corky

Instead of cutting cooler line is there a test port that I can use to install a tranny temp gauge sensor? I really don't want to splice into the hydraulic line. Thanks

NavyDood

None of the test ports have constant fluid flow. Stagnant fluid at best which will read heat soaked temps.

Spooler

Buy a line already done and keep you stock one. Mass Diesel can supply one for you or Dieselmanor. Take your pick.

OOPS

If you want it to be accurate, buy/make the line. That is where the fluid is the hottest.

OldDodgeOwner

I bought a B&M Drain plug from Geno's Garage. Part #80250. Makes it easy to drain to service the transmission, plus it's got an 1/8"NPT port in the plug to read temps in the pan.

AH64ID

Hot line temps are what you want to read. The fluid will fail from heat before the trans, so you want to know the state of your fluid.

http://www.dieselmanor.com/dm_products/DM-CLG3.asp

hoot

Unfortunately you will get readings through the roof at times with the sensor on the cooler line. Pull a 10,000 lb load up a steep hill and you will see 280-300 deg.

Do we change the fluid every time we do that?

AH64ID

If that was my trans I would be dumping that fluid ASAP!

You need a bigger cooler.

hoot

Do you have a temp gauge with sensor on the cooler line?

BTW: I have read many posts of members here and on other sites experiencing 280 and over during hard pulling. The newer fluids are supposedly designed to handle it.

I do have a nice Derale fan driven aux cooler but it just can't keep up with the heat generated by the slipping TC. The key is locking up the TC sooner.

AH64ID

I don't have an auto trans on my current truck.

Modern fluids can handle a great deal more heat than older fluids, but 280 is pretty darn hot.

If your pulling the hill in 2nd gear and the shift lever is in D it won't lock, but if you put it in 2nd it will lock and drop the heat considerably.

IIRC this chart is based on dino fluid.

hoot

I don't buy any of that for todays transmissions. I've been researching this trans temp thing for years now and have learned that they seem to have dealt with trans issues with the synthetic fluids and better torque converter designs. That chart doesn't tell me anything because I will guarantee you if you set up a gauge in these Dodge diesels with automatics and put the sensor on the cooling line reading the fluid as is exits the converter, you will see the same temps I see.... 260+ with spikes over 280F when pulling a load up a hill. You don't see the trans going out according to that chart.

I would also like to know how they compiled the data for that chart. How did they get the trans temp reading when the majority of vehicles don't have a trans temp gauge.

Again, I think the key is getting the TC to lock more often in tougher situations. I'm going to put the mystery switch in as soon as I get some time. I have all of the parts.

AH64ID

I don't know what temps the modern synthetics start to break down at, but I do know that the leading cause of auto failure is from lack of lubrication from a fluid that got cooked.

I agree, locked it good for everything.

OOPS

What is the "mystery switch" and what does it do? Is there a write-up on doing it?

hoot

Come on now if I told you it wouldn't be a mystery, would it?

It's a switch you install that will ground #7 wire in the harness that goes to the trans. That's the TC lockup circuit wire. By grounding it you tell the computer to lock! Only problem is it will stay locked so you have to remember to turn it off when you stop. Also not good leaving it on as it shifts under heavy loads.