motuman

When towing with the 4 speed auto, I have heard you are not supposed to use overdrive, correct? I believe this is because of concern for heat buildup and "hunting", i.e. rapid toggling back and forth between 3rd and 4th.

My question is, if I add a tru-cool trans cooler to the truck, and use overdrive only on flat roads where the tranny is not "hunting" is there any risk to towing in overdrive?

With the price of gas these days it would sure be nice to use ovedrive on the long, towing road trips we take.

mkgarrison5

i pull a bass boat and on highways i use overdrive but around town or back country roads i use the ECT button.. well i use that anyway on highway or not.. i have a tacoma v6 auto

Homer666

Hi motuman;

I tow an 18ft travel trailer that is around 3,800 lbs when loaded. On the flat, my tranny temp stay around 140 when O/D is off (increasing slightly on the hills); when travelling with O/D on however, the temp really climbs quickly to past 200 at which point the O/D comes off. The increase in temperature still occurs even without any transmission "hunting". I do have a tranny cooler (an RV type - just can't remember which one LOL)....

As an aside, anyone know what temperature could lead to transmission damage? (I don't want to hijack the thread but the question seems to fit with motuman's initial query).

Stay cool;

James

seanz0rz

you guys also need to keep in mind that when you tow, you have more than two axles, and your new speed limit is 55. the auto tranny will shift up at 40 mph if the OD is engaged and you are not at wot.

gilby4runner

Not to hijack but is it better to tow with the ECT engaged?.

I tow an 18ft bass boat with the OD off... should i use the ECT also?

mkgarrison5

i pull a 22ft bass boat and i use the ECT on highway and country roads... now as far as overdrive i only use it on highways and etc.. i dont mind burning a lil extra gas to help save the tranny...

mkgarrison5

is this in cali only??? just curious

gilby4runner

I agree about spending a little more in gas.. better than 4 Grand on a new trans. I just wondered if the change in shift points helped or hurt the trans while towing

mkgarrison5

no it would be best if you used the ECT atleast. all it does is extend the gears a little bit... taking it out of OD will just knock out top gear.

Kerby J

when in the city or taking off u should never and i repeat never use o/d because there is a crush sleev that works with the o/d and if u frequently tow in o/d, it will eventually crush it completely and then o/d wont work and u will have to have the crush sleev replaced and that can be cosly and ur o/d wont work untill u get it replaced
so dont tow around town or start off in o/d but after u reach crusin speeds u can turn it back on as long as u dont have ny hills comin up on the freeway

seanz0rz

as far as i know, the 55mph speedlimit is nation wide for trucks (18wheelers) and autos with trailers. you should see those signs on the side of the freeway. pay attention.

regardless of the speed limit imposed by govt., i wouldnt drive any faster due to the dangers involved. trailers are not designed to be highspeed.


also, everything im reading around the internet (its been a boring day...) says towing in OD is bad as long as you are accelerating (this includes going up hills) but is fine on absolutely straight, flat ground

kevin444

keep od off, save your tranny.

yamataco

I only tow using O/D going down long hills, like when I'm coasting. My 18' trailer is about #3500, plus dirt bikes in the bed. Normal towing speeds for me are never over 65, normally 55-60. And I always manually downshift early enough to climb hills without using much more that 1/2 throttle, even if I gotta go kinda slow. I'd rather go slow than buy motors or transmissions...

mkgarrison5

guys the only time i would use OD would be at cruising highway speeds.. other than that i dont use OD when pulling the boat.

KD7NAC_07FJ

Every truck maker will recommend not towing in OD for all the reasons mentioned above. Mainly because OD is not a "power gear" its "over drive" in-other-words your tranny is rotating faster then the engine.

Lets look at the new Tundra
4.7-liter with 5-speed ECT
1st 3.520
2nd 2.042
3rd 1.400
4th 1.000
5th 0.716
Reverse 3.224

You'll notice that 4th gear is 1:1 gear ratio. That means the tranny is turning the same RPMs as the engine. Most manufactures do not recommend towing with gears over 1:1 (or under depending on how you look at it).

So in 5th gear the tranny (output shaft) is turning faster then the engine. The faster you turn the tranny the faster it will heat up and ware out. Put all that under load (towing) and you exponentially increase the heat/ware.

I've even seen some cases where towing in OD can void your warranty.

mkgarrison5

interesting... well there you have it. dont tow in OD! haha

gpcollen1

That said, dont be afraid of a few RPMS when towing with OD off.

Pest

Whenever we tow the big camper, it's usually OD off, especially when climbing up through the mountains. Acutally, climbing up the infamous I-70 hill right out of Lakewood (everybody in Denver should know what I'm talking about), is usually done in 2nd gear, doing maybe 40 MPH or so. The only time OD is used is when we're in a valley, going downhill, or on a fairly flat road. Any hills = OD off, otherwise use OD and save the Gas!

kmcc78240

What about manuals, I tow in 4th gear. Should we stay out of fifth.

mkgarrison5

use your best judgement guys. if the truck is stuggling. lower the gear for the autos if its switching in and out of 4 and OD then turn the OD off.