New E450 with tow/haul question

I never leave home without Tow / Haul turned on. Your E450 is running at max load therefore, be nice to your transmission and turn it on.

DAS26miles wrote:
So on the long grade into Death Valley I believe the speed limit is 50 or 55 mph. I have a choice of dropping it into 3rd or using the tow/haul. Going up the long grade from Panamint is it better to drop it into 3rd or use the tow/haul? It doesn't seem clear to me. Is 3rd the same as the 4R100 Drive with O/D off?
Actually, here are the transmission gear ratios from another forum
4r100 gear ratios:
1st - 2.71
2nd - 1.54
3rd - 1.0
4th - .71

5r110 gear ratios:
1st - 3.11
2nd - 2.2
3rd - 1.54
4th - 1.0
5th - .71

So dropping my 5R110 down to 3rd actually would be the equivalent of dropping my old 4R100 down to 2nd. How could I drop it to 4th, nothing on shifter?

In general what I like to see on long upgrades-especially in hot weather- is to have the torque converter locked and the engine RPM in the middle to upper middle ranges of the engine's capability. In the case of the V10 under hard grade I prefer to keep it 3200-3800 RPM. Of course it will not hurt it a bit to to go higher if necessary to get more speed, or passing performance.

As for converter locked, with practice you can feel it by feeding in more throttle and the RPM tracks speed not engine output. Or Scangauge instruments may show it. If converter is locked it isn't generating nearly as much heat. The tow-haul feature has no other voodoo to reduce trans temp other than this-but it may help you achieve this. Several ways to skin a cat here.

In general torque converters generate most heat when active (unlocked) low speed at high load. Poor airflow thru coolers contributes such as backing up or heavy tailwind on steep grade.

FWIW there should be two indicator lights on the dash of all cars/trucks lit when-
1. Torque converter is unlocked.
2. Engine is in open loop (fuel air mix related)

I have relatively light 25' class C and use tow haul primarily as braking aid on mountainous downhills. Otherwise I find the shifting excessive (sometimes on brief brake applications) and forces needless high RPM. I can see in some scenarios where there is potential to keep transmission cooler by using more mechanical gearing and less torque converter. OTOH I have never heard of any excessive (IMO) transmission temps when not operated in tow/haul-and of course the PCM has the data and can shift transmission according to temperature if they're excessive.

Bottom line: for me engine braking only when needed. I have no concerns about transmission life when serviced properly. Also E450 has more favorable axle ratio for reduced transmission heating than the E350-lower overall gearing.

I use the t/h on our E-450 based Lexington towing a Subaru, from the moment I start it till I turn it off.
The feature is really not needed on an empty chassis, but these rigs are loaded out almost from the moment they roll off the rv manuf. floor, so you are almost always "hauling".
Just saves a lot of ware n tare on the trans.
Also, I replaced the original wimpy trans cooler with one rated over 4 times the rated cooling of the oe unit. OE is rated around 15000 btu , one I installed is rated at 64000 btu heat dispersion.
Grumpy

I don't tow but with the new E-450 I noticed about a 10 degree increase in transmission temperature on my scangauge climbing north up the I-5 out of Santa Clarita toward the Grapevine versus my old E-350, (200-2045 for the E-350 and 210-215 for the new E-450 + 2,500lbs). So using T/H will drop the temp, good to know and will try it on the climbing and descending to Death Valley.

I'm a convert. I only used my t/h while in the mountains to assist with descents. Hated the shift points and assumed it affected mileage negatively. Then I had occasion to ride in an F450 tow truck and really liked the way it assisted with the braking, and decided to give it a second try on the flatlands. No appreciable change in mileage. No appreciable change in tranny temp either, but I do love the assist in braking. Now, if I'm towing, my T/H is on. Guess an old dog can learn a new trick.

If you are not using Tow Haul you are abusing your transmission with needless, excessive heat which will undoubtedly shorten its working life. The use of tow Haul reduces trans fluid temperatures significantly, read your owners manual. If you just have OD instead of TH, turning off OD will generate similar results

Recently drove through Death Valley from west to east (104* and climbing at 1000), and you better believe we had TH engaged the entire drive but then running our E-350 near its GVWR and often towing a 960# bike and trailer I utilize TH about 90% of the time.

Even on a fairly slight uphill grade your trans fluid temps will creep up and engaging TH will drop them 12 to 15 degrees in just a couple of miles. On long and/or steep downhill grades I cannot imagine not running with TH engaged. I can cruise down a 6 to 8% grade for 10+ miles and usually never have to touch the brakes.

The folks that don't use TH probably don't have the ability to read trans fluid temps... if they did they would use it. A Scan Gauge, or any of the many other gauges available, will provide this essential piece of information.

As always.... Opinions and YMMV.

:C

So on the long grade into Death Valley I believe the speed limit is 50 or 55 mph. I have a choice of dropping it into 3rd or using the tow/haul. Going up the long grade from Panamint is it better to drop it into 3rd or use the tow/haul? It doesn't seem clear to me. Is 3rd the same as the 4R100 Drive with O/D off?
Actually, here are the transmission gear ratios from another forum
4r100 gear ratios:
1st - 2.71
2nd - 1.54
3rd - 1.0
4th - .71

5r110 gear ratios:
1st - 3.11
2nd - 2.2
3rd - 1.54
4th - 1.0
5th - .71

So dropping my 5R110 down to 3rd actually would be the equivalent of dropping my old 4R100 down to 2nd. How could I drop it to 4th, nothing on shifter?

I have never used the tow/haul for going up hills. But, I do use it occasionally for steeper down hills. It does a good job of maintaining speed going down with only a tap on the brakes now and then. At lower speeds, it will cause the tranny to downshift even if not necessary. I have read stories on this site and others about RVs losing their brakes on steep descents ending with bad outcomes.

If you travel mountain roads, I would suggest using the function.

As Sam says, Tow/Haul changes the programming of the transmission in various ways, altering the shift points and also the torque converter lock-up to try to be more sensible when carrying a big load and to try to keep the transmission temperatures down. I think it also enables or increases automatic engine braking when descending a hill (press the brake and it downshifts). Note that it does not lock out overdrive.

I probably would generally travel with it engaged if I had that option; a motorhome is a permanent heavy load. As it is, I have the older unit with the 4R100 and the simple "don't overdrive" button.