Trans temperatures.

[MyM8V8]

I have been told by numerous people that I need to fit a fluid to air trans cooler.

The truck has a (stock) fluid to fluid cooler within the radiator, and having logged the temperetures it never goes above 93 C, even if it is being flogged to death.

What is the temperature at which the fluid starts to break down and cause damage?

[ScarabEpic22]

Sorry Im not used to thinking in Metric (wish the US would switch over, all chemistry/etc in schools is done in metric...) but Ive heard for the 4L60Es that normal operating temps are 180-200F, anything over about 220F is getting in the danger zone and 240F do a fluid swap immediately and see if its burnt or not. I have a $50 TRU-COOL (aka rebadged B&M) 18000gvwr cooler on my 4L60E in my 02 TB and it dropped the temps by about 20F consistently and up to 50F sometimes.

Makes a big difference when towing but for you with a stall it'd be a huge help.

[joecar]

93°C is is right on 200°F... it's ok as long as you don't consistently go over that.

[Mr. P.]

Well for a 4200 stall that's actually a lot better temps than what I Would have expected.

According to GM - Dexron-III begins to break down at 175-degrees; according to their tests, every 25-degrees over 175* will cut transmission life in HALF. So operating at 200 you will only get 1/2 of the life of your transmission (as compared to running at 175-degrees). Increasing ATF temps to 225 will cut that life in half again (only 1/4 of stock life). In my own truck, I get best performance when the transmission temp is 160-165 degrees, that is where it shifts fastest/firmest and grabs hardest. Also, with the 4L60E every time I have seen a trans that would not stay below 180 it was because the 3/4 clutch pack was completely glazed over; in your case this may not be the case since you have that loose-assed converter.

The factory external cooler on the GM trucks is a *joke* - replace it with a bar/plate design cooler, like the TruCool unit, at least a 12" x 12" in size, or best the TruCool Max (12" x 24").

Mr. P. :)

[ScarabEpic22]

Wow, thats pretty good now that joe did the hard work for me converting it!

When Im cruising on the hwy at 75mph in the dead of winter (20-30F ambient temps), Ive seen the TFT be as low as 135F for the whole trip in 4th with the TC locked up.

As with Mr. P., my 4L60E likes to run in the 150-165F range, nice firm shifts and they are consistent. Ive had a few customers with the stock radiator "coolers" complain their shifts soften up as the drive more, this is the reason, the fluid gets hotter and the trans shifts softer.

[joecar]

http://www.onlineconversion.com/

[ScarabEpic22]

Eh too lazy! :D

[MyM8V8]

93°C is is right on 200°F... it's ok as long as you don't consistently go over that.

Just going through my logs again, I must have typoed. It's actually 73 Deg C.

[joecar]

73°C (163°F) is great...

I logged mine, and it was around 82°C (180°F), I have the stock cooler (integral with engine coolant radiator).

I've been using Mobil-1 ATF for about 7 years; I change it every 15K miles.