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Old 09-16-2009, 06:48 AM   #11
mtnguy
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I am pulling a heavier trailer now, but some of this info might be helpful here.

I always thought my 1st downshift from OD (4th) was back to 3rd.......NOT!!! After buying a ScanGauge II and setting it up to monitor gear ratio and torque converter slippage, my 1st "downshift" is actually my torque converter unlocking. If I use the button to lock out OD, then both the tranny goes to 3rd, and the torque converter unlocks, but if the engine is not under a heavy load, then the torque converter locks right back up. Pulling my full sized trailer on the interstate, and manually shifting the OD off and on as needed in the hill country around here, the tranny temp. stays in the 155 to 170 degree range. The pull up the winding mountain roads around here in 2nd gear, torque converter unlocked will send the tranny tempurature to 200 degress on a hot day. The problem there is that I have to slow down for the curves, so the speed has to stay down...hence 2nd gear and torque converter slipping. On more straight line Interstate over the mountains where I can keep my momentum, then 3rd gear with the torque converter locked is the norm......keeping up with traffic is no problem.

I do intend to replace the tranny fluid every 30,000 miles or so.
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Old 09-16-2009, 07:27 AM   #12
Bill
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As a couple posts have mentioned, this thread really shows how a gauge - an actual calibrated gauge - can save big bucks and big worry. I set mine up to monitor transmission temp, and at the same time, like MtnGuy, to show me what gear I am in. The 6-speed automatic transmission on my Explorer shifts so smoothly that I can't always tell what gear it is in, and I can almost never spot the subtle change that happens when the torque converter unlocks.

A Scan-Gauge ($170) or a AeroForce Interceptor ($250) is pretty cheap insurance if you have any concerns at all. They install simply by plugging a cable into a socket that is under the dash of all modern vehicles.

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Old 09-16-2009, 09:18 AM   #13
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I'm not sure that either of those would help with a Sienna.

If you know otherwise, please let me know!
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Old 09-16-2009, 11:17 AM   #14
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Have you emailed either one to ask about it? I know the guys at Aeroforce Technology are really helpful.

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Old 09-16-2009, 01:30 PM   #15
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Quote:
Originally Posted by ThePair View Post
I'm not sure that either of those would help with a Sienna.

If you know otherwise, please let me know!
And I will add to Bill's post that the ScanGuage people are very helpful also. I emailed them several times before deciding to buy a unit. Like you, I have a 2006 year model, and it can give me all sorts of information. Probably everything that goes through your vehicle computer can be displayed on the Scan Guage, but only 4 things at a time. Thank goodness, or I wouldn't be able to watch the road.

Check out: http://www.scangauge.com/
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Old 09-16-2009, 02:23 PM   #16
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I know ScanGauge does not show Trans temp for the Sienna -- I asked them.

The AI...I didn't even see the Sienna listed anywhere on their site, so I wasn't sure it would work. I'll need to look into it a bit more...
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Old 09-16-2009, 03:55 PM   #17
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Wouldn't it be nice if all vehicles with a towing package had the transmission temperature displayed on the dash?

Overheating a transmission due to overheating while towing with no transmission temperature gauge is a design flaw that should be covered under warranty for the life of the vehicle. After all, the factory intentionally chose to hide the transmission temperature from the driver.

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Old 09-16-2009, 05:09 PM   #18
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If I keep buying all these gadgets, I'll never be able to buy a later model TM.......

I actually installed a temp guage on my trans when I installed the trans cooler but now you've got me thinking about this stupid thing......... I used to have one of the older versions but my (portable) tool box got stolen a few years ago and that went with it.
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Old 09-16-2009, 06:46 PM   #19
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I’ve been designing and selling industrial power transmission equipment for 3+ decades.
Industrial applications are “purer” in the sense we don’t deal with automatic transmissions, differentials, A/C compressors, power steering, ECUs, sensors, vacuum leaks, and all the other crap associated with today’s automobiles, but the basic energy principles are the same.

