transmission Fluid Temps: Any Thoughts?

[fortunate1]

I found the article in the last TDR magazine interesting enough to get off the dime and buy a guage for the transmission. I used the dipstick sensor method for its ease and low cost. After about 1000 miles of various driving conditions, I've found that the temps follow a fairly consistant pattern. After things have warmed up and I'm driving a constant highway speed, the guage reads 130 degrees F for hours on end. If I get off the highway and drive stop & go or in 1, 2, or 3 unlocked, the temps will go up to about 150 degrees F. In a real stop & go jam for about 1/2 hour, the temps got up to about 190 degrees F. No air through the coolers there.



I know that the temps in the pan are going to be cooler than temps coming out of the transmission and warmer than temps coming out of the last cooler. How much, I don't know. Do these in-the-pan temp readings seem normal? I don't tow and keep less than a 1000 pounds in the bed. Also, I bypassed the radiator coolant-to-ATF cooler and installed an air-to-ATF cooler in its place. I've also installed a fairly large air-to-ATF cooler under the cab. It's routed in-line between the front grill cooler and the re-entry into the transmission. The pan is a Mag-Hytec DD unit.



I'm going to get "trends" and "averages" here with this method, but am I going to miss a "spike" that will damage the ATF? Ideas?

 

[chuck3]

Those readings are real close to mine, I have it reading from the pan. The 190 seems a little high, but only maybe 10 degree are so.

 

[Steve Roseman]

I get my reading out of the stock pan and they sound about identical to mine.

I have seen 190 but only once. I just happened to be going through Birmingham when someone decided to blow up a bridge. The traffic on the detour was more stop than go and temps got up there. Normal is between 125 and 150 for me.

 

[fortunate1]

Thanks for the replies!

I'm glad to see that my readings are in the ballpark. I may get an electric fan to help out in those nasty traffic jam/stop & go situations.

 

[Dieselnerd]

I get my reading from the hot line coming out of the transmission. Towing my fifth wheel, it runs 140-150 degrees locked up. Unlocked, same towing conditions, pulling long grades, I have had it go up to 200 degrees. Stop and go traffic, same towing conditions, typically runs about 175 degrees. It gets the hottest during parking of the fifth wheel and I have had it go up to around 225 degrees or so. This is very short duration and I'm sure the pan temperature never gets near that. The transmission cooler seems to be more than enough for me. Remember, you don't want to run them too cold either.

 

[BillGotthelf]

The numbers you are quoting are pretty close to my numbers for my 96. Other than using amsoil trans fluid my temps rarly see over 175 in the pan and thats towing 13,000 lbs+. Funny my 99 sees 180 most of the time and in lockup drops to about 165 and thats towing nothing.

 

[Clinton]

I just moved my sensor from the cooler line to the pan when I put on the Mag-Hytec deep pan this past weekend. Haven't driven the truck yet so I don't know what I'll see. Mine seems hotter at about 165-170. I run alot of highway miles nearly unloaded and the guage rarely moves. One of the reasons I moved the sensor was to check it. I bought the truck barely used and it has one of the wierdest things: it's a remote Wix #51515 oil filter mounted under the front cross member. I'm not sure which way the ATF is flowing, but the fluid passes through this filter either on its way to or from the cooler (with my temps I'm guessing its on the way to the cooler). It's out of the way and doesn't leak so I guess it's alright. The sensor was in the mount for this filter. Anyway, your temps seem to be cooler than than mine. I'll do some driving and reply again.

 

[Chipstien]

I have mine in the hot line out of the trans and see around 130 cruise and 160 stop and go. Haven't been in a major jam yet since the trans mod so I am curious to see those when the time comes.