How far out should an ATF's viscosity go?

[TomJones76]

I have a transmission where I sampled the ATF (Mercon V, actually) and got a viscosity that seems out of whack to me.
The ATF in my '02 Sable is at 6.38 CST, but the Mercon V fluids I found online have a CST of 7.5.
How far out of line can your ATF go before it actually causes damage?
Another question:
Could some uneducated person have put the wrong oil in my transmission?
Is there an ATF that has a viscosity in the 6.4 vicinity?

The ATF UOA that causes me to ask this question is posted at:
http://theoildrop.server101.com/ubb/ultimatebb.php?ubb=get_topic;f=50;t=000022;p=1#000004

 

[TR3-2001SE]

I am sort of new to reading these transmission reports but it seems to me you need to do a complete flush. Your iron is high, your aluminum is high, your copper is high and your viscosity is slightly off. I have done research on Honda transmissions fluid analysis and if my numbers where close to yours I would do a complete change. I know you only have 30,000 miles and you just did a change but that, I think is the best solution.

 

[benjamming]

Have Terry do a "read" for $20.
2nd question: Yes, so could an educated person.

 

[unDummy]

ATF shears pretty quickly. The notion that ATF is good for 30k miles is a farce.
Don't even bother asking my opinion on lifetime fluids. The BITOG server will overly edit my comments.

When doing ~50%(pan drops, via drain plug, or siphoned using extractor) ATF changes, you should try to change it every year/10k miles, or more frequently.

Noone has studied the effects of overly sheared ATF which occurs rather quickly. There aren't too many used oil analysis on ATFs as it is. Most wear numbers are pretty high so don't worry too much.
My experience is that those who overly maintain their transmissions will not need the rebuild as quickly as those who don't.

And, add external filtration. Use a permacool ATF filter kit, the magnefine filter, or Ford's own kit installed during dealer RWD rebuilds. This will reduce some of those normally scary numbers in the ATF UOA.

 

[TomJones76]

I found Amsoil's "ART" has that viscosity. It appears to be their "racing" ATF.
Also some fluids intended for Caterpillar transmissions.
I can't imagine "L&M Towing", the garage, using Amsoil in this vehicle.
So either someone flushed it with a fluid normally used in heavy commercial transmissions, or there's a transmission fluid I'm missing, or....... it just sheared out that bad.
I'll try to find $20 to pay Terry with, and I'll also start getting quotes on an ATF flush.

 

[MolaKule]

Newer ATF's are changing to lower viscosity fluids for the same reason that Ford and others are going to thinner engine fluids, economy.

And ATF's do shear down one or two cSt over 30,000 miles.

See:

http://theoildrop.server101.com/ubb/ultimatebb.php?ubb=get_topic;f=4;t=000450