Help! Very Fustrated

[joeyjarvis23]

Ok so i have A 97' f 250 with 3.55 gears and 35" tires tranny went out so i installed a heavy duty new ford one E4od. Tryed to pull my 10,000 lbs camper and i cant get over 50mph .. I have to stay in second, because if i put it in drive it hits 300 degrees and the tranny starts shifting or tc lockup and unlock not sure about every 30 seconds.. then my egts start to climb.. Please help. ive already had the pcm flashed.. maybe the gears in rear diff are the problem?

[Dave]

35's and 3.55s are a problem.

But it definitely sounds like you cooked your new trans.