How hot is transmission fluid supposed to get?

[jason07-1zzfe]

I do agree about the slippage on modern trannies, but it does look like DJ was correct.

Pulled temps first thing this morn before it was started and ambient guage was 68F, coolant 78F, intake temp 73F, and tranny temp...........145F!!

So who knows what my temp is. If I can be sure it's 70-80F high across the board my peak temps should be around 200F.

Needless to say I will be contacting AutoEnginuity.

 

[MolaKule]

quote:

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Do esters have lower surface tension and better heat transfer in the cooler?

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Esters primarily have better lower coefficient of friction than mineral oils and PAO's; secondarily, the specific heat of conduction and convection is higher than for mineral oils.

 

[ExDelayed]

quote:

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Originally posted by Jason Troxell:
John is that temp accurate? That is scary because I just got a scan tool recently and the tranny temp even after being babied was 220F and after I drove it for a bit romping on it a little was up to 280F. This is in only 60F ambient! On a 2001 GTP.

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My results are quite similar to yours Jason, just in a Ford Contour instead of a Pontiac. My car has its trans cooler mounted after the radiator cooler, but it sits in front of everything else. The unit is a small Hayden stacked plate unit. The temp sender is mounted before either cooler in the filter adapter about 18" away from the trans. On the freeway the other day (55-much faster) I had it sitting between 180-195. Climbing the small but long hill to my house later in the day (35 mph) I bumped 250.

Im working on fitting an 11x11x1.5" stacked plate/fan/t-stat which should solve all of my heat problems.

 

[unDummy]

If you follow the fluid flow of your transmission, you might argue that the ATF temp should be measured in the pan. This would be more of an average temp and not at a point when the fluid temp is the highest.

If you pick the highest temp point, usually right before the cooler, you'll get a false sense of danger.

The tranmission life vs temp chart measures the temp where???? If you're worried about the clutches/seals....than a better place to measure temp is at the ATF pickup(hint- THE PAN).

A good point was made. How does a hot radiator cool hot ATF? It doesn't. When my cars are running, there is no hot or cold side on the radiator. It'll burn you anywhere!

When in doubt, use the biggest cooler you can fit. Use a thermostat if you have cold winters. Use a synthetic for better protection and hot/cold temp performance.

 

[Patman]

I decided to keep an eye on my trans fluid temperature in my 98 Corvette on my trip home from work today, which is a 25 mile trip that takes me close to an hour due to brutal traffic.

At the halfway mark I took note of the trans temp, it was 180F. Coolant was 194, oil was 198. The outside temp showed 77F. When I got home I checked them all again, the trans temp was up to 185, the coolant at 192, oil 201, ambient temp now 79F. I didn't really drive it super hard today though. I'll check it again one day after I've done a bunch of full throttle runs. It is nice to know that in stop and go driving nothing gets too hot. It probably helps that I've now got custom tuning which turns my coolant fans on at a lower temp. Having the coolant stay under 200F makes the trans and oil temps stay nice.

 

[nascarnation]

quote:

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Originally posted by unDummy:

If you pick the highest temp point, usually right before the cooler, you'll get a false sense of danger.

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not necessarily
heat breaks down oil
the oil doesn't care where it is in the transmission when it gets to a temperature

 

[TC]

Transmission temp is supposed to be about this much (I'm holding my two fingers a bit apart). In hot environments, such as towing through Death Valley, about this much (holding 'em farther apart). If that's not good enough for ya -- and stop being so d*mn picky! -- look here:
http://ca.autos.yahoo.com/maintain/automatic_transmission1.html