I have a 95' 4X4 that records error code 648 (4th speed ratio error). This only occurs when going more than 60 mph and then accelerating to force the tranny to shift out of OD, then as soon as you ease up and the tranny shifts back to OD, the OD light begins to flash. This consistently happens and can be repeated each time. The transimisson was recently rebuilt. I notice no problems with the performance of the transmission. After the OD light starts flashing, the transmission lightly thuds when shifting in and out of the 1st gear. this effect stops as soon as the error code is cleared. Any thoughts?