Does the torque converter lock? It should lock on both 3rd and 4th gear.
How are the engine temperature and temp gauge? The 4T60-E requires decent temp information to run normally, othw it goes to "limp mode" and will not engage 4th nor lock.
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The torque converter and clutch are the point where the engine and the transmission engage.
The transmission may not shift or engage in forward or reverse until the car warmed up for a few reasons. Two examples of why the transmission will not engage is low or no fluid levels or a leak.
Overdrive is the normally allowed position in a Ford Explorer automatic transmission , once the vehicle speed is fast enough ( my Ford Explorer is 50 MPH ) the automatic transmission will automatically shift into overdrive
Bad transmission rebuilder
transmission won't engage when you push the button on john deer 155c automatic
Does the transmission engage when you shift it into drive?
To engage or disengage the engine from the transmission.
Yes It Wil If The Vacuum Leak Is In A Hose That Gos To you Transmission
Low fluid level if your lucky.
There is no hydraulic fluid in the transmission. However, there is hydraulic fluid in the clutch system. If the clutch fluid reservoir is empty it would cause clutch not to operate.
Most of the time this is caused by a bad seat safety switch. Under or along the hinge area of the seat you will find a plug. It can operate two ways. If it's normally closed, unplug it and try to engage the blades. If it's normally open, unplug it and put a jumper wire between the two contacts and then try to engage the blades. If either of these two work then you need to replace the switch.
When climbing a steep incline. The automatic transmission will always try to engage a high gear.