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Re: [GMCnet] Transmission Tmp gauge - should I ? where? [message #351716 is a reply to message #351516] Wed, 22 January 2020 11:05 Go to previous messageGo to previous message
powwerjon is currently offline  powwerjon   United States
Messages: 849
Registered: March 2013
Karma:
Senior Member
I am with John and Russell on the transmission temps. Mine tpicall run at
about 165F which is near the bottom of the temp gauge range. I had a
torque converter failure that damage the transmission too. My gauge in the
pan when to over 300F+. IMHPO if your transmission temperature is anywhere
over 210F+ for extended periods then you need to look into the possible
causes, granted if your climbing any grade it will increase with the
extended load and you should downshift to S to get the motor speed up and
not lug the engine or transmission. When I had the 77 coach with the 403
and 3.55 gears I could climb most any grade and not have the speed fall of
much below 50 mph.

Regards,

J.R. Wright
GMC Great Laker
GMCGL Tech Editor
GMC Eastern States
GMCMHI
TZE Zone Restorations
78 Buskirk Custom 29.5' Stretch
75 Avion (Under going Frame up Restoration)



On Wed, Jan 22, 2020 at 8:48 AM Russell Keith via Gmclist <
gmclist@list.gmcnet.org> wrote:

> The THM 375/400/475/425 Troubleshooting Guide by GM states a normal
> operating temperature of 170F.
> http://www.bdub.net/manuals/THM_425_Trouble_Shooting.pdf
>
> Other transmission related websites say an "Ideal" operating temperature
> is 175F.
> https://aljetsautomotive.com/transmission-fluid-flush-tips
>
> https://mechanicbase.com/transmission/normal-operating-temperature-for-an-automatic-transmission/
>
> If you look at the many transmission fluid temperature charts online,
> you'll see that transmission life and transmission fluid life are greatly
> reduced at temperatures sustained over 200F.
>
>
> https://www.google.com/search?q=transmission+fluid+temperature+chart&sxsrf=ACYBGNQaUEqnina7kD2Cbe07foDyUHe9DQ:1579706774434&source=lnms&tb m=isch&sa=X&ved=2ahUKEwiFq46pwpfnAhWvmuAKHZZZDy0Q_AUoAnoECAsQBA&biw=2133&bih=1076
>
> My transmission temp gauge usually stays between 150F and 180F; while my
> coolant temperature gauge hovers around 190F (190 thermostat). I do not have
> an auxiliary cooler.
>
> The consensus is definitely "cooler is better" for transmission life. If
> you can't keep it under 200F, then other measures should be taken to reduce
> the temp, such as an auxiliary trans fluid cooler, or reduce the load, and
> change the fluid more often.
>
>
>
> --
> Russell Keith,
> 1978 E2 "Harry" 403 (still carbureted), Danny Dunn Tranny, Thorley, Stock
> Brakes w/Remote Vacuum Brake Booster, Quad Bags, Dakota Digital Dash, 6.5 kW
> Onan, Dunedin, Florida
>
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