Warm rear differential...

mkirsch wrote:

mosseater wrote:
I don't know about the rest of you, but my diff gets pretty darned hot when I tow. Always has. You're not going to lay your hand on it very long after a trip on a summer day. To me, that's over 200 degrees.

140 degrees is hot enough where you are not going to want to lay your hand on it, and that's still pretty darned cool by lubrication standards.

If you can hold your hand on something even approaching 200 degrees, you must be from another planet.

Regardless, there is no way for the differential to transmit noticeable heat to the floor of the pickup bed, UNLESS the truck is a slammed low rider, OR the differential is on fire.

Ha, don't know if I'm from another planet or not, but I'm talking about touching it for a few seconds, not making a hand warmer out of it. Our parts washers at work run around 160-180, the feed pipe on my boiler out to the radiators runs about 160, heck even a radiator cap that's 220 or so I can touch for a second. When it get to where you can't literally touch it for one second, that's getting above 200 pretty good. My diff has been so hot after towing in the summer that I literally couldn't touch it for 1 mississippi. That's hot, prolly like 250-300. I'll have to shoot it with the IR gun next time just to see.

I agree that it isn't the diff. It is normal for the diff to get around 100 degrees over ambient air temp while towing but that's not hot enough to heat up the bed of the truck.

mosseater wrote:
I don't know about the rest of you, but my diff gets pretty darned hot when I tow. Always has. You're not going to lay your hand on it very long after a trip on a summer day. To me, that's over 200 degrees.

140 degrees is hot enough where you are not going to want to lay your hand on it, and that's still pretty darned cool by lubrication standards.

If you can hold your hand on something even approaching 200 degrees, you must be from another planet.

Regardless, there is no way for the differential to transmit noticeable heat to the floor of the pickup bed, UNLESS the truck is a slammed low rider, OR the differential is on fire.

I don't know about the rest of you, but my diff gets pretty darned hot when I tow. Always has. You're not going to lay your hand on it very long after a trip on a summer day. To me, that's over 200 degrees.

Thanks for all the replies. I think it's when in regen as it doesn't happen all the time and everything else looks the way it should.

It is the exhaust. If you look under the truck, at the heat shields above the exhaust, the shield ends in the center of the truck. The heat will roll off the shield and up to the bed, in the center. The differential will not generate that much heat under light load or short distances, unless it has a problem or low on fluid. If it is the problem, believe me, you will hear it!

Paul Clancy wrote:
I'm betting it was in regen.

x2. For a diff to get hot enough to transfer heat all the way through the floor of the bed, that oil would need to be smoking!

Never thought about regen.

Not sure about your 2011 AAM axle but my previous 06 Ram AAM called for service every 15K miles full synthetic oil. IIRC the manual called for 90 and Dodge later had a recommended weight of 120 for towing heavy.
Moot point IMO though, I can't see the pumpkin heating up your bed :W

I'm betting it was in regen.