Towing with a Tundra - Page 3

Dave-O · 07-27-2003, 09:38 PM

My manual said the same thing. I stand corrected. Hey, maybe there is some more good info in that thing!

I KNOW I didn't just pull that out of my arse. Someone I know ruined a tranny by doing a long trip with a big trailer in OD. I think it was an early 90's F-150.
Maybe this is true for some models?
Maybe someone should start a new thread so we can get more heads in on this. I need facts

-dAvE

Silvertwinkie · 07-28-2003, 06:53 AM

When in OD, the trans fluid pressure is a bit different than when it's in normal non overdrive.

While in overdrive, RPMs tend to be a bit less and as such in some cases, depending on the design, the torque converter will not lock. A non-locked torque coverter will run far hotter than a locked torque converter.

If the vehicle has a low lock RPM, you can use overdrive, however, if the vehicle is jumping gears frequently, you will toast the trans. Maybe not today, maybe not tomorrow, but it will die prematurely.

Having heavy duty cooling is a must. The hardest working component in any car when towing is the trans. It take the brunt of the loads.

I am unsure how the tow/haul selector works in the GMs, but I would theorize that it somehow limits the shifts and possibly locks the torque converter sooner than later, but that is just a guess.

I have towed both in and out of overdrive with my '96 with a 4L60E trans. I have had the powertrain control module that controls all engine and trans functions set so that the T/C locks at 51mph regardless of engine RPM or torque output. I have added a flywheel ram air that keeps the T/C a bit cooler and added a deeper pan, the same used on the Silverado to my Chevy sedan along with going fully synthetic for the trans.

In all cases, the trans and engine remain at a constant temp unless I pull up a steep grade. So as not to temp fate however, I keep my towing in OD to a minimum.

I would suspect that Jack has a tow/haul switch making it more acceptable to tow in overdrive.....Jack, do you have that feature?

**jcanavera** · 07-28-2003, 08:16 AM

Quote:

Originally posted by Silvertwinkie
I would suspect that Jack has a tow/haul switch making it more acceptable to tow in overdrive.....Jack, do you have that feature?

Eric, yes I do have tow/haul in the new van. The tow/haul switch does raise the shift points. You notice the RPM's are much higher prior to the transmission shifting to the next gear. I don't believe that the inverse is true since I did pull the transmission out of OD a couple of times to get more power on some Ozark hills a couple of weekends ago.

What allows a transmission to tow successfully in OD is probably a factor of the components used, oil flow, and cooling capacities. I know the transmission used in my 3/4 ton Savana van is a heavier duty unit than what comes with the 1/2 ton van. I also have an external transmission cooler that comes with the towing package that wasn't present with the 1/2 ton.

I know it was tempting on flat pavement to allow the tranny to use OD on my old van, but I'm a believer that the manufacturer knows best. If they say no OD then it means no OD.

Jack

Silvertwinkie · 07-28-2003, 08:42 AM

A good bunch of it has to do with the torque converter although I know that you are right with some of the other things. I have a similar setup since the police packages have most of the heaviest cooling possible. Still GM suggests with mine not to and if I didn't mod the car based on understanding how the drivetrain behaves and through extensive testing, I would never attempt to drive in overdrive.

Being one that can't leave well enough alone though, I have made the mods and do overdrive on the strait even roads. Most of the mods enhance further the already beefy cooling systems GM had in place.

The fact that you mention how it changes the shift points and has a higher RPM indicates to me a bit higer RPM than normal overdrive has, but less than if you were in 3rd. This is a classic case of GM basing the torque converter lock on RPM rather than MPH. If I recall right you have either 3.73 or the 4.10 gears too producing more RPM than 3.42s or smaller gears and better for the TC to lock.

**jcanavera** · 07-28-2003, 05:44 PM

Eric, the higher RPM is really the fact that the the shift points have been raised so that when you do shift you don't get the fall off in performance that would occur in a transmission tuned for economy mode. I don't believe that there are any gearing changes going on. BTW, my axle is a 4.10.

Jack

Silvertwinkie · 07-28-2003, 06:26 PM

Gotch ya. I don't think there are any gearing changes either. However, if GM is consistant here, raising the RPM band also helps ensure that the torque converter stays locked. A locked converter is a happy converter when towing extra weight. That is one of the main reasons (not the only one) as to why we towed in 3rd. In GM land they tune the trans to lock on my car at between 1400 and 1800 RPM depending on torque output.

Going 55mph in my car in OD puts the RPMs at about 1500. That does not ensure that the TC is locked. Now if I go into 3rd, I'm at 1950 RPM. If GM again was consistant, the higher shift point also means the engine RPM is higher and as such hopefully the TC remains locked and a locked TC is a much cooler trans overall.

That's why I think they added that tow/haul feature. Better than using 3rd, but not quite regular overdrive.

Ajrandzin · 07-29-2003, 06:22 AM

I checked my manual on 1990 ford E150 with AOD tranny and it doesnt state wither to use OD or not when towing. I will for, safety sake, use OD as your conversations on converter lock up make a good point.

Silvertwinkie · 07-29-2003, 06:47 AM

Most manufacs have a toll free number you can call. For example, Chevy has a number you can call and ask almost any Chevy related question and if they don't have the answer, they will get back to you with it. Perhaps Ford also has such a contact number.

Eric

**jcanavera** · 07-29-2003, 08:45 AM

Quote:

Originally posted by Ajrandzin
II will for, safety sake, use OD as your conversations on converter lock up make a good point.

Don't consider use of OD in your towing application the safe bet. Get ahold of the manufacturer and check it out. Dependent upon your transmission, OD towing may earmark you for transmission failure.

Jack

**CanoeStream** · 08-03-2003, 10:00 PM

I like Toyota products and am looking at Tundras. The idea of towing a 25' Safari with it is a marginal proposition. I have spent the last 6 months studying these forums as a 'guest' and could be deciding any time here... Vehicle and trailer loading discussions have been repeated enough times that it isn't drawing the experienced replies this time.

The Gross Combined Weight Rating (GCWR) of a 2003 V-8 Access Cab Limited 4WD Tundra is 11,800 lbs (with towing package of course). Without any options, fuel, driver or passengers this 1/2-ton truck weighs 4,675 lbs. Adding gas, 2 people and tongue weight pushes it to at least 5500 lbs (no cargo, bed liner or topper yet).

Any 25' Airstream except the Classic starts at 5,000 lb "Factory weight, w/o options or variable wgt." Add a spare tire, an anti-sway/WD hitch, propane, reasonable water.... see where I'm going? Clothes? Food? A 2nd pair of shoes? This can be made to just squeak in under the 11,800 GCWR load, but adding many truck & trailer options, bringing a few toys along, or returning the Christmas fruitcake to Aunt Mabel busts the bank.

Let's research further. Click on the "Search" function above and enter: GCWR. I can suggest reading these 3 strings:
Towing a 25' Airstream with a Yukon
Towing 22 foot International CCD
Newbie Towing Questions
I have come to appreciate certain contributors as consistently offering thoughtful and knowledgeable input -- see what you think. There certainly is no question about Tundra's wheelbase. Many opinions throughout airstreamforums.com and elsewhere suggest keeping loads somewhere below 75-80% of GCWR.

A 25' Safari would be very rough on a Tundra, especially as travel conditions become more harsh. Be careful with the resale value of your tow vehicle. We all evolve with our equipment and travel objectives. On the horizon are rumors about Toyota offering a bigger V-8 with more towing capacity for the 2005 model year -- whispers only so far (try a Google search on: Tundra, engine, and 2005). Anybody know more about this?

Happy (and safe) trails!