OD for Towing or Not

[Lemming]

I believe that this has been discussed but I have to bring it up again. How many of you are towing trailers in overdrive? Yes the manual says not to (F-150, 4.6L) but on flat to slight inclines my truck really has no problem maintaining 70-75 in OD (pulling a 6 x 15 v-nose trailer). At 73 mph the revs are right around 2200 and I only have to lock the OD out on hills. On my first trip (about 100 miles) I only had to lock the OD out about 8 to 10 times. Locking OD out and running at 72 or so runs the engine at around 3300 rpms.

 

[hoosierf]

I never tow in OD.

 

[Rooster]

I have a sticker right on the door frame that says not to (5.7l GM). I don't pay much attention to it unless the tranny starts dumping out of OD to make speed. Running in D burns WAY too much fuel for my wallet.

 

[JWW]

The only time I take it out is going up long slow steep hills. My 4.0 Ranger will pull the flats with no problem in OD.

 

[Highbeam]

98 chev K1500, 350, auto. Usually towing a lighter trailer, 1500+ lbs.

My manual says to tow in OD unless the tranny is "hunting".

I stay in overdrive until the tranny makes its first downshift on a hill. It may just be unlocking the torque converter, I can't tell. As soon as it downshifts and the hill is reasonably long I bump it down into 3rd and cruise until the terrain flattens out and then I bump it back into OD. I don't tow above say 65 so 3rd isn't screaming, maybe 2500 rpm. I just don't like the revs high unless they are needed and I don't like to speed up and slow down just to prevent downshifts. My method keeps the truck speed constant and allows the tranny time to cool between shifts. If someone thinks shifting on the fly is a problem, please speak up.

As long as there are several minutes between shifts, your tranny should be fine. Hunting causes the excessive heat and hot spots that ruin the tranny. All tow vehicles with an AT should have a tranny temp gauge.

If this common debate leaves you with no conclusion, just do what the manual says and slow down until the revs are acceptable. Just think, if you buy bigger tires the revs will be lower in 3rd while towing, is that a good excuse or what?

 

[Okiewan]

unless it's falling in and out of OD. At 65, it rarely comes-out of OD. OD is nothing more than 4th gear, you can't burn it up if it's not shifting in and out.

 

[lawman]

i have an f-150 with the 5.4L & heavy-duty tow pkg. i tow in od all the time, unless i get in the mountains & it starts to hunt. never had a problem.

 

[a454elk]

Actually, towing in OD can hurt the trany, even if it isn't shifting in and out. The gear for the OD is way small and when you are towing somehting, even though it feels like it's pulling fine, there's alot of strain on that little gear. Usually OD gears are less than 1:1 ratio. GM has the tow/haul button on the shifter and it works by holding the shift longer. When the tranny gets into the upper gears, there is more strain so by keeping the motor a little higher on the RPM longer, it gives the tranny time to "catch up".

I usually tow in 3rd, even though the rev's are a little higher. Just my .02.

 

[mx547]

Originally posted by Lemming
How many of you are towing trailers in overdrive? Yes the manual says not to (F-150, 4.6L) but on flat to slight inclines my truck really has no problem maintaining 70-75 in OD

same truck, similar trailer, i do the same thing. 117,000 miles, no problems (yet). i have the transmission serviced regularly.

 

[Birken Vogt]

The question is, what transmission is it? The 4R100 (E4OD) has just as strong of gears in OD as any other gear. It CAN be run in OD all day but just like other said so long as it is not shifting back and forth and wearing out the clutches. But does the F-150 4.6L have a 4R100? I don't pay attention to the baby trucks. I did have a friend with one, though, behind a 300 six (4.9L). Great truck till he center punched a pine tree with it....

 

[Lemming]

Stupid question of the day - how can I determine what transmission is in my truck:eek: My manual states that it could be the E40D or the 4R70W?

 

[Okiewan]

The F150's (except Lightnings) has the 4R70... The Lightning and Super Duty's have the 4R100. I did tow with the 150 for 2 years with no problem, of course that's not saying much.

 

[OnAnySunday]

I'm not too sure about new auto overdrives, but the older ones (ie:early eighties to late eighties) over drive is a direct mechanical linkup.
Instead of being run thought the torque converter.
In fact i think drive was something like 75% converter 25% solid link.
I have no idea how this works, so dont ask me.
It's just something a Ford engineer told me at a car show in detroit many many moons ago.
( i'm probably screwing up the explanation anyways.)
I used to worry about that little "solid gear thingy" (for lack of better nomenature) getting damaged whilst towing, but the ol' B2 has 137,000 and still ticks away. )knock wood(
(rated towing capacity is 4,500 lbs. max. by the way)
The manual says:
"When towing a trailer with a vehicle equipped with an A4LD transmission, operate in Drive rather than Overdrive. This will eliminate excessive downshifting and upshifting to maintain speed."
So i assume (yea YEA i know the meaning of ASSUME) :D that if your on a level or fairly level road where it wont be shifting alot that OD is OK.
Right????? :confused:

 

[splatt]

What most of you are experiencing is the torque converter clutch locking and unlocking. That is what is taking all the abuse when you tow in OD. When it feels like it downshifts it`s actually the converter unlocking. What makes it feel like it has down shifted is because the converter is doing what it was designed to do ,multiply torque. This can be felt in drive in some OD trannies as well. My 85 Chev truck you can feel the converter lock and unlock all the time I thought it was downshifting until I got to talking to someone at a tranny shop that specializes in OD trannies. If you want to find ut more check out their website @ jetchip.com.

Steve

 

[lawman]

hmm, i checked my manual, here's all it ('00 f-150) says about this: "Use a lower gear when towing up or down steep hills. This will eliminate excessive downshifting and upshifting for optimum fuel economy and transmission cooling."

 

[Lemming]

Thanks for all the replies but I believe that I have solved my problem as of this afternoon. See below :)

 

[Highbeam]

Nice, the grey one too. I'm jealous. That is the best configuration I think.

A torque converter can not multiply torque. Unless it is 100% locked it is always a torque robber. Nothing in your tranny/drivetrain can increase or multiply torque. By slipping when unlocked the torque converter allows the engine to rev to a point where it makes more torque so your tranny will get a "boost" from the torque converter unlocking. When the torque converter is unlocked, a much larger amount (%) of the engine's torque is lost through the slippage but even more additional torque is being made by the engine so your truck goes faster. However, more heat is generated since all the slippage causes heat. We should all have huge tranny coolers.

If you try really hard, you can hear your tranny shift through way more than 4 gears on its way to cruising. So I believe you're right that the downshift felt while towing at high speeds is just the torque converter unlocking. Plus I have a little more evidence of this. I tow I drive in overdrive until it "shifts" down on a long hill, then I select 3rd gear. When I do this it downshifts again to locked 3rd so I know that there was an unlocked 4th that I was in before manually downshifting.

What this tells us is that unless you feel the tranny downshift twice (this also happens on big hills while in OD) then your tranny really didn't shift at all and your torque converter is the device getting hammered.

It looks like we all have 8 speed trannies. :yeehaw: