Transmission Gurus, Question on Shoebox Ford 3 speed what broke?

A friend has a 51 Ford V8 non OD and today about a block from home he said it broke. I went by there thinking it was probably linkage related and what I found is that it will shift into all gears normally and shifts feel right but while in first or reverse it will clunk loudly and jump out of gear, if you put it back into gear it will move about 1 foot and do it again. It seems like perhaps its one revolution of the gear inside and it knocks it out of gear again. 2nd and 3rd gear works normally. I suspect maybe a broken tooth on the cluster? Any ideas Thanks.

 

Cluster or 1st reverse slider.

 

if you're lucky it's the reverse idler. have you priced a cluster gear lately?

 

was always 2nd and cluster in mine, 11 of them
(I was young then, what can I say)

 

Next to a cluster gear , price a syncronizer assembly complete . scrubba

 

Thanks guys he found a complete take out tranny so he is going to have it checked out and if its good (they took it out for an automatic) and swap it out.

Would the reverse Idler kick it out of 1st too?

 

First-reverse SLIDER !! Rev idler will only cause issues in reverse.