Engine/Transmission (1994 - 1998) TPS - OD - TCC - Lockup - arrggggh

[Blue Coyote]

After doing lots of reading here I am still confused.

Truck - 97 3500 4x4 47re <rebuilt, billet single disc TC>. Linkage set per specs.



Running empty it shifts through all the gears / OD / lock up - sort of.

OD off - Any more that 60% throttle the TC unlocks

OD on - will shift into OD, and lock up if you are less the 50% throttle. TC will stay locked / OD on unless speed drops off.

When towing it still functions, but have this issue:

OD off - will only lock up at less than 50% throttle, and more then 60% throttle the TC will unlock. Makes towing difficult.

OD on - will shift into OD, and lock up if you are less the 50% throttle. TC will stay locked / OD on unless speed drops off.

Basically any more then 50 to 60% throttle will cause the transmission to unlock and shift out of OD.



Towing is done in area of heavy traffic (So Cal) and the mountain / desert roads. Want to be able to tow with OD off and TC locked up to 80% throttle (desert / mountain roads), and then OD off / TC unlocked (So Cal traffic).



From what I have read the TPS control the OD function. But does it also control the TC fundtion when OD is off?

Will adjusting (elongating mounting holes) the TPS achive what I want to do?

Or will I need to do the 3 position switch and the in-cab potentiometer conversions?

 

[Howard Durand]

Have you adjusted the TV cable? At full throttle, there should be about 1/16" of travel left in the throttle valve lever at the transmission. After that, there are several options for OD control. I don't have any experience with the 47RE but it does behave similar to the RH in which overdrive is controlled by the PCM. With the RH, TC lockup seems to have a mind of it's own.

The first thing you have to do is get control of OD. Your TPS is probably most of the problem. Replacing it with a potentiometer, does give you control of OD and eliminates problems caused by by a dirty TPS or electrical noise in the signal wires. Different vendors have their versions of controllers that allow the driver more control of the transmission and may be the best route to go.

If you like to play with the electronics there are several things you can do.

The potentiometer is a good place to start.

 

[Blue Coyote]

Thanks for the responce Howard.

Here is what I have done so far

Checked resistance - 2680 across, 440 & 220 between the center and the ends. No erratic readings through out the entire range.

Idle voltage 0. 95 t0 1. 01

WOT voltage 3. 90

Removed and cleaned up the TPS. Rechecked and got the same values.

All the readings are within spec - but will make a potentiometer set up.

TV cable - set to 1/32 slack at idle

If OD is off, TC will lock up at 40% and unlock at 50% <very bad>

With OD on , truck will shift into OD at 50% throttle. <okay)

Will hold OD & lock up to 80%+ throttle <good>

Does the TV cable have something to do with the unlock with OD off but not OD on?

 

[Ridesamule]

Just going out on a limb here, is there an engine speed correlation between your 40-50% OD off and 80+% OD on? I don't know if the speed sensor has any impact on an RE at all but... .

 

[Howard Durand]

Your TPS voltages appear to be right on and response with OD on seem to be normal except the statement that OD and TC lockup hold up to 80% throttle. Do they downshift above that point under normally advancing throttle without your actually doing a "kickdown"? If so, that is a bit strange too.

Once again, I am not familiar with the 47RE but I believe it is supposed to be more responsive to electronic signals than the RH.

The behavior of the TC with OD unlocked does not seem to be reasonable at all. Who did your transmission work? I would call them because it sounds like there is something abnormal in the way the throttle valve is functioning or throttle linkage is messed up somehow. You may want to have the PCM checked.

 

[KLincoln]

put a tc lockup switch on it. that way you lock it up on the highway and keep it out of lockup in town