having trouble w/tran. not shifting right . got a 761 code & replaced the C solenoid. but didn't help. it will shift into 2nd & 3rd , but won't go into O/D , i have 2 leave the O/D off ,& it will run good , but no 4th,, can't go over 60 (3300 RPM ),if i turn on O/D it start 2 slip & completely dis-engage, until i turn off O/D ,,,have changed fluid & filter ,,anyone have same problem ??