Originally Posted by Crazy001

Just a guess, but with O/D off there is lots of stuff in that transmission spinning faster than it would be if you let it shift into 4th gear. Why would you shift out of overdrive? Will it hold O/D if you let it?

Mine drug 15,000 lbs across the country in November, and I did it with O/D on nearly the entire time. Better than 95% of the time was spent at 2,100 RPMs at 60 MPH with the torque converter locked. There was no reason to lock out O/D because it wasn't shifting around frequently, and I saved lots of gas as a result.

Originally Posted by DaveandJennyP

In Overdrive it feels like i'm lugging it if there is a headwind or hills. You have 4.30 gears, that's got to be a big difference. The reason I asked my question is I would think that in 3rd, which I believe is direct drive, no gears doing any work, it would run cooler, I would think.

Originally Posted by Mark Kovalsky

I have heard several people say their 4R100 runs cooler in overdrive than in third. I don't know why this would be the case. Third gear is direct drive and that should run cooler.

Originally Posted by Bigpipes 35

I am not sure either but mine always ran 15 to 20 degrees hotter in drive that overdrive. That is until I installed the 6.0 cooler now it stays about the same...

Originally Posted by rhouse1938

Thanks Tom. I appreciate every idea out there. I like your approach. Here's my problem. Could this new gage be wrong? Somehow I'm thinking if the stock cooler is
plugged internally, then the tranny has something seriously wrong with it from what?
Shavings from metal inside, clutch debris, what? How does the cooler get plugged
inside without something bad inside which I don't even want to think about. As far as I can tell the tranny is working fine except for that heat gage. I wanted to remove the gage this morning and check it in a pan of boiling water. Probably more wasted time. OK, so what about this Tom.......if I disconnect the stock cooler, take it out, how can I check the flow through it? Pour some tranny oil in it and use an air
compressor and blow it out? I'm sure you can tell I'm not a very good mechanic, but I try. I hate those 85 to 100 dollar an hour labor bills when I can use my own time.
Well, it's Sunday morning and I want some coffee.

Appreciate your comments Tom. And I know what you mean about throwing money and parts at it. The shop mechs do that a lot these days. But, in my own defense I guess, I was figuring if the bypass valve only cost 50 bucks I could do that and still come out ahead of a shop charging me 80-100 dollars just to check it.

Not to beat a dead horse, but let's say I uninstall the stock cooler and it appears plugged. What would have caused that? Don't tell me bad news. LOL. Not being a mechanic I'm back to thinking 'stuff' from the tranny and that's a whole nother problem. So, you think I should uninstall and blow compressed air thru it and see how much pressure comes out the other end? Thanks again. Bob. That's the r as in Robert in my email address rhouse1938@comcast.net.

Originally Posted by Mark Kovalsky

I have heard several people say their 4R100 runs cooler in overdrive than in third. I don't know why this would be the case. Third gear is direct drive and that should run cooler.