A friend of mine in the Seattle area had the 4R100 rebuild by some local shop recently. It's in a 2002 SRW dually 2x4.

She said the while towing through the mountains temps were fine until she started coasting downhill, while pulling maybe 20k combined....then the temp gauge went to 240-245. She slowed down, then pulled off to check the fluid level...appeared fine. The on the road again without issue.

Had a new cooler installed as well.

Ideas?

 

That's strange, I'm curious of the thermostat bypass on the trans, were the cooler lines hookup too. It bypasses the cooler till the temp hits a certain temp, It's that metal line that connects the two cooler lines together, wonder if while coasting there is not enough line pressure to over come the stat? that's a good one you got. Any one else have any ideas?

 

I'm hoping Mark K drops by.

 

And here I am. There isn't enough information here to offer any kind of opinion.

Did she let it idle to cool it down? Did it take a long time to cool? Did it cool in a minute or two? Where is the temperature being measured?

Please ignore David7.3's post. There isn't a shred of fact in it.

There is NO thermostat on the 4R100 transmission. None.

What he is referring to is a pressure bypass. It is only opened when the coolers are plugged and cooler line pressure (which has NOTHING to do with line pressure) gets too high. It doesn't take pressure to overcome it.

 

I will get the info Mark....thanks

 

Mark,

It kinda' burns my behind that there are people who haven't a clue that continue to sound professorial while spouting nonsense.

I suspect some folks just don't absorb the facts as they are presented by the people who really KNOW what they're talking about, and just shoot from the hip, often just repeating Old Wives' Tales.

Thank goodness we have you around to set things straight when it comes to this trans. You've been a Godsend! Can you imagine the thinking that might have surrounded this trans if you hadn't found us here?

Keep doin' just what you do!

Best!

Pop

 

I cant tell you how many times I have had arguments with internet no it alls that swear that its a temp bypass and to remove it...

I nearly lost a trans because a builder thought it would be a good idea to delete it... Then installed a filter backwards...

Pressure bypass... Has nothing to do with temp.

 

We can assume that the engine was idling while coasting downhill. Is it possible that there was not enough airflow through the cooler/radiator because of a faulty fan clutch? On a long climb it takes a little time after reaching the top to dissipate that excess heat from the transmission. This is pure guesswork of course!
Larry