Rear Differential Temperatures

[heefageLA]

So ive changed my rear diff fluid recently and have noticed the diff cover is pretty dang hot after a bit of driving. Its hot enough that I can only hold my hand on it for ~5 seconds before I cant stand the heat.
I used the recommended 75w85 GL-5 gear oil from Redline. I would say I got about 5 quarts in there. The internet is saying my axle should hold around 4.45 quarts, so im close on fluid levels.
The internet is showing me that normal operating temperatures will range from 170-220 degrees. I dont have a temp gun, but based on how hot my hand gets I would bet im on the upper end of this temp range.
What worries me is this temp is from driving about 30 minutes at 65 mph with NO LOAD. Im scared of hooking up a loaded gooseneck and going 100+ miles.
75w85 seems kind of light for a heavy duty truck, but im ignorant on the subject.
What temps are guys having with a 2500? What gear oil are you running? Any advice or opinions are welcome.

 

[Units]

Go by what the owners manual says and you’ll be fine.

 

[Wild one]

So ive changed my rear diff fluid recently and have noticed the diff cover is pretty dang hot after a bit of driving. Its hot enough that I can only hold my hand on it for ~5 seconds before I cant stand the heat.
I used the recommended 75w85 GL-5 gear oil from Redline. I would say I got about 5 quarts in there. The internet is saying my axle should hold around 4.45 quarts, so im close on fluid levels.
The internet is showing me that normal operating temperatures will range from 170-220 degrees. I dont have a temp gun, but based on how hot my hand gets I would bet im on the upper end of this temp range.
What worries me is this temp is from driving about 30 minutes at 65 mph with NO LOAD. Im scared of hooking up a loaded gooseneck and going 100+ miles.
75w85 seems kind of light for a heavy duty truck, but im ignorant on the subject.
What temps are guys having with a 2500? What gear oil are you running? Any advice or opinions are welcome.

You can buy infared temp guns fairly cheap,and then you can get an idea of the temp the diffs running at.

Amazon.com : infared temperature guns

 

[danielmid]

That's kinda wild to me they spec 75w-85 for the rear axle. Seems super thin to me seeing as my 1500 calls for 75w-140.

I know you just put it in, but if it's hot enough you're worried about it, thicker oil would be my first step. Amsoil lists the 75w-85, but also lists 75w-140 for the DRW axle but the same axle model so that's what I'd try.

 

[danielmid]

You can buy infared temp guns fairly cheap,and then you can get an idea of the temp the diffs running at.

Amazon.com : infared temperature guns

https://www.harborfreight.com/121-infrared-laser-thermometer-63985.html

 

[Daw14]

When I swapped from 3.55 to 4.56 , I used 75-140 in my 1500 .
I measured the temps while breaking in.
I do have a b@m aluminum cover .
Highest temperature after after a 50 mile run was 180 degrees.
I checked the temps up to 500 miles and that was the highest temp. Ambient temperature was 82 *

 

[heefageLA]

Go by what the owners manual says and you’ll be fine.

page 514 of the manual for 2023 Ram 2500 says use SAE 75w-85 GL-5 Synthetic Axle Lubricant.

 

[heefageLA]

That's kinda wild to me they spec 75w-85 for the rear axle. Seems super thin to me seeing as my 1500 calls for 75w-140.

I know you just put it in, but if it's hot enough you're worried about it, thicker oil would be my first step. Amsoil lists the 75w-85, but also lists 75w-140 for the DRW axle but the same axle model so that's what I'd try.

Thats whats weird to me also. The SRW and DRW are the exact same axle internally. I was debating on trying an intermediate weight like 75w-110

 

[Wild one]

Thats whats weird to me also. The SRW and DRW are the exact same axle internally. I was debating on trying an intermediate weight like 75w-110

Buy a temp gun and get a reading on the diff,and if it's running closer to 200 then 180,i'd go right to a 140 gear oil

 

[heefageLA]

Buy a temp gun and get a reading on the diff,and if it's running closer to 200 then 180,i'd go right to a 140 gear oil

Ordering one as we speak. I feel stupid for not knowing the temp before the fluid change, but no one really looks for issues on a factory vehicle.

 

[Daw14]

Ordering one as we speak. I feel stupid for not knowing the temp before the fluid change, but no one really looks for issues on a factory vehicle.

