[chuckies76ta]

I need some info on a mod that is done on page 129 in your book GM turbo 400. In pic 7 it says to drive a steel check ball in bottom of the accumulator bore.

I'm wondering if this will firm up the 1-2 shift?

I have a Hughes Reverse manual valve body ( no trans brake) which has a very soft 1-2 shift. It's very annoying. I traced the circuit on the valve body and the separator plate for the intermediate circuit and it has a 1/8 hole that is open to this accumulator. I'm thinking this is what is causing my 1-2 soft upshift.

I tried increasing pump pressure from 160 -180 psi with a new spring from Hughes with no results. still shifted the same.

Thanks for an help.

[Half-Inch Stud]

Hmmm, i'd provide advice but i'm not familiar with Cliffs book, nor the advice to drive a steel checkball into accum bore.

If you are talking about the 2-3 acuum: Case leave stock. Valvebody remove big "valvespring" and toss it away, then flip puck and re-install puck and E-clip as it cannot stroke up-down anymore. Might have to grind 3 Cast feet flat off piston bottom so it can go in all the way. Firm 1-2 right there. Well reuse only 3 checkball in the Separator plate; the 3 that form a fairly straight line down the middle of the Case.

2-3 shift improvement involves a few steps in seal removals. And pluggin a weep hole in The sep plate.

[chuckies76ta]

Thanks for the advise. My Hughes FMRVB doesn't use any check balls. I had it out today and it seemed somewhat better. I'm having an issue with a worn out detent selector which has also cause problems with shifting. Changing out tomorrow will see how it performs.

This is what I'm chasing. Someone posted this on another form about 1-2 soft upshift.
Most TH400 manual and tranbrake units create this problem in my opinion.
When the shift to second gear occurs, second gear oil has to fill the 1-2 accumulator circuit which is a rather large void.The filling of the area under the low/reverse band servo slows the 1-2 shift.
I modify this circuit on high horsepower applications to eliminate this problem.
There some tranbrake valve bodies out there which have already fixed this problem.

[Half-Inch Stud]

Well, i assumed a factory iron VB and missed the Hughes FMRVB read. Yea, My advice was Not applicable for your deal.

[chuckies76ta]

Ya I realized that, but Thank you for you post.