my 99 F350 will run fine until you put it into reverse or when you turn a corner. When you put it into reverse the service engine light comes on and then you get a very sluggish rough idle. This also happens when you turn a corner. Running
straight down the road nothing happens except I'll say every now and then at about 65 or 70 it will do it. It sounds like it is only running on about 4 cyl. If you catch it just right you can put it into neutral and it will clear up. It shows to have 132,000 miles on it but the previous owner had it unhooked and he says it has more like 432,000 on it. I don't know if this is going to be fuel or electrical.
I overheated the transmission and someone said the way the trucks are it might have something to do with it. we had to replace the neutral safety switch on it. This is a farm truck and it goes through a lot of mud and water when and if it rains. Also when in 4wd and you need the power it does this which is very aggravating or it seems just to lose horsepower. I have not found anyone that seems to know what is wrong or how to fix it. I did have a mechanic put his computer on it and no codes came up. Please help if you can.

 

seems electrical to me due to the fact that you say it does it everytime you put it in reverse and when your going around a corner. I would check the block ground strap first, when you go into reverse it will kick the motor the opposite way in the engine mounts and when you go around a corner its flexing also. and with the mud, and water that wouldnt surprize me either. i would just go through and check all your electrical connections, clean your battery terminals and grounds real well. I dont think its this but look for burned wire and connectors where the harness goes into the valve covers also, it still could be.

 

Barebackjake-I was in a hurry but crawled under the truck did not have a light. Not to sound stupid but where would the strap be located? I could not find it. While I am at it there was diesel on the front axle and stabilizer bar an frame. The drain valve on the bowl is closed but sitting there idiling it drains fuel. Also I already had the valve cover gaskets replaced because it was acting very similar then it ran fine but shortly thereafter started acting up again after I overheated the trans but will check wires.