looks like I'm going to have to look beyond the trans temp sender and the TPS to fix my problem: the trans shifts smooth as silk in all gears, runs okay in Cruise Control, but just will not make the shift from 3rd to 4th.

So, having only a Haynes manual which gives next to nada info on transmissions, where do I find the Overdrive Solenoid, and how do I replace it?

I just put in a new trans filter and did a full flush on the fluid, which looked black but had no bits of anything in the pan or on the magnet.

So I really am hoping to get the OD function reestablished. Never had any indicators of any trans problems. OD had been working, but just went out while highway trip. Maybe due to being 1 - 2 qts low on fluid due to the crack in the trans cooler line, or who knows?

So, who has redone their OD solenoid and how do I know if there is enough line pressure?

thanks

lester

 

with OD locked out, will the PCM engage the converter clutch?

FYI, the solenoid is mounted to the valve body on the drivers side right next to the converter solenoid.....inside the trans.

 

got Diesel?

thanks for the reply. If I understand your question; the truck does lock the torque converter when the dash OD button is pushed and lit. The rpms drop about 250 rpm in 3rd gear when OD is locked out., running about 1800 rpms @ 55mph. i have a 3.54 rear end. and 4X4.

Incidentally, our roads are pretty iced up, so the truck stays in 4x4. I tried a brief run in 2 wheel drive, no difference.

regarding the OD solenoid, I guess it is accessible after removing the pan & filter?

thanks

 

the reason I asked is if your sending unit were okay as it sounds like you might have tested it.......but there were a wiring fault somewhere, this test would show it. If the problem were PCM/temp sender related, the converter also is disabled along with overdrive, if a high temp or low temp condition is present. Since TC lock-up works, the associated sending unit input and output wiring are okay, along with the sender itself.

Yes the OD solenoid is just inside the pan, mounted in a "pack" along with the TC solenoid, on the driver side of the valve body. There will also be a harness running to it. The next thing to check it that harness. It is somewhat common while performing a filter change for the wires to be moved out of position and when re-attaching the filter, become pinched or cut by the filter attaching bolts.

I will also check to see which of the wires going into the trans is the OD solenoid wire. Then you can check this wire for PCM signal and narrow it down considerably.

Be in touch

 

gotDiesel,

Thanks very much for your help with this. I had the problem before doing the fluid change. Maybe the solenoid has failed or needs to be disconnected from the wiring harness to reset.

The PCM is way over my head, and the Haynes manual that I have.

thanks again

lester

 

I am bumping this thread to get any new input or instructions I can for how to approach this NO OVERDRIVE problem.

The truck runs good. Our roads are finally clear of ice, so I would like to restore the Overdrive function. 16mpg at 55mph is not bad, but 20+ is better, and the noise level is more pleasant too.

I lost the OD function while driving. All was okay at 55mph, came to a stop sign and the OD never came back.
Changed the trans fluid with complete flush and filter.
still no OD, but shifts were smoother. Feels like it wants to shift-up and the torque converter will lock up.
OD button works; pushed in it raises the rpms to @ 2300 @ 55mph
Cruise Control works,
I took the TPS apart and cleaned it, tried adjusting it by removing the mounting bushing inserts. I could detect no change in the rpm time for TC lockup.

Over drive and Cruise worked fine before, so I have not taken the wire loom apart.
I installed a new Napa trans temp sensor; no change.

In the course of all this I disconnected the batteries to reset the PCM and detected no difference.

I guess I will need to pull the pan and look for the TC solenoid etc.
Maybe the solenoid itself is stuck?

As I live 80 miles from a tranny shop of unknown ability, I would rather do this myself.

The trans oil was pretty black, but was 2.5 years old, it did not smell burnt and there was no grit or shavings in the pan, on the magnet, or fluid.

Ideas would be very welcome.
thanks

Lester

 

Did you ever get this figured out? I am curious to know what you ended up doing....

 

No, never tried grounding the wire from the OD switch.

Still get about 15-17mpg w/o the Overdrive function and truck drives fine. Still feels like it wants to shift and drops maybe 100-200 rpm once warm and with over 45mph speed.

The cruise control works fine. I tested the speed sensor solenoid and it has been fine. Not like I drive more than 6k miles in a year anyway....

Need to drop the pan and change the fluid soon. Maybe will try to get into it again. Diesel is $3.60 per gal where I live so sure would like the extra 5-7mpg the Overdrive gives....

 

If your OD button raises the rpm when pushed in, doesn't that mean it was in OD? Are you sure it's not the TC that is not locking?

I believe the valve body has to be dropped to access the OD solenoid, the governor solenoid and transducer can be changed by removing the filter.

There have been numerous problems like this, check the 7 pin plug on the drivers side of the trans, just behind and below the front band adjustment. Make sure it's not wet with tranny fluid, causing shorting between the pins. If it is, you may have to buy a new gear selector sensor, and stop the fluid from leaking on the new sensor.

On that same 7 pin plug, #7 pin is the TC lock, #6 pin is the OD/3-4 lock(the numbers are on the plug, pull it out and look at it's face). If you splice into them(seperately), and insert a switch and a 22 ohm 1/2 watt resitor to ground, you can test them at will. If they operate with the switches, then you know they(solenoids) are mechanically "ok".

Let us know, Jess

 

Hi Jess,

Thanks for your interest. Yes, pushing the O/D Off button does raise the RPMs but only by about 100-150. When functional, the motor would drop from 2200 to 1700 RPM at 55mph.

I appreciate the pointers and need to change the fluid soon so maybe I'll find the connector is not making contact.

thanks again!

 

Hello, Im interested in what you are saying. Why would I need a switch and a 22 ohm 1/2 watt resistor to ground the OD gear selector? Would grounding the wire say to the cigarette lighter or dash ground be sufficient with out a switch?

 

hi
have you checked the stoplight switch adj .
i believe it also will disingauge od if not set correctly / or defective ?

 

Dash ground is sufficient, you need the switch to disengage, otherwise you will be locked in OD all the time. The 22 ohm 1/2 watt resistor is to keep from throwing codes and going into limp mode.

If you do both circuits, remember to put a resistor and switch in each one, and at least a 22 ohm in a parallel circuit, 33 ohm would be better. Some people, including me, originally used 10 ohm resitors, however in parallel, two 10 ohm's, become 5 ohms, and it's too close to the bottom range of the sensor and it will also cause codes and limp mode.

 

got diesel my trans is doing the same thing but when i hit my o/d button on nothing happens the trans could have gotten hot i just bought the truck so what is the best way to find to what is wrong also it shifts great 123 just wont go in 4 thanks neal

 

Bring the brake pedal to you while you are going fast enough to engage overdrive and see if it goes in. If so, the brake light switch needs to be moved forward closer to the pedal. Peace out