99 Jimmy shifting in and out of od

Redtrash

My 99 Jimmy has just recently started shifting in and out of overdrive and feeling sluggish. Had her for 5 years and never had a idiot light come on. I'm assuming it's a vacuum problem at transmission or transfer case. Any ideas? She now has 217000 miles on her.

Mr_Shiftright

My guess is a problem with the torque converter clutch solenoid which is in the transmission valve body. Might be best to scan for codes first though--the clutch itself could be worn.

Redtrash

Thank you, I'll scan those this week. I also have the 4X Auto option for the transfer case. I was told it takes a different oil. Is this true? and if so what type?