3rd - 4th shift

[nd1983]

I've noticed over the past for weeks. my 99 montana seems to be staying in 3rd gear alot more. It will shift into 4th at 70km/h (44mph) or 2000rpm which ever comes first under normal driving conditions.

is this normal?
should i flush the trans?
i don't remember this happening before and my fuel usage is up becuase of the excess use of 3rd

 

[sergeimoskva]

Hi!
In transmission 4T65E (and a similar) shifting is allowed engine speed 1500-2000. It all depends on the pressure in the pipeline transmission. Check the oil level in the box. The oil must be clean. If the oil is black and has a smell, perhaps problem in the friction.

 

[melsg5]

Do not flush the transmission if you decide to service it. Drop the pan, replace the filter and add fresh fluid.