Here's a mod that will up your line pressure beyond the max you can get out of it with the adjuster screw but without finding a new spring, buiding a spacer, etc. This will up line pressure in forward gears, but won't affect line pressure in reverse. Drill a hole in the passage marked in yellow. . . that's it. Drill it from the other side of the valve body though.

The theory of how the reg valve works and how the mod affects it:
This passage is where "one of two" of the "reaction areas" on the pressure regulator valve sit (a reaction area of a valve is the part of a valve where the oil pressure pushes on it to make it move). Oil is fed into this passage and pushes on the regulator valve. As the pressure builds up and reaches a certain pressure, the reg valve starts to move against the spring, until the valve opens up an exhaust port. This is how line pressure is created.

What does this mod do? It's easy if you think of it in turbo terms. The drilled hole is a "bleed". If you wanted to up the boost using a bleed, you'd put a restrictor in the wastegate line, and throw in a bleed valve. The hole that you drill in the valve body bleeds off some of the pressure, so *more* pressure has to build up to start moving the valve. The feed line to this passage is small enough that it can be considered a restrictor orifice.

As mentioned above, there are actually two passages and two reaction areas on the reg valve that the pressure tries to push on to move the valve. Pressure is fed to both passages (to try and move the reg valve) in all forward gears. But pressure does not get fed to this passage in reverse gear, which is why the line pressure jumps way up in reverse only, and is also why this mod won't affect the line pressure for reverse (which is a good thing).

How big of a hole to drill? I don't know exactly, as I haven't played with this mod on vb's other than my own. (I resized the feed hole (made the orifice smaller) on my mvb's so a "bleed" hole of .046" gives about 100 psi with the adjuster screw turned all the way in; and it give about 150psi at WOT). If I were to drill the bleed hole in any other valve body, I wouldn't go any bigger than a drill bit of 1/16", which is .062". This size bleed hole will probably get the pressure in the ball park of what I get. With this mod, each turn of the adjuster screw will result in a pressure change of around 5 psi (ultimately dependent on the size you go with the bleed hole). Have fun drilling, and not having to worry about finding a new spring.

Chad Kilback "Kil-time Tranny Tuning"
Now taking orders for Reverse Pattern Manual Valve Bodies and Trans-brakes
Calgary, Alberta SDAC
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