68RFE Maximum Temperature Question?

[KOwens]

Hey TDR Gurus,



What is the maximum allowable transmission temperature for the 2010 68RFE automatic? My EVIC will display the oil/transmission temperature, but I don't know what the maximum "sustainable" temperature is before the ATF begins to break down. I know the newer oil can take higher temperatures, but what is the rule of thumb "not to exceed" number? I want this transmission to last a long time, and not break down because I'm doing something stupid.



Anyway, just wondering, since it does go up during hot weather while towing, and this is the first truck I've owned with a transmission oil temp gauge.



Any advice you could provide would be appreciated.



Thanks, Kevin

 

[turbo606]

I know oil breaks down and bearing failure will start at 250. 0F I wouldn't go over 220-230ish to play it safe. I am a heavy duty mechanic and I know on the Cat's that I work on. The trans/torque will over heat at 250. F and can push all day at 220. 0F

 

[KOwens]

Thanks for the info Turbo606,



Do you know any specifics about the Cummins 68RFE transmission?



Not sure if it has a similar range, but I've never seen mine above about 200 degrees.



Thanks again, Kevin

 

[turbo606]

I would think that you'll be ok. 200. 0F is opearting range for a trans/torque. I have a 2008 6. 7 with the 68 RFE. I haven't seen mine over 208. 0F pulling 13000 lbs. I would think anything over 230. 0F is starting to push it in these trucks. The hotter the oil, the more effiecncey you will lose and the greater chance of slipping the trans.

 

[Hoefler]

In my 08, while climbing the Big Horn pass in gravel, extreme road construction, pulling my 40' 5ver for 2 1/2 hours at 3-8 mph. My transmission peg my gauge at 285* sendig unit mounted to the cooler line to the cooler. Then the engine fan came on. Then the transmission warning light came on. Long story short, after putting my truck in 4 low to get the converter locked up, temperature came down and drove into Yellow Stone and into Jackson Hole. The next morning, I checked the fluid, still bright red, no signs of being burnt, smelled good and all. Called my dealer and asked him if I should get it changed before going home. He said it would be OK and not to worry about it. Drove the 1100 miles home with out any indication of a problem at all. Took it to the dealer for them to inspect it, changed the fluid just to make sure, all was OK and as expected. Said it really didn't have any ill effects at all. The factory transmission gauge in my 2010 has 300* as an upper limit on it, so I would guess that the engineers would expect it to get close to that high at times.

 

[KOwens]

Thanks guys,



Sounds like I can work this beast a little harder! Ha!



Thanks again, Kevin

 

[RSchwarzli]

200 is not too bad. Once you get as previously mentioned above that 250 mark oil starts reaching its limits. If you see higher temps, just be sure to service the transmission more often.



Robert

 

[mpaulson]

I have the sending unit in the hot cooler line also and two summers ago I had it up to 265!! I haven't had a problem 30,000k later, now at 130k. After that summer I added an auxilery cooler with a fan and mounted it under the truck behind the transfer case. It comes on at 180 on it's own and I added an override switch so that I can put it on if I see the temp rising or know that I'm going to cause it to warm up while moving the trailer at a slow speed for a while. Last summer I never seen any temps over the 210 range and that was with some hard, slow climbs and/or offroad at 24,000lbs while on camping/holiday trips.

It's nice to know that the factory guage on the 2010 goes to 300 as a top end ok range. I'd assume that it reads from the hottest place which would be straight out of the converter which I believe would be the same as the hot cooler line which I think is fed straight from the converter.

 

[Cosmo]

Towing a ~15k trailer up a 10% grade to Mt. Rushmore the speed limit/traffic speed was about 25-30 mph and it caused my trans to get as hot as it ever has - about 230 degrees. These things have great cooling and in order to overheat them you really have to work them hard.

Look into the H&S Overdrive trans reflash. It's awesome.

 

[EricBu12]

I have the Mag-Hytec pan on mine. don't have a gauge yet. Looks like the added fluid capacity of it will help the temps huh?

 

[mpaulson]

I also have PML deep pan that I was able to see before and after temps from stock vs/PML as I had the sending unit in the line before. I didn't notice any difference right away. All I think the deep pans do is delay the time it takes to get the pan fluid temps up higher due to the volume of fluid, BUT then I think that it takes longer to cool the fluid down due the same volume issue that it has to cool down. Take a cup of hot water that only has a 1/2" of hot water in it and blow on it to cool it down, cools rather quick, now take a full cup of hot water and blow on it and see how long it takes to cool it down. the extra fluid in the pan buys us more time on a long hard climb etc. before the volume of fluid gets too hot, thats all. The time that I hit 265 degrees was before I had the deep pan.