84 d150. S/6 833 od. Think I need to replace my harmonic balancer. Napa and rockauto list for an automatic but not manual transmssion. Is there actually a difference here? My timing seems to be moving, distributor hold down tight. Either this or timing chain jumped. Suggestions/advice would be appreciated.

for a replacement damper check out Damper Dudes,, they may have one in stock or will rebuild your existing unit.
Automatic or manual transmission will have no effect on the damper.

https://www.damperdudes.net/

Concerning your timing moving,, is the Lean Burn still controlling the ignition on your 84 D150?
Once I changed my 83 D150 over to a HEI ignition the timing stayed steady.
With the Lean Burn the timing mark would move several degrees at idle.
However if the timing chain has never been changed out, that too would be suspect

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Doo Ron Ron and the Duke of Earl are friends of mine.....
https://www.youtube.com/watch?v=uX8Nj8ABEI8

Lean burn already deleted, gm hei installed. I thought the dampers would be the same, not sure why the parts list don’t show manual transmission. Thanks

I have purchased from both of those vendors, they do OK,
however as in the history of the slant six the timing marker on the timing chain cover has moved
from side to side to side over the years, I would do a careful inspection - comparison of the relationship of the
damper keyway to the damper timing mark if I was doing anything other than having my OE damper rebuilt.
Even if I was having my OE damper rebuilt I would mark it to be sure that I was getting my OE part back and even then I would verify TDC
with the rebuilt damper,,but that's just me.

_________________
Doo Ron Ron and the Duke of Earl are friends of mine.....
https://www.youtube.com/watch?v=uX8Nj8ABEI8

Your chain is most likely sloppy as well if it's still the original chain and the engine has over say 30,000 Miles on it.


Greg

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http://www.youtube.com/hyperpack