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  1. #1
    Join Date
    Mar 2008
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    Denver
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    641

    Default TH400 governor mod

    Does anybody have the article on changing/ trimming the fly weights in the shift governor? I used to have it in the book with the 70 Stage 1 one the cover but I either lent the book our or lost it . Anyway, the article is about trimming the secondary weights to change the shift points. I have one that shifts at @4100 rpm now. I'd like to move it to @5100 rpm. The pictures showed how much to trim in order to get it close. Also, does anyone have a source for the correct style pins to use instead of nails from the hardware store?

  2. #2
    Join Date
    Sep 2004
    Location
    Michigan, USA
    Posts
    14,967

    Default Re: TH400 governor mod

    Fuel & Brake Systems Engineer
    "I can live with doubt and uncertainty and not knowing. I think it's much more interesting to live not knowing than to have answers which might be wrong." - Feynman
    "Good data is precious. The problem I have is when some damned fool fails to use it properly." - Slingerland

  3. #3
    Join Date
    Mar 2008
    Location
    Denver
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    641

    Default Re: TH400 governor mod

    Thanks for the help. The picture of the 5k weight is exactly what I needed. I can settle for nails.

  4. #4
    Join Date
    Sep 2004
    Location
    Michigan, USA
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    Default Re: TH400 governor mod

    Quote Originally Posted by N360LL View Post
    I can settle for nails.
    Glad to help, and that's what we all use anyway.

    Devon
    Fuel & Brake Systems Engineer
    "I can live with doubt and uncertainty and not knowing. I think it's much more interesting to live not knowing than to have answers which might be wrong." - Feynman
    "Good data is precious. The problem I have is when some damned fool fails to use it properly." - Slingerland

  5. #5
    Join Date
    Feb 2002
    Location
    Oakland Gardens, N.Y.
    Posts
    21,569

    Default Re: TH400 governor mod

    I have used the B&M kit several times. Makes changing weights and springs easy. It is time consuming testing for sure, but the results are worth it. I recommend modifying a second governor, that way you can always go back to what you had. Once you have removed material from a weight, you can't put it back. There is no absolute recipe for a certain RPM shift, all combinations will react differently. That is why I recommend the B&M kit. Before you start modifying things, make sure your kickdown is connected and functional. Without the kickdown, the trans will shortshift for that reason alone.
    Larry
    1998 "Fully Optioned" SC3800 Riviera
    70 GS 455 Stage1, TSP 470, 602 HP@ 5900, 589 TQ @ 4900
    TA Hyd Roller Cam, 230*/238*, 112, .544"/.577" lift, 4-7 swap
    MSD Digital 6+, Ignitionman Distributor w/MSD trigger
    1967 BT Switchpitch ST-400, Gear Vendors OD
    with TSP 3200/1800 converter
    AED 1000 HO Carb, 800 CFM 7042240 Quadrajet
    8.5 10 bolt, 3.73's
    11.67 @ 115.49 MPH
    Larrymta@verizon.net, GSCA #291
    BPG # 1063
    N.E. GS/GN Club Assistant Director

  6. #6
    Join Date
    Sep 2002
    Location
    atlanta
    Posts
    1,872

    Default Re: TH400 governor mod

    Larry,

    Will it short shift at WOT or just cruising? My car didn't come with the th-400 so I don't have the wiring to hook it up. Anyone know how to do that?
    Mike C.
    '66 Skylark Conv. w/455
    1/4 mile - 12.49@107.40 w/1.77 60'
    1/8 mile - 7.97 @ 89.3 w/1.76 60'
    '66 Sportwagon, You mean I still have this thing?

  7. #7
    Join Date
    Sep 2004
    Location
    Michigan, USA
    Posts
    14,967

    Default Re: TH400 governor mod

    Mike, what car? The early cars had transmission detent switched on the throttle linkage next to the carb. Later cars had the switch on the gas pedal linkage in the passenger compartment. If you try some searches here for "kickdown" or "detent" you should find what you need.

    Devon
    Fuel & Brake Systems Engineer
    "I can live with doubt and uncertainty and not knowing. I think it's much more interesting to live not knowing than to have answers which might be wrong." - Feynman
    "Good data is precious. The problem I have is when some damned fool fails to use it properly." - Slingerland

  8. #8
    Join Date
    Aug 2004
    Location
    Massachusetts
    Posts
    11,768

    Default Re: TH400 governor mod

    You need to buy a big block engine wiring harness and just plug it in on the trans. Then you need the big block gas pedal bracket and the switch that attaches to it. The under dash wiring should have the connector already there but taped up unused. Bet you did not know that. I think Mike garrison may make the gas pedal bracket or I have some used ones for sale. This is if you want it stock. well worth the effort. The biggest expense is the engine harness about $160
    Dave, Seeing Yellow
    71 GS Stage-1 Now Sold.

    Now have real 70 GSX 4 Speed QQ

  9. #9
    Join Date
    Feb 2002
    Location
    Oakland Gardens, N.Y.
    Posts
    21,569

    Default Re: TH400 governor mod

    Quote Originally Posted by msc66 View Post
    Larry,

    Will it short shift at WOT or just cruising? My car didn't come with the th-400 so I don't have the wiring to hook it up. Anyone know how to do that?
    WOT
    Larry
    1998