The question is, what is a safe temperature for a rear axle or fluid when towing heavy?? Running a Dana 70 with Mobil-1 75/140 synthetic.

What is the safe maximum temperature?

I am towing this 5th wheel monster for the first time.

Thanks in advance, Don

This is nowhere near scientific. But my old mechanic always told me "if you put your hand on it and it's warm, it's ok. If you put your hand on it and it's hot, there's a problem".

You're using the right oil for the Dana 80 (at least on my '01 F350, that's the right one). Make sure to add the LSD additive if you have a LSD equipped axle.

JP

Dad has a 99 Dodge 3500 2wd gasser dually that he tows a 28' gooseneck with, loaded down with cherries in the summer. I scaled the rig with a load of sweets at over 37,000 lbs myself last year.

Don't know the actual temp, but the rear diff gets hot enough to give your hand a 1st degree burn pretty quickly. You can't rest your hand on it for more than a couple of seconds at most.

The truck has around 40,000 miles on it, and no signs of differential problem. Even the limited slip is still tight. It also gets an oil change annually.

This is nowhere near scientific. But my old mechanic always told me "if you put your hand on it and it's warm, it's ok. If you put your hand on it and it's hot, there's a problem".
Nope.:flipoff2: :flipoff2: :flipoff2:

I use my Infrared temp monitor, generally I haven't seen over 200F on anything. (Which will burn you)

Dana 70 w/ 5.13s and Detroit fresh setup in my Dodge, highest it got was 175.

14 bolt in my tow rig, 4.10s gov lock, pulling 11 000 lb at 100 deg F, about 180.

Dana 80 pulling 15 k, don't recall over 180....

I think if you run synthetic, I doubt you'll have to worry unless you have some sort of bearing failure or such.

This is nowhere near scientific. But my old mechanic always told me "if you put your hand on it and it's warm, it's ok. If you put your hand on it and it's hot, there's a problem".

You're using the right oil for the Dana 70 (at least on my '01 F350, that's the right one). Make sure to add the LSD additive if you have a LSD equipped axle.

JP

Unless you swapped the 70, the factory rear axle should be a 10.5 for SRW, or Dana 80 for DRW.

I run a diff temp gauge in my truck (99 DRW Ford), with Mobil Syn fluid, and the warmest Ive seen so far is 130 on the highway for 12hrs running 75mph. This was unloaded however, and in the winter. I also have a PML diff cover and 3 extra qts in the diff. You should have anything to worry about until you get up to the 210 range or so.

WOW! In all my years I have never had a customer acutely measure the temp of his rear-end you guys have a lot of free time to worry about thing that don’t matter much. This is something that normally is done in semi trucks but not light trucks.
If you burn up a rear end with just heat I would love to hear about it because it just doesn’t happen if you use good oil and keep up on maintenance. In most cases you will find that your rear end will run around 200 degrees and a bit hotter when towing.


Mac

WOW! In all my years I have never had a customer acutely measure the temp of his rear-end you guys have a lot of free time to worry about thing that don’t matter much. This is something that normally is done in semi trucks but not light trucks.
If you burn up a rear end with just heat I would love to hear about it because it just doesn’t happen if you use good oil and keep up on maintenance. In most cases you will find that your rear end will run around 200 degrees and a bit hotter when towing.


Mac

I actually just carry the I/R temp gauge to check brakes, but when I'm checking things out, the extra 10 s to check the diff doesn't feel like too big of a deal. And not i haven't burned up or saved any rearends, but I has helped diagnose some break problems. :rolleyes:

That's correct, it's a D80. I mistyped.

JP

Unless you swapped the 70, the factory rear axle should be a 10.5 for SRW, or Dana 80 for DRW.

I run a diff temp gauge in my truck (99 DRW Ford), with Mobil Syn fluid, and the warmest Ive seen so far is 130 on the highway for 12hrs running 75mph. This was unloaded however, and in the winter. I also have a PML diff cover and 3 extra qts in the diff. You should have anything to worry about until you get up to the 210 range or so.

Thanks for all the replies. I towed the 39 ft W/Warrior to Grass Valley for the Winter Fun Fest this past weekend. I had no problems and the diff cover was very hot to the touch but I could hold my hand on it for a short while.

Whose differential gauge did you install and where did you place it? I'm running a D70.

Thanks again, Don

Thanks for all the replies. I towed the 39 ft W/Warrior to Grass Valley for the Winter Fun Fest this past weekend. I had no problems and the diff cover was very hot to the touch but I could hold my hand on it for a short while.

Whose differential gauge did you install and where did you place it? I'm running a D70.

Thanks again, Don
interested myself

had some friends towing their 35ft 5th wheel travel trailer over the grapvine 90+mph, 99 CTD 4x4 boil the gear oil in the rear axle. had to stop on the grade to let it cool down. one of the rigs they were caravaning with radioed him and told him he had smoke coming out the back of the truck. stopped and found gear oil spitting out of the breather and the diff was too hot to touch. let it cool, found the next major stop and changed the rear end oil in the parking lot. drove down into mexico and back with no further troubles to this day, although he dosent run as fast anymore with the trailer...

chris:cool2: