I have to agree with skipnchar. If you have a truck made in the last five or six years let the computer do all the work. It is smarter than we are anyways.
Bill & Lori Nardini finally on the road!
2008 Tundra SR5 doublecab
2009 Jayco 31 RKS G2
Don't know the rig that the OP has so answering his question for his situation is useless at this point.
In my case I leave OD on and use Tow Haul mode and the rig tows like a dream, with no strain or fuss and the tranny temps are always within spec. I figure I paid for the ECU, TCU, tranny cooler, etc. in the truck and I expect it to do its job.
Just went on a 4000 mile road trip to Canada with ambient temps while driving between 90 - 100 deg.F and have had no problems whatsoever. Highest elevation going towards the Great Smokies in Tennessee was about 1200 ft or so and worst grades were allegedly 6 or 7%. Speed was set with cruise control to the maximum of my tires (65 mph) and the truck did its thing. Occasionally passed slower moving traffic with bursts up to 75 mph. No problem. Trailer was about 3800# and with my 3.08 rear axle the truck is limited to 7000# towing. Engine revs never exceeded maybe 3500 rpm, typically cruising at 2500. Might have hit 4000 when passing.
So there is the data and the feedback from my perspective.
My 04 150 likes it better with the OD turned off. It actually gets better MPG, and is running cleaner, and happier. In OD, it seems to be lugging, or working awful hard to stay in OD. Out od OD the RPMs come up, the engine sings, I have way more throttle response, running in the power band. Yep, Me and the truck both are more happy running in 3rd.
nrg2brn wrote: New TT. the last one was very heavy, so od off, no brainer but this one is very light, and when towing, I stuck at 2,700 rpm most of the time except for hills, when it hit the passing gear. Not a lot of weird "hunting" rpms going up and down....I know the od is not a power gear, I dont want to hurt my tranny, but Id like to stay in od if its safe, im sure it saves gas...but then again I got 10 with the overdrive on, so I guess I just like the fact that with od on the rpm's are lower, seems nicer to the engine. I dont know, im not an engineer. :-{
Dave
Dave not sure what you are driving because features seem to be different for different vehicles.
The 2003 Escalade Tow Mode not only changes shifts points but increases transmission line pressure leading to less slipping/heat which I think is a good thing. OD will not engage until you are hit 60 MPH the best I remember.
I drive a 2006 pathfinder. 4.0 liter. the transmission is beefy - made for the larger engine. it has a tranny cooler. On the way home, I turned od off, and kept the rpms at about 2,750, the speed right at 65, and it seemed very smooth. I think this is ok. I dont know how you guys tell the temp of the tranny, my truck does NOT have a tranny temp guage. I will call nissan, but I believe my TV is not designed for od. thanks for the input. what I DO make sure of, however, is good fluid. I noticed my tranny fluid was dark at 85k, when it says to change at 100k, I changed it anyway. we do a lot of towing, and city driving. got to keep that fluid light.
Get yourself a Scan Gauge (Google them), and you will get a lot more than just transmission fluid temperature. The mileage displays can get you an additional 8/9 percent better mileage if you pay attention to them. Also a code reader and a couple of dozen other gauge/displays. About $150 on Amazon.
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