What gear to tow with?

[Gypsy]

I have a 99 Tahoe. I pull a 3000 lb boat. The manual says to use OD/Drive with a circle around it unless you are in hilly terrain.
At freeway speeds the rpm drops from about 2500 to 1700 when I shift from 3rd to OD.
My typical haul is 75 miles on flat ground at 75 mph. The last 40 miles are a mix of flat ground and some fairly steep hills at 60 mph.
Should I leave it in OD and let in downshift, or drop it in third? I don't mind running the higher rpms and using more gas if it is saving the tranny.

 

[Ugly3]

For me, this is an easy one. Pull trailers in third gear. Engine is spinning easy (2,500 RPM is a "walk in the park"), the trans is not shifting, and the extra RPM does not consume a hugh amount of extra gas.

 

[unDummy]

What engine/tranny?

If the tranny shifts too frequently, lose the OD.
If not, leave it in OD. Its an automatic and should downshift when needed all by itself.

You should install an ATF gauge. The temp will let you know whether to downshift or not. A deeper pan and a larger ATF cooler should be considered. I'd install a shift kit to quicken the shift and prevent slippage.

 

[mechtech]

Do as the Mfr recommends.
It IS an automatic trans.
I'd get the biggest aftermarket trans cooler and install it, though.

 

[Bret Chase]

I'd run it in D... nearly 25 years of experience that basic transmission (TH700R4/4L60/4L60E) design have proven the worthiness of towing in D. while the newer ones handle things better in [D], they still suffer from the same hard parts problems of the last 15 years.

Now if by chance you've got a 4L80E in it, just slap 'er in Tow/Haul and leave it in [D]. the '80 is vastly stronger than the '60E. The '80E is a TH400 with a OD unit hung off the front.. sharing 75%+ of hard parts. the '60E is an evolution of the TH350, reconfigured to 4 speeds.

 

[Mike242GT]

We're probably talking apples and oranges here, but the owners' manuals of my Volvos have always clearly warned NOT to tow in overdrive, either with a manual or automatic transmission.

 

[Big O Dave]

Since YOU have to foot the bill when your tranny dies just outside of warranty (

), do yourself and your tranny a favor and NEVER tow in overdrive.

 

[eljefino]

If you dropped the speed even to 70 you'd be doing your rig a favor too. That wind drag must be fierce. Skip a restroom break or something to make up the time.

 

[nascarnation]

here's the basic theory:
on those trannys, in 3rd you are direct drive 1:1 ratio and no torque thru the planetaries.
in OD you are running the OD planetary set with about a .7:1 ratio
so durability is guaranteed to be better in direct (less fatigue cycles on the gears)
also when towing any shifts in/out of OD which can occur frequently due to hills are high energy shifts which are hard on the clutches and the fluid.

 

[TheTanSedan]

Towing above 62-65 mph under even "ideal" conditions is foolish. 55 - 62 is best.

Neither you nor anyone else is able to emergency brake and manuever effectively above that speed simply because the loads, lateral and otherwise, are too high. You may not care about yourself, but give the rest of us a break. It's worse than a drunk driver on a cell phone.

3000# pounds doesn't seem like a lot (a light load for your vehicle to pull), but it is . . . and "the tail wags the dog in towing". I doubt the trailer tires are even rated for these speeds as the manufacturers are no fools in liability assignment.

The best hitch, the perfect balance, etc, are irrelevant. Many states regulate tow rigs to lower speeds for this reason.

That said, direct drive, not overdrive. An auxiliary cooler, auxilary filter and best quality ATF belong in the system. And most high temp spikes happen at low, manuevering speeds (it ain't the highway that kills them first, it's the campground, boat ramp, etc).

 

[hone eagle]

I thought CA state law was 55 when towing- no exceptions

 

[Steve S]

quote:

---

Originally posted by hone eagle:
I thought CA state law was 55 when towing- no exceptions

---

Hone Eagle, Calif. state laws are just a guideline ,unless you get caught.

 

[hone eagle]

AH- ok I get it

 

[Gypsy]

I would argue your point about the drunk driver with a cel phone being safer than my situation.
I drive I-5 and if you do 62 you will be crushed by 85,000+lb big rigs that ride 5' off your butt.
Traffic flow is between 75 and 80. I try to stay close to 70. I agree that 55 would be safer, if I was the only one on the road.
Thanks for the concern and the good advice.

 

[Radio]

Just in point of fact, it is a rare truck that is actually pulling over the usual 80,000 lbs. Heavy haulers are vastly outnumbered by the majority of Class 8. Perhaps a typo?

"Traffic flow is between 75 and 80" may work for cars but NOT for trucks, as you seem to imply. For what it's worth, a very large percentage of company-owned trucks are speed-limited in the engine computer and CANNOT get up to even 70mph, let alone 80. Moreover, if you ARE able to roll a big truck that fast in CA, the CHP will love you for the extra revenue, and every professional driver is well aware of it. Speeding tickets will cost the driver personally several hundred dollars, NOT the company, and points will be issued against his CDL... which can directly impact his ability to make a living or get/keep his job.

I've driven I-5 many HUNDREDS of times; the cruise was comfortably set at 58mph and I always got to my destination on time without fear of hassles from the CHP. I darned sure wasn't the only one. Not that a speeding, tailgating truck didn't happen to you, and doesn't on occasion, but don't try to make it sound like it's normal. Sorry you might have encountered a bad driver or two but they're definitely in the minority.

--Radio

 

[TheTanSedan]

I've also driven I-5, at max load (80m#) in a truck governed to 68 mph, as well as empty and with partial loads. There are plenty of Interstates in the US with higher traffic loads, a worse surface and visibility, and a far, far higher number of trucks (I40 through West Little Rock, AR, for one).

You may not like what I have to say. You have also apparently not seen the results of drivers with your attitude as often as have I. One learns, hopefully, from others. I've been called on my driving habits before, and lived to think it through and adapt.

You'd do fine at 62 mph in the open -- at 1/2 mile or more from traffic in front of you or in back -- and slide off the cruise when the "pack" goes around you.

The cell phone driver above the legal limit stays . . . controlling a trailer in an emergency is more than the solo drunk has to control.

Direct drive, with an eye on the mirrors and swtching off the cruise numerous times works well.
Arriving safely and in one piece is all that matters.

Good luck