Voodoo Pops

I have a '78 911SC. The engine & trans sat in the mechanic's shop for about 4 years while the car was being re-painted, etc. (a very long story). There was no noise in the trans originally but now that the car's back together, there's a very noticeable and loud rattle in the trans. I only hear in 1st thru 4th (not 5th & reverse). It doesn't change frequency with RPM but seems a little louder at low RPM. The car runs and shifts just fine. I don't hear it when I'm idling. The mechanic (who's done very good work on the car for years) thought that perhaps there was some slight corrosion or some gunk from the trans fluid because of it sitting so long and that perhaps something wasn't disengaging 100%. He thought I should run it a while to see if it works itself out before tearing down the trans. I trust him, but it seemed to be a new one on him.

Any thoughts or advice?

Thanks from a newbie to the list.

Howard

First, you should get a new mechanic !
I had a similar noise which only occurred at idle with the clutch released, with the clutch depressed the noise would disappear, it turned out to be a bad throwout bearing. Your problem sounds to be associated with the gearbox itself since it only surfaces in gears 2,3,4, but it's only a guess. It seems that it has to be the pinion or input shaft and any "clunking noise" can't be a good thing in the gearbox. As you increase speed does the noise increase as well? Do you hear the noise with the clutch engaged ?
More info would help !