Towing a boat and transmission temp

[burelom]

Recently I towed a boat (~3500 lb) and according to the SCII the TFT was around 225 at some points - mostly uphill. Granted it was through quite steep mountains... Should I be worried or it's just a normal temp in such conditions?

Another question - should I keep the tranny in D position or switch to 4?

PS. It's V8 4WD

 

[Ti-Ben]

Those numbers seem high to me. What was the outside temp and do you have a transmission cooler?

I tow a 25 feet travel trailer and keep it in 4th gear. Trans temp stays under 180F. Where I live it is pretty flat though.

 

[webby]

I just towed our new 21.5' travel trailer from 1000 to 7450 ft elevation in 120 miles. My scangauge showed alarming numbers for the trans fluid temp. On hills it was consistently over 200 deg and often up to 232. Once it actually hit 250. Not acceptable. Outside temp was only 80 to 88.

My tow vehicle is a 2008 SE V8 4WD 4Runner, 50K, very well maintained, just had the entire cooling system flushed and tranny fluid changed. The trans generally runs 192 or less even well over 100 degrees when not towing.

This 4Runner has the (small) factory trans cooler, but obviously it is not enough for towing my TT. Temps here in the summer are often 90 to 110, so I plan to add a larger aftermarket trans cooler. Anyone have any suggestions as to type, size, and make? I have read that one has to be careful to not get one too large, or the trans fluid will take a long time to reach operating temp, which is also not a good idea. Do any of these have a thermostat to open after the fluid reaches operating temp?

 

[rebelbowtie]

225 is fine but you are closely approaching what is considered the safe operating temp for transmission fluid. over 250-260 degrees and fluid viscosity decrease and oxidation starts.

as for driving in OD or switch to 4th that is totally dependent on how your truck is driving, if it shifting in and out of 5th gear looking for the sweet spot or constantly unlocking the TCC you are in danger of sending your transmission to the grave.

 

[Ti-Ben]

I also got a 2008 V8 with 50k on it. When you stay in 4th gear, it will turn on the engine breaking, which is not enabled when in OD. You will also use more gas by keeping it in OD, the engine load is too high.

I have an aftermarket transmission cooler, I didn't know it would make such a big difference. I've never seen the fluid temp reach even close to 200F.

I'll post a picture and post it, can anyone take a picture of the oem cooler to do a comparison?

 

[webby]

I also got a 2008 V8 with 50k on it. When you stay in 4th gear, it will turn on the engine breaking, which is not enabled when in OD. You will also use more gas by keeping it in OD, the engine load is too high.

I have an aftermarket transmission cooler, I didn't know it would make such a big difference. I've never seen the fluid temp reach even close to 200F.

I'll post a picture and post it, can anyone take a picture of the oem cooler to do a comparison?

Towing in OD, I found that the trans was not searching between gears, so I often left it there rather than 4th. My experience re fuel consumption was the opposite of yours. I used way way more fuel in 4th than in OD, so as long as it wasn't searching for a gear (never did), I left it in OD. I tried part of the trip leaving it in 4th, and I found that the trans fluid temps were not affected one way or the other by towing in 4th or 5th.

I've got to leave shortly, so don't have time to snap and post a pic of the OEM cooler. If I get time in next few days, will do so. The OEM cooler looks quite small to me. Did you remove the OEM cooler when you added your aftermarket cooler? Couldn't one just leave the OEM cooler on and add an additional aftermarket cooler?

Thanks for your response and info.

 

[Ti-Ben]

You're right about the OD when towing a boat. There is a huge difference compared to towing a travel trailer. It is a million times more aerodynamic than a travel trailer.

I found the problem when leaving it in OD is that you can feel it work hard at very low rpm and always searching for a gear at highway speed. The TT is about 5k lbs when loaded. When I'm below 45mph, I'm almost forgetting there is something behind but the parachute effect is crazy on the highway.

There was an oil cooler before the aftermarket one was installed. I don't know which one it is though, it was there when I bought the truck.

I don't know about leaving the oem and adding another one. I guess there is a pump for the fluid and I'd be afraid to lose too much pressure doing that.

 

[webby]

You're right about the OD when towing a boat. There is a huge difference compared to towing a travel trailer. It is a million times more aerodynamic than a travel trailer.

I found the problem when leaving it in OD is that you can feel it work hard at very low rpm and always searching for a gear at highway speed. The TT is about 5k lbs when loaded. When I'm below 45mph, I'm almost forgetting there is something behind but the parachute effect is crazy on the highway.

There was an oil cooler before the aftermarket one was installed. I don't know which one it is though, it was there when I bought the truck.

I don't know about leaving the oem and adding another one. I guess there is a pump for the fluid and I'd be afraid to lose too much pressure doing that.

Here is a pic of the OEM trans cooler on my 2008 SE V8 4WD. It's pretty dinky, I would say. It only measures 10" wide by 3.5" tall.

That's a good point about leaving the OEM one and adding an aftermarket trans cooler -- it might overload the pump.

Towing a travel trailer is like pulling a barn door down the road. Wind resistance is as large or perhaps a larger factor than weight.


gif hosting

 

[Ti-Ben]

Here is mine, 11 x 7 x 1/2.

And yes I need to clean the engine bay!

 

[webby]

Here is mine, 11 x 7 x 1/2.

And yes I need to clean the engine bay!

Is that aftermarket?
If so, what brand?
And lastly, do you have a trans fluid temp gauge and if so, does your trans cooler cause it to take a long time to come to operating temperature?
Thanks!

 

[Ti-Ben]

Yes it is aftermarket, I don't know the brand though. I have a temp gauge, but can't really tell you if it takes more time to reach operating temperature, I've always had this fluid cooler.

 

[burelom]

Thanks for all the comments!!!! In normal conditions the temp runs about 150 (not towing). I noticed it goes up in stop and go traffic - maybe close to 170. The outside temp is about 70-75.

While towing on the flat road the temp stays 170 - so I would say it looks normal. I also noticed the temp goes up if you driving downhill - no brakes, still in the 5th gear. Next time I'll try to switch to 4th gear to see if it helps...

So I guess if in the hills I can keep my temp within 200-210 I should be OK and don't need an aftermarket cooler.

 

[OrdnanceMarine]

Here's my recent observations having towed my trailer and spend some time offroad this weekend now that I can read transmission temps on my ScanGaugeII where I saw lots of time above 220 and touched the low 240s:

http://www.toyota-4runner.org/towing/117854-transmission-temps-observations-revelation.html#post1095843

Thanks for all the comments!!!! In normal conditions the temp runs about 150 (not towing). I noticed it goes up in stop and go traffic - maybe close to 170. The outside temp is about 70-75.

While towing on the flat road the temp stays 170 - so I would say it looks normal. I also noticed the temp goes up if you driving downhill - no brakes, still in the 5th gear. Next time I'll try to switch to 4th gear to see if it helps...

So I guess if in the hills I can keep my temp within 200-210 I should be OK and don't need an aftermarket cooler.

If you're never seeing anything higher than 210 I think you're in good shape. I wouldn't worry about the transmission temp rising when going downhill as long as it's in the normal range that you usually see. It may be that what you're seeing isn an artifact related to the placement of the sensor or how much fluid is flowing, etc. What kind of temp rise are you seeing when coasting downhill in 5th? Over how long of a downhill? What were you doing just prior?