Tranny Temp?

[Blk03PSD]

What temp readings would one expect to see on an a-pillar tranny temp gauge under normal highway/city driving conditions? The sending unit is in the high pressure test port on the drivers side of the tranny.

 

[tonkadoctor]

From http://www.timskelton.com/lightning/race_prep/powertrain/tranny_mods.htm regarding the 4R100 tranny

According to the Automatic Transmission Rebuilders Association

1. 90% of all transmission failures are caused by overheating,
2. If fluid temps can be held to 175°, ATF will last almost indefinitely
3. As a rule of thumb, every 20° increase in operating temperature above 175° halves the life expectancy of a transmission.

According to 4R100 guru Gregg Evans:

"Should run around 150-190 most of the time, anything over 200 is something you should watch, if it stays above 200 most of the time there is a problem."

Hope this helps

 

[Blk03PSD]

Thanks, that helps a lot. I have a Banks gauge with a scale that starts at 140. During normal driving, the temp never reaches 140 and it starts to climb toward the 170 mark while pulling my TT. I just couldn't figure out why the gauge never would register anything during normal driving, but if I am in the optimal operating range, then great.

 

[Russ]

Noraml would be about 90 deg over ambient air temps.

 

[tonkadoctor]

You're welcome.

Keeping nice and cool like that I wouldn't worry about it. If you wanted to calibrate and test it to make sure it's fairly accurate you could put the probe in a pot of distilled water and bring it to a boil on the stove...The gauge should read 212F

BTW...you can test questionable thermostats the same way using a calibrated candy / meat thermometer you steal outa da kitchen before Mama catches you to see if it actually opens at the correct temp. Calibrate a candy or meat thermometer in a glass of Ice water, it should read 32F

The tranny temp gauges on my semi trucks hardly ever moved when running light or empty. Running cool is fine and if the tranny cooler is working properly the temps shouldn't be too awful much higher than ambient temp, heat is the big killer on your friction parts right up there with too much torque breaking both friction and hard parts.

Poor maint and too high or too low fluid levels will kill them too.

 

[tonkadoctor]

Noraml would be about 90 deg over ambient air temps.

There you go. Couldn't remember the general range over ambient. CRS is kicking today . Thanks Gruss

 

[Blk03PSD]

The truck has 53K on it and I am having the tranny serviced for the first time next week. Since I am relatively new to pulling a load, I just wanted to make sure I wasn't operating in the danger zone, and I never really did get a reading out of that gauge until I started pulling the TT.

How do you go about testing the gauge? Boil water under the truck? Take the whole gauge assembly off? I'd like to test, but it seems rather invilved.

 

[tonkadoctor]

You need to take the gauge off prefferably. I do this stuff on the cooktop in the kitchen under Mama's close supervision if she catches me

 

[Blk03PSD]

10-4. I need to weigh the cost/benefit of pulling the gauge since it is firmly installed. BTW - Always a good idea to keep Mama happy...!

 

[tonkadoctor]

BTW - Always a good idea to keep Mama happy...!

There couldn't be a truer statement on this whole forum

 

[Mike]

Since I am relatively new to pulling a load, I just wanted to make sure I wasn't operating in the danger zone, and I never really did get a reading out of that gauge until I started pulling the TT.

Under ALL circumstances, keep the tranny under 250 degrees. That is your danger zone. If you see it creeping into the 225 zone, back out of the throttle and let it breathe.

Other than that... 90-100 above ambient is normal cept for during really cold spells. Its not unusual for my tranny guage to never come off the bottom peg in the winter time.

 

[Russ]

Under ALL circumstances, keep the tranny under 250 degrees. That is your danger zone. If you see it creeping into the 225 zone, back out of the throttle and let it breathe.

Other than that... 90-100 above ambient is normal cept for during really cold spells. Its not unusual for my tranny gauge to never come off the bottom peg in the winter time.

I'm with you there Mike. I still can't prove whether my new tranny gauge is any good or not.