Keeping an Automatic transmission Cool while towing

[LPMorgan]

I have a 1999 Ram Diesel with an auto transmission.

The transmission is a Hill Killer and not stock.



My issue is keeping it cool while towing 10,000 pounds up mountains,



I have ONLY a 28,000 pound cooler at the radiator. The stock cooler is gone.

To cool the transmission better, should I find a stock cooler in addition, add a smaller coolers in front of the radiator, or get an add on that goes under the truck. I do use the truck on gravel roads a lot (not towing) so rocks are an issue.



I have also heard of a coolant that allows hotter temperatures.



Any suggestions welcome.

 

[Bob4x4]

Not sure by your post which stock cooler you bypassed... ..... You can add a much larger cooler under the truck than any where else but it will need some healthy fans as there will be much less natural air flow than up front. The gravel should not be a problem if it is mounted in a good location. Worst case scenario use some hd mesh to protect it.

A member here offered a pkg already designed to be used for something like what you are doing.

 

[CUMMINZ]

This will go a long way to help. I purchased PML pans from Geno's Garage.



#ad

 

[fox]

The single best thing to lower trans temps while towing will be a tighter converter.

The stock fliud coupling generates a LOT of heat because it slips until lock up.

Next would be a lock up switch! Search it.

 

[AEdelheit]

Just out of curiosity could someone install a bypass on the heat exchanger so after the cooler it doesnt go back through the coolant/atf heat exchanger? I know the 3rd gens are that way and think the 2nd gens do too but I may be wrong. I was thinking of putting a bypass hose on there so in winter light driving you could run it thought the heat exchanger to keep the ATF at operating temps but if you need to keep it cool could open the valve and bypass the exchanger... ... somthin I was thinkin about

 

[LPMorgan]

Try to clarify

I think I must be giving the wrong impression.

I am talking about the radiator-like transmission cooling device that is, coincidentally, in front of the radiator.



I did not bypass the stock cooler -- it is GONE. I think when I had the Hill Killer transmission installed, it was never put back one. It could have been earlier since I had the torque converter replaced when I bought the truck in 2004.



I do have transmission lock, and the torque converter heat is apparently less of an issue than the stock version.



I am towing a 10,000 pound trailer up a mountain. How can I increase cooling to the transmission? I do not have room for a second 28000 pound cooler in front of my radiator. I do have my two old 10,000 pound coolers with a smaller intake line. Can I split the coolant input line and send some to the 28000 pound cooler and some to a smaller cooler? I know two coolers can be used in series, but I do not know about using them in parallel as I would need to do.



Is it worth the cost and effort to find a stock transmission cooler and install it?



Also does anyone have any experience with the high temperature transmission fluid?



One more thing. Does anyone have a brand name of an additional cooler with fan for under the truck? If anyone is using one of these, I would like the name as a starting point for my research.

 

[LPMorgan]

Since I am running a 4x4 with a transmission protector, I was concerned about the deep pans and clearance. Do you have a setup like mine, or do you have 2wd. Thanks

 

[LPMorgan]

Not sure by your post which stock cooler you bypassed... ..... You can add a much larger cooler under the truck than any where else but it will need some healthy fans as there will be much less natural air flow than up front. The gravel should not be a problem if it is mounted in a good location. Worst case scenario use some hd mesh to protect it.

A member here offered a pkg already designed to be used for something like what you are doing.

Bob4x4, more information on the product would be useful so I can track it down.

 

[JMarketos]

I added an additional cooler in series with the return line, where the return goes back into the trans pan. (few years ago). I got mine from Summit racing equipment- it is a B&M trans cooler, I believe they call the series "B&M super coolers". They come in different sizes. I got the biggest one, has a fan mounted to it. I mounted it under the truck, just rear of the xfer case (just ahead of the fuel tank). Mounted using angle brackets. Mounted the cooler at an angle, with fan facing down. (fan covers vast majority of the cooler, so the fan grid acts also as stone guard). The cooler has an integral thermostatic switch in the fluid path. I wired mine with a 3-position SPDT switch so I can choose: always off, always on, or on controlled by the thermostat. I put a small 12V light across the motor, light located in dash so I can tell when it's on. I don't drive the truck much any more, and when I did, I towed very light compared to most of you guys.
=
I don't have any specific data about additional cooling from the trans pan itself, but I do know that my trans temps were reduced significantly by adding the trans cooler, even with the fan OFF. i have a trans gauge, probe in the pan. Sorry it has been a while since I towed, I don't remember specific #s. I have been very happy with the added trans cooler. I don't think the cooler thermostat has ever brought the fan on automatically- that is, fluid has never gotten to the temp where the thermo sensor would turn on. Again sorry I can't remember specific trans pan temp gauge #s.

 

[mwilson]

I have a 1999 Ram Diesel with an auto transmission.

The transmission is a Hill Killer and not stock.



My issue is keeping it cool while towing 10,000 pounds up mountains,



I have ONLY a 28,000 pound cooler at the radiator. The stock cooler is gone.

To cool the transmission better, should I find a stock cooler in addition, add a smaller coolers in front of the radiator, or get an add on that goes under the truck. I do use the truck on gravel roads a lot (not towing) so rocks are an issue.



I have also heard of a coolant that allows hotter temperatures.



Any suggestions welcome.

By the statement "The stock cooler is gone" you mean that the heat exchanger/cooler unit mounted to the engine is not there anymore??



What are you seeing for transmission temps???



Mike.

 

[LPMorgan]

By the statement "The stock cooler is gone" you mean that the heat exchanger/cooler unit mounted to the engine is not there anymore??



What are you seeing for transmission temps???



Mike.

I don't let the transmission temp get too high. If it goes over 235 I find a place to pull over. I do, however, find myself in lower gears than I would like to prevent temperature from climbing.

I would like 5% in overdrive, 6% in drive, 7% in second. Now I have to go to first at 6%.

Of course I have to "manually" shift in cities and go to neutral at all stop lights.

 

[LPMorgan]

This will go a long way to help. I purchased PML pans from Geno's Garage.



#ad

Does the deep pan actually help with towing a heavy load up a mountain? We pull our travel trailer all over the country.

 

[MasterLow]

I have a Mag-Hytec pan, similar to the PML above, and driving around the city unloaded it's 150-155. Once I hit the highway, it drops to 120ish. Towed a small tool trailer through some mountains and never went above 140, but it was wet out. Very happy with it, holds an extra gallon of oil and is easy to drain.

 

[amsoilman]

I would find a high grade of Synthetic ATF, such as Amsoi ATF. I have seen as much as a 30 degree drop in temerature.

 

[fox]

I think I must be giving the wrong impression.

I am talking about the radiator-like transmission cooling device that is, coincidentally, in front of the radiator.



I did not bypass the stock cooler -- it is GONE. I think when I had the Hill Killer transmission installed, it was never put back one. It could have been earlier since I had the torque converter replaced when I bought the truck in 2004.



I do have transmission lock, and the torque converter heat is apparently less of an issue than the stock version. I am towing a 10,000 pound trailer up a mountain. How can I increase cooling to the transmission? I do not have room for a second 28000 pound cooler in front of my radiator. I do have my two old 10,000 pound coolers with a smaller intake line. Can I split the coolant input line and send some to the 28000 pound cooler and some to a smaller cooler? I know two coolers can be used in series, but I do not know about using them in parallel as I would need to do.



Is it worth the cost and effort to find a stock transmission cooler and install it?



Also does anyone have any experience with the high temperature transmission fluid?



One more thing. Does anyone have a brand name of an additional cooler with fan for under the truck? If anyone is using one of these, I would like the name as a starting point for my research.

I don't let the transmission temp get too high. If it goes over 235 I find a place to pull over. I do, however, find myself in lower gears than I would like to prevent temperature from climbing.



Do you have it set up to lock in the lower gears? If not,

This is where the heat is generated.

Maybe you are just looking at the wrong things, but I don't see why you need a higher temp fluid on these trucks IF you fix the issue and that is converter slip.

 

[LPMorgan]

Heat in Transmission

I don't let the transmission temp get too high. If it goes over 235 I find a place to pull over. I do, however, find myself in lower gears than I would like to prevent temperature from climbing.



Do you have it set up to lock in the lower gears? If not,

This is where the heat is generated.

Maybe you are just looking at the wrong things, but I don't see why you need a higher temp fluid on these trucks IF you fix the issue and that is converter slip.

I do not have the means to totally rebuild a transmission and force lockups.

I am supposed to have lockup at whatever gear I use (1,2,D, OD)

I Set the truck to the lower gears,

First gear can pull the truck and trailer up a grade without overheating.

I am trying to investigate options that I might be able to make work,

Additional transmission cooling and higher temperature fluid appear to be the best bets.

 

[fox]

If you are using lock-up in second gear and temps still rise to 200+, something is wrong.

 

[LPMorgan]

If you are using lock-up in second gear and temps still rise to 200+, something is wrong.

Do you tow in tall mountains? It is a lot different than in Illinois, I have no heat trouble in the midwest.

 

[fox]

I have towed up some grades.



Right out of St. Louis, on I-55, there is a grade increase for the next 90 miles.

I believe the elevation changes at least 50-75 feet!!!!



What kind of answers are you looking for with your over heating issues? I should of asked if you know where the heat is coming from.

 

[jtwcummins]

I have never had the trans temps go past 180* until I went up 120 toward Yosemite. Had to climb New Priest Grade in 100* temp. Max speed is 20-25 mph with some corners 15 mph. Trans temp climbed to 220* quickly. NPG is a 5mile slow steep pull and when having to go slow the trans goes to 1st gear and TC doesn't lock. I am going to get a Derale remote cooler w/fan before I make that pull again.



Problem caused by air flow, even w/fan roaring, being to low to cool the trans fluid and engine. Engine was pushing 220* also. The Derale coolers are available at Summit & other vendors. Found best price for the unit I want at Amazon. As a note, Old Priest Grade does the same climb in 1. 5 Miles. When you look at Old as you climb NPG it looks like 45* plus angle.