Towing in 3rd gear on a 1300 mile trip

[Bruce1963]

I have a 1997 GMC k1500 Z71 5.7 liter with 20000 miles and a 4L60e transmission with only 2000 miles, I will be towing a 3000# dry weight TT from Louisiana to Colorado. I plan on breaking the trip into 2 1/2 days of travel, question is will it be OK to travel for 10 hours or so at 2500/3000 rpm in 3rd gear towing around 3500#? Will it be too much of a strain on my engine/transmission?

[Wishin]

I used to tow with my '96 Buick Roadmaster wagon when I had a "lighter" 5600 lb trailer. It only had 2.93 rear gears (which were better than the standard 2.56 gears). It was always in 3rd and at 65 that was about 2500 rpm. I towed about 8,000 miles that way over 5-6 years. The main thing I would notice if I tried to tow in OD, the torque converter would unlock a LOT and the tranny temp would climb.

I just finished a 5300 mile trip to the far side of the rockies and back towing my current trailer (nearly 8,000 lbs) with my 2500 8.1L Suburban with 4.10 gears and a 4-speed. Due to a lot of windy days, much of the trip was in 3rd gear which is over 3,000 rpms a the speed I was going. No problem.

Do what works best for your vehicle, trailer and current conditions. If it is towing easily in 4th with the torque converter locked up, you are fine. If it is unlocking much at all, keep it in 3rd. Due to the spacing of the gearing in my wagon, it spent 90% of its time in 3rd with the TC locked up and any hill put in 3rd with the TC unlocked. I was pretty much never in 2nd unless I was below highway speeds or going over a mountain pass (also going slower).

[ib516]

Won't hurt a thing. I have a small 17 foot 3500 lb RV, and my 2006 with a 5.3L pulls it in 3rd all day long. Setting cruise at 65-68mph, and using tow/haul mode, it drops into 4th (OD) but loses speed and then downshifts to 3rd (direct - meaning 1:1) and stays there @ about 2700-2800 RPM. It's the wind resistance of the 8' wide RV more than the weight when towing on flat terrain. The weight has a greater effect in the hills.

Just as an FYI, in previous vehicles that had an "instant" mpg readout, while towing, using one lower gear and higher RPM gave roughly the same mpg as one gear up at lower RPM. The vehicle I'm referring to is my previous 2014 RAM 2500/6.4L Hemi. It would tow in 4th (out of 6) or 5th. The RPM was lower in 5th obviously, but the mpg was the same in both gears.

[falconbrother]

mkirsch wrote:
A 700R4 or 4L60 transmission is just a Turbo Hydra-Matic 350 with an overdrive scabbed on.

Those old Turbo 350's went MILLIONS of miles in 3rd gear, because that's all they had.

Good to know!

[mkirsch]

A 700R4 or 4L60 transmission is just a Turbo Hydra-Matic 350 with an overdrive scabbed on.

Those old Turbo 350's went MILLIONS of miles in 3rd gear, because that's all they had.

[Atlee]

Don't know your transmission, but if it's a 4sp, then 1300 miles in 3rd shouldn't hurt it at all. Most 4 sp automatic transmissions that I know, 4th is OD, and 3rd gear ratio is 1:1.

[blt2ski]

For kicks and giggles. Here my C2500 350 rpm at 60, running at around 14000-14500 lbs total.yesterday.......
In directionality.4.10 gears, 2600 t.v. locked, 3000 unlocked
In OD, final ratio 3.08, 1900.
Assuming OP has typical 3.42 or 373 gears, they will be about 2200 3rd direct or 2400. I did level reasonably in OD. But it did.shift into.direct on grades above 2-3%. I would assume a 3.42 geared rig would shift sooner yet.
As.noted.by many, if the.trans is shifting gears lot, or unlocking and locking TC, probably better to shift lever down. Be it od to direct, or direct into 2nd on steeper free at grades etc.

Marty

[falconbrother]

One other thought.. My old motorhome had a 454 in it with the turbo 400, 3 speed transmission. At 70MPH that sucker was reving but good. I don't know the exact RPMs as it didn't have a tach. But, it took a little getting used to. I drove it thousands of miles screaming like that. It never complained and it wasn't hurt at all. If a 454 can go thousands of miles like that in 100 degree weather I'm sure a 350 can do it. There's less metal being slung around in there. I was pulling a Honda CRV behind it all day like that too. Some days I miss that 454.

