I'm about 400 miles away from home getting ready to drive this '67 1800 back with me. I put on some known-good carbs which fixed the poor running condition. I fixed the rumbly driveline (transmission mount broke). I fixed the lack of OD (wire off and 1/2 quart low on oil). Before I topped off the oil, It would do this wicked noisy jump out of third gear. Now third is OK but it won't stay in 4th, any little blip of the throttle and it pops out of gear. It's not really noisy otherwise. The car has been doing this for a while and the PO's solution was to keep his hand on the shifter in 4th.

I've got another unknown condition D-type M41 in the trunk. I don't want to change it out here. The trip is almost all highway miles for which I'd like to use a large orange bungee cord tied to the passenger seat to assure that I remain in fourth gear. So does anyone know what is worn out in there and whether that worn out part is likely to lunch my transmission somewhere in the middle of the Navajo reservation?

Thanks!

Bob in AZ.