Engine/Transmission (1994 - 1998) Another O/D OFF switch for T/C lockup

[DConrad]

Has anyone ever used a second O/D OFF switch for a T/C lock switch? I know there is no mechanical latch in the switch but that can be overcome with an electrically latching relay. My truck already is wired for a T/C lock switch but Diesel Nerd took the switch out thinking I wouldn't want it. I do. Locking at 42 MPH isn't so cool when an eighteen wheeler is breathing on my fifth wheel's bumper. I've got another "Nerd" working on the schematic, but in the mean time I'm looking for some feedback from folks who may have tried it or know someone who did. I could just put another switch in but I'm looking for something a little different. Thanks.

 

[Ridesamule]

I moved my TPS to the cab, placed a potentiometer next to my brake controller. If I need to quickly unlock the converter vs. badly slipping it at low rpm (semi barreling down on me). I just give it a quick spin raising the voltage and unlocking the converter. When up to speed i just turn the pot back to operating range and drive with normal ecm/speed control again.



By the way after using this system I never use my mystery switch anymore, the converter will stay locked up after taking my foot off the throttle until OD/3rd lockup speed reduces to the point that the ecm unlocks it, or I touch the brake pedal.



This works well towing down hill, just take foot off the throttle and use the hand control for gooseneck on long down hills.

 

[Howard Durand]

Ridesamule's setup is pretty innovative as it eliminates the TPS completely but if you want absolute control over TC lockup a switch is still not a bad thing to have.

An OD switch can be used even though it is momentary. Latching relay schemes aren't too difficult to build. Do you want it just to lock the TC or do you also want to be able to unlock it as well?

Being able to keep it unlocked requires a little more circuitry but is handy sometimes.

 

[DConrad]

The more function the better, I think. What are the benefits of both. THe original idea was a three position switch. One would be normal operation (leaving the T/C lockup relay installed and the ECM handling the business); the second would be lock, and the third unlocked. THe schematic builder was handling the setup for that but he hasn't come through with it yet. I need to get it done quick. Camping season is looming. I'm in AK for a few weeks (without truck) but when I get back I'd like to get it knocked out. Lots of CTD's up here. We outnumber the Fords 10:1 by my survey.

 

[Howard Durand]

Is your schematic builder going to build the control for you or just make up the diagram?

If you can do your own assembly, I can send you a diagram of a circuit that works well.

 

[DConrad]

I can do the assembly. The diagram would be appreciated!

 

[Howard Durand]

Here is a drawing of my TC switching scheme. Look it over and if you have any questions let me know. My scheme uses a 3 pole double throw toggle switch with center position off but a rotary switch will work fine and may be easier to find.

The relay is small and plugs into a 16 pin DIP socket but any DPDT 12 volt relay will work.

 

[DConrad]

It looks pretty straight forward. I think I can handle that. Thanks for keeping me current!

 

[Ridesamule]

Nice scematic Howard, I have recieved a few questions about how I do the in cab TPS but lack home software and have no spare time at work to do so. I think I will start a new thread an see if I can get something going.

 

[Joe G.]

Ridesamule,



I use MS Paint for drawing schematics. Plus I have captured a bunch of electonic graphics symbols. If you would like to look at some I have done and/or want some of the symbols e-mail me at -- email address removed -- .

 

[Howard Durand]

I use Turbo Cad to draw the schematic. I had a dickens of a time getting it to fit the requirements of the forum before I could show it here. The drawing was converted to JPEG but it kept coming up in landscape and was too wide.

I have another program called Adobe Photo Deluxe that came with my CD burner and, with it, I can cut out all of the fat from a picture or drawing without shrinking it.



I would think converting the TPS signal to a fixed voltage would be easy to accomplish. I am really considering it. If you want to start a new thread about it, we could discuss this further there.

 

[DConrad]

Before I find this new forum and show my ignorance to all... . what is TPS?

 

[Howard Durand]

Throttle Position Sensor.

According to the service manual, it is used in diesel trucks only that have the automatic transmission.

 

[DConrad]

OK... I knew I had heard it before. I guess the cool air is getting to the gray matter. What's that advantage of make the signal a constant voltage? Looking for new thread now...

 

[biggy238]

If the PCM doesn't sense the correct amount of voltage, it won't allow the TCC torque converter clutch to lock up... pergatory for your transmission... It also controls the shifts along with the VSS.





My TPS few apart internally at the dealership a few years back and they put it back together broken... . I drove home in 2nd gear. . I had to remove it, turn the internals to a working position and drive it the 30 miles back... . It worked fine in that constant position.