What Auto Trans Temps are safe?

[Matt400]

For those of you that run your auto's hard enough that you keep an eye on the trans temp gauge.....

What temps tell you when to back off or pull over?



I know the cooler the better and the factory DC software lights a red l. e. d. @ 275 but that seems like it may be too late.

 

[Prairie Dog]

If the truth is known 250 is safe but I wouldn't want to see it any higher than 225 to 230.

 

[Spunkys Ram]

I try to keep it below 240 myself.

 

[Rosco]

You have to take into consideration the location of the probe. 225 degrees in the pan is different than 225 degrees at the output port going to the cooler.

 

[Matt400]

Originally posted by Rosco

You have to take into consideration the location of the probe. 225 degrees in the pan is different than 225 degrees at the output port going to the cooler.

True, according to B&M transmissions they say 165-195 operating range is good to shoot for as a norm for a healthy life. Thats measured in the pan where it seems the majority of probes go.



With the converter producing the most heat and the fact that the converter outputs to that front line it makes sense to consider that temps measured at the output line are not necessarily temps the transmission is being subjected to but are temps the converter is raising the fluid to.



I am beginning to think maybe a twin led warning lamp would be better with a 275 turn on point at the front line and a 240 turn on point in the pan or in one of the trannies test ports.



So far I have only found switches that will close at 275, 240 and 225. They then re open approx 7 deg lower so using the 225 for towing may produce a lamp on too often on hills.

 

[jimnance]

Originally posted by Matt400

For those of you that run your auto's hard enough that you keep an eye on the trans temp gauge.....

What temps tell you when to back off or pull over?



I know the cooler the better and the factory DC software lights a red l. e. d. @ 275 but that seems like it may be too late.

Heat breaks down the transmission fluid and cooks the clutches. Short bursts to 250F is probably OK, but you should plan on changing your transmission fluid more often.



My transmission shop showed me a graph of fluid life expectancy from 100F to 300F. At three hundred the fluid was toast in just a few miles. At 100 F it will last a very, very long time. The curve was fairly flat from 100F to 180F only gradually decreasing fluid life. Once beyond 180F the curve increases more quickly and shoots out of sight beyond 250F.



The short answer - above 250F is not good and 180 F is OK. Cooler is better. If you run it hot change the fluid more often.

 

[Matt400]

Originally posted by jimnance

The short answer - above 250F is not good and 180 F is OK. Cooler is better. If you run it hot change the fluid more often.

I think thats sound advise, I change every 15K but may re think even that after setting up a 240 deg warning lamp.

Thanks...

 

[Matt400]

Originally posted by Rosco

You have to take into consideration the location of the probe.

Hey Rosco,

Thanks for bringing that to my attention because it made me do a little more research on what I am trying to do.

According to the helpful staff at DTT 225 in the pan is considered the "hot" point while 270 on the cooler out line is the "hot" point.

Both numbers are not uncommon to see while backing a trailer or towing hard.



They have no data for temps at any of the test ports as they claim that is stagnant fluid and is not a good measurement.



So my idea of having a 240 warning lamp in the out line won't work cuz I will see it on too much while towing hard and then end up ignoring it.



Available switches have me over a barrel for a warning lamp,



I can choose to be warned @ 240 in the pan which is better than the factory 275 or 275 in the line.

I don't want to know when its hot all the time but warned that it is in fact time to pull over, same as what DC intended just not at 275

 

[y-knot]

The life of ATF is reduced by 1/2 for every 10 degrees you go over 190. So if you thought 30,000 miles was a good change interval, go 200 only once and the life is down to 15,000, go 210 once and now it is down to 7,500 and so on and so on.



For my truck the normal everyday unloaded trany temp is around 160. Even with my 15,000+lbs trailer it maintains 170 on the open road. Do a little city stop and go traffic and it will creep to 190 after a while. Worst thing you can do with this transmission is back a trailer, especially a heavy trailer. The gearing is close to what second is and the constant slip in the converter gets things hot very fast. If you are having trouble getting into a spot with your trailer, remember to take a time out and let the trany cool off. Just place it in neutral, set the brake and let if cool off, if it got really hot, hold it at a high idle while in neutral. Remember any damage you do, is permanent till rebuilt. The high temps cause the ATF to break down and varnish, and the clutch plates to glaze, neither can be reversed.

 

[wlowe]

y-knot



I see that you have the 2 wheel low mod. Does it help keep the transmission temps down when backing a trailer or is it more of an airflow issue? I might get the Bob V kit if it helps with the trans temps. Which kit do you have?



Thanks

Bill

 

[Matt400]

Originally posted by y-knot

The life of ATF is reduced by 1/2 for every 10 degrees you go over 190

I am finding that the majority of OEM's and the aftermarket compile that kind of data based on a sump measurement. I could do a warning lamp on @ 220 but won't go off till 190.

For my truck the normal everyday unloaded trany temp is around 160. Even with my 15,000+lbs trailer it maintains 170 on the open road. Do a little city stop and go traffic and it will creep to 190 after a while.

Good info to know for those of us without a gauge. The 220 on switch would be nice if it would open back up sooner at say 205 or 210.

With your low temps I assume your measuring the sump temp.



Thanks for the info!

Matt

 

[y-knot]

Yes It does, that was the main reason for installing it. I never had any high temperature problems with the automatic, until I started backing this new trailer. It is very heavy and when backing it on perfectly level ground, but in grass, the wheels sink enough to cause a problem. Also I have a tri-axle, which introduces alot of resistance win turning while backing. Without the 2WLOW kit, my transmission shoots up very fast, and I didn't want to cook my new one. I have hit 230-40 in only a short distance while backing with my old trany, I would never had believed it if there wasn't a gage to prove it. The problem is the truck is running slow, so you get little help from the coolers. The reverse gears is much closer to second gear then first, and the TC is un-locked and under a huge load which produces alot of heat. The fact that I can now switch to low range, and not have the drive-line in a bind, makes for a world of difference. The transfer case provides a 2 to 1 reduction which is now well lower then first gear, and makes everything much easier. No more heat issues with the transmission, and the low gear makes it very easy to back into position.

 

[Matt400]

Originally posted by y-knot

I have hit 230-40 in only a short distance while backing

My TT is only 6000 lbs but I have been known to back it as much as 75 yards on twisty jeep type roads (doing some forward and back maneuvers) to get into that perfect camp spot. I do use low range those time but had no idea temps may be shooting up like that.



Just today I found a switch for the pan that will turn a warning lamp on @ 235 and then off @ 205 which sounds like a good idea but I may do something else... .



If I go with a SPA Dual gauge and read EGT/Trans temp it has user selectable warning lamps plus can also be programed to do other things at specific user selected temperatures like:

Turn on a HD electric pusher fan for example @ 205 deg. or what ever you like.



The warning lamp idea would allow me to have an EGT/Boost gauge in my single Pillar mount but trans temp is looking to be more important than boost at the moment.



Thanks for those backing up temps

 

[wlowe]

y-knot



Thanks for the info on using 2 wheel low for backing a trailer. I'm buying a fifth wheel in the near future so it looks like the 2 wheel low kit will be my next bomb.