New noise in transmission when put in gear!!

New noise just began this week after I changed the vacuum advance*. The noise is loud enough that it can’t be missed and sounds like metal stress in the transmission as if something is moving or wants to move and it occurs when I engage in gear (from P to R, R to D, D to R and R to P; but not when going from D to 1/2 nor back to D from 2/1). Inspected connections of the vacuum line going to transmission and looks fine, checked the shifter to transmission rod link and replaced the plastic bearing insert that was desintagrating but that made no difference. Level of transmission fluid is in spec. Anything easy I could look at before going to the expert? Thanks.

  • membrane was not as tight as before so combustible vapors were allowed to enter in the distributor (when car was stopped hot) and it was popping up on first ignition spark when restarted shortly after (say 15-30 minutes later)

Wonder if somehow the rod is hung up & not completely in. Also check to see that the one you replaced matches the new one in length & color band

Rod is fine and well adjusted. Front Ujoint had little loose, replaced but made no difference. Transmission mount is now the suspect as it appears to be cracked and rubber dammaged, will be replaced today… I hope this will solve as I miss my Cat with all the nice weather we have these days!!

Broken transmission mount was the problem, one of the 2 bolts supports was completely detached and rubber completely torn. New mount was installed today and now it’s back to normal.
The cause of failure remains unknown though… the mechanic lowered idle down to 850/500 on park/gear (from 1,000/750 before). That is sure not going to help with the stiffer PS situation that I have at lower RPM when car is hot and barely moving (such as parallel parking for instance).