What is the normal operating transmission temperature? And what is the high temperature that could cause damage?
2005 4.0
4 speed Automatic 42RLE
2005 4.0
4 speed Automatic 42RLE
Last edited:
Transmission Temperature?
- Thread starter JP13
- Start date
Michael Roberson
TJ Enthusiast
The Factory Service Manual says 240° is overheating.
I think the normal operating temps should stay around 120-160°, but in my temp gauge & IR thermometer have shown it runs around 180-200° in stop and go traffic on a 90°+ summer day. in the mountains, climbing switchbacks in 1st and 2nd @ 15-30mph, it runs very hot, around 200-240°.
the radiator runs at 210°F, and the tranny fluid is running through that. Both "hot" and "cool" trans lines pass less than 1/2" away from two catalyitic converters with a heat shield radiating 600-700°F. I tend to think the 42RLE runs very hot in the TJ.
It's programmed to lockup whenever possible, in an attempt to reduce the temps. Also note every other 42RLE equipped Jeep came with a big ass auxiliary tranny cooler (thinking of the Liberty specifically).
I think the normal operating temps should stay around 120-160°, but in my temp gauge & IR thermometer have shown it runs around 180-200° in stop and go traffic on a 90°+ summer day. in the mountains, climbing switchbacks in 1st and 2nd @ 15-30mph, it runs very hot, around 200-240°.
the radiator runs at 210°F, and the tranny fluid is running through that. Both "hot" and "cool" trans lines pass less than 1/2" away from two catalyitic converters with a heat shield radiating 600-700°F. I tend to think the 42RLE runs very hot in the TJ.
It's programmed to lockup whenever possible, in an attempt to reduce the temps. Also note every other 42RLE equipped Jeep came with a big ass auxiliary tranny cooler (thinking of the Liberty specifically).
Which is why I always tell everyone with a 42RLE transmission that by not running a transmission cooler, they're shortening the life of their transmission. People seem to dismiss that, but it's really an accessory that has a tremendous benefit to it.
I personally run the Derale transmission cooler, which is a plug-and-play affair for the most part. It was designed for our Jeeps and works tremendously well.
Jerry did a write-up on it here: How to install a Derale 20561 transmission cooler on your Wrangler TJ
The only time i use OD is on the highway, 65-70 mph.
It's out of habit now.....start engine, disengage OD.
Oh and big tranny cooler.
It's out of habit now.....start engine, disengage OD.
Oh and big tranny cooler.
OP
OP
Have 3.73 and can run 90mph. I keep it between 65 and 75 on the interstate. Regearing won't happen soon.
Turing off the overdrive puts your at a pretty good rpm on the highway, but it doesn't change the fact that your first 3 gears are now taller,than what you had with stock tires, and the torque converter has to slip more every time you take off from a light. It's exactly like towing a trailer. I'm not saying it will kill the tranny, but it is working harder, and that can cause an increase in temperature.