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Discussion Starter #1
OK gearheads: I have searched, but what I'm really looking for is a little mechanical discussion and factual experience regarding the torque converter in the X. I'm good with the basics of towing and installing coolers on the transmission, but I want to dig a little deeper if possible.

Specifically, I'm looking to nail down the stall speed and hammer out some driving techniques with respect to gear/RPM selection to minimize heat loads while towing. For example: is it better to downshift to 3rd gear and maintain a slightly higher RPM (say, 3K or something above the TC stall speed) while towing a trailer uphill, or is it better to simply drive a reasonable speed (55 mph or so) and let the transmission govern itself?

Does it even make a difference?
 

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With modern lock up torque convertors the cruising speed doesn't really affect the transmission. It is old school non-lock up transmissions that are really bad about cooking fluid in the convertor when pushing a lot of torque through the convertor at low speed (excessive slip makes excessive heat). The convertor should be locked at cruise, this will keep the convertor from slipping and creating heat.
 

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OK gearheads: I have searched, but what I'm really looking for is a little mechanical discussion and factual experience regarding the torque converter in the X. I'm good with the basics of towing and installing coolers on the transmission, but I want to dig a little deeper if possible.

Specifically, I'm looking to nail down the stall speed and hammer out some driving techniques with respect to gear/RPM selection to minimize heat loads while towing. For example: is it better to downshift to 3rd gear and maintain a slightly higher RPM (say, 3K or something above the TC stall speed) while towing a trailer uphill, or is it better to simply drive a reasonable speed (55 mph or so) and let the transmission govern itself?

Does it even make a difference?

It's easy to measure stall speed, just stand on the brake hard and start giving it some throttle. At some point, your rpm will stop increasing. Just don't kill anyone while doing this.

Since you really don't have control over when the TC locks, you're going to have to base how your driving it on the perceived load on the engine/trans. Of course, you could add a trans temp gauge and be more scientific about things. The bottom line is that depending on several factors (outside temp, trailer height and weight, hill incline, speed limit, etc.) you may or may not need to modify what Nissan has programmed into the trans for shift points. In a worst case scenario (5,000 lb tall and wide trailer, going up a 7% grade and speed limit in excess of what you can actually achieve and 100+ degree temps), anything less than full throttle is going to be easier on the trans and engine, BUT, you might not be going as fast as you'd like to. In this scenario, you wouldn't even have the choice to use 4th or 5th. No matter what, the trans is going to kick down.

What's the trailer weight? Is it small, like a pop-up, or big like a toy hauler? You might end up needing to use lower gears even on a flat road with a big trailer. It's extended time at load that I'd be worried about, not the 10 minute hill climbs...
 

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Discussion Starter #5 (Edited)
FWIW, I use a BullyDog to monitor transmission temp. Not towing, with no skids installed, the BD indicates a transmission temp of 145-150F on the highway at 70mph and 90+ degree ambient temp. Taking the skids off and installing a bigger transmission cooler lowered the highway transmission temperature 15-20 degrees F, so that helps. The other good news is there should be significantly cooler outside temps during my trip at the end of October.

rockhd, you hit the nail on the head: I'm towing a 5x8 cargo trailer that will only weigh around 2K, so the biggest factor over hundreds of miles a day is wind resistance. On my short test runs, it tows fine up to 65mph, but you can really feel the drag above 45. I will probably just lock out OD and hope for the best, and slow down when I have to. I plan to drive 60-65mph on flat highways, but I will dial back to save the transmission as necessary, especially on the hilly parts.

Thanks for the responses. Stay tuned for a "Find my X" contest while I'm driving across the country next month! Your best best might be the nearest mechanic along I-40. (just kidding, I hope...)
 

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Have fun climbing the hill up to Flagstaff! But, at least the air temps will be lower :) and 2000 lbs isn't really that much at all.

If you're towing that cargo trailer, just keep your speeds lower. Remember, doubling your speed increased drag by 4x. It's 4x harder to drive 60 mph than 30 mph. Oh, and plan on getting REALLY bad fuel mileage lol
 

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I pulled a 5x15 box with a 7 foot roof height from home to Chicago and back (2500 miles) and saw better mileage with a load in the trailer versus unloaded. Also, I was able to maintain 70 mph with the loaded trailer. Just watch your distance with the big trucks, nothing like backwash to start a trailer swaying. I can't comment on transmission temps though, I have a manual. Truck towed it just fine though, only issue was animals. New York and Pennsylvania are loaded with deer and we crossed both states at night.
 
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