Moving my Transmission cooler

[h1x2]

Do you have any idea what the thermostat valve is behind the transfer case?

I’m trying to diagnose my transmission overheating within 30 minutes of driving. Everyone is calling the heat exchanger under the radiator a cooler but I almost feel like it’s designed to heat the trans fluid to get it up to temp in the winter. Maybe I’m wrong but it makes more sense to me.

I think my issues could be in that valve that you called a thermostat. Do you think that valve opens to allow flow up to the aux trans cooler when the fluid gets too hot?

 

[h1x2]

Well I guess they are calling the front heat exchanger a cooler also. On this they call that thing a thermostatic valve that directs flow to the aux cooler. I think mine may be stuck closed. Anyone ever have that happen to them or have one apart?

Even with my fans on 100%, my trans is overheating. It’s gotta be that valve.

 

[Third From Texas]

Do you have any idea what the thermostat valve is behind the transfer case?

I’m trying to diagnose my transmission overheating within 30 minutes of driving. Everyone is calling the heat exchanger under the radiator a cooler but I almost feel like it’s designed to heat the trans fluid to get it up to temp in the winter. Maybe I’m wrong but it makes more sense to me.

I think my issues could be in that valve that you called a thermostat. Do you think that valve opens to allow flow up to the aux trans cooler when the fluid gets too hot?

Yeah, it's a cooler.

Never made sense to me that all cars with automatic transmissions ran "cooling" lines into the car/truck's radiator to be bathed in boiling coolant. But that's how it works.

I'm adding a aux trans-cooler to my rig. It's the same one mounted upright on the M1089 wreckers (it's the BIG one). I'm going to plumb it like a standard add-on RV trans cooler. I may add a bypass to assist warming the engine in cold weather, but my goal in life is to stay the f away from cold weather.

 

[h1x2]

Yeah, it's a cooler.

Never made sense to me that all cars with automatic transmissions ran "cooling" lines into the car/truck's radiator to be bathed in boiling coolant. But that's how it works.

I'm adding a aux trans-cooler to my rig. It's the same one mounted upright on the M1089 wreckers (it's the BIG one). I'm going to plumb it like a standard add-on RV trans cooler. I may add a bypass to assist warming the engine in cold weather, but my goal in life is to stay the f away from cold weather.

How are you planning on routing that? Are you just going to run both coolers in series and then back to the trans?

I’m going to take this thermostat valve apart tomorrow and see if it’s stuck. If it’s not salvageable, I may be looking into running them both in series. I wonder if the reason they don’t do that is the aux cooler will rob engine heat in the winter.

 

[Third From Texas]

How are you planning on routing that? Are you just going to run both coolers in series and then back to the trans?

I’m going to take this thermostat valve apart tomorrow and see if it’s stuck. If it’s not salvageable, I may be looking into running them both in series. I wonder if the reason they don’t do that is the aux cooler will rob engine heat in the winter.

That's my plan.

Or I may go all ghetto red neck and delete the OEM cooler.

I have a lot of research to do given mine is a C7 (no telling what the computers will do or think if I add or delete things), but I've seen CAT/Allison powered RVs with aux coolers so the basic idea is out there.

 

[h1x2]

That's my plan.

Or I may go all ghetto red neck and delete the OEM cooler.

I have a lot of research to do given mine is a C7 (no telling what the computers will do or think if I add or delete things), but I've seen CAT/Allison powered RVs with aux coolers so the basic idea is out there.

I may end up doing that tomorrow. I’ll let you know how it goes. Probably should start my own thread instead of hijacking this one. Just wanted to jump on here because there seemed to be some good knowledge on it.

 

[Ronmar]

Do you have any idea what the thermostat valve is behind the transfer case?

I’m trying to diagnose my transmission overheating within 30 minutes of driving. Everyone is calling the heat exchanger under the radiator a cooler but I almost feel like it’s designed to heat the trans fluid to get it up to temp in the winter. Maybe I’m wrong but it makes more sense to me.

I think my issues could be in that valve that you called a thermostat. Do you think that valve opens to allow flow up to the aux trans cooler when the fluid gets too hot?

