Transmission cooling issues

[jampants]

I'm trying to decipher why my transmission seems to be running a bit hot, creeping up to 220F after 30 mins driving. I'm not towing, but since my engine swap to the Jim B specification I'm wondering if the higher torque Cam is generating more heat. I also changed to the Superior Aluminium Radiator at the same time so I know the cooling system is all new. Engine temp is steady 180F at all times.

Using a laser thermometer on the pan itself it is reading 160-170F, and the transmission cooler lines to the radiator appear to be reading hotter going into the bottom of the radiator than the top. This seems wrong I thought hot went into the top connections, cooled back out the bottom.

So I wondered;

Could my transmission lines be wrong way round, should hot line go into the top of the radiator, and cooled come out the bottom?
Do I need to forget the radiator all together and just go straight to an external cooler? That seems an easy answer but I thought this setup should at least keep me in normal operating range without towing.

Anyone else running a similar setup? Or did you all go straight to external trans coolers so don't see this?

Thanks.

 

[LQQKatJon]

Yes. External cooler!!

The superior radiator cooler is not much. If you were to look down the cap hole before you installed it,
It is just a coiled looking brake line.

Doesnt matter the direction.

Install a 40,000 gvw tru-cooler and your temp problems will go away.

 

[jampants]

Yes. External cooler!!

The superior radiator cooler is not much. If you were to look down the cap hole before you installed it,
It is just a coiled looking brake line.

Doesnt matter the direction.

Install a 40,000 gvw tru-cooler and your temp problems will go away.

Thanks! - I thought as much.

I'll get hold of a 40,000 BTU cooler and put that in and bypass the Superior cooler all together.

Does anyone happen to know the connection size at the radiator end are? The Superior radiator website is terrible! It seems to imply maybe 3/8NPT ?

 

[Bhart]

You may also want to replace the original 5/16" transmission cooling lines with 3/8"

 

[RF_Burns]

Don't forget that the steel transmission cooling lines to the radiator serve the second purpose of bonding (electrically grounding) the radiator and the engine. When you remove those lines from the radiator you will need to run a ground wire from the engine to radiator. Our resident Chemical Engineer with experience in engine cooling systems and antifreeze (Emery Stora RIP) stated this at a GMCMI Tech Session. I believe he said it was even more important with aluminum radiators.

 

[jampants]

Thanks for feedback all!

I saw the references to the electrical grounding on the forum so will be sure to put a new ground in place - defo sounds important.

The cooler I'm looking at uses AN10 connections as its in Europe, so I need to go from AN10 to what I think are 1/4" NPT connections if my measurements are correct.

I'd love to replace the lines in full, but was slightly nervous about the connections at the transmission side. Has anyone done this - I was worried that any issue on the transmission unit connections makes repair hard.

I am currently away in the coach so this upgrade is being done while a long way away from home

 

[jampants]

This is my connection at the transmission end - looks rusty as hell.

I measured the lines and they are 5/16" lines so would defo like to upgrade. Does anyone know if that second bolt unscrews from the chassis and is actually an adaptor? So would leave a female opening in the chassis I can connect into?

 

[sailor man]

I'm trying to decipher why my transmission seems to be running a bit hot, creeping up to 220F after 30 mins driving. I'm not towing, but since my engine swap to the Jim B specification I'm wondering if the higher torque Cam is generating more heat. I also changed to the Superior Aluminium Radiator at the same time so I know the cooling system is all new. Engine temp is steady 180F at all times.

Using a laser thermometer on the pan itself it is reading 160-170F, and the transmission cooler lines to the radiator appear to be reading hotter going into the bottom of the radiator than the top. This seems wrong I thought hot went into the top connections, cooled back out the bottom.

So I wondered;

Could my transmission lines be wrong way round, should hot line go into the top of the radiator, and cooled come out the bottom?
Do I need to forget the radiator all together and just go straight to an external cooler? That seems an easy answer but I thought this setup should at least keep me in normal operating range without towing.

Anyone else running a similar setup? Or did you all go straight to external trans coolers so don't see this?

Thanks.

