2004 ranger question

Ok so this probably isn't the right place to post this but i really need help with this one. My grandpa's got a 2004 ranger with the 4.0 v-6 and auto tranny, 4-wheel drive. When you are very light on the gas the truck shifts fine but if you lay into it (which my grandpa likes to do) right after it shifts from lie second to third it will shift back to second and then back to third. Any ideas why this could be happening? Sorry for the long winded post.

 

This is what the Haynes manual says:
"Automatic transmission malfunctions may be caused by five general conditions:
poor engine performance, improper adjustments, hydraulic malfunctions, mechanical malfunctions or malfunctions in the computer or its signal network. Diagnosis of these problems should always begin with a check of the easily repaired items: fluid level and condition and shift linkage adjustment. Next perform a road test to determine if the problem has been corrected or if more diagnosis is necessary."

Having said that, is the Check Engine Light on?
Transmission Codes can be scanned for free at an auto parts store.
Check the fluid level and condition: Is the fluid clean and measuring full on the dipstick. Take a white piece of paper and drop some of the fluid from the dipstick onto the paper, then next to that drop - place some transmission fluid from a new fluid container to compare fluid condition. Feel the fluid between your fingers, is it gritty or slippery, does it look dark colored or smell burned?
Mileage: Has the truck had a transmission fluid and filter change?

I may not have the solution, just trying to help.

 

I've owned 10 rangers....I had this happen to one and it needed the tranny filter and fluid changed. Shifted great after that....not saying that's what his needs but could be a option.....when's the last tranny service?

 

As far as me and my grandpa know the tranny has never been serviced and the trucks little over 60000 miles. Thanks for moving this to the right section for me. And thank you for the quick replies. Will be servicing the tranny this weekend and seeing if this works.

 

hope it works man

 

Good luck man and let us know how it turns out

 

Ill keep ya posted.

 

Wow, ok so here is whats happen. Looked at the fluid for myself, wasa asking grandpa how it looked, needed to be changed was slightly milky colored. So he is driving my thunderbird till he gets around to getting his truck serviced. so by end of week it should be done.

 

ford motor company reccomends having the tranny flushed every 70,000 miles...