It is the thing mounted to the plate, seen between the hoses he has his fingers on in this picture… Note the P6/rear transmission cover in the background…

it is probably a diverter, and has a thermal element like the bypass thermostat in the engine. It sends flow one way(like back thru the engine or liquid cooler, until it shifts due to temp increase and shifts all the flow the other direction(thru radiator or aux cooler). If yours was stuck in the hot position, it would be sending flow thru the aux cooler but with the fan control based on engine temperature, it is not being cooled properly…

The heatexchanger down in front of the oil pan is indeed a cooler. Just like they put the transmission cooler inside the bottom of the transmission on every automatic transmission vehicle I have ever seen. The 2.5-5 tones have nothing else that could cool the transmission…

Did you ever setup your fan for manual control like I suggested in your other thread? That would at least allow you to confirm the hot fluid is headed to the aux cooler and being cooled that way with you manually activating the fans... I guess you could also confirm this by driving it till the trans is hot and confirming that the aux cooler is hot/full of hot fluid…

In the case of this setup, that valve doesn’t make all that much sense With the engine temp controlling both fans. It would make more sense and satisfy my simplistic streak by simply putting the aux cooler in series with(after) the liquid cooler. Without the aux cooler or radiator fans running the aux cooler does not provide that much cooling, so I doubt you would ever over cool and the engine thermostat will recirc as needed to maintain engine temp. If it was being operated in such extreme cold, you would probably want a cover over the aux cooler just like you would the radiator anyway… I like simple…

 

[h1x2]

It is the thing mounted to the plate, seen between the hoses he has his fingers on in this picture… Note the P6/rear transmission cover in the background…

it is probably a diverter, and has a thermal element like the bypass thermostat in the engine. It sends flow one way(like back thru the engine or liquid cooler, until it shifts due to temp increase and shifts all the flow the other direction(thru radiator or aux cooler). If yours was stuck in the hot position, it would be sending flow thru the aux cooler but with the fan control based on engine temperature, it is not being cooled properly…

The heatexchanger down in front of the oil pan is indeed a cooler. Just like they put the transmission cooler inside the bottom of the transmission on every automatic transmission vehicle I have ever seen. The 2.5-5 tones have nothing else that could cool the transmission…

Did you ever setup your fan for manual control like I suggested in your other thread? That would at least allow you to confirm the hot fluid is headed to the aux cooler and being cooled that way with you manually activating the fans... I guess you could also confirm this by driving it till the trans is hot and confirming that the aux cooler is hot/full of hot fluid…

In the case of this setup, that valve doesn’t make all that much sense With the engine temp controlling both fans. It would make more sense and satisfy my simplistic streak by simply putting the aux cooler in series with(after) the liquid cooler. Without the aux cooler or radiator fans running the aux cooler does not provide that much cooling, so I doubt you would ever over cool and the engine thermostat will recirc as needed to maintain engine temp. If it was being operated in such extreme cold, you would probably want a cover over the aux cooler just like you would the radiator anyway… I like simple…


View attachment 869665

I did add an override and even with the fans running 100%, the trans is still overheating. That makes me think that valve is stuck closed and not allowing fluid to the aux cooler. Going to confirm tomorrow. Hopefully that valve is serviceable.

 

[Ronmar]

I did add an override and even with the fans running 100%, the trans is still overheating. That makes me think that valve is stuck closed and not allowing fluid to the aux cooler. Going to confirm tomorrow. Hopefully that valve is serviceable.

Well unless you are towing something heavy, the liquid cooler should be providing all the cooling you need, like it does for all the trucks that don’t have an aux cooler.

Another thought is that someone pulled the core out of that thermal regulator, you know, engines overheating, lets remove the thermostat. That doesn’t work in a bypass cooling system…

Or it has failed in a way or has been connected in a way that is not directing fluid toward either cooler. IE: the path of least resistance is out of the transmission, thru that valve block and back into the transmission and it cannot develop enough differential pressure to flow fluid to a cooler…

Have never been able find a diagram of this system…

That or something is making a whole lot of load/heat…

 

[GeneralDisorder]

Do you have an IR temp gun or a thermal camera?

https://www.amazon.com/FLIR-One-Thermal-Imager-Android/dp/B0728C7KNC

Thermal cameras are pretty dang cheap now. I have a couple of the things for various uses - they are amazing for troubleshooting things like cooling systems, looking at exhaust headers to see which cylinders are firing/rich/lean, looking for hot components on circuit boards. They come in real handy.

As Ronmar suggests - unless you are towing or hauling a lot of weight around..... in the Afghan desert at noon - I would focus on the heat exchanger first. My A1R M1079 is hauling around 3,000 extra pounds over an M1078 just with it's fat self and no cargo. S&S didn't see fit to equip it with an aux cooler and I have zero issues.

 

[Third From Texas]

Do you have an IR temp gun or a thermal camera?

https://www.amazon.com/FLIR-One-Thermal-Imager-Android/dp/B0728C7KNC

Thermal cameras are pretty dang cheap now. I have a couple of the things for various uses - they are amazing for troubleshooting things like cooling systems, looking at exhaust headers to see which cylinders are firing/rich/lean, looking for hot components on circuit boards. They come in real handy.

