RAM 1500 Diesel Forum banner

Coolant lines on rear axle

12K views 25 replies 12 participants last post by  Hammer 
#1 ·
I’ve searched and can’t find an answer so forgive me if this is addressed elsewhere.

While checking my spare tire, I found what appears to be coolant lines terminated on the rear axle. What is the purpose of these lines? If I’m not mistaken these are used to cool eTorque battery packs, but there’s no eTorque garbage on these trucks.

What say you? I’ll post pics in a few…
 
#4 · (Edited)
When these trucks came out the printed materials showed that those lines are to keep the rear axle cool under heavy towing conditions.

Personally I look at it as another future failure point to worry about so I didn't get it on mine.

Also, I'm pretty sure the manual specs different service intervals and lube for those axles, so look into that.
 
  • Like
Reactions: MAS
#9 ·
When these trucks came out the printed materials showed that those lines are to keep the rear axle cool under heavy towing conditions.

A quote from the director of Ram Truck Engineering, Rob Wichman:
After the engine has been on for a few minutes, and the cabin heater performance has reached a certain level, coolant is sent through metal tubes, along the frame, down through “jounce hoses,” and into a water jacket in the rear differential cover. That warm coolant heats up the oil in the rear differential, thinning it, and reducing the energy needed for the internal gears to shear the fluid as the axle spins. The result is better fuel economy.
Doubt the engine coolant system will be much good for keeping the diff cool when the coolant usually stays around the upper end of what you want gear lube to be. Unless your running fast and overloaded the differential isn't going to overheat.
 
#17 ·
honestly though... they should not get insanely hot. if they do, your backlash may be too tight. I'd expect something like 250F at max tow up a serious grade. while that would benefit from some cooling, 99% of the time the diff oil should be nowhere near that.

It is possible that with the 9.25, the engineers knew they may have a heat issue. heat is generated by friction obviously. on a small diff, you will have a very concentrated point of friction compared with a large diff. so its plausible the system does double duty. Warm the fluid when cold, cool it when warm.

Most of the time though, it would likely serve to keep the fluid warm when it would otherwise be operating at temps well below the engine coolant.
 
#22 ·
It totally astounds me how many people don’t RTFM or just walk outside and look at the damn truck… The coolant through the transmission circuit ya goons! Not directly from the engine The tranny heater/cooler aims to keep the transmission between something like 180-210F which is fine for any fully synthetic gear oil. Know how I know? I googled it up from a reputable source. 'Bright Idea' For Short Detection | MOTOR The article is complaining about finding a modern coolant leak but clearly describes how this works in the Ram 1500s. But then I did something really insane. I took 15mins to trace the lines and verify that my ‘22 ram 1500 ecodiesel 2x4 3.21 indeed has a tranny cooler in front of the radiator. The hardest part was removing ~12 plastic shroud clips. I took pics but I won’t share them unless you PM me. I’d kinda like to know who’s so lazy they won’t take 15mins to do the same thing. On a side note, this also means it’s reasonable to blast heat in your truck with the windows down to cool your transmission if you feel you’re running too hot… so that’s a fun tip.
 
#23 ·
It totally astounds me how many people don’t RTFM or just walk outside and look at the damn truck… The coolant through the transmission circuit ya goons! Not directly from the engine The tranny heater/cooler aims to keep the transmission between something like 180-210F which is fine for any fully synthetic gear oil. Know how I know? I googled it up from a reputable source. 'Bright Idea' For Short Detection | MOTOR The article is complaining about finding a modern coolant leak but clearly describes how this works in the Ram 1500s. But then I did something really insane. I took 15mins to trace the lines and verify that my ‘22 ram 1500 ecodiesel 2x4 3.21 indeed has a tranny cooler in front of the radiator. The hardest part was removing ~12 plastic shroud clips. I took pics but I won’t share them unless you PM me. I’d kinda like to know who’s so lazy they won’t take 15mins to do the same thing. On a side note, this also means it’s reasonable to blast heat in your truck with the windows down to cool your transmission if you feel you’re running too hot… so that’s a fun tip.
[/QUOTE
Some models have a heated rear differential that use…. Engine coolant to heat it. The transmission cooler up front uses air flow not engine coolant. There is a transmission warmer on the side that heats the transmission fluid but once the temp gets high enough the thermostatic bypass moves and sends the transmission fluid to the cooler up front. Cranking the heat wont cool your transmission but ac well since it turns the fan on.
 
#24 ·
Given the length of tubing required, wouldn't an electric heater be as cheap and likely faster? It wouldn't help with cooling, of course.
 
#26 ·
just reinforces the point..... the goal was fuel economy not to stick a fat ass cummins in there for all us few thousand people towing with it. it was to fix their fuel mileage EPA problem and a massive marketing move. no sane engineer would spend that kind of money to bring up an oil temp unless your into NASCAR, indy, or autosports in general or have a real problem with fuel mileage. that is just homer-ism at its finest, there is NO NEED for that ON THIS TRUCK.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top