appadv

Already searched the forum, but didn't find what are the engineered optimum temperatures for the A6 transmission and radiator coolant. Only saw what other people were running, such as 217' max or something like that for the A6 and 198-228 for the coolant.

I know that the fans in the radiator come on at around 228 degrees, so I would assume that is the engineered maximum temperature for the coolant to get up to. Which makes sense because the middle of the temp gauge is 220 degrees, with steady highway cruising at 198'. The coolant temp has never gone past 228'.

But what about for the A6 transmission? Steady highway cruising is always under 172 degrees, but stopped in traffic for a while yields temps into the 210's. Heck, leaving the car parked in the winter with the engine running to keep warm gets the A6 temps into the mid 190's. On the other hand, driving on flat highway roads yields a consistent temp. in the 150's, with mountainous highway driving in the high 160's.

Is there no optimum temperature range for the A6?

appadv

Anyone?

My mechanic (and family friend) says the transmission temperature should be "at or around the halfway mark" on the A/T temp gauge.

Since there is NO temp gauge, only a DIC display, what should the temperature range be?

matt_lowry123

I have an A6 2008 and it's always about 210

Glen1224

My A6 '07 runs 198-210. It depends on outside temp and my driving.

appadv

Thanks, so normal temperature for the A6 should be around 210.

Makes sense...

When stuck in heavy traffic the temperature is 210 +/- 5 degrees. On the hwy the temperature is 160 +/- 12 degrees. Generally below 160 too.

Gearhead Jim

The manual for our 2009 A6 says the trans temp warning comes on at 270', and you should allow it to cool below 230. To me, that means anything below 230 is "acceptable", but I prefer to keep it below 200. Since i don't have an extra cooler, it does what it does.

Highway driving gives about 170, city gives 190-200.

Highet I've seen in normal use was 219' in bumper-to-bumper traffic for an hour, outside temp 90'.

I did see 225' after some time under high power and paddle shifting on a very twisty road. It got up there pretty quickly, but i ran out of road and did not see what would have happened with more time.

dragpak

190-220 degrees is what Ive seen in the last three months of ownership. When it was 90+ I saw 220 degrees. Hope this helps.

appadv

Interesting, your highway value of 170 seems accurate, but the city temps are only 190-200? Just starting the car and letting it idle brings the temp to 198, I know that because the dealer left the car running upon delivery for more than an hour and the temp was 198'.

I find there is a 50' difference (or even more) between highway driving (around 160') and heavy city traffic (around 210') on the same day. Just to be on the same page, by "heavy city traffic" I mean traffic that is completely stopped up, you can be creeping along for hours to go 2-3 miles!

Gearhead Jim

I've never let mine idle for more than about 10 minutes without driving, or at least trying to drive, so i can't give a good comparison.

That's similar to what got me up to 219, it did take a while to get there.

appadv

There was a reason why the dealer left the car running on the day of purchase, I don't remember why, but it did have to be jump-started to get going. After that never had to jump start the car. The long idle time of more than an hour caused the A6 temp to be almost 200'.

MisterMidlifeCrisis

When you are highway driving, most likely your torque converter has mechanically locked, so the fluid is not being used to transmit power. It's then probably as warm as it is because it's heated up in the radiator. Otherwise, it might run even cooler.

appadv

Thanks everyone, you guys really know your stuff!

Davyducky

If a ls3 vette runs at 220' in stop and go traffic with the outside temperature of 75' is that within the normal range?

appadv

Yes! I was worried about trans temps until I spoke to a transmission shop (Banner Transmission in LI) who said this is normal. The temps will go up and down based on ambient temperature and also usage (stop and go vs. highway). If you are over 230' then something is wrong.

Now that I've moved away from NYC, my max trans temp is 205' in suburban traffic, but nothing like it was in NYC when temps were 210-216' regularly.

appadv

Also, when you say stop-and-go traffic do you mean heavy city traffic or suburban traffic? Since I've moved to Iowa the A6 runs much cooler (highest was in Iowa City with 2-3 minute long traffic light cycles), driving on the interstate yields temps in the 150's.

HOXXOH

Regardless of operating conditions like heavy stop and go traffic vs flat highways or local ambient temperatures, the longest lifespan for transmissions is when the fluid is in the 160-190 degree range.

The A6 and several other electronically controlled transmissions will shift erratically at WOT when too cool. Most people won't know that without scanning with a program like hptuners, since you have no basis for comparison. On the other hand, the lifespan gets increasingly shorter as the temps continuously exceed 200.

Since I have the triple whammy of a high stall converter, a much hotter than average climate (99* during a Phoenix Summer is considered a cool day), and stop 'n go afternoon rush hour traffic, I watch the trans temps religiously. If it gets to 230, I'll pull over to let it cool down.

With 117K on the clock and over 400 trips down the 1/4 mile, my A6 is still surviving.

appadv

HOXXOH,

How do you get the temps so cool if you are driving in city traffic? Do you have an external cooler? Also, how do you keep your temps up in the winter?

Now that my commute sees more highway driving I may be at 113' all day long, if all I do is highway driving in January weather. That seems to be too cool to be in the "optimum" temperature range. Likewise, any stop-and-go traffic in the summer brings the temps up to 205' or so. Heavy traffic goes even higher up to the 210-220' range. Is this a problem or will the trans continue to operate fine? (75k miles)

With trucks that use the 6L80E transmission, their temperature gauge goes from 100'F (minimum), 200'F (middle), and 300'F (max) so it seems like GM engineers want you to be around the 200'F range, if I'm reading the gauge correctly.

Either way, any advice on getting the temps closer to your recommended range would be greatly appreciated, as I've always seen 200+ in stop-and-go traffic.

Bill Dearborn

Looking at the Service Manual one of the warning messages that can happen with an A6 Transmission is Transmission Hot, Idle Engine.

That message comes on when the transmission fluid is at 266 deg F.

When that happens they want you to pull over and idle the engine to cool down the transmission. If you don't idle the engine the fluid doesn't go through the cooler in the radiator so the transmission doesn't get cooled fast enough.

Bill

HOXXOH

I do have an external cooler and for a few years my winter temps were too low unless I purposely forced the converter to create more heat. Last Fall I rerouted the lines to go through the radiator before returning to the transmission and I could maintain somewhere in that ideal range. This is my first Summer with that routing and I've seen 220 on a couple of occasions, but it mostly runs in the 180-200 area. My next step if it gets worse is to go with either a lot bigger cooler or two smaller ones and a 180* inline t-stat. That's basically to go over capacity on the cooling and then regulate the minimum.

appadv

When you pull over and idle the engine, the temp goes down to 198 and stays there, at least from my experience. Once you get rolling up to 50MPH, the temps drop significantly from 198 and stabilize in the 160's.

So it seems like with the converter locked (50MPH) the trans actually runs cooler than just idling in neutral when pulled over. Either way, if GM says idling the engine is the method to cool the trans in an over temp situation, that's probably the best way to do it, according to the GM engineers.