wiring in manual OD switch

BgBlDodge

BgBlDodge

Hates hippies
Joined
May 7, 2007
Messages
16,647
In case I can't get this POT mod working I'm going to wire in a switch that allows me to engage OD. It will be temporary till I can scrape up the cash for a TPS. Anyone know which wires to tap in to on the tranny to accomplish this? I've already got a lock up switch. I was looking through the FSM some last night but couldn't figure it out.

If I'm correct, for this to work I'd have to get in 3rd gear, flip lockup, get up to speed, turn lock up off, turn OD on, and turn lock up back on. And when slowing down just disengage lockup and OD and come to a stop.
 
You may shift into third, lockup then OD without disengaging lockup.

However, without a TPS signal your line pressure will likely be at minimum which is very bad- kinda like limp mode with a 3rd gear start.
 
I was still planning on using the POT to keep the voltage up and subsequently the line pressure.
 
I didn't think the TPS controlled the line pressure, I thought the TV lever controlled the line pressure.

Also the OD is a momentary switch. Hit is once to toggle it on, hit it again to toggle off.
 
TPS is used to calc engine load, which is used to adjust shift points and line pressure.

also hes not looking to turn overdrive on and off, hes trying to shift into overdrive, so no momentary switch.

by the time you are done screwing around with this you are going to have more money and time into it than just buying the 12v tps....
 
Doubtful more money. TPS is $200, switch is $5, wire is free LOL.

In all honesty I'm waiting till I get paid next week so I can buy a TPS but in the mean time I'm trying to get my truck back on the road.
 
ok you are going to want to jump the TRANS relay in the PDC

the torque converter wire is the orange/black one from connector 2 (middle) of the PCM (pin 11) ground that to apply the converter clutch

the overdrive solenoid wire is the brown wire from connector 2 (pin 21), i beleive you will want to ground that also.

if it were me i would put them both on one switch, so you will have 1st, 2nd, 3rd, flip the switch for 4th locked up until you can get the TPS
 
zstroken said:
I didn't think the TPS controlled the line pressure, I thought the TV lever controlled the line pressure.

Also the OD is a momentary switch. Hit is once to toggle it on, hit it again to toggle off.
Click to expand...
Are you sure TPS doesn't affect the governor pressure solenoid?
 
Is that a trick question brandon? I honestly don't know much bout how these autos work. That's why I pay others to make them work.
 
joefarmer said:
Are you sure TPS doesn't affect the governor pressure solenoid?
Click to expand...


It may mod the gov solenoid a little bit.
Here is what i remember there are 4 algorithms for the gov solenoid.
low range, WOT, cold temp, and normal.


Your biggest impact on the line pressure is the TV lever.

Picture this if gov pressure and line pressure were closely linked, at 0 speed you would have zero line pressure.

Basically the gov solenoid just uses PWM average out a pressure that some what is proportional to mile per hour. Once you reach a certain mile per hour the solenoid stops and gov pressure equals line pressure.

TV pressure works in coordination with gov pressure to control your shift points.
 
Rollin Coal said:
TPS is used to calc engine load, which is used to adjust shift points and line pressure.

also hes not looking to turn overdrive on and off, hes trying to shift into overdrive, so no momentary switch.

by the time you are done screwing around with this you are going to have more money and time into it than just buying the 12v tps....
Click to expand...


How does the TPS adjust line pressure?

Gov pressure is gotten from PWM of the gov solenoid using line pressure.
 
Pulse width modulate. Basically since it is an on/off solenoid, to make things variable it will turn on, then turn off and vary the time it is on or off to make it "average" out to what it wants to be.

Basically if you want low gov pressure it turns on for just a short time, then is off for a longer duration.


To make it even more tricky it really doesn't turn on, it is a normally open solenoid. Basically when you remove the voltage accross it is open(to make limp mode the power to the powertrain relay is dropped, taking the 12V away from the gov solenoid allowing it to stay open, which means line pressure equals gov pressure which gives you third gear). Voltage accross the coil closes the solenoid.
 
zstroken said:
It may mod the gov solenoid a little bit.
Here is what i remember there are 4 algorithms for the gov solenoid.
low range, WOT, cold temp, and normal.


Your biggest impact on the line pressure is the TV lever.

Picture this if gov pressure and line pressure were closely linked, at 0 speed you would have zero line pressure.

Basically the gov solenoid just uses PWM average out a pressure that some what is proportional to mile per hour. Once you reach a certain mile per hour the solenoid stops and gov pressure equals line pressure.

TV pressure works in coordination with gov pressure to control your shift points.
Click to expand...
Thansk for the explanation. I was thinking TPS was more involved than it actually is.

If you don't mind I'd like to go through the reason why the pot mod doesn't work for Tyler- Are the other parameters besides the TPS not being met? Or can his VB not play with the pot mod?
 
There was a product out several years back that manipulated the PWM to the gov solenoid to modify the shift points electronically. One of the major tranny manufactures swore that manipulating the gov like that could cause bind up. The name of the product escapes me and I believe the designer has since deceased.

Dodge attempted to modify the shift points electronically with a TV motor. I never did figure out why they didn't mod the gov algorithm instead.
 
The pot mod should work for tyler. I have heard of folks that adjust the pot too far and the tranny won't lockup and stuff like that. Picture shoving the throttle to the floor the tranny usually unlocks.

Chrysler seemed to take a program and milk every bit out of it. Trannys engines, first gen trucks. The line that the 48RE cases were made on, was installed in the late 60's early 70's. They just added to the line to put an OD unit on, put electronics on it, put a TV motor on etc, etc.
 
See I don't understand why the POT mod wouldn't work for me either other than the 24v PCM and 12v PCM, even though both come with 47re's, must take in to account more than just throttle position to control lockup and OD. I've tried moving the pot from one extreme to the other and it does drastically affect shift points. But I've tried middle and full left and right and spots in between with nothing. Once the weather improves slightly (16* windchill is not my idea of wrenching weather) I'm going to put a voltmeter on it and set it at around 2.1v (bout midway between .3-.6v at idle and 3.6v at WOT) and see what happens.
 
You must log in or register to reply here.
Back
Top