I installed new Ragusa finned aluminum transmission and final drive covers to better control the transmission and final drive fluid temperatures.
This also allows for more fluid in the system and no moving parts.
I hope that this will result in lower operational temperatures.
At least it requires no more plumbing or maintainence.

Transmission Cover: $325.00
Final Drive Cover: $249.00

 

[LQQKatJon]

This is my connection at the transmission end - looks rusty as hell. View attachment 16394

I measured the lines and they are 5/16" lines so would defo like to upgrade. Does anyone know if that second bolt unscrews from the chassis and is actually an adaptor? So would leave a female opening in the chassis I can connect into?

You need a certain adapter for the transmission to go to the 3/8” likes. There was info on this in the gmc photo site. Certain thread pitch that screws into the softer transmission case threads…. And you have to drill out those adapters as well to bring the inner up to match 3/8” ID.

A local club member had bought a bunch of the brass fitting/ adapters and gave me a couple. So no idea where to get them.

I do know at one time applied kept them in stock. Looking now they have lines and adaptors for $150.

 

[jampants]

You need a certain adapter for the transmission to go to the 3/8” likes. There was info on this in the gmc photo site. Certain thread pitch that screws into the softer transmission case threads…. And you have to drill out those adapters as well to bring the inner up to match 3/8” ID.

A local club member had bought a bunch of the brass fitting/ adapters and gave me a couple. So no idea where to get them.

I do know at one time applied kept them in stock. Looking now they have lines and adaptors for $150.

Thats great thanks.

I knew it would be straightforward.

My current plan is I'm going to put a Setrab 19 row, 403mm oil cooler in front of the radiator and connect to the existing 5/16" hard lines with compression to AN6 converters. Then run the new cooler in line before the radiator cooler. This should add 25,000ish BTU/hr of cooling according to their spec.

Then in the future I'll upgrade the existing lines to those 3/8" hard lines you kindly linked to improve flow as well.

I'm a bit nervous about messing at the transmission end as it all looks quite fragile so I'll defer that bit for now!

Will post some pictures up once done.

 

[jampants]

View attachment 16413
I installed new Ragusa finned aluminum transmission and final drive covers to better control the transmission and final drive fluid temperatures.
This also allows for more fluid in the system and no moving parts.
I hope that this will result in lower operational temperatures.
At least it requires no more plumbing or maintainence.

Transmission Cover: $325.00
Final Drive Cover: $249.00

Thanks!

I don't know which I'm more envious of - the cooler setup or the ramp setup.

I'm going to add an oil cooler first as its easiest to install in my case, then I may also have to add this pan but will need to build some ramps for that.

 

[Biggamehunter]

You need a certain adapter for the transmission to go to the 3/8” likes. There was info on this in the gmc photo site. Certain thread pitch that screws into the softer transmission case threads…. And you have to drill out those adapters as well to bring the inner up to match 3/8” ID.

A local club member had bought a bunch of the brass fitting/ adapters and gave me a couple. So no idea where to get them.

I do know at one time applied kept them in stock. Looking now they have lines and adaptors for $150.

You can adapt AN line to the radiator, trans oil cooler or the trans. A plus to AN lines is you can get stainless steel coved and not have to run a ground to the radiator. Check with the vender of the cooler you are looking at. You can loop the radiator heat exchanger in and use a thermostat, so you do not over cool when it is cold out. FYI AN numbers are in 1/8" sizes so an6 is 3/8"

 

[jampants]

You can adapt AN line to the radiator, trans oil cooler or the trans. A plus to AN lines is you can get stainless steel coved and not have to run a ground to the radiator. Check with the vender of the cooler you are looking at. You can loop the radiator heat exchanger in and use a thermostat, so you do not over cool when it is cold out. FYI AN numbers are in 1/8" sizes so an6 is 3/8"

Yeh I've gone for stainless steel braided. I'll leave one of the 5/16" lines fully intact from the transmission to the radiator which should keep the ground.

I figured AN6 for the extension was about right, I could go up to AN8 but not sure thats needed.

I think the trans has a 1/4" NPT port, in which case in the future when I'm feeling a bit brave I'll try and go 1/4NPT adaptor to AN6 steel all the way through both coolers.

