Newbie Towing Question

[ThePair]

Originally Posted by MudDog

I also have a Sienna and have looked at the ScanGauge. It looks like it provides useful info as part of the standard gauge but, from what I can tell, it looks like to get transmission temp you need to use the XGauge functionality (a way of adding additional codes your vehicle supports).

See below for a link to the current X-Codes: (Sadly, the only Toyota vehicle listed in the extended codes is a Prius)

http://www.scangauge.com/support/pdfs/XGAUGE.pdf

I saw that, but without a listing for Sienna, I'm not sure that the XGauge will have Trans Temp for that vehicle.

I guess I'll shoot them an email and see what they say.

I will try to find my manual as it had some additional info.

[roned2]

Thanks for all the replies. My question is still very basic. When I am in the mountains do I shift manually down the gears from 4th on the Triptonic going up the mountain or do I let the transmission drop it down to the lowest gear possible. Do I have a choice? If the transmission changes by itself what is the difference if I have it in overdrive. The Highlander does not have an overdrive button to push only a D for drive. In the Triptonic setting I can choose which gear to use.

Originally Posted by roned2

Thanks for all the replies. My question is still very basic. When I am in the mountains do I shift manually down the gears from 4th on the Triptonic going up the mountain or do I let the transmission drop it down to the lowest gear possible. Do I have a choice? If the transmission changes by itself what is the difference if I have it in overdrive. The Highlander does not have an overdrive button to push only a D for drive. In the Triptonic setting I can choose which gear to use.

The short answer is that you can let the transmission shift into a lower gear when the rpms drop too low. I often help it out a little by pushing down on the accelerator to force the downshift when going up a steep hill. But there's also no problem doing the downshift manually.

I believe that you do have a button on your shift handle that will lock out overdrive. I have a 2006 Highlander and the little black button on the driver side of the shift handle locks out the overdrive. It can be hard to see because of the larger button above it that allows you to move the shift lever.

If I can offer some advice, I would suggest that you never tow your TM without locking out the overdrive. The weight of your 3124ks is very close to the max towing weight (3500 pounds) of the Highlander.

Hope this helps

[roned2]

Thanks. I see no mention of a lockout button in the manual but I will look this morning. By the way, the '08 Highlander has a tow rating of 5000 pounds. The 08 Hybrid is listed at 3500 pounds.

You're probably right about not finding the lockout button. I just went to the Toyota website and looked at the quick reference guide. It appears that the tranny settings are different than on my 2006. You have an "S" position that lets you downshift rather than 3-2-1 that I have.

Check the section in your manual on towing. If it doesn't say anything about locking out overdrive, you're probably OK. On both my 2006 Tundra and Highlander, that's where it told me to lock out overdrive.

[roned2]

The manual does state not to tow in overdrive especially if it is changing up and down. I am just not sure how it will not shift up and down even when it is not in Drive(5th gear). I am just not understanding the mechanics involved.

[Bill]

RonEd -

In one form or another, your question is fairly common, and no definitive answer seems to have emerged. I am not a transmission expert by any means, so take what follows with a grain of salt.

First, with regard to a lockout button. If there is one, it simply tells the transmission not to use the top one (or two) gears. For example, my 2002 Explorer had a 5-speed transmssion, and the lockout button told it not use 5th gear. My 2007 Explorer has a 6-speed transmission, and the lockout button tells it not use the top two gears (5th and 6th). Either way, the purpose is to prevent the transmission from "hunting" among the top gears. ("Hunting" means repeated shifting up and down and up and down in an attempt to find the right gear at the moment.) If you don't have a lockout button, you can do the same thing simply by shifting manually to a lower gear whenever the transmission starts to "hunt". The transmission will not use any gears higher than the one you selected.

Regarding manual shifting, I have communicated with a transmission expert (ken bachellerie at thedrivetrainpage) by a series of emails. He explained that from the point of view of the transmission, a shift is not a single operation. It is a carefully-orchestrated sequence of two operations - release the mechanisms of one gear, and then engage the mechanisms of the next gear.

Next, he pointed out that if the vehicle is struggling to get up a grade, and you let the vehicle shift for itself, the shift will always occur at WOT (wide open throttle). In other words, the engine is developing the max power possible, and when the computer decides that a shift is necessary, the transmission leaves one gear and SLAMS into the next gear. That is quite hard on the transmission. He suggested that when you sense the need for a shift, you momentarily take your foot off the accelerator, then manually shift into the next lower gear, then re-apply the throttle. This ensures that the shift occurs at a moment of minimum stress on the transmission. It takes a bit of practice to do this smoothly - it is easy to take your foot off the gas for too long, and that isn't helpful either - but I personally think it makes sense, and so it is worth doing.

Again, remember the grains of salt ...

Bill

[roned2]

Thanks. Your explanation helps me understand. Now on to the mountains.

Originally Posted by ddnavar

Heather & Ron
I have an older 4-runner with a 3.4 liter v8 "183 hp" and also tow a 3124KS.
Your 2008 Toyota Highlander is most likely a 3.5 V6 at 270 hp with a 5 speed trans. From what I understand, towing with the overdrive on uses a planatary gear which gears it more than 1-1 ratio. 4th gear should be a 1:1 ratio, but I may be wrong because I am not familiar with the Highlander.
I constantly go up and down 1-70 from Denver which is a 7% grade in about 3 places. I always leave my overdrive off increase my braking on the trailers electric brakes and use my engine compression downhill when I can. The brake rotors are fairly thin on the 99 4runner and they will warp fairly easy when overheating them.
Going uphill -- 6% grade 55mph, 7% grade 25-30mph.
Happy camping.

Look here if you want to solve your brake rotor problems.
http://www.larsdennert.com/4runner/brakes/index.html

As far as overdrive is concerned. The reason not to tow with it is because the torque converter will not stay locked under moderate load. While towing this will overheat the transmission fluid which will in turn burn out the seals and eventually be cause for a new tranny. Locking out the overdrive does two things. It tells the tranny not to use a gear ratio greater than one to one and it tells it leave the converter locked (except when shifting of course). The actual shifting that happens while towing is not dangerous or damaging.