Nadams01
Well-Known Member
- Joined
- October 29, 2019
- Messages
- 135
- Reaction score
- 83
- City, State
- Castle rock, Colorado
- Year, Model & Trim Level
- 1991 explorer eddie bauer
After much research, wiring and testing I have successfully installed a manual lock up switch in my ex and have been running it for 5 months now, and I want to clear some of the information that was speculated around doing this. I wanted to install this MOD due to living in Colorado and going up into the mountains frequently I would lose lock up on my torque converter causing a lack of efficiency and excess heat build up in the trans. I'm going to take us through a deep dive of the HOW WHAT and WHENS for the factory lock up system and more.
What is it:
The torque converter does exactly as it's stated, converts torque produced by the engine to the transmission without a physical connection to the engine like a clutch and flywheel so the vehicle can roll to a stop without stalling. Issue being, these converters use fluid spun by the engine to then spin the input shaft of the transmission and cause a loss of power that would other wise exist if it was bound by a clutch. A stock A4LD conv. stalls around 1200RPM, meaning the flywheel must spin atleast 1200RPM to begin moving the input shaft of the transmission. This is a higher stall speed then most factory conv. Usually I see anywhere from 500RPM to 800 RPM but never any higher then 1000RPM. This does have its advantages, it alows the vehicle to start moving when the engine is in more of a preferable power band but comes at a loss of efficiency particularly in higher gears, 3 or 4th in particular. The TCC is a solenoid which actuates fluid through the valve body and locks the stater and impeller together between a set of friction discs, much like our limited slip rear ends and locks the converter together as one piece, and would act as if it was mechanically bound to the flywheel like a clutch. This drops our RPMS by a significant margin, which is good for fuel economy and is much more efficient at developing instant torque and horsepower to the rear wheels. As a result the transmission is kept at a much lower temperature due to the lack of friction the converter would otherwise be producing if it was unlocked.
How does the factory TCC work:
The A4LD is a hybrid electronic and hydrophilic controlled transmission. Your 1-2 and 2-3 shifts are controlled through pressure regulators in the valve body much like an old school transmission. Once in 3rd or 4th the PCM will take a variety of readings to determine the shift patterns or lockup functionality. The 4-3 downshift is controlled by the PCM, however if the vacuum modulator is within its maximum range and the kick down cable is depressed far enough the 3-2 downshift is controlled by the transmission. If you have selected overdrive as your drive gear, and are cruising around 55mph, here are the variables the PCM will look at to actuate the TCC solenoid.
BARO > 23 inHG
TPS input: no rapid tip ins or rapid tip outs of throttle movement.
ECT: above 100 or 130 depending on year range.
BOO: brake on and off switch, a additional wire is added to the brake switch as to tell the PCM if the brakes are applied. If they are, the PCM will disengage the TCC.
This may sound all fine and dandy, however there are major disadvantages to fords management system. First of all, and slight movement in the throttle will cause the TCC to disengage throwing us into 4th gear unlocked and on the highway through traffic, you can really feel a major drop off in torque and power when the converter unlocks particularly in 4th gear. I know these are not fast vehicles, but 4th gear unlocked is border line useless for highway driving. The major player, especially if you live in the mountains like I do is when your over 7500 feet, and the BARO sensor detects a pressure below 23inHG it will prevent locking of the solenoid due to high altitude performance concerns. The last thing you want when climbing vail pass is to do it while the conv. is slipping the entire time.
Why should I install a manual TCC switch:
Being able to leave the converter locked in 4th or 3rd gear makes the vehicle much more easy to drive. These 4.0 don't produce any power, and especially not up high, if your over 2250 RPM your around the peak power and torque that the engine will make and it wont climb enough at the upper RPMS to justify having a 1200 or 1500rpm stall. Don't get me wrong, yes you will make more power at 4000RPM then at 2250, but with the converter unlocked it is not worth the excess RPM unless you are full throttle due to the major loss in efficiency. I was so excited when I put the trans in 3rd, and pulled from 50mph to 70mph with the converter locked with ease. This simple MOD will change the way you drive your explorer, and has made a huge difference in daily driving for me. In 4th, you can just plow your foot down to a good 75% throttle without the PCM kicking down into 3rd and pull pull pull with such a huge difference.
