Trans cooler check valve

[BHanna]

I'm really glad I have a trans temp gauge in the hot line of my 48RE. It just saved me a bunch. Over the last couple days, I saw my trans temp spike up to 240 or 260. Yesterday it pegged my gauge at 280. Luckily each time I was just on my way up the hill to the house so those temps didn't stay up for long before I could shut down.



I did a little searching around and found that the check valve in the hot line often gets clogged up and causes the trans to overheat. I found a couple recommendations for how to deal with it. One was to try to gut the valve which looked pretty tough to do. I opted to replace the valve section with about a foot of 1/2" rubber oil line. I had to cut off the flared end of the hard cooler line with a pipe cutter and just used hose clamps to hold the rubber line on. No leaks that I can see after driving it around all day. Also haven't been able to get the gauge above 200.



I should say that even when my gauge was showing in excess of 280, the trans temp light in the dash never came on. I'm thinking that light is worthless and your trans is probably dead by the time it lights. If you don't have a gauge, I'd definitely recommend getting rid of that check valve.

 

[sag2]

It depends where your sensor is located. The factory sensor in mounted to the valve body/solenoid pack so it is measuring the pan temp. I also assume the cluster smooths out the input for temp spikes, so the light does not come on/go off repeatedly if the temp is hovering just above and below the light threshold.

 

[NavyDood]

Like sag2 said, the factory sensor is on the valve body. Even though your temps where what you saw, the fluid was getting cooled off going through the cooler before getting back to the transmission. You didn't do anything to hurt the fluid or transmission.

 

[BHanna]

I hope I caught it before any damage was done. Has anyone else found a better way to fix this problem than rubber hose and clamps? I guess I could get a new line/valve from the dealer but I don't mind putting the trans in neutral for a few seconds in the morning if that's the only thing the check valve does.

After a couple days, the trans is definitely running cooler without the valve. It was getting up to about 210 pretty often sitting in traffic. Now it's about 170-180. Going up a long hill at 35 MPH or so with the TC unlocked, I'm now only getting it to 200 degrees.

 

[cerberusiam]

Just drill the check ball out of the old one. I did it on the truck but its a lot easier if you put it in a vice. As long as you used hose rated for at least 150 psi and high temps double clamping in and a periodic check should be good.



If it fails its gonna be messy though, why I opted to drill the check ball out of the old one and used the OEM connections. Already blew the vibration damper portion of the hot line several times until got the right hose and good clamps.

 

[DF5152]

picture of where this is located?

 

[BHanna]

I wish I'd thought to take some pictures while I had the driver's front wheel well liner out. It's hard to see unless you do that. The cooler lines go into the bottom left corner of the radiator and the check valve is in the top line. The valve is a little over an inch long and is brass but it's crimped onto about a 6" long section of rubber hose and that whole assembly removes as one piece. It's connected to the radiator with a fuel line fitting and at the back it has a flare fitting with a 3/4" (IIRC) nut that connects to the hard line from the heat exchanger.

 

[cerberusiam]

picture of where this is located?

Under the driver side battery. Should be the only two small hoses coming out of the rad support. Easier to get to them if you remove the wheel well liner on driver side.

 

[Matt400]

Interesting you brought this up Brian.

I would be concerned why it clogged since all it is, is a ball & spring that takes 2 psi to move it. Might be a good idea to change out the fluid & filter for a look in the pan.



What I often wonder about is the thermostat mounted in the cooler, book says its serviceable but is it really needed, can it be removed and whats the harm to remove it?

Without seeing a cutaway of the cooler I don't know if removing it would cause the cooler to be in full bypass or full cooling.

 

[cerberusiam]

What I often wonder about is the thermostat mounted in the cooler, book says its serviceable but is it really needed, can it be removed and whats the harm to remove it?

Without seeing a cutaway of the cooler I don't know if removing it would cause the cooler to be in full bypass or full cooling.

IIRC, both. Its a spool type valve that covers and uncovers ports, as a guess it would open all ports all the time. Gvien the fluid is going to take the path of least resistance, probably the bulk right back to the pan all the time.

 

[BHanna]

Interesting you brought this up Brian.

I would be concerned why it clogged since all it is, is a ball & spring that takes 2 psi to move it. Might be a good idea to change out the fluid & filter for a look in the pan.

I've been dropping the pan, changing the fluid and filter and adjusting the bands about every year and just did it a couple weeks before my temp issue got bad. I always have quite a bit of clutch material on the magnet and in the filter so I'm sure that is what clogged the check valve. I didn't find much about the check valve on TDR but there's some stuff on other forums that indicates the clogging is pretty common. The trans still shifts well and feels pretty good overall so I don't think there's anything wrong with it.

 

[Matt400]

Well I am glad you posted about it so others are aware including me!

 

[brods]

If the check valve is removed and the converter partially drains down, what will happen if the truck is started and left in park for a minute or two at high idle? Would that harm the converter in any way? Would it cause the oil to become highly aerated?



And out of curiosity, what is the reason Dodge prevents the flow to the converter in park? As a safety feature?

 

[cerberusiam]

There is about a pint of fluid left in the pump once everything shuts down and drains. A couple minutes of idling won't hurt it, however, until the TC charges the truck won't move well if at all. Morereason to idle in neutral or fix the no circulate in park issue.



Have never heard a competent explanation why the OEM design does not allow circulation in park. It is such a minor change to make it work that it is really sad that in some 40 years that small item was never changed.