TH400 shift hesitation

I have a TH400 with a B&M transpak shift kit and B&M megashifter. The problem I am having is when I ratchet to the next gear there is a delay before it actually shifts. This is affecting drag race consistency. I have 150 psi line pressure. Fluid level good.
One thing that I thought could be affecting it is the all rubber vac line to the modulator. Could the flex create a delay?
Also I am not certain if I have the electric kickdown working properly. I was hoping someone could shed some light on how this works/what it does and how to set it up properly. Switching to a different carb made the pedal stroke different.
Another thing I have heard and am going to check is that the shift linkage could need adjusting. It could be in between gears or something.

I have a TH400 with a B&M transpak shift kit and B&M megashifter. The problem I am having is when I ratchet to the next gear there is a delay before it actually shifts. This is affecting drag race consistency. I have 150 psi line pressure. Fluid level good.
One thing that I thought could be affecting it is the all rubber vac line to the modulator. Could the flex create a delay?
Also I am not certain if I have the electric kickdown working properly. I was hoping someone could shed some light on how this works/what it does and how to set it up properly. Switching to a different carb made the pedal stroke different.
Another thing I have heard and am going to check is that the shift linkage could need adjusting. It could be in between gears or something.

Welcome to AF.

The electric kick down is only for passing gear.

Unshift is modulator vacuum controlled.
On a normal take off what is unshift speeds?

Also get good engine vacuum to modulator valve .
They make a adjustable modulator valve for fine tuning shifting.
They also like clean good filters.
Check and change transmission filter with a pan drop.
MT

Thanks for responding.
I have the adjustable modulator.
On normal take-offs the upshifts seem at normal speeds. The speedo isn't right so I don't know for sure what they are at. Both at slow and high speeds there is a delay when manually shifted. The filter and fluid are new.
Is it possible that when i shift, the governor isn't letting it happen, and then it happens right after. Do you think the rubber line would affect how fast the modulator reacts? I have about 10'' vacuum at idle.
It seems the kickdown can be ruled out on this.

Thanks for responding.
I have the adjustable modulator.
On normal take-offs the upshifts seem at normal speeds. The speedo isn't right so I don't know for sure what they are at. Both at slow and high speeds there is a delay when manually shifted. The filter and fluid are new.
Is it possible that when i shift, the governor isn't letting it happen, and then it happens right after. Do you think the rubber line would affect how fast the modulator reacts? I have about 10'' vacuum at idle.
It seems the kickdown can be ruled out on this.

No on the rubber as long as it is good vacuum hose.
No on governor as long as up shifts are at right speed and upshifts.
But that is way vacuum to low.
Are you hooked direct in to engine vacuum or carb?
Gas engine?

Chevy 454 with 10'' from hole on intake runner. Idles rough from cam.
Is this too low for it to work? How can it shift by itself if it is too low?

Low vacuum will affect the shifting but not keep it from shifting .
Just will not shift good or right and may cause transmission wear from low pressure.

But the main problem with low vacuum is the engine will not run right and if engine is not running right the transmission will not shift right.

If you get the engine vacuum up to par it should work better.
Good luck
MT