My 1991 F150 has a E4OD transmission that shifts hard at times and other times it shifts normal. I had a scan ran on it and got 3 errors. A 332 EGR flow, a 628 converter error, and a 634 MLP sensor. Would any of these three cause the hard shifting? Thanks

 

From what I understand the mlp could cause that. I would think the converter error could also but not sure on that.

 

https://www.ford-trucks.com/forums/9...-problems.html Read the post by Subford in this link, it tell you how to test the MPLS (also known as the Transmission Range Sensor).
Also make sure that the pins in the plug connector to it are clean and tight.

 

Thanks, Lazy K