th400 1-2 accumulator secondary spring

[yevgenievich]

Was looking for number 16 spring info from the picture, but after looking at what it does I am better off leaving it out anyway

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[Matt69olds]

Leave out the spring. Use a piece of copper tubing about and inch long, drop the tube into the bore, install the valve, the bore plug, then use a punch and tap the bore plug just enough to reinstall the roll pin.

If you want to experiment with different springs, supposedly the return springs from the low/reverse piston Out of a Powerglide work well. The heavier the spring, the less influence engine vacuum will have on shift smoothness. Please notice I didn’t say shift quality! I kinda like a solid thud during shifts.

 

[yevgenievich]

Leave out the spring. Use a piece of copper tubing about and inch long, drop the tube into the bore, install the valve, the bore plug, then use a punch and tap the bore plug just enough to reinstall the roll pin.

If you want to experiment with different springs, supposedly the return springs from the low/reverse piston Out of a Powerglide work well. The heavier the spring, the less influence engine vacuum will have on shift smoothness. Please notice I didn’t say shift quality! I kinda like a solid thud during shifts.

Thanks for advice. This is going in a 4x4 on 38" tires so firmer should be better. Also blocked 3rd accumulator feed. Any other tips on making th400 last for a bit longer?

 

[Matt69olds]

I assume you have done the dual feed modification? The stock blue spring with 2 of the horseshoe shims should provide about 180psi of line pressure. Did you block the 2-3 accumulator feed hole in the valve body?

 

[yevgenievich]

I assume you have done the dual feed modification? The stock blue spring with 2 of the horseshoe shims should provide about 180psi of line pressure. Did you block the 2-3 accumulator feed hole in the valve body?

i have the 2-3 accumulator feed hole blocked. Did not do the dual feed as was thinking should not be done with original style iron seals. The basic seal kit that I bough came with thte iron seals instead of teflon seals. But everything still in pieces if fine to dual feed with everything else stock. Obviously this is my first venture in to th400. 4l60e went well, so figured th400 can't be any harder to deal with

 

[Matt69olds]

As long as your not running fixed line pressure (vacuum modulator is still hooked up and functional?) then the iron rings are fine. It’s the constant high pressure that tears up the iron sealing rings. Remove the second ring from the top of the center support, leave the seal out of the direct drum (the seals on the piston need to remain!!). Either weld closed the small hole in the spacer plate that feeds reverse (the round hole next to the center support bolt) or use a Dorman 555-003 freeze plug to block the hole in the case. Install all 16 return springs in the direct drum. Measure .410’ inch in from the outer diameter of the direct drum and drill a .060 hole. Using all 16 springs, and the small bleed hole wil prevent centrifugal apply in 1st and 2nd gear. That drum is spinning almost 2 times engine speed backwards, the tiny amount of fluid still in the drum can force the piston to apply slightly. The hole provides a release orifice.

I would assume you have a early style drum that will accept a 34 element sprag? The later roller clutch style won’t last long with the big tires!