[Sam_Spade]

ExxWhy wrote:
On relatively flat roads with the load you plan, it should tow in 4th gear with no problem.

And I just DON'T understand why someone would make a plan to stay in 3rd gear all the time during the trip without even trying it first.

There is a really LOT of flat land in the middle of the country where it should do just FINE by putting it in D and driving happily down the road.

When the terrain changes, you change your strategy. Easy.

[ExxWhy]

I owned the same truck, same year. Just gave it to my son last winter. It did some relatively light towing over the years, 16ft fiberglass boat, car haulers, and some with my old 22' travel trailer. I used OD most of the time as long as it wasn't hunting gears or unlocking the converter.

That transmission does something that most others won't do. It would unlock the torque converter and depending on load stay in 4th gear with the converter unlocked. RPM would go up about 300. Driving like that gets the fluid temp up quickly, so you want to avoid that no different than if it was actually downshifting frequently.

It will positively use a lot more fuel if you stay in 3rd gear all the time. On relatively flat roads with the load you plan, it should tow in 4th gear with no problem.

[Durb]

Growing up in the 60's Chevrolets with small block V8s were mated to Powerglide 2 speed automatics with a 1:1 second gear. 3,000 rpm in top gear at 60 MPH was standard proceedure.

[RinconVTR]

My Toyota 5.7L with 155k, I tow in 4th gear @ 3100ish RPM 80% of the time at 68-72mph.

Non-Turbo Gas engines need RPM's to produce power. No need to baby the motor. If something is so old or worn out its ready to fail, it will fail while towing whether you baby it or not.

[JIMNLIN]

I thought that also with my old '90 5.7 vs the wifes old '06 5.3....however her new '16 chevy ET3 5.3 engine with 355 hp and 3873 torque pulls my same old blue tractor much much easier. Nothing like my Cummins but the new EcoTec 5.3 with the 6l80e and 3.42 gears gets it done a whole lot easier with much improved low rpm torque over the old '06 5.3 version.

Run the old 4L60e in drive (3rd) when towing. Trying to use OD (4th gear) when towing will lead to early problems.

[falconbrother]

parker.rowe wrote:
I tow with a similar vehicle, in my signature. Mine has 132K miles. My camper is a bit heavier though. (6500 gross, around 4500 dry IIRC)

I always lock it in 3rd. With the extra weight and wind resistance it kicks in and out of OD, or unlocks the converter in OD, whenever it hits a hill. I did a test where I ran a leg in overdrive, with the cruise set, and let the computer decide. Trans temps were ok, but my gas mileage was actually worse then just locking it in 3rd.

Does a great job in 3rd. With 3.73's and 33 inch tires I am usually between 2500 and 3000 rpm depending on speed. Anything over 60 and the gas mileage starts dropping.

I feel the Vortec 5.7 is much better suited for towing than the Vortec 5.3, especially with a 4 speed auto. Both are great engines though.

I got 8.5 mpg on my last trip hand calculated. Not bad for a 20 year old gas truck towing a brick at 55-60mph.

I think I agree with you one the 5.7 vs. the 5.3. The 5.3 in the Burb, at least the first gen 5.3, gets really decent gas mileage for a big vehicle. But, it's not a monster tow-er. From experience I'd say that the old 350/5.7 felt like it pulled better. With that said, over the period of a year, I'd rather feed the 5.3.

[parker_rowe]

I tow with a similar vehicle, in my signature. Mine has 132K miles. My camper is a bit heavier though. (6500 gross, around 4500 dry IIRC)

I always lock it in 3rd. With the extra weight and wind resistance it kicks in and out of OD, or unlocks the converter in OD, whenever it hits a hill. I did a test where I ran a leg in overdrive, with the cruise set, and let the computer decide. Trans temps were ok, but my gas mileage was actually worse then just locking it in 3rd.

Does a great job in 3rd. With 3.73's and 33 inch tires I am usually between 2500 and 3000 rpm depending on speed. Anything over 60 and the gas mileage starts dropping.

I feel the Vortec 5.7 is much better suited for towing than the Vortec 5.3, especially with a 4 speed auto. Both are great engines though.

I got 8.5 mpg on my last trip hand calculated. Not bad for a 20 year old gas truck towing a brick at 55-60mph.