 

[sailor man]

View attachment 16413
I installed new Ragusa finned aluminum transmission and final drive covers to better control the transmission and final drive fluid temperatures.
This also allows for more fluid in the system and no moving parts.
I hope that this will result in lower operational temperatures.
At least it requires no more plumbing or maintainence.

Thanks!

I don't know which I'm more envious of - the cooler setup or the ramp setup.

I'm going to add an oil cooler first as its easiest to install in my case, then I may also have to add this pan but will need to build some ramps for that.

It is not a ramp. My coach was on Cliff Golby's lift outside his shop. In Florida, there are a lot of outdoor lifts because you can use them year round and don't have to spend the money for a building to house them.

 

[tmsnyder]

Did you mention where you are measuring this temperature?

The outlet from the transmission will appear hot, however that fluid will quickly be cooled by the radiator .

I went down that road one time, put the temp gauge on the outlet and was shocked at the temperatures. But it's so brief it doesn't matter, the oil will be fine. It's really a useless reading.

The only temperature that matters is the pan. If the pan is fine, you are fine.

For cooling you should run to an auxiliary cooler, then run the lines to the radiator. On cold days this will reheat the fluid to the proper running temperature, and get the fluid up to operating temperature.

Flow is out the one nearest Passenger, returns to port closer to driver.

 

[werewilfs]

Yes. External cooler!!

The superior radiator cooler is not much. If you were to look down the cap hole before you installed it,
It is just a coiled looking brake line.

Doesnt matter the direction.

Install a 40,000 gvw tru-cooler and your temp problems will go away.

This. I run the same cooler as Jon and am always around 180/190. Highest is 210 after cresting a long hill but the temps shoot down very quickly on the other side of the hill.

 

[LarryW]

If you are switching to 3/8" lines going to the transmission cooler, Call Jimmy K at Applied GMC or Jeff Sirum at Sirum GMC and make sure you are getting the correct adaptor. The correct adaptor has standard SAE straight threads and a washer that seals it at the transmission casing. The wrong one has NPT tapered pipe thread. It will go into the transmission and seems to fit and the threads are close enough to SAE that it will thread right in. BUT it is tapered and will tighten as you thread it into the trans. Tighten it a little to much and you can crack the transmission case. You now have a junk transmission. Please be certain of the adaptors you use.

 

[LarryW]

Yeh I've gone for stainless steel braided. I'll leave one of the 5/16" lines fully intact from the transmission to the radiator which should keep the ground.

I figured AN6 for the extension was about right, I could go up to AN8 but not sure thats needed.

I think the trans has a 1/4" NPT port, in which case in the future when I'm feeling a bit brave I'll try and go 1/4NPT adaptor to AN6 steel all the way through both coolers.

It is NOT NPT. It is standard SAE straight thread. See my other post on this thread.

 

[jampants]

Did you mention where you are measuring this temperature?

The outlet from the transmission will appear hot, however that fluid will quickly be cooled by the radiator .

I went down that road one time, put the temp gauge on the outlet and was shocked at the temperatures. But it's so brief it doesn't matter, the oil will be fine. It's really a useless reading.

The only temperature that matters is the pan. If the pan is fine, you are fine.

For cooling you should run to an auxiliary cooler, then run the lines to the radiator. On cold days this will reheat the fluid to the proper running temperature, and get the fluid up to operating temperature.

Flow is out the one nearest Passenger, returns to port closer to driver.

Hi, yes the temperature is coming from my sender unit. I read 220F after driving stop start traffic for 30 mins, or a bit higher on hilly roads.

That sender is in the transmission unit, off to the left just above the pan as you look down in the engine hatch.

Sender looks factory fitted - though I understand it seems a bit hit or miss whether these units came with senders from what I read.

 

[jampants]

It is NOT NPT. It is standard SAE straight thread. See my other post on this thread.

Thanks - yes I did a bit more searching last night and discovered this from another forum.

It appears to be 1/4" NPSM? I found some 1/4" NPSM to AN6 converters which I assume would work.