[btal21]

i have a 94 grand cherokee the trans shifts 1st 2nd and 3rd manually but when i put it in d it takes off in 3rd and wont go into o/d can anyone help?

 

[ImperialCrown]

Welcome to Allpar. Which engine?
Any 'ck eng' light or fault codes? http://www.allpar.com/fix/codes.html
Does the 'O/D off' light stay on?
It may be a governor issue. Most were electronic by 1994.

 

[Bob Lincoln]

Do we know which transmission this is? Most won't go into O/D if the computer thinks the engine coolant or the transmission fluid is too cold (or if the car overheats). An incorrect sensor reading could be the cause.

 

[btal21]

its has a re42 it doesnt overheat or anything

 

[ImperialCrown]

You might want to confirm it with a wiring visual inspection and scan tool diagnosis first to be sure, but the 42RE has a 2-piece electronic governor (sensor and solenoid). The pressure in PSI should track along with the MPH, one per one. This can be watched under PCM inputs.
If it hasn't been done recently, also change the filter, fluid and pan gasket. Synthetic ATF+4 is preferred.

http://www.amazon.com/56028196Ad-Pressure-Transducer-Governor-Transmission/dp/B005OD0H7E

Watch:
http://youtu.be/kvl-_-vY6rk