The wife said she had the tach up to 4000 rpm the other morning when the outside temperature was -7. I tried it next day and it feels like the transmission fluid is too thick for a few minutes, until it heats up, then everything seems fine. I understand this is a Toyota transmission and there is a dip stick that is hard to get to. Does this problem mean it's time to change the fluid, and what fluid does it use.

 

What year is your Equinox?
If it's 2008 or newer, which engine does it have?
Is it AWD or FWD?
How long have you had this vehicle?
Have you ever had the transmission serviced or fluid changed?

It sounds like you are describing the Aisin AF33 transmission used in the 2005-2009 Equinox (w/3.4L engine) so I'll assume that is what you have. The tach getting up to 4000 rpm isn't anything to worry about unless the transmission is hesitant to upshift. Even then, there are actually certain scenarios where this would be normal. On GM vehicles, the AF33 transmission does have a "Cold Mode" which makes shifts occur at higher than normal engine RPM until the engine coolant temperature exceeds 122°F. This could be what you're experiencing.

If the vehicle has more than 100,000 miles, I'd recommend changing the transmission fluid if it has never been done before. Even if you just do a drain & replenish which only replaces slightly more then half the fluid (about 4.3 qts to be exact), this will help prolong the life of the transmission. It is generally very reliable with regular fluid changes. I recommend changing the fluid every 50,000-70,000 miles. Toyota T-IV fluid (Toyota p/n 00279-000T4-0) is the correct fluid and is available from any Toyota dealership for a reasonable price of about $5.50/qt. The official GM T-IV (p/n 88900925) fluid is the same stuff, but GM dealerships want $20/qt for it.