I’ll try to put this in a way that everyone gets…

Horsepower and torque are like weird cousins… they can’t exist without each other, but they really aren’t the same, and the balance of each can vary greatly in any situation.
I’ll give a few basic examples in extreme to try to help everyone understand what I’m getting at…

Example of torque:
Theoretically, if you take a 1hp/1750rpm electric motor and mount it on a table and turn it on, it produces 1HP and spins at 1750rpm. A strong guy with good gloves could probably stop the 5/8” diameter spinning shaft with his hands, since the motor itself produces very little torque.
Now take this same 1hp/1750rpm motor and connect it to a 50 to 1 reduction gearbox.
The first thing you will notice is now the output shaft of the gearbox is probably about 1 1/2” in diameter. If you could measure the power at this shaft you would probably now have something like 3/4hp (loss due to drive inefficiencies/friction) and the shaft would be turning at only 35rpm.
(Piece of cake to stop this, right? …. Wrong! If you attempted to stop this shaft with your hand you would wind up in a bloody ball in the corner of the room.)
While the output HP has actually been reduced, the output torque is now many times the input torque.

Another example of torque due to gear reduction is your basic electric drill. Very little input torque, but gobs of output torque.


Example of HP:
Today’s modern Formula 1 race cars produce roughly 800hp from a rather small 2.4L V8. To produce this HP, the engine runs at very high rpm….idles at 4000rpm and is governed to a max of 19,000rpm. This engine produces tons of HP at these high rpms, but very little torque due to it’s very high rpm powerband and limited displacement. When racing on a hilly track, the main thing that gets it up the hill is momentum, and the HP keeps this momentum going as long as the car is moving at a good rate of speed.
Now if you could theoretically use this same 800hp F1 car and try to tow your TM from a standing start up the same hilly track, you will find you won’t get very far due to the very limited torque of the engine, along with the high gearing of the tranny. (Not the ideal towing package!)

So in summary, you can have lots of torque with very little HP, as well as have lots of HP with very little torque. You can’t have one without the other, but the amounts of each can vary greatly, depending on the application.

Basic “rule of thumb” engine principles:
Smaller, faster rpm gas engines produce very little torque.
Larger, slower rpm gas engines produce lots of torque.
Diesel engines produce even more torque at almost any displacement, and at lower rpm than gas.
(Diesel engines will usually produce less HP at a given displacement than a gas engine, but with much more torque.)

So with some basic understanding of the above, you could then theorize that if you could take the same load and course (lets use the E350 towing a TM, going from NOLA to HTX, and use cruise control to maintain speed (no human variable input)) but have three different setups… the first would be the v6, then the v8, then the v8 diesel. Basically the only thing different is the engines, which of course all offer different HP and torque numbers.
We'll say they all weigh 8000 lbs and the cruise is set to 65mph.

The v6 will struggle the most trying to stay in the powerband and produce the HP and torque required to go up the hills with the load and maintain the set speed.
(The slower the vehicle is moving, the more torque required to get it moving.)
(The faster the vehicle is moving, the more HP is required to keep it moving.)

The v8 will struggle less due to the additional torque and HP.

The v8 diesel will struggle even less due to its tremendous torque at the lower rpm ranges.
I doubt that the engine/tranny would even react to the hills/overpasses.

In simplest terms, torque is what starts your vehicle moving, or headed up hill, or accelerating, while HP is what maintains this once moving, but they both must be present in certain degrees in both instances.




Now getting back to the overdrive issue…
To successfully use OD while towing, you need to be very conscious of many variables.
First, you would need enough HP to maintain speed of your rig without the need to downshift to increase torque to climb hills/overpasses. Most smaller vehicles (v6’s) would lack this ability since they lack HP/torque, and a downshift would be required to produce more HP/torque to maintain speed up the hill. The downshift would actually produce more HP from the engine as well since the engine would move into the “sweet spot” in its powerband. This constant changing is what you want to avoid.
This means you would need to find that correct highway speed for your load and your TV to produce enough balance of HP to lock the converter without it needing to kick in and out. While I may agree that today’s TVs with larger v8’s and for sure diesels, would have this ability under good circumstances, the v6 would certainly not.
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Old 09-16-2009, 07:03 PM   #20
ED-n-KEL
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Transmission failure is seldom due to a one time event, unless a major "Hard part" just happens to fail due to stress of that one time event. Most transmissions fail from an accumulative effect of abuse over a long period of time.
Your trans failure while towing your boat probabaly fell into one of the catagories.
No way Wayne. I killed this tranny. I take full responsibility.
I killed it in about 6hrs towing in a manor that I shouldn't have.
At the time (almost 20yrs ago), I was a bit surprised at the outcome, but now in my "older/wiser" years, I fully accept the deed.
This was a very well maintained TV that was rarely used for anything remotely heavy. The longest towing trip it had probably ever made prior to this was 30 miles or so and at normal (45mph) street speeds.
The combination of not finding that "balanced speed" I speak about in my other post, and wind resistance, and the almost 6hr drive without stopping, were the killing factors.
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