It did not occur to me until I changed the gears , then it went straight to the front of my brain . Paranoia kicked in ,for no good reason whatsoever. Love OCD.

It almost seems like the heavy oil would have been spec’d for the heavier trucks . Anyone have any idea , besides that .0002 mpg difference ?

 

[06 Dodge]

page 514 of the manual for 2023 Ram 2500 says use SAE 75w-85 GL-5 Synthetic Axle Lubricant.

I use Amsoil oil 75-90 in all of my 2500 diffs with out any problems to date, btw when i fill mine I fill it to 1/8 inch or just at the top of the fill plug..

 

[heefageLA]

Ok guys. I borrowed a temp gun from our mechanic's shop. Its pretty beat up and I had to replace the 9v battery but it works. I drove home which is about a 15 minute drive with my cruise set at 65 mph.
Soon as I pulled off the highway I stopped and checked the temp and it read 154.8 degrees... Maybe im just being paranoid, but that diff felt like the surface of the sun yesterday.
I still will get my own temp gun from Harbor Freight this weekend and check with a new one. At least now I can drive without worrying my rear end is about lock up.

*Whispers* Maybe, just maybe, my hands have gone soft. I dont have the calluses, cuts, and cracks like I used to. Perks of climbing that corporate ladder, I guess.

 

[Wild one]

Ok guys. I borrowed a temp gun from our mechanic's shop. Its pretty beat up and I had to replace the 9v battery but it works. I drove home which is about a 15 minute drive with my cruise set at 65 mph.
Soon as I pulled off the highway I stopped and checked the temp and it read 154.8 degrees... Maybe im just being paranoid, but that diff felt like the surface of the sun yesterday.
I still will get my own temp gun from Harbor Freight this weekend and check with a new one. At least now I can drive without worrying my rear end is about lock up.

*Whispers* Maybe, just maybe, my hands have gone soft. I dont have the calluses, cuts, and cracks like I used to. Perks of climbing that corporate ladder, I guess.

You need at least a 1/2 hour or more,closer to an hour is even better,before it'll be at full operating temp,15 minutes isn't near long enough to get a diff up to temp,especially a heavy duty one,that has a pile of steel to heat.Take it for a good hour long drive and run it up to 70+ mph for a bit,as that's closer to most highway speeds

 

[heefageLA]

Sounds like a good excuse to drive to Harbor Freight and back.

 

[dieselscout80]

Ok guys. I borrowed a temp gun from our mechanic's shop. Its pretty beat up and I had to replace the 9v battery but it works. I drove home which is about a 15 minute drive with my cruise set at 65 mph.
Soon as I pulled off the highway I stopped and checked the temp and it read 154.8 degrees... Maybe im just being paranoid, but that diff felt like the surface of the sun yesterday.
I still will get my own temp gun from Harbor Freight this weekend and check with a new one. At least now I can drive without worrying my rear end is about lock up.

*Whispers* Maybe, just maybe, my hands have gone soft. I dont have the calluses, cuts, and cracks like I used to. Perks of climbing that corporate ladder, I guess.

Hot water is between 120 and 130 typically and most people mix cold water with it to wash hands/body.

What I’m saying is 154 degrees is going to feel really hot, but it’s not too much for gear oil.

 

[TC]

If the temp was 200 degrees you would not hold your hand on there for 5 seconds. If you can hold your hand on there for 5 seconds, its probably 185 degrees, max. Let us know what you find out.

 

[Longhorn1500]

When I do the oil change on my 2500 differential I'm going to install the Banks diff cover. I kind of like the looks of the MagHytec one better, but I think the Banks one will provide more cooling. I'll also install a temperature probe.

 

[heefageLA]

When I do the oil change on my 2500 differential I'm going to install the Banks diff cover. I kind of like the looks of the MagHytec one better, but I think the Banks one will provide more cooling. I'll also install a temperature probe.

Ive looked at some of those. Some of them are kind of gimmicky to me.
You want one with alot of deep heat sinks milled into it. The Banks seems to have deeper grooves, and is $100 more expensive.

 

[Grams]

Rear differential temp worries tell me you need to find a new hobby. In other words….this is one thing you should forget about. Completely.
Also, forget about Designer gear oils. Use what Mopar suggests.
(Retired rear differential tech)