What temperature is too hot for my Automatic 42RLE Transmission?

TerryMason

Administrator
Staff member
I just upgraded my transmission temp gauge, and I was wondering what you guys would consider the max temp (where you'd pull over). Mine seems to stay around 185°
 
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keep in mind heat transfer metal to metal contact etc.. If your motor hits 220-230 its going to get hurt before your transmission. but safely speaking 215 is about as high as I would personally be comfortable with.
You could always talk to your local trans shop for thier recomendation.
 
You might be able to go slightly Higher -- Under SEVERE Driving Conditions. Probably about -- 220F -- On a HOT Day - while climbing a hill! I would expect the Normal Transmission Temp. To be around: 180 to 195F. Several Factors come into play: 1. Thermostat Temp. (195?). 2. Do you Have Installed on your Jeep an: Auxillary Trans Cooler? 3. Driving CONDITIONS. -- These Factors. Will determine your. "Normal" Transmission Temp. Chrysler Factory Service Manual says: Temp. OVER 240F is OVERHEATING. But --- Let's. ASK this QUESTION: What HAPPENS as Transmission Temp. GOES UP?? Gentlemen: HERE IS THE CHART ---- Let's Call it: TRANSMISSION LIFE EXPECTANCY CHART -- OK?

1. Trans. Temp. --- 195F - Low Heat; LONG LIFE - 75K+ Miles.
2. Trans Temp---220F -- Warm --- But OK!
3. Trans Temp--- 240F -- Varnish Forms! (Maybe pullOver!!).
4. Trans Temp--- 260F -- Seals Harden (Bad - start damage!).
5. Trans Temp --- 295F -- Plates Slip (Real Bad)
6. Trans Temp----315F-- Seals and Clutches. BURN OUT ! VERY BAD -- Maybe 250-500 Miles ! TRANS FAILURE

So the MORAL of the Story: KEEP UR TRANS COOL! LONG LIFE-- NO PROBLEMS! Hope this. Sheds a little light on this Topic. Happy New Year -- To All our fellow Jeepers! - JB
 
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What Jimbob said is very much so accurate. By keeping the transmissions internal components at a cooler temperature it allows for the machine to operate at the most efficient rate. Once the temperature begins to rise in a transmission, the internal components can expand and will eventually fail. My 42rle overheated completely and ultimately failed while I was pulling a trailer with a couple of ATV's loaded down.
 
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C0E88598-EDFF-4585-86A3-D5E4A6A11141.jpegOn another SUV build I added auxiliary PS and trans coolers to ensure the temps will not get too hot. Both coolers are in series with the OEM coolers. Both auxiliary coolers are hard mounted on custom brackets.
 
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