check the engine mounts and rear transmission mount for breakage or the bolts are tight

check to see that the transmission is "flush up" to the block all the way around (nothing caught in between) and the bolts are tight...........

next, remove the bolts between the converter and the flywheel.....slide the converter back away from the flywheel........then look for any cracks in the flywheel.............now bring the converter backup to the flywheel....install one bolt very loosely......rotate the flywheel and compare the distance between the flywheel and each mounting tab of the converter........you are looking for a noticeable difference in the gap between the flywheel and tabs............if the flywheel is in a "bind" when you bolt up the converter , it will cause a loud "hard hitting" noise from the flexing and will soon crack the flywheel.....
crossbones

 

Will you let me know what fixes this, I am having the same problem with my 94 e350 1 ton.

 

Haven`t done much more about it. But i promise that if I ever find the reason, I`ll post it here!

 

Did you check the oil pressure with a manual guage....... the narmal sender is on the rear of the engine block top... on the turbo when turbo equiped I think..

I have seen flywheels on auto trans crack and cause these noises, also loose torque convertor bolts.

Mine has a knock when cold probably a wrist pin, but once warm it goes away and runs fine......

Yes the pan can be removed in truck, but your about 5 steps from complete removal which would make things significantly easier. With the noise appearing after the trans repair I would remove the engine...... the trans would still be in place and easily checked over.

If you want R&R instructions for pan or engine send me a PM with your email addy ask for: Engine and pan R&R