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Thread: Line pressure mod in valve body and theory

  1. #1
    Mitsu booster
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    Line pressure mod in valve body and theory

    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
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  2. #2
    Garrett booster
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    Re: Line pressure mod in valve body and theory

    NICE!!!!

    My trans pegs the pressure gauge in reverse with it's monster regulator spring!

  3. #3
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    Re: Line pressure mod in valve body and theory

    I should upload pics of my broken case at the reverse anchor. I use a heavy spring though. (I don't drill bleeds) It had 400 psi in reverse at 1500 rpm. Now I delete reverse boost so my sensitive cases don't blow apart there.... (has 150 in reverse now same rpm) I was very lucky it broke in my driveway! LMK if anyone wants pics........

  4. #4
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    Unhappy Re: Line pressure mod in valve body and theory

    Chad,

    Did the mod, drilled a 1/16 hole exactly as described. Did part of another mod where you said to trim the kickdown valve slightly, did not change TV spring. (I think this was to raise throttle sensitivity? I can't remember at the moment.) I am not yet sure which change created a problem.

    I have run the homeade shift kit ( block accumulator, shuttle valve, drill seperator plate, etc) for many years. I also had the line pressure screw raised as far as it would go and shimmed. It shifted ok but I was hoping to firm up slightly more.

    I have low throttle pressure, cannot shorten cable enough to get kickdown or get rid of mushy shifts. From years of driving same car I can feel when the TV pressure is low in my throttle pedal. It is definately lower than before. Also flares bad 2-3, it never did this until I did the mod. I even went in and reshimmed my line pressure spring like I had before, and is not really any better. Shift points are lower too, so I think line pressure is the culprit. Have not had time to check the line pressure, is hard to do with accumulator blocked. Did double check that TV lever was pressing on throttle valve, is OK.

    This is in a neon with a turbo, (300 torque at wheels) late style valve body w/lockup. 3.02 Final drive. Fresh, OEM, clutches and bands, took trans apart to be sure were OK. All looked good. Clutch packs are set to tight end of spec, bands 2 turns or so.


    Any more suggestions? I am going in to plug the bleed and swap out the throttle valve.

  5. #5

    Re: Line pressure mod in valve body and theory

    thanks Chad, now I don't have to go out and find a spring. this info is priceless

  6. #6
    Mitsu booster
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    Re: Line pressure mod in valve body and theory

    Quote Originally Posted by neonturbo View Post
    Chad,

    Did the mod, drilled a 1/16 hole exactly as described. Did part of another mod where you said to trim the kickdown valve slightly, did not change TV spring. (I think this was to raise throttle sensitivity? I can't remember at the moment.) I am not yet sure which change created a problem.

    I have run the homeade shift kit ( block accumulator, shuttle valve, drill seperator plate, etc) for many years. I also had the line pressure screw raised as far as it would go and shimmed. It shifted ok but I was hoping to firm up slightly more.

    I have low throttle pressure, cannot shorten cable enough to get kickdown or get rid of mushy shifts. From years of driving same car I can feel when the TV pressure is low in my throttle pedal. It is definately lower than before. Also flares bad 2-3, it never did this until I did the mod. I even went in and reshimmed my line pressure spring like I had before, and is not really any better. Shift points are lower too, so I think line pressure is the culprit. Have not had time to check the line pressure, is hard to do with accumulator blocked. Did double check that TV lever was pressing on throttle valve, is OK.

    This is in a neon with a turbo, (300 torque at wheels) late style valve body w/lockup. 3.02 Final drive. Fresh, OEM, clutches and bands, took trans apart to be sure were OK. All looked good. Clutch packs are set to tight end of spec, bands 2 turns or so.


    Any more suggestions? I am going in to plug the bleed and swap out the throttle valve.
    I believe the only mod I ever mentioned about grinding the kickdown valve would have been an experimental mod that I haven't had time to play with. It's a mod to modify the kickdown and throttle valve (and spring too) so you can crank line pressure as high as you want but not have it raise WOT shift points. This would be of course with an automatic shifting vb and the governor in place.
    Grinding the "butts" of the kickdown and/or throttle valve will only affect WOT shift points (and only if you grind enough off). You'd have to change the TV spring to mess with regular shift points.

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    Chad Kilback "Kil-time Tranny Tuning" ckilback3@nucleus.com
    -----------------------------------------------------------------------
    Calgary, Alberta SDAC
    88 Daytona Shelby "Zedd" Yeah, It's got a transbrake
    12.43 @ 111 quickest time
    12.6 @ 113.00 fastest time
    87 New Yorker "Norker Zedd" 2.5L TII 14.6 @ 93
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  7. #7
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    Re: Line pressure mod in valve body and theory

    hey chad, you going to mopars in vernon this year? (i know, a bit off topic)

  8. #8
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    Re: Line pressure mod in valve body and theory

    I will try this one day if I ever have a running TM again.
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  9. #9
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    Re: Line pressure mod in valve body and theory

    Just want to say that I have a RMVB from Chad(Thanks again) and I think I turned the screw a turn before install(It has a small bleed hole in it). I check the pressure in 2nd gear yesterday and it was ~150psi(idle) and spiked to ~170psi(when reved to ~2000rpms)). I shut it off and turned it 3-4 turns and was ~120idle and ~140 reved.

    Now I'm not sure exactly how long it would hold up at those pressures Last I knew Rob was running ~140 prob when reved up. I also read that SMP ran 150-155psi.

    Whats the acceptable limit for wear and tear on seals/bands/servos ect.?
    Mine was built by myself, 1st time opening a tranny, but did lots of research and mods. Everything works great and 3rd gear hits hard
    Last edited by Speedeuphoria; 06-10-2007 at 07:40 AM.

