Long term wear from towing. Real world data on what to expect.

[FinallyGotOne!]

Thanks for the responses. Much to ponder. I can't buy that "...more RPM equals more gas sent to engine." in all cases. Lugging an engine in a higher gear under load is definitely sending more gas than is running it free in a lower gear higher up in the power band. And that what has always kept me thinking.

It's really about load presented to the crank. One will realize higher mpg when towing in a higher gear if on level with a little tailwind or a slight decline then with a lower gear because the load presented to the engine is below the start of that nebulous high load region to which TeCKis300 referred. But in my experience, without a tailwind and/or even the slightest incline, my mpg is going to suffer (as is my engine) if I don't go to 4th.

And that, folks, is why I find myself manually shifting to 6th when I am going down and 4th when I am going up and stressing the entire time. Kudos to those of you who can just sit back in 4th, burn the gas, and enjoy the ride!

Great discussion! Thanks!

 

[TeCKis300]

Agreed with your intuition. There are very long gentle downhill grades that I may shift into higher gears too. Sometimes 5th. Rarely ever 6th but that may be because of the upsized tires, the larger trailer, and the speeds I hold towing.

On grades that could justify 6th, I'm generally using some form of engine braking so that calls for lower gears than 6th.

If we had a readout that showed injector duty cycle or injector time, that would be the ultimate to show fuel utilization. There's conditions that letting the engine drag in lower gears can actually save gas as the injectors will literally shut off. Versus somewhat coasting in a taller gear at low rpm where some fuel is being consumed. But you have the right idea.

 

[FinallyGotOne!]

Well said. I've really gotta spend some time understanding and correlating some of the OBD2 values that I can see using my Torque app. Throttle position, absolute load, obviously fuel flow, and one or two others that I can't remember right now all portray a picture of how hard the engine is working, but taken at face value they are more difficult to understand than simple transmission and cat temps. Don't want to hijack the thread. Perhaps somewhere else I'll mention how absolute load and throttle position don't seem to have a consistent relationship to incline, load or speed.

 

[OregonLC]

I've watched my AT pan and torque converter temps in all gears and 4th almost always generates the least heat. The exception is occasionally when on very long gradual downhill descents particularly at higher elevations I've found running in 3rd will actually be a bit cooler than 4th - presumably because of the speed fluid is circulating.

On all three Land Cruisers I've owned (A343F, A750F, AB60F) the temp has been higher in the decent than on the climb. My assumption too has been that the pump is driven off the input shaft and when the rpms drop the fluid spends more time in contact with the hot bits and therefore reads higher, even though the actual heat being generated has decreased. You seeing a temp drop in 3rd supports this theory.

 

[linuxgod]

On all three Land Cruisers I've owned (A343F, A750F, AB60F) the temp has been higher in the decent than on the climb. My assumption too has been that the pump is driven off the input shaft and when the rpms drop the fluid spends more time in contact with the hot bits and therefore reads higher, even though the actual heat being generated has decreased. You seeing a temp drop in 3rd supports this theory.

Yep I have the same theory. The cooling system on the 200 is well built, but it's a matter of circulating fluid through it fast enough.

There are a few times I've seen temps run a bit cooler in 5th or 6th gear - on a looong gradual descent at lower elevation when ambient temps are moderate and I'm going fast enough to keep RPMs up. But in general I just run in 4th because it's easy and there's little mpg or wear difference but a lot of effort to try to optimize everything.

 

[GordJ]

I must be alone on this because I follow the manual and use the same rules for towing that I use every day. Put it in drive, let the tranny shift like I thought it was made to do and I downshift going down hills. I have started to use the power button lately and find that it downshifts on hills better, especially on cruise.

 

[coleAK]

Here in Alaska we drive Anchorage to Seward and back often with our camper. Keeping it in S4 then entire time with the occasional shift to s3 on longer downgrades I get 8.5 mpg as long as there isn’t strong winds and I keep it 55-60mph max. I’ve tried where I shift to 5 and 6 where appropriate on downgrades when I don’t need the engine braking and have never gotten better than 8.7 mpg. The largest factor towing a camper is speed if I run 65mph on the sections I can and try and run 45-50 up the steep grades then i get 7.5-7.9mpg

 

[coleAK]

I must be alone on this because I follow the manual and use the same rules for towing that I use every day. Put it in drive, let the tranny shift like I thought it was made to do and I downshift going down hills. I have started to use the power button lately and find that it downshifts on hills better, especially on cruise.

The manual says to put the trans in sport and use ECT power when towing.

 

[GordJ]

I re-read my manual and I don’t see any reference to ECT and only to S when going downhill to assist engine braking so the manual has changed or I’m having trouble reading, which is most likely.

 

[OregonLC]

It will absolutely work to leave it in D. It will absolutely work and do so at a lower temp if you manually keep it in a lower gear. Will it wear out and fail before you sell it using either mode? Who knows. I’m of the camp that heat is bad as is continuous up/down shifting. YMMV.