Addressing common questions about the TCC lock up:
Can you lock this up in 2nd or 1st? No, the actual hydrophilic portion of the solenoid needs correct fluid pressure from the valve body passages, and will not receive any if you are below 45MPH and are not in 3rd or 4th, even if the electrical portion is bypassed. When your coming to a stop, and you leave the switch locked up it will not stall the engine, the TCC will remain locked up until a kickdown from 3-2 is forced which hydrophilic will unlock itself. Can it upshift and downshift between 3rd and 4th while the conv. is locked? Yes, it will, the 4-3 downshift is firm with the conv. locked however it will not do damage to the transmission. If a manual kick down to 2nd is called for it will unlock itself while going into 2nd, then upon the 3 up shift immediately lock again. When upshifting from 3-4 I prefer to lift of the throttle a decent amount to allow the overdrive sprag to fully engage, this went bad on a previous trans build so its something to keep note of. Sometimes it will down shift back and forth from 3 - 4 until it is fully seated if you bury your foot into it between shifts. Be a little gentle when its upshifting. Leaving the conv. locked is not uncommon in the automotive world. I have worked on tuned diesel trucks and this locking of the converter while shifting is very common, example I had a 2012 dodge 3500 24v 5.9l cummins. It had a shift kit and other mods performed but when entering 3rd it would lock the conv. to apply more load to the engine and spool the turbo. a 2019 Hyundai sante-fe came in for some trans related codes stating the TC slip was out of specification, essentially how much the converter is slipping by comparing the engine RPM and input shaft speeds while the TCC was applied, and in 5 6 7 and 8th gears were all shifted and downshifted while the TCC was locked from the factory. Is it any faster then leaving it unlocked? no, but actually yes. If you were WOT the unlocked converter would be slightly faster, however and other amount will be far faster and more efficient than with the TCC unlocked. Just try a locked 3rd gear pull with it locked and you will understand. Do the temps stay lower? Yes, by allot which I will explain when I go into my setup. Can you fry your PCM by doing this mod? No, the TCC solenoid gets 12v IGN, the only side of the PCM we are tapping into is a ground side.
My setup for trans and switch.
I have a built A4LD with a transgo shift kit and upgraded valve body, upgraded 5r55e gears and clutch packs with all new solenoids and bands and drums. I run a external cooler from a F350 and have a trans temp gauge before the cooler. On a normal day 80 degrees or so the trans will be around 140 with the converter left in stock form and with it locked the majority of the drive will not exceed 120. When I was driving through Wyoming on a 100 degree day it got up to 175 with AC cranking the entire time. Also keep in mind these are pre-cooled numbers. I have removed the pan and filter after several months of usage and found no abnormal clutch wear or damage. I took the signal wire from the PCM which is pin 53, please count the terminals on the connector itself as the 91 has 2 tan/white wires. One for the TCC and one for the injector signals. I "Y"d it into a separate 2 pin On OFF switch which the secondary pin goes to ground. This allows me to either A allow flow through the factory wire and retain factory style lock up engagement or over ride it with a ground signal regardless if the PCM is commanding a ground. I drilled a hole on the panel below the steering wheel to mount the switch, so I just reach below my leg and flip it on or off. One day I will make it all fancy by using green and red LED with a display to show if the PCM is commanding a lockup VS my manual lock-up but this is perfectly functional.
This works, and I feel is a must have mod to improve the driving experience for any A4LD.
What is it:
The torque converter does exactly as it's stated, converts torque produced by the engine to the transmission without a physical connection to the engine like a clutch and flywheel so the vehicle can roll to a stop without stalling. Issue being, these converters use fluid spun by the engine to then spin the input shaft of the transmission and cause a loss of power that would other wise exist if it was bound by a clutch. A stock A4LD conv. stalls around 1200RPM, meaning the flywheel must spin atleast 1200RPM to begin moving the input shaft of the transmission. This is a higher stall speed then most factory conv. Usually I see anywhere from 500RPM to 800 RPM but never any higher then 1000RPM. This does have its advantages, it alows the vehicle to start moving when the engine is in more of a preferable power band but comes at a loss of efficiency particularly in higher gears, 3 or 4th in particular. The TCC is a solenoid which actuates fluid through the valve body and locks the stater and impeller together between a set of friction discs, much like our limited slip rear ends and locks the converter together as one piece, and would act as if it was mechanically bound to the flywheel like a clutch. This drops our RPMS by a significant margin, which is good for fuel economy and is much more efficient at developing instant torque and horsepower to the rear wheels. As a result the transmission is kept at a much lower temperature due to the lack of friction the converter would otherwise be producing if it was unlocked.
How does the factory TCC work:
The A4LD is a hybrid electronic and hydrophilic controlled transmission. Your 1-2 and 2-3 shifts are controlled through pressure regulators in the valve body much like an old school transmission. Once in 3rd or 4th the PCM will take a variety of readings to determine the shift patterns or lockup functionality. The 4-3 downshift is controlled by the PCM, however if the vacuum modulator is within its maximum range and the kick down cable is depressed far enough the 3-2 downshift is controlled by the transmission. If you have selected overdrive as your drive gear, and are cruising around 55mph, here are the variables the PCM will look at to actuate the TCC solenoid.
BARO > 23 inHG
TPS input: no rapid tip ins or rapid tip outs of throttle movement.
ECT: above 100 or 130 depending on year range.
BOO: brake on and off switch, a additional wire is added to the brake switch as to tell the PCM if the brakes are applied. If they are, the PCM will disengage the TCC.
