69 stock TH400 still shifts pretty soft

Yes I agree I should leave well enough alone. Thanks for all your input.

Three.

 

3 checks balls in those locations should have worked. You could try adding a 2nd c style washer under the pressure spring located in the front pump which is accessible after removing the pan.

 

I wouldn't raise line pressure first without knowing it.......its just as easy to put a higher pressure spring in rather than shim it. But too high of pressure in early units with steel sealing sleeves causes them to cut into the bores they are ment to seal.

And in honesty a stk pressure trans can shift pretty damn hard.......so if your needing to add those bandaid just to get back to.normal it means there is still an issue somewhere

 

Would adding a percentage of f type fluid to try to make it "grippier" be a good idea?

 

One of the things affecting shift hardness is the vacuum modulator.
The after market unit you have has a tiny screw where the hose goes
on, turning it in increases hardness. It might take half a dozen turns
to make a real difference, I experiment and write down the changes
till I get it right. good luck, Bruce Roe

 

Thanks. I have done some adjustments but I believe from reading the modulator affects part throttle shifts only, not wot. Wot is what I am striving to firm up a bit. I have tightened screw two turns and it slightly firmed part throttle shifts...... I am going to loosen screw 2 turns on my GS to soften part throttle shifts and will report results.

 

Yes I'm sure. I rode with to pick it up from the dealership in 1969. My grandmother gave it to me before she passed. Lots of memories in it.

 

try something very simple, adjust the transmission modulator, start with one full turn on the adjustment screw. Use a very small screw driver make one turn, it will firm up the shifts, if that doesn't work, put another turn in. My first to second is soft and quick, like 6 mph quick, put in one turn, it helped. I plan on putting another in to it.

 

I have a 69 PS Pontiac 350 HO TH400, has all those mods and more and you cant feel a thing. It does chirp 2nd gear from outside the car but you'd never know inside. I have a KB TH400 in my 73 that bangs every gear including reverse, and that gets old quick. They say the best TH400 is the one you forget all about, so I'd be happy with what you got

 

Make sure kickdown is working. It has a noticeable effect on full throttle shift firmness since it increases line pressure.