jcole

Manual transmissions are a direct hard mechanical linkage throughout. Gears turning gears. The heat caused by this is from metal on metal friction, but, there isn't a huge amount (of friction or heat).

An automatic transmission uses a fluid coupling device (torque converter) which is always slipping slightly (ok there is a lockup but I'm keeping the explanation simple). The transmission fluid is passed through the converter and the converter is spinning/slipping. This gives the transmission the ability to shift and come to a stop without stalling the engine (similar to a clutch in a manual, but pretend the clutch is always slipping and burning slightly). All the slipping and heat (especially when towing, climbing or crawling) causes failure of the fluid which results in less lubrication and cooling to the soft parts of the transmission.

This is why you need an external cooler on an auto trans but not a manual. In racing, some people set up coolers for their manual trans, engine oil, and even differential(s).

jason0341

Haven't added one yet, would like to but I'm not sure what kind and how

Pylot7

I have the thinner of the two B&M coolers on my JK. I also have an Aeroforce scanguage. I live in Denver and we usually head out to go wheeling on I 70 west.

So I have been watching the gauge and the outside air temp as I go from Golden around 5000 Feet above sea level up into the mountains.

I always put the trans in D2 and run it up the hill at the legal limit which is usually 65 mph. The tranny normally runs between 130 and 140 in street driving including freeway driving.

The first time I watched the gauge I ran it all the way to the Eisenhower tunnel which is the first high point at 11,000 feet. The peak temperature was 189 degrees which it actually hit in the tunnel. The oat was 60 degrees. All the way over to Grand Junction including Vail pass it never got up to 189 again.

I ran it up last weekend with an oat about 65 degrees and at the first place where it goes level (Chief Hosa exit at 7700 feet above sea level) to downhill the trans was up to 165 degrees.

It routinely goes up to 160-170 when I crawl on a trail in 4 lo.

Everything I have read says that when you heat it up to 220 you half life the fluid and hotter than that it degrades fairly quickly. If you ever make it brown it is way past ruined. So far mine is still nice and clear and red.

ronjenx

I installed a temp sensor in the pan before I knew about the AeroForce gauge.
I put it in the pan because....

This is what my research has revealed about trans temp probes located in the various points on the 42RLE transmission.
The following is what I have concluded based on my best effort to get the facts.

Line out to the cooler:
This will show temperature of fluid coming out of the trans, but it will be variable with short term spikes as the TC locks and unlocks. Short term temp spikes are normal and not detrimental to transmission fluid life. A probe in this location can lead to unnecessary anxiety.

Line from cooler to transmission:
This will show the fluid after cooling, and will be lower than what the pump picks up from the pan.

In one of the many pressure ports on the side of the transmission:
This will show temp of the fluid only when the particular circuit is in operation. You would have to choose which port to monitor. They are: torque converter clutch on; torque converter clutch off; reverse; low/reverse; 2/4; underdrive; overdrive.

This brings us to the pan:
This will show temp of fluid the pump picks up and sends through the transmission. The sump is sort of a "dampener" for fluid temperatures. It reflects the steady state temperature of the fluid. Long term temp rise, which is what degrades the transmission and fluid, will show in the sump. As mentioned above, short spikes in temp as the fluid leaves the transmission are not a factor.
The transmission's factory temp sensor monitors the fluid in the sump. The normal programs in the tranny controller respond to sump fluid temperatures.
The troubleshooting charts and operational limits are based on sump temps.
Some brands of transmission temp gauges recommend an inline probe location IF installing it in the pan is not possible for some reason.
Several local transmission shops recommend the pan location. However, they say most people choose one of the inline locations for ease of installation.

Based on what I have learned, I have installed the temp sensor in the pan.

mikesjk

What has everybody used to cut the tranny line?

dadgummit

I used tin snips but a good knife will do as well. it is just rubber, a little thicker than fuel line.

wheezer

Carefully with a razor blade.

mikesjk

Razor blades and I don't get along. My thumb lost the battle with one.

jason0341

I used some garden shears and they worked great. Very quick and painless....eventhough I was completely nervous cutting the line

angermgmt

I just finished my B&M upgrade this morning. Went off without a hitch. Thanks for all the help, it sure makes the projects much easier. Did a test drive up Mt. Baldy grade to ensure no leakes. Right as rain and all set for our NoCal trip in a few weeks.