Hi,
I have Trailblazer 4*2 , and sometimes the gearbox switch from D to N while the car moving any idea why this happened
Thanks

 

Have you checked/ flushed the transmission fluid recently?

Also how long does this happen for? And does it happen at random or when the car hits a certain rpm?

What you are describing sounds like the transmission is slipping and it may need to be checked out by transmission "specialists"

 

Thank you for your reply , please find my answers below
Have you checked/ flushed the transmission fluid recently?
[no from long time , but I have changed it after this issue]

Also how long does this happen for? And does it happen at random or when the car hits a certain rpm?
[it happened two times when the rpm between 20 to 40 ]
What you are describing sounds like the transmission is slipping and it may need to be checked out by transmission "specialists"
[ yes the sound link the transmission is slipping and I have checked by a specialist but he wasn't be able to detected the problem as the transmission working probably at that time

 

It could be the clutch pack in your transmission.