Tranny/torque converter question

[texas mike]

Howdy,
Getting ready to go for a new F350.
Question.
On my old 2001, the torque converter does not lock up in first and second gear. Can cause high tranny temp when climbing and no engine braking when going down hill.

How does the new six speed handle these situations.

Also, I have read that the engine braking works best with cruise control set. On slow, steep down hills, does the cruise shut off (release speed).
If so, can you use the manual gear selector in tow/haul mode?

Thanks for info,
TM

[PerryB]

Tow/haul and manual mode are mutually exclusive. I THINK lock-up begins in 3rd with this trans but am not 100% sure. I know that you can perceive the lockup beginning with 3rd. I used to have an '02 that would overheat the trans. badly when pulling a stiff hill in 2nd with a big trailer on. It was the primary reason I sold the truck. I even replaced the original air cooler with one approx. twice the size to no avail.
I now have an '11 - F350 and a trailer that goes about 14k in typical fashion. I pulled it through Utah last July (it was very hot, but based on your location you probably wouldn't know about that!) and had no trans temp issues whatsoever. The oil temp will get up pretty high, so if you get the truck, spring for the cost of a good synthetic engine oil such as Rotella.

[Hdslider]

The converter locks up 3rd thru 6th.

[edjunior]

Originally Posted by texas mike

Howdy,
Getting ready to go for a new F350.

Also, I have read that the engine braking works best with cruise control set. On slow, steep down hills, does the cruise shut off (release speed).
If so, can you use the manual gear selector in tow/haul mode?

Thanks for info,
TM

Not sure where you read this. On slow, steep down hills, you should not be using cruise control. And besides, cruise control would be counter to what the engine braking is doing. Cruise control is trying to keep a constant speed, while the engine braking would be trying to slow the truck. The engine braking starts when you hit the brakes. As you slow down more, and/or apply more brake, the tranny will downshift as needed to help slow the truck. Once you hit the brakes, the cruise control is disengaged anyway. The best way to see how the engine braking works is to stick it in tow/haul and play with it.

[Painted Horse]

Not true Ed.

I frequently will crest a steep grade and set my cruise for the speed I want to hold down the grade. i.e coming over the top of Parleys Canyon on I-80, speed limit is 70mph, but I usually want to hold 50-55 mph with my rig because of the few curves on the 20 mile downhill run into Salt Lake. I set the cruise at 50 and let the cruise worry about what gear it should use to hold the grade. It will downshift all the way to3rd gear by itself and hold the truck in the 50-55 mph range at 3500 rpm on that 7% grade. If I hit some flat spots in the downgrade, the cruise just holds the speed and adjust the gears, as soon as the grade returns, it downshifts.

If I touch the brakes, The cruise disengages and then I have to determine the gear that I want. i.e. touch the brake repeatedly to get it to down shift to 3rd. or use the +/- to force downshifts.

The trick with the Ford Exhaust Brake is to be at the speed you want to hold down the grade at the start of the grade and get into the right gear. Don't be going 70 mph and hope the exhaust brake will slow you to 50 mph.

I've done the same process for going down Logan canyon into Bear Lake at 40 mph in 2nd gear (7-8% grade) and coming out of Eaglewood ( 12% grade) at 25 mph in 1st gear. All of these with 10,000 to 13,000 lbs trailers in tow. I just set the cruise and let it do its thing.

[MK160]

Mine works just like Painted Horse's as well. Set the cruise and forget it.

MK160

[edjunior]

Interesting. I will have to play with it more as well! Of course I don't have any grades to speak of and dang little in the way of hills. Maybe that's why I use mine differently.

[KJ Smith]

Originally Posted by edjunior

Interesting. I will have to play with it more as well! Of course I don't have any grades to speak of and dang little in the way of hills. Maybe that's why I use mine differently.

About the only way you see it around here is on one of the big "flyovers".

Every once in a while if the road is clear and the CC on mine will drop into 5th on the downside to maintain speed.

Before Thanksgiving we took a trip up through Arkansas. You see how well the engine braking and CC work there.

BTW, 1600 miles, 20.7 mpg average on the trip, non towing.

[Painted Horse]

Help me understand this torque Convertor locking up.
Like I said, I've come off some 12% grades in 1st gear at 3500 rpm.
If the TC does not lock up in 1st or 2nd gear, how can the engine hold me back?

I know on my 2006 truck, I had the B&D Exhaust brake. One of its features was to lock the TC during exhaust braking. But it would only lock the TC above 25 mph, So even when I had the EB engaged, if I dropped below 25, the truck started freewheeling and my speed would pick up. This was so the locked up TC didn't stall the engine.

If my current 6.7L is holding my truck and trailer back on a steep grade in 1st at 20-25 mph, Is not the TC locked up? Same thing in 2nd gear at 40 mph coming off several steep mountain passes. If the TC didn't lock up in 2nd, would not the truck continue to free wheel and pick up speed? Seems ther are different programing for the Lock up depending on what the truck is doing.

Just wondering?

[Mark Kovalsky]

The torque converter does not need to be locked to provide engine braking. You get about 10% more engine braking with it locked than unlocked.

When the wheels are driving the engine he torque converter acts as a fluid coupling. It will transmit torque in that direction, but it cannot multiply torque as it does in the driven direction.

[Blue12]

Don’t all modern transmissions have something called an overrun clutch that opens to allow the truck to coast when it wants to go faster than the engine? It’s what allows the truck to coast forever when you lift the accelerator when not in tow haul mode. It exists for fuel economy. The overrun would have to be after the torque converter to work right. The converter lock itself would be between the input and output of the converter preventing efficiency loss when locked. So, in braking mode (tow haul), the overrun would stay locked even if the converter lock is open in 1st or 2nd gear. Mark—your thoughts.

Len

[Painted Horse]

Thanks Mark, Was hoping your would comment,

Thanks for your insight

[Mark Kovalsky]

Originally Posted by Blue12

Don’t all modern transmissions have something called an overrun clutch that opens to allow the truck to coast when it wants to go faster than the engine?

No, there is nothing like that in any transmission that I've ever seen.

[Blue12]

Ok, must be a GM thing—I have seen a overrun clutch referred to, but (obviously) don’t know anything about it. So, when I’m driving down the road at 65 MPH in 6th with the torque converter locked (tow haul off), and I completely lift my foot from the accelerator, the truck will coast seemingly forever. Does the converter lock open up to allow easier coasting? It is hard to believe that it would coast that long with the converter locked. Then, when I get on the fuel again, does the converter just lock up again? Since the manual says you have to be in tow haul for engine braking, then the converter must never unlock in tow haul?

[PerryB]

Len, Maybe you're thinking of the coast clutch? It does sort of the opposite of allowing overrun. You'll know if this fails because when you pull your foot out of it at highway speed the engine will drop right down to idle and not be "pulled" by the transmission. At least thats what the 4R100 (POS) would do.