: Transmission temperatures?



mstrjon32
07-17-11, 05:46 PM
So I was driving on the Autobahn yesterday and was doing about 130 mph for about 30 miles continuously (the roads in Bavaria are awesome, BTW). I always like to watch my oil temperature and I'm comfortable seeing it run up into the 230*'s or more on long, high-speed drives...but I happened to thumb over to the transmission and noticed that it was running at 255*, which is near the "red line" on the gauge.

Should I be worried about running it that hot? The heat must be coming from the exhaust...is it worth wrapping the exhaust in header tape near the transmission to try and force some of the heat away from it? I'm running Amsoil in the transmission, but still, I feel like 255* is quite hot...

rand49er
07-17-11, 06:07 PM
Funny you should post this. I've just been tooling around the area (suburban driving) and noticed how warm (not burning hot, but hotter than I'd think it should be) my shifter stalk seems to be. Only have a little under 20k miles on the Royal Purple in there. I didn't think to scroll over to the tranny fluid temp, but it's never run very high before.

255 deg seems darn warm.

darkman
07-17-11, 06:41 PM
The Service Manual says to change the transmission fluid as often as every 3,000 miles if the transmission is subjected to temperatures of 290 degrees Fahrenheit without an axillary cooler.

mberisha
07-18-11, 04:35 AM
Mine's never got over 235F cruising the same speeds and and distances....

BTW...were you in 5th or 6th.....and were "racing" them M3s?

mstrjon32
07-18-11, 12:36 PM
I was in 6th. The heat in the transmission must be coming from the exhaust...I wonder if yours is running cooler because you're running the Borla exhaust and it's routed farther away from the transmission...or just flows better and runs cooler?

I was driving on my own when it got that hot, though I did have a a 330Ci drafting me into the wind doing about the same speed on the drive back, I moved over to the center lane, he stayed left and then started to fall back. I went to move back left and he flashed me to get back over in front of him so he could get back in the draft. It was pretty amusing, though if I had to brake he was going to come right up my ass.

AG'S-V
07-18-11, 03:21 PM
Dayum, that's pretty warm!

Cruising in TX for long periods at about 90ish with it over 100 deg I've never seen anything over 195 on the gauge.

zzilla
07-20-11, 09:59 AM
So saying all this has anyone installed a trans cooler?

If so please share

I have all the parts for it , cooler, pump, etc... just waiting for the car to get finished a the fabrication shop so I can install.

JimmyH
07-20-11, 04:18 PM
That is funny. I have a dedicated trans temp gauge in the Camaro, and it never gets that high. However, with this heat lately, I have noticed some periodic warm spots on the console covering the transmission tunnel.

darkman
07-20-11, 08:02 PM
So saying all this has anyone installed a trans cooler?

If so please share

I have all the parts for it , cooler, pump, etc... just waiting for the car to get finished a the fabrication shop so I can install.

As you probably already know GM Performance sells one, Part Number 25534462. Luke at Lindsay can probably get them and they are available elsewhere. Current marker prices appear to be between 13-14 hundred dollars.

yooper
07-21-11, 12:06 AM
I picked up the GMPP Trans cooler from Luke at Lindsey Cadillac last year and have been running it with great success. The pump is activated by a contact switch installed on the outside of the case and comes on at 190F. The kit is plumbed through the trans fill and drain fittings and does not include a 1/2" pipe thread T fitting needed to retain the trans fluid temp sensor. Looking for an aluminum T because I don't want to hang any more weight off the side of the drain plug area than necessary.

Depending on the track layout, the pump typically comes on about 15 minutes into a run and will continue to pump fluid through the cooler for about 25 minutes after you shut the car off. The pump is loud and you know when it is on. Can't remember what the draw is, FWIW it did not run my battery down.

Will report back after next event with temperatures.


So saying all this has anyone installed a trans cooler?

If so please share

I have all the parts for it , cooler, pump, etc... just waiting for the car to get finished a the fabrication shop so I can install.

odla
07-21-11, 07:55 AM
Any pictures?

AG'S-V
07-21-11, 09:38 AM
Yes...pics and temps plz

djgershom
07-21-11, 11:03 AM
Funny, I was actually speeding from houston to san antonio with a few other people 100-120mph for about the same distance around 30 miles or so (didnt want to risk it) and noticed that all my oil temperatures dropped, not only that but my fuel economy went way up! I was shocked to say the least.

mstrjon32
07-23-11, 11:46 AM
I don't understand what is making the transmission so hot, though. I feel like it must be the exhaust heating it up externally...what inside of a gearbox would cause it to get that hot?

The transmission cooler is interesting, but I feel like there must be something else I can do to get the temperatures down...

darkman
07-23-11, 02:53 PM
I don't understand what is making the transmission so hot, though. I feel like it must be the exhaust heating it up externally...what inside of a gearbox would cause it to get that hot?

The transmission cooler is interesting, but I feel like there must be something else I can do to get the temperatures down...

The heat in the transmission comes largely from the gear friction, for lack of a better term. Part of the 19% driveline-related parasitic loss in horsepower between the crank and the rear wheels in these cars involves the conversion of energy into heat both in the transmission and the differential. Additionally, the amount of parasitic loss is a variable rather than a constant and, therefore varies with the level of horsepower at play - thus faster driveline speeds translate into incremental heat.

JNR
07-23-11, 05:58 PM
Was this the oem gauge?

If so, good to know it goes higher than 199 F...I was on a long drive up north and it was like ~97 F the whole way and the temp stayed at 199 F the entire way (only doing 75-80 though) and thought maybe it didn't read higher, lol, as that was weird. Otherwise, it stays pretty cool most of the time, relatively speaking, according to the gauge.

However, if I were concerned, I wouldn't rely on the oem gauge...over 200 F does sound sort of high though, but not sure in a damaging way, just wouldn't be comfortable with it...don't these use ATF for lubrication? Autos can and do run hotter (esp with high stall), so wouldn't worry about the fluid breaking down and since they're manuals, doubt it's anything to be too worried about.

Be curious what the diff temp runs, anybody know?

JNR
07-23-11, 06:01 PM
As for the part of the exhaust bringing the temps up, hmm, not too sure about that...I mean, exhaust runs hotter than the transmission, but there is also some air gap between it and would think sufficient airflow enough so the residual heat wouldn't make the trans any hotter than it already is from operation. That is, unless it's touching or something, but even then...the body is aluminum and dissipates heats pretty well (not as good as copper or silver, etc. of course) esp with the airflow...

See if you can run another temp gauge (quality mechanical) to double-check to at least rule out the oem being off.

kevm14
07-24-11, 09:37 AM
Well it could be radiation heat, which you can't blow away. In other words, infrared heats up the aluminum case, which transfers it handily to the fluid.

VfastCaddy
07-25-11, 02:57 PM
I watch my trans temps very closely because of the autocrossing I do in very hot weather. Normal highway driving in hot weather I see high 190's. I've seen 255 momentarily after a 3rd autocross run on a 95 degree day. Leave the engine idling and it gradually comes down. I once did a school where I did a bunch of back to back runs and got an overheat warning for a second. Not sure what temp causes that. I think I saw 265F on the readout but it may have spiked higher. I've been told that the old rule of thumb was that over 250F and your oil is breaking down.