As Ronmar suggests - unless you are towing or hauling a lot of weight around..... in the Afghan desert at noon - I would focus on the heat exchanger first. My A1R M1079 is hauling around 3,000 extra pounds over an M1078 just with it's fat self and no cargo. S&S didn't see fit to equip it with an aux cooler and I have zero issues.

Yeah, it's that extra weight in the RV build combined with the 11 months a year 90 degree S. Texas heat that I want to add the aux cooler.

But like you say, most trucks won't need it unless they are heavy towing.

 

[GeneralDisorder]

Yeah, it's that extra weight in the RV build combined with the 11 months a year 90 degree S. Texas heat that I want to add the aux cooler.

But like you say, most trucks won't need it unless they are heavy towing.

Cant hurt to have additional capacity both in fluid and cooling......

That said - these trucks were meant for 130 degrees in the Iraqi desert fully loaded pulling their M1082 trailer or gen-set, running their AC full blast with PVT Snuffy buried to the floor mat on the accelerator.

If you even came close to overheating the transmission in Texas running it as an RV I would be surprised.

 

[h1x2]

Today I bypassed the thermostatic valve. Temps are finally within range and functioning normal. I looked under my M1088 and it doesn’t have that valve. It just runs both coolers in series. I took some temp pics of before and after. The first pic shows high temp at the input of the aux cooler. It’s just the hot temps climbing up the hose from the valve when it was hot. Second pic shows after I bypassed the valve and had full flow through the cooler.
Actually

 

[Third From Texas]

Cant hurt to have additional capacity both in fluid and cooling......

That said - these trucks were meant for 130 degrees in the Iraqi desert fully loaded pulling their M1082 trailer or gen-set, running their AC full blast with PVT Snuffy buried to the floor mat on the accelerator.

If you even came close to overheating the transmission in Texas running it as an RV I would be surprised.

It's SOP for me to be pulling my M1082 down the beach at 30 mile stretches in axle-deep sand, so I'll take all the cooling I can get.

 

[Lostchain]

It's SOP for me to be pulling my M1082 down the beach at 30 mile stretches in axle-deep sand, so I'll take all the cooling I can get.

Do you air down the tires on the M1082 for that or just the truck tires?

 

[Third From Texas]

Do you air down the tires on the M1082 for that or just the truck tires?

Just the truck.

I've only ever had one occasion where I had to get the shovel out as a result of the trailer and that was more my fault for coming to a stop when I knew that I shouldn't have. In my experience, floatation/footprint is far less of an issue with trailers (no steering, no drive/traction).

 

[Ronmar]

Just the truck.

I've only ever had one occasion where I had to get the shovel out as a result of the trailer and that was more my fault for coming to a stop when I knew that I shouldn't have. In my experience, floatation/footprint is far less of an issue with trailers (no steering, no drive/traction).

Yea, unless they are really loaded heavy…

 

[ramdough]

Today I bypassed the thermostatic valve. Temps are finally within range and functioning normal. I looked under my M1088 and it doesn’t have that valve. It just runs both coolers in series. I took some temp pics of before and after. The first pic shows high temp at the input of the aux cooler. It’s just the hot temps climbing up the hose from the valve when it was hot. Second pic shows after I bypassed the valve and had full flow through the cooler.
Actually View attachment 869708View attachment 869709

My truck bypassed the rear cooler (unloaded ) and never got hot. Now that it is plumbed in, still don’t have the fan hooked up in the new location.

Just a reference point. I am sure weight is the deciding factor here.


Sent from my iPhone using Tapatalk

 

[h1x2]

My truck bypassed the rear cooler (unloaded ) and never got hot. Now that it is plumbed in, still don’t have the fan hooked up in the new location.

Just a reference point. I am sure weight is the deciding factor here.


Sent from my iPhone using Tapatalk

The first time my trans overheated I was hauling 33k lbs so I thought that contributed to it. Now it overheats just driving the truck for an hour. I no longer think the trans cooler is the problem. After talking to Allison about the trans, I’m gonna be ordering a reman trans and put that in. It’s pretty costly. I wish the previous owner had disclosed the issue. He knew about it but didn’t tell me.

 

[Ronmar]

The first time my trans overheated I was hauling 33k lbs so I thought that contributed to it. Now it overheats just driving the truck for an hour. I no longer think the trans cooler is the problem. After talking to Allison about the trans, I’m gonna be ordering a reman trans and put that in. It’s pretty costly. I wish the previous owner had disclosed the issue. He knew about it but didn’t tell me.

Well thats weird, if it was flowing all that hot fluid to the heat exchanger, it would be raising the engine coolant temp and the engine fan would be constantly engaged…