93 4runner overdriver

have a 1993 toyota 4 runner that when its cold dnt want to shift into overdrive but when warm works fine. putting in reverse an backing up seems to help speed up it shifting into O.D. for some reason

I would start with draining the fluid and changing the filter?

I agree with knfenimore. Start with a fluid and filter change. Be sure to use the proper Toyota-approved fluid. However, many transmissions won’t shift into highest gear until they’ve warmed up a bit by design. Is this a recent development/change?

yeah recent problem i already changed all fluids didnt help toyota does say it has to be at operating temp. before it will go in O.D. but seems like takes to long and once you reverse alittle seems to help and then its fine till it cools down again. weird i know. thanks for any help you can give me

It is normal for the transmission not to shift to overdrive until the engine is up to operating temperature. It should be warn enough in about 3 or 4 miles, or maybe 5 minutes, in all but the coldest temperatures.

When you say it works fine when warmed up, how long are you saying it takes?

last night in 16 degree weather took bout 6 miles when i stopped put in reverse and back to drive and all worked fine

Yeah, that’s just about right. It would have worked just as well without putting it into reverse. Completely normal.

You might check the calibration of the Coolant Temperature Sensor or may just replace it. This is not the sensor that drives the temperature gauge. If the ECM thinks the engine is still too cold overdrive engagement will be blocked until the engine is at operating temperature as the ECM sees it.

Also, have the thermostat opening temperature checked. If it is opening too soon, that will also affect the attainment of operating temperature. You might be able to spot this on the dash gauge as a slow or low reading.

Hope this helps.