I have a 69 with ST300 2-speed auto.
Only when slowing to a stop, I can hear and feel a "clunk" in the drivetrain at <5mph.
Otherwise shifts and drives perfectly.
?U-joint or motor mount if problem only when slowing to a stop
?the tranny itself
Any help appreciated before I take to mechanic for $$$.
Thanks

Thats the case of beer in the trunk hitting the back of the seat...

now why didn't i think of that?

You sure it's drivetrain? Could be suspension. A bad lower control arm bushing will do that.

Eyeballs settling back into place after the lightning starts?

wouldn't i experience the clunk going over bumps or at other times if control arm bushing?
this occurs ONLY when slowing to a stop and can hear and feel

Cant be that, it's behind the passenger seat within easy reach

Seriously, when the trans down shifts?
Not on up shifts?
My 1st one did that back in the 70's.
Couldnt here or feel on accelleration do to 2.5" pipes going thru the gutted side pipes
Thought it was trans or ujoint.
Found rear joint worn, so replaced it.
Now i'm go'n from beer gut memory as Fbody69 says...it helped, but still had a clunk.
Wanting to go faster, installed a TH350 and 12 bolt rear.
Clunk was gone.
My buddy put the ST300 in his car, and claimed no clunk.
Decided to look at the case/ring & pinion before selling the 10 bolt.
Turned out to the pinion shaft had egg shaped the case, and was moving back and forth.
Any way, that's what i think caused mine.

I had a washed out passenger side lower control arm bushing that made a clunk only when I put the brakes on usually under 5 mph. Your description reminded me of it. A quick check; Turn your steering wheel all the way until it hits the 'stops'. Watch the front wheel on the side you are turning into. Left side for left turn. If you have a bad lower bushing the wheel will take a funny tilt right at the end of the travel. Try that in both directions. The steering pushing up against the stops puts enough pressure on the control arm to shift it if the bushing is worn out. It's easy to check if you have a helper to turn the steering wheel for you.

will check, thanks

I'd check the rear axle, our '02 Ram does the same thing, had the rear end rebuilt 30K miles ago (at 30K) and it's back.

I serched for that clunk for a year. Found it to be a loose subframe bolt!

My buddy's '05 Trailblazer did that and he was told it was the pinion gear.

Could be that too.
If the ring & pinion back lash isnt correct, it will make a clunk sound when letting of the gas pedal.