  10. #10
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    Re: Line pressure mod in valve body and theory

    Bump for some info

    Is this pic of the VB the same for the older TA rmvb's. Not sure what all was changed. This would be for someone who allready had a TA and wants to do this mod.

  11. #11
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    Re: Line pressure mod in valve body and theory

    Would this work well with the "drill 2 holes bigger and leave 1 ball out" mods as the only mods on an A670. Just wanna get shifts firmed up a bit. (I've got no concept of which mods go together and which are independant)

  12. #12
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    Re: Line pressure mod in valve body and theory

    Okay, any ballpark estimate of where pressure should be if I do a 1/16 hole and leave adjuster set in stock position?? Or alternatively, what's the ballpark starting point for the adjuster being all the way out?

    1/16 be the smallest bit I can get my hands on conveniently.

  13. #13
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    Re: Line pressure mod in valve body and theory

    Okay, gave it the "full monty" today, drilled the plate, left the one ball out, shimmed the shuttle and bypass valves, blocked the accumulator and put a 1/16 hole where indicated, wound out the spring all the way on the regulator, hoping that just makes it about 15-20 over stock or something, didn't want it too harsh or my wife will complain. Hoping for vrooom-tuk-vrooom shifts not vroom-BANG-vroom, previously it was vrooom-blehharghshudder-vrooom.

  14. #14
    Moderator Turbo Mopar Staff Vigo's Avatar
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    Re: Line pressure mod in valve body and theory

    ^ update us on that asap, im curious to see how it turns out.

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    Re: Line pressure mod in valve body and theory

    Let us know what you find. I might play around with this after the van gets going,
    1989 FWD Turbo Caravan-2.5 TIII, GT35R, auto, a/c, cruise, pwr windows/locks, fully loaded with interior and ran with full exhaust. RETIRED FOR A FEW YEARS! 12.57@104 :O)
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  16. #16
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    Re: Line pressure mod in valve body and theory

    the older vb's(like the TA) are a little different than the newer ones that the pics are from. The place where this hole goes, the passages are a little different shaped, but should work the same.

    On another note, Carl's(aka dbltrbl) site has been updated w/ new springs for higher line pressure.

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    Re: Line pressure mod in valve body and theory

    Quote Originally Posted by Speedeuphoria View Post

    On another note, Carl's(aka dbltrbl) site has been updated w/ new springs for higher line pressure.
    I am using one out of a Gil Youngers 727 kit and maybe thats why I kept breaking the lo/reverse servo? I turned it down 2 turns and haven't blown the seal out of my billet piston again, knock on wood,
    1989 FWD Turbo Caravan-2.5 TIII, GT35R, auto, a/c, cruise, pwr windows/locks, fully loaded with interior and ran with full exhaust. RETIRED FOR A FEW YEARS! 12.57@104 :O)
    1984 Chev Getaway van, 6.2 Diesel with a remote mounted turbo setup burning WMO-For sale.
    2003 GSW 2.0L TDI, auto, fully loaded, modified, 360K-wife's.
    2004 GSW TDI, 5 speed, fully loaded, modified.

    Aurora ignition wires for sale. Link to info

    Super60 roller cams or custom/billet cams. Link to info

  18. #18
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    Re: Line pressure mod in valve body and theory

    Seems to have worked okay....

    Got her off the jack stands for the first time today. Filled tranny with 4 quarts of TDH universal tractor fluid, then that wasn't enough so had to put 2 quarts ATF in as well. Think the torque convertor must have drained 'coz she was sitting around so long. Also was into the diff an there was about a quart in there that didn't drain from the pan. Still not sure she's quite full yet, I'll check her again tomorrow.

    Went for a drive... she changed up with a bang the first time, kinda wasn't ready for it, think I lifted off, was trying to be easy on the gas pedal until I hit the open road 'coz I was laying a smoke screen. Shifts are nice and firm, not quite sure whether they are up the RPM range a bit, if so it's not by more than a hundred RPM. It took me a little while to get used to the tranny again, I only need a quick foot flick on the gas to make it change up if I want it to, rather than having to lift nearly right off. Everything seems to grab hard, no issues with any of the shifts. Don't know how much pressure I've got, blocked the accumulator so can't use that port. At a guess I'd say somewhere between 10-20% over stock, but that's about what I wanted for now. Don't have any overlap issues. Torque convertor seems to be working more efficiently (That was meant to be a benefit of the TDH too) seem to need less RPM. Get good lockup on the highway, cruising at 100kph before I needed 2800 RPM, now it only needs 2600. Kickdown works good, didn't get much chance to sensitivity test, was going 50kphish and it did kickdown to first, but changed up at 5500 as it should.

    Hmmm thinking about the upshifting, I'm not actually sure it's really later, just seems like it, shifts seem to complete at the right RPM, but don't start so soon if you catch my meaning. The shift is faster and harder, so seems like it's missed the point for the shift to start, but it just goes in, tunk, right where it usually would.

    Heh, mostly got a major feeling of relief right now I didn't screw anything up, so not so exciteable about how it's shifting. Seems like it's gonna be GREAT when I get more spirited with it, but didn't so far, 'coz I was feeling my front end out, think I need to try aligning it again.

  19. #19
    Supporting Member Turbo Mopar Contributor mock_glh's Avatar
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    Question Re: Line pressure mod in valve body and theory

    Quote Originally Posted by Torqueflite View Post
    Drill a hole in the passage marked in yellow. . . that's it. Drill it from the other side of the valve body though.
    So the casting I'm looking at gets drilled on the other side into the port that is marked in yellow?
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  20. #20
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    Re: Line pressure mod in valve body and theory

    I looked at it and thought.... "F that" and drilled out from it

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