915 troubles: shifter jamming (loosing gears)

I have a 915 with a serious problem and several quirks. I am wondering if a rebuild is in order and what other things need attention?

The worst problem is that I keep loosing the first 4 gears - only 5th and reverse work. I have traced this problem to shift forks out of position. I found that the shift fork for 1st and 2nd was out of neutral position compared to 4th and 3rd. Consequently, I could engage either fork. With a screw driver I repositioned the fork and shifting worked for about another 2 dozen shifts (under moderate driving) and then I lost it again.

I also think that the transmission also has bad 1st synchro problem (I can only get it in 1st when the car is at full stop by passing the transmission through 2nd gear first.)
It also occassionally hammers out of 2nd or 3rd during hard up shifts (under hard acceleration).

Note that this 915 is trying to handle a 400+HP turbo motor (both 915 and motor have only 30kMiles). My first diagnosis is the gearbox is toast but I am worried that some of these problems could be also something else such as linkage problems and clutch adjustments.(The clutch has approx 2k miles on it).

I have the same turbo (400+hp) with 915 setup. I don't have the same problems as yours though. Mine shifts fine as long as I don't slam it in gear. The shop guys say as long as I'm smooth it should be fine.
One note, I've just modified the engine so it only has a few thousand miles with 400+hp, the other 30k were stock turbo power.

BTW, I checked on converting to a G50, it is big bucks.
Good luck,
Chuck

... actually the last lock up occured under casual driving. I was upshifting and accidently put it in fifth from 2nd. I will admit that I have not a lot of experience with this car but it is possible that whilst getting in 'tune' with the car I have finished the transmission. For instance I was occassionally had trouble such as finding 1st instead of 3rd even under casual driving. But now, I suspect that the linkage, and/or the shift forks need attention. The chassis has over 130k on it and maybe shift bushings etc need work too. Any Ideas?