6 speed manual will not shift into reverse or low
 

I have a 2000 F350, Turbo diesel with 223 000 miles.
6 speed manual transmission will not shift into reverse or low.
Any solutions

Just won't go in, or it grinds?

Can you give more detailed description?
One problem I had with my 6 speed was that the joint on the shifter got loosen bolts and when 1 bolt come out, the shifter would not shift the gears. Pull the floor boot and check if the bolts are holding?

6 speed will not shift into low or reverse
 

No grinding.
Gradually got harder to shift into low or reverse.
Feels like it will almost shift, but does not.

I have pulled boot. Bolts look fine. Interior boot is oily

Check the shifter like Katjek1 said...

put pressure on the shifter and slowly let out the clutch so the gears turn a bit...

thanks. going to mess with it this pm

Does it shift when the engine off? You may be seeing the results of the clutch not entirely disengaging.

If that were the case, at the very least, reverse would grind, unless it has a synchro which I doubt ;)

As far as I can tell, both reverse and low have some level of synchronizers. They don't seem to work as well as the synchro's on the other gears, however. It's a lot more difficult getting the tranny in reverse and low than it is other gears. Especially when it's cold.

That's just my experience.

Edit: Yes, according to the parts explosion diagram, Reverse-Low is synchronized.

It will not go into low or reverse at all with engine on or off. The rest of the gears are fine. It got gradually harder to get it into reverse and low.

If you make the truck roll a little, can you get it into reverse? start in 1st and make it roll forward and then shift into low or reverse?

It is not a clutch issue.
I would suspect an issue with the linkage or transmission. Im not sure but i believe the shifter enters the transmissin from the top so it is either the stick is binding internally or an issue with the shift collar. You may need to have the tranny removed.

Not sure on the older trucks but i know the newer trucks Low gear is non syncronized.

FWIW, my 2008 has synchros on low