Best Advice on Towing with T/C Lock - Diesel Forum

MOUNTAINMAN444 · 06-25-2006, 09:20 PM

A few questions for the experts on the best way (least harmful way) to tow my 8k – 9k travel trailer.

1.When going down the expressway at 70 mph and 2000 rpm, should I manually lock the torque converter so it won’t unlock when you start up a hill? Will this hurt the transmission or make it last longer.

2.When pulling a long slow grade in the mountains, should I lock the T/C while still in third so when the transmission shifts down to second on the hill, the T/C is locked and pulling or will this hurt the transmission?

3.Going down hill, should I keep the T/C locked when I have to downshift to second or just let it spin freely?

4.Lastly (maybe), can I downshift to first and let the transmission hold me back or will this burn out the coast clutch (I heard that it would burn it out but I don’t know and don’t want to find out)?

I would like your knowledge and advice on these situations. I can’t afford mistakes because of my stupidity. ’02 7.3 PSD, 4R100 transmission, 3.73 rear, 108k miles.

Thanks, Joe

Birken Vogt · 06-25-2006, 11:04 PM

I assume from your comments that you have a manual lockup switch. I wonder about the long term health of the transmission using one of those things, consequences unforseen such as transmitting lower RPM engine vibrations into the transmission, or trying to stay locked at too low of a pump RPM where the line pressure is not sufficient causing slippage. This is just speculation. It sounds like you keep your engine RPM up which is good both uphill and down, uphill it's easier on the engine than lugging and downhill it keeps the brakes from catching on fire.

1. I think the TC stays locked on its own pretty much all the time you are in 3rd and 4th gear travelling at highway speed.

2. I don't know how it works on the later models but I also thought that it stayed locked in 2nd most of the time if the speed is high enough. Just watch the temperature and if it starts to get too hot (210 pan, 250-275 cooler line) then you need to do something about it, otherwise don't worry.

3. Going downhill I would keep it locked, this is one thing I hate, it unlocks as soon as you hit the brake pedal and doesn't lock again unless you step on the gas. Not good for hills where you descend with a combinations of foot brake and engine braking.

4. Well I am not exactly sure of this question but I would not engage the TC lockup in 1st normally, it will be pretty harsh. Some large Allisons do it if 1st is manually selected and it definitely holds the truck back, almost too much under normal conditions. Without lockup it should be fine.

Birken

eddywallace · 06-26-2006, 12:47 AM

I do not mess with Ford trans much (mine is manual) but I do build Allisons. The more you keep the TC locked up when towing, the cooler the trans will run. I would unlock it during the shift if it seemed to shift to hard. I would try shifting both ways and if it was not REAL hard with it on then leave it on most of the time.

MOUNTAINMAN444 · 06-26-2006, 09:41 PM

Let's try one more. If I keep the rpms above 1200 so the pump is flowing good, are there any situations where it will hurt my transmission to run with the T/C manually locked.
Joe

Birken Vogt · 06-26-2006, 10:21 PM

I can't imagine why there would be but I also don't know if 1200 or any other number is good or bad.

Birken

PSDWILDERNESS · 06-27-2006, 12:48 AM

The only time you should need to be locked is on a decent. If you have to shift down another gear while on the decent, unlock then shift then relock. You can lock it while up shifting for a while but eventually you will waste the torque converter and maybe more. These transmissions are designed to slip when shifting to eliminate shock loading. Basically don't lock it if there is a chance of it automatically shifting up or down. Also, make sure it isn't locked when manually going in or out of OD. Randy

Birken Vogt · 06-27-2006, 03:12 PM

I think that some of the shifts are done with the convertor locked under normal conitions but I don't know that for a fact and it may also do funky things like easing up lockup clutch pressure during shifting. But to be sure, the safe way to do it is to unlock the convertor for shifting. There is very little official information available on these transmissions espeically regarding aftermarket stuff like this.

Birken

PSDWILDERNESS · 06-27-2006, 04:30 PM

[ QUOTE ]
I think that some of the shifts are done with the convertor locked under normal conitions but I don't know that for a fact.

Birken

[/ QUOTE ]

Trust me on this one, mine is never PCM locked during any shifts. I have played around with the lockup switch and there is a major difference in shifting with the TC locked and unlocked. The whole truck shudders on locked shifts and I have never felt that when not manually locked. Randy

WannabePSD · 06-27-2006, 11:37 PM

I'm curious on this also. I have a John Woods tranny and part of his "deal" is to install a TC lock switch. I really haven't the foggiest idea how to use it. I thought I did... [img]/ubbthreads/images/graemlins/shrug.gif[/img]

I got going pretty good up a hill in OD. Pulled it down into 3rd (appx. 2400rpm) and flipped the switch. The rpm's went down immediately and I lost momentum. I don't get it. So, I just keep it in 3rd going up hill and I have no problem going into 2nd if needed. And then there's the downhill application...ugh!! Since I have that hole drilled in my lower dash, I'm thinking about cutting it off and using that hole for my DP chip rotary switch here soon. [img]/ubbthreads/images/graemlins/rolleyes.gif[/img]

Alin

duallycruzer · 06-28-2006, 07:31 PM

1. When on the highway turn it on and leave it on unless your speed gets below about 30mph.

2. Leave it locked. unless your speed drops below about 30mph or it feels like it's starting to lug. Situations like this is what the T/C lock is all about. It keeps your engine in the power band and keeps your trans fluid from getting as hot because your not getting the heat caused buy the fluid couple in your T/C.

3. Like I said. Keep it locked unless your speed gets below about 30mph. Uphill you get more pulling power and down hill you get more hold back.

4. With a stock trans never manually down shift into 1st to slow down. You will either burn up your coast clutch or first gear clutches.

my3wags · 06-28-2006, 07:58 PM

[ QUOTE ]
[ QUOTE ]
I think that some of the shifts are done with the convertor locked under normal conitions but I don't know that for a fact.

Birken

[/ QUOTE ]

Trust me on this one, mine is never PCM locked during any shifts. I have played around with the lockup switch and there is a major difference in shifting with the TC locked and unlocked. The whole truck shudders on locked shifts and I have never felt that when not manually locked. Randy

[/ QUOTE ]

Don't know about yours but when I installed my TC lock I also taped into the PCM T/C lock line with a LED. I can see when the PCM locks the T/C it does before O/D...

Good Luck
Big E

MOUNTAINMAN444 · 06-29-2006, 10:44 AM

[ QUOTE ]
1. When on the highway turn it on and leave it on unless your speed gets below about 30mph.

2. Leave it locked. unless your speed drops below about 30mph or it feels like it's starting to lug. Situations like this is what the T/C lock is all about. It keeps your engine in the power band and keeps your trans fluid from getting as hot because your not getting the heat caused buy the fluid couple in your T/C.

3. Like I said. Keep it locked unless your speed gets below about 30mph. Uphill you get more pulling power and down hill you get more hold back.

[/ QUOTE ]

This is what I thought you should do but I wasn't sure. Does it hurt for the transmission to downshift into second with the T/C manually locked?

[/ QUOTE ] 4. With a stock trans never manually down shift into 1st to slow down. You will either burn up your coast clutch or first gear clutches.

[/ QUOTE ]

I had read this before, is there a reason for this or is it just the way it is with the 4R100?

Joe