Optimal TH400 line pressure and adjustment

[Pablo]

I have a TH400 recently built of unknown origin with a reverse manual valve body and brake. I was having issues with high cooler line pressure so I restricted the converter feed to 5/64s which seems to be a bit smaller than what most recommend. I ended up at about 55 psi dead cold and it comes down to about 40 when hot. I finally got around to checking the line pressure which I should have done in the first place and it seems to be on the high side from what I have read. In park through 4000 rpm I am between 215 - 220 psi. As I rev up the rpm range the pressure seems to drop slightly - maybe 3 to 4 psi.
I checked the fluid level and it seems to be a bit low (maybe 2 quarts). With a deep pan, could this have caused the slightly decrease in pressure?

Is it safe to say that if it was closer to 190-200 psi I would have lower cooler line pressure?
Will lowering the line pressure damage the transmission if it was built specifically to use that line pressure?

Can anyone give me a color code or dimensions of pump springs that correspond to different pressures?

The trans will be out of the car shortly and if there is anything that I can easily check to help answer these questions I will do so. The engine is coming out to do the thrust bearing, its .008 out of spec.

BTW this is for a combo that should run mid 10s reliably.

Thanks for your help

 

[turbobitt]

Sounds like it may have a stiff spring with maybe one horseshoe shim. If its like most, Use the spring with no shims and it will give you 200 psi.
Allan G.

 

[Pablo]

Thank you for the tip. Is there any color coding to these springs?

 

[turbobitt]

Stock spring is blue. Aftermarket spring can be anything.

Allan G.