den

 

I smell a dying throttle position sensor...

 

I've been searching for the coolant thermo switch with 2 terminals. I was only seeing the single terminal sender. Was thinking my manuals were full of it because of the half year stuff. I finally found it hidden under the intake, near the KSB thermal switch behind a bracket for ???? (resister for KSB?).

I'll have to check it out tomorrow if I can reach it. Make sure it's clean and working properly. Been looking for DAYS for that darn thing.

I tested the TPS and all looks good. Have it set at 1.00v at idle and it goes up to 3.85v at full throttle. Also slowly opened and closed the throttle and no jumps or funny stuff on the meter.

Den

 

Sounds like you've got all the bases covered. I'm surprised you haven't found it. Hydraulic problem?

 

You may have the TPS voltage set too high....
Try an idle value of .6 vdc as a starting point.....also the total increase from idle value to WOT value should range between 2.25 vdc and 2.75 vdc higher.
The higher the TPS idle setting the later the OD shift happens.

bob....

 

Be sure to clean the TPS connector. Mine O.D. was really screwed up and I was
at the point of replacing the TPS. I cleaned the connector real good and put some dielectric grease on it and have had no problems for over six monthes!!

JJ