This may sound all fine and dandy, however there are major disadvantages to fords management system. First of all, and slight movement in the throttle will cause the TCC to disengage throwing us into 4th gear unlocked and on the highway through traffic, you can really feel a major drop off in torque and power when the converter unlocks particularly in 4th gear. I know these are not fast vehicles, but 4th gear unlocked is border line useless for highway driving. The major player, especially if you live in the mountains like I do is when your over 7500 feet, and the BARO sensor detects a pressure below 23inHG it will prevent locking of the solenoid due to high altitude performance concerns. The last thing you want when climbing vail pass is to do it while the conv. is slipping the entire time.
Why should I install a manual TCC switch:
Being able to leave the converter locked in 4th or 3rd gear makes the vehicle much more easy to drive. These 4.0 don't produce any power, and especially not up high, if your over 2250 RPM your around the peak power and torque that the engine will make and it wont climb enough at the upper RPMS to justify having a 1200 or 1500rpm stall. Don't get me wrong, yes you will make more power at 4000RPM then at 2250, but with the converter unlocked it is not worth the excess RPM unless you are full throttle due to the major loss in efficiency. I was so excited when I put the trans in 3rd, and pulled from 50mph to 70mph with the converter locked with ease. This simple MOD will change the way you drive your explorer, and has made a huge difference in daily driving for me. In 4th, you can just plow your foot down to a good 75% throttle without the PCM kicking down into 3rd and pull pull pull with such a huge difference.
Addressing common questions about the TCC lock up:
Can you lock this up in 2nd or 1st? No, the actual hydrophilic portion of the solenoid needs correct fluid pressure from the valve body passages, and will not receive any if you are below 45MPH and are not in 3rd or 4th, even if the electrical portion is bypassed. When your coming to a stop, and you leave the switch locked up it will not stall the engine, the TCC will remain locked up until a kickdown from 3-2 is forced which hydrophilic will unlock itself. Can it upshift and downshift between 3rd and 4th while the conv. is locked? Yes, it will, the 4-3 downshift is firm with the conv. locked however it will not do damage to the transmission. If a manual kick down to 2nd is called for it will unlock itself while going into 2nd, then upon the 3 up shift immediately lock again. When upshifting from 3-4 I prefer to lift of the throttle a decent amount to allow the overdrive sprag to fully engage, this went bad on a previous trans build so its something to keep note of. Sometimes it will down shift back and forth from 3 - 4 until it is fully seated if you bury your foot into it between shifts. Be a little gentle when its upshifting. Leaving the conv. locked is not uncommon in the automotive world. I have worked on tuned diesel trucks and this locking of the converter while shifting is very common, example I had a 2012 dodge 3500 24v 5.9l cummins. It had a shift kit and other mods performed but when entering 3rd it would lock the conv. to apply more load to the engine and spool the turbo. a 2019 Hyundai sante-fe came in for some trans related codes stating the TC slip was out of specification, essentially how much the converter is slipping by comparing the engine RPM and input shaft speeds while the TCC was applied, and in 5 6 7 and 8th gears were all shifted and downshifted while the TCC was locked from the factory. Is it any faster then leaving it unlocked? no, but actually yes. If you were WOT the unlocked converter would be slightly faster, however and other amount will be far faster and more efficient than with the TCC unlocked. Just try a locked 3rd gear pull with it locked and you will understand. Do the temps stay lower? Yes, by allot which I will explain when I go into my setup. Can you fry your PCM by doing this mod? No, the TCC solenoid gets 12v IGN, the only side of the PCM we are tapping into is a ground side.
My setup for trans and switch.
I have a built A4LD with a transgo shift kit and upgraded valve body, upgraded 5r55e gears and clutch packs with all new solenoids and bands and drums. I run a external cooler from a F350 and have a trans temp gauge before the cooler. On a normal day 80 degrees or so the trans will be around 140 with the converter left in stock form and with it locked the majority of the drive will not exceed 120. When I was driving through Wyoming on a 100 degree day it got up to 175 with AC cranking the entire time. Also keep in mind these are pre-cooled numbers. I have removed the pan and filter after several months of usage and found no abnormal clutch wear or damage. I took the signal wire from the PCM which is pin 53, please count the terminals on the connector itself as the 91 has 2 tan/white wires. One for the TCC and one for the injector signals. I "Y"d it into a separate 2 pin On OFF switch which the secondary pin goes to ground. This allows me to either A allow flow through the factory wire and retain factory style lock up engagement or over ride it with a ground signal regardless if the PCM is commanding a ground. I drilled a hole on the panel below the steering wheel to mount the switch, so I just reach below my leg and flip it on or off. One day I will make it all fancy by using green and red LED with a display to show if the PCM is commanding a lockup VS my manual lock-up but this is perfectly functional.
This works, and I feel is a must have mod to improve the driving experience for any A4LD.
