This is due to a bad radiator. Replace radiator fixes problem. Don't want to replace radiator cuz you think it's still good....cover half of the front of the radiator so air only goes thru half and the radiator in turn will run a little hotter...this will also fix your problem but the heart of the issue is the radiator.
How do I change out
On a 1996 4runner the transmission shift solenoid is under the pan in the valve body. There are two shift solenoids on the 4runner.
There is no recall for the Toyota 4runner transmission. Some Toyota's have had break problems that may have started the recall rumors on some Toyota products but, there is no recall for the Toyota 4runner transmission.
There is no "switch". To cancel overdrive move the gear lever from "D" to "4".
The 2006 Toyota 4Runner has a 5-speed automatic.
The 2008 Toyota 4Runner has a 5-speed automatic.
The 2002 Toyota 4Runner has a 4-speed automatic.
The 2001 Toyota 4Runner has a 4-speed automatic.
The 2003 Toyota 4Runner has a 4-speed automatic.
The 2007 Toyota 4Runner has a 5-speed automatic.
The 2004 Toyota 4Runner has a 4-speed automatic.
The 2009 Toyota 4Runner has a 5-speed automatic.