4-speed sweet spot

I've got a 66 F-250 with a 390 in it. I've posted some pictures a while back. I don't know if this is the correct forum to post this in but I didn't see a tranny forum.

Third gear on this truck has a sweet spot. What I mean by that is that if you don't hit it just right you're fighting and wiggling to get the bugger in gear. It can be VERY frustrating. I've sucessfully rebuilt two auto trannies and put in a coupla clutches but I'm not really all that familiar with a manual transmission.

So my question is, from the way that I've described this do you understand what is wrong? Is it a simple fix and can you describe to me what I would need to do to repair it/replace?

Any help is appreciated.

TIA

Dusty

I am in no way an experienced transmission guy---but---manual transmissions have a component called "syncro rings". I don't know how they work, only that they exist, and they so something to align the gears to give smooth shifts. How's that for vague???? If we can get Denny to chime in here, he seems to know everything that I don't (which is quite a lot)---he might shed some light on the subject.

Manual transmissions have synchronizer rings - usually made of brass - to help align the gears during a shift. If the synchros get worn or blunted, it becomes difficult to shift. Take a look at the following article.

http://www.secondchancegarage.com/public/207.cfm

Here's another good article:

http://members.cox.net/elans4/Transmission.htm

Those were some helpfull articles. I think a better way to describe what is happening is that there seems to be excessive play in the shifter/shifting forks/rods connecting them. I never have trouble with grinding just finding. If I drive the truck for a few hours I know just where to shift and have flawless shifting all day long. Thanks for the help and all the replies. I understand now that I do need to pull it and take it apart to have a look inside.

Any idea what kind of hard parts availablilty I'm looking at for this old tranny?

Thanks again

Dusty