2004 F150 transmission studder

Recently had engine replaced in 2004 F150, as soon as I drove out notice transmission has shutter going from 3rd into overdrive (45 to 50 mph). never had it before. Mech. took it to local trans shop and they say needs rebuilt. I still think this might be an engine issue, any thoughts on what should be checked before rebuiling a trans.

thanks
JDSDAM

If the engine has a small misfire it will give you your symptoms. The trans probably does not need rebuilt. Worst case scenerio is the torque converter would need replaced. A lot of times a complete drain and refill will cure the problem. This includes the torque converter and transmission cooler. There is a product made by Trans Medic that is an anti shudder additive that works very well.

Thanks for the reply, it seems like all my research would indicate a misfire not a transmission problem. The transmission place that checked it, changed the fluid and it didn't stop it. I haven't drove it yet, but find it hard to believe it just went bad right after they changed out the engine.
Thanks again,