1970s THM 425 Question

[bcroe]

What are you actually adjusting in the aftermarket modulators?  I was thinking it was basically response time, not travel.

The Vac mod does not have delay.  But turning an
after market screw in (clockwise) will cause the
shift to be raised to a higher speed, and it will
be harsher.  I find they take a lot of turns, one
of mine has 7 turns.  1/2 turn will probably not
be noticeable. 

Because I do not like harsh shifts, I tend to
adjust the vac mod to the harshness I want, then
change weights/springs on the governor to get the
shift speed I want.  My switch pitch trans in high
stall helps smoothness too.  Bruce Roe

[Big Fins]

Revisiting this one...

The OEM modulator valve does not have any adjustment as shown in the FSM. It's just a flat face on the outboard end. I did however replace the little rubber section of hose from the steel line to the carburetor and at the carburetor itself.

While not fully in spec, it is a lot better. The original rubber lines were cracking and I guess, leaking.

I like it when little projects make a difference.

[TJ Hopland]

Same thing up at the carb so may be worth a look at that end too to make sure its making a good connection. 

[Big Fins]

Same thing up at the carb so may be worth a look at that end too to make sure its making a good connection. 

I corrected that as needed too.