should my tranny be running so cold??

[Plug Ugly]

Just installed some gauges on my 02 auto. At first I thought I had gauge problem, put a heat gun to it, and I think it is right. My tranny seems to be operating at 135 after running on the freeway (unloaded) for 100 miles. In fact, it runs that nearly all the time.

Now, every other ford tranny I have EVER had has run 190 to 210 all the time, unless I bypassed the radiator 'cooler' and put a fanned cooler on the tranny.


Is there anything that has changed in these 4r100's or whatever they are called? Isnt it just a glorified E40D?


Or, is my gauge still screwed up along with my heat gun?

[jesilvas]

135*F sounds perfect. 190 and up is too hot.

[BryceB]

You hear a lot of numbers thrown around the forums about transmission temps.

The 4R100 in a 7.3 PSD truck does run sort of cool but will fluctuate with outside air temps.

I see a lot of folks posting 50-60 above air temp and 70-80 above.

I get 75 above outside air temps with mine according to my gauge with its probe in the test port on the drivers side of the transmission. Mine truck has a Ford Reman HD 4R100 with new lines and coolers with about 5000 miles on it. It climbs up to 75+outside air temp after about 20 minutes and sits here until I stop when unloaded. With my travel trailer in tow and all our junk, add about 10 deg to it.


Depending on your outside temps, you're about right. In Sacremento, it looks like your highs are about 60, so you're right in line with mine. Similar weather in GA and 130-140 is wher I've seen mine.

[Plug Ugly]

wow, never would have thought this should be right. Thanks for the info guys.

[nodd89]

Pretty sure trannys start to melt at 200

[jesilvas]

Eh, I've had em up to 210*F. Pulled over quickly
But yes, the fluid degrades quickly by then and much more it starts going sooner.

[Plug Ugly]

unless there is something special about this tranny, it should be abe to run up to 235 for a short period. Would need to change the fluids much sooner than regular, but it shouldnt MELT at 20 by an stretch