1999 f 350 7.3 diesel automatic transmission will not move in drive.
 

I have a Ford F 350 Super Duty, with an automatic transmission it is a 7.3 diesel it goes in reverse beautifully, but drive goes nowhere. If you really slam it down in the low you can see the drive shaft barely want to move for a second. We dropped the pan and put a new filter in it, the pan looked pretty clean some clutch no metal shavings. Don't want to have to pull transmission if it could be some kind of sensor or something silly like that.

A good place to start would be to remove the electrical plugs on the trans and check for any corrosion. There is the possibility of interruption of signal to solenoid pack.

I've been busy, but today I had enough time to start it up and look at the electrical plugs on the transmission. at first it seemed to be the same, no Dr just a clunk when you put it in low, very slight clunk.I put it in reverse and went back about a foot, and as it rolled forwards I put it in low and gave her some gas.I did this 3 times and the third time I heard a clunk and my drive works again. I took it up and down the road seems to be doing just fine again. I am told this is the second time it did it same similar problems back in July. They changed a speed sensor and it worked again. seems to me something internal is sticking what do you think it could be? What could be done to correct this problem?