When to Cool

[JWMiller]

So how hot is to hot?
This was taken pulling my 37 ft. 5th wheeler at 65 MPH at 75 degrees.
I am using 50wt Mobile Synthetic in my G56.

 

[Jim W]

That doesn't look out of line to me. When I tow my Cedar Creek I normally see between 190F to 200F @90F ambient temperature. I have a 68RFE auto in my truck. I do not worry at all until the transmission oil would rise above 220F. That is when the oil in the transmission would start to deteriorate due to temperature of the oil. As the oil temp increase the life expectance of the transmission oil will shorten.
It also depends on where you have the probe installed for your transmission oil temps. This oil could be hotter and or cooler than the reading you are showing.

 

[JWMiller]

The sending unit is in the bottom of the PTO cover on left side. Temp was as high as 210. This was the first time pulling since installing the gauge.

 

[Jim W]

Here is a chart on transmission temperature range and theoretical life of the transmission to failure due to oil temperatures! I copied this from a towing RV forum that I am on. I do not know what oil this applies to such as non-synthetic or synthetic, but it is a general range chart in my opinion. If you keep the oil under 200F for the most part and change per the manufacture recommendations you should not have any issues. The real problem is heat tends to cause the oil to degrade and this is what will cause the failure to components.

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[cerberusiam]

Under 200 will extend the life of the trans but that will require a cooling system. If you change on a regular basis and never exceed 210 degrees it becomes harder to justify a cooler. However, if that temp is on the flat it is going to be higher when you really start working it.

 

[Cummins12V98]

My AISIN towing 35K combined runs less than 180 even with temps in the 90's pulling West Coast grades.

 

[KATOOM]

200* is not out of line... But if you want to cool it down, tow in 5th gear because 1:1 direct ratio will run the coolest as there's no ratio compound. The engine may thank you too since more air will be pumping through keeping oil pressure up and EGT's down.

I tow a 15k 5th wheel in triple digit summer heat with my 4500 and I tow in 4th gear (1:1). Transmission towing temps usually run around the 155* - 185* range unless I have to run a steep grade in 3rd for extended time. Then it can eventually reach 200* - 210* if the hill is long enough. Towing in direct drive helps a lot.

I also installed Fastcoolers to help keep the fluid temps down, and they help.

 

[JWMiller]

This temperature is on a G56 six speed manual. Since this picture was taken I have pulled over some passes when the temperature exceeded 225 in 4th gear.
Has anyone used a set of Trans-Cool coolers from Geno's? I would like to see some ratings and reviews.

 

[Wiredawg]

Gents, standard transmission is a different animal than auto... Never had a G56, but my 5600 could get up to 240' pulling heavy in 100'+ outside temps. Standard transmission correlates more to rear end in temps than an auto transmission, IMHO. Iwas running 8Klbs over recommended GCWR, that I did add FASS coolers to the transmission for more cooling. If you're within recommended weight ratings, you're fine.

You're fine.

 

[AH64ID]

Here is a chart on transmission temperature range and theoretical life of the transmission to failure due to oil temperatures! I copied this from a towing RV forum that I am on. I do not know what oil this applies to such as non-synthetic or synthetic, but it is a general range chart in my opinion. If you keep the oil under 200F for the most part and change per the manufacture recommendations you should not have any issues. The real problem is heat tends to cause the oil to degrade and this is what will cause the failure to components.

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Old post, but this is very old information. This chart is based on 30-40 year old non-synthetic ATF.


For the OP you’re fine at the temps you’re seeing on a manual trans.

 

[JWMiller]

Gents, standard transmission is a different animal than auto... Never had a G56, but my 5600 could get up to 240' pulling heavy in 100'+ outside temps. Standard transmission correlates more to rear end in temps than an auto transmission, IMHO. Iwas running 8Klbs over recommended GCWR, that I did add FASS coolers to the transmission for more cooling. If you're within recommended weight ratings, you're fine.

You're fine.

Pictured below 2007 2500 6.7 G56 Pickup and trailer 2019 Montana 5th weighed in at 22,500.
I also have an 01 2500 QC LB with the NV5400 and the cast iron case keeps the case from growing (expanding) in the heat. I hear the G56 aluminum case expands with heat and bearings loose there preload.
If I could find a donor pickup with an auto, use an electric pump and put on all the stock trans cooler, lines, fittings and hoses.

 

[AH64ID]

There have been a few folks that have put coolers on their G56’s, but if you look at the numbers I’m just not sure it’s necessary.

The G56 is the most prolific manual trans in the Dodge/Ram with a Cummins, and put behind the highest power Cummins with the most ratings. It’s a pretty stout transmission.

 

[Jim W]

I just wish people would look at when the discussion (post) was made before commenting on an old post. Although I guess old post never die!

If you want to make a comment or post a question start a new conversation if the post is a couple of years old!

 

[AH64ID]

I just wish people would look at when the discussion (post) was made before commenting on an old post. Although I guess old post never die!

If you want to make a comment or post a question start a new conversation if the post is a couple of years old!

Considering that the OP brought it back to life I am fairly certain he knew how old it was... and when I commented on your post I mentioned it was an old post.

 

[Jim W]

I know John but if you look he has brought up a few old posts!

 

[MichaelOverfield]

Yes, I have the Geno's trans coolers (fastcoolers), one on each PTO cover, and I also made a custom electric pump, filter, cooler with electric fan to circulate and cool even more, and it helps quite a bit. I'm running mostly the AMSOIL 50wt, with about a quart of synthetic ATF mixed in. I have the pump cooler set on a thermostat, but it has not yet attained that temperature (225F if I recall, but it can get over 200F, I periodically run the system in manual to provide filtration when the oil is hot. I think I posted elswhere on my system details, but do have a picture handy. From what I read, the concern on high temps with G56 is the thermal expansion of the case, the synthetic oils can handle it pretty well, but that expansion causes other issues, as such I aimed to keep the temps as low as possible. I only see the higher numbers when towing at highway speeds or on long up-hill grades, but my trailer is not a big load for this rig, at about 6000lbs full load. In the image (under truck looking up, driver's side, front to right) on the left you see the cooler and behind it is an electric fan, the orange filter is for the transmission, the other 2 white filters are for fuel. The pump is in the upper right side, that is for the transmission cooling loop. I drilled and tapped the fastcoolers for 3/8NPT fittings and flow from one side (Pass side) to the other from the bottom of the fast coolers. For fast leak isolation, I also installed 90 degree ball valves as a just in-case, have not needed them.

 

[NIsaacs]

I know John but if you look he has brought up a few old posts!

If you don't, then you get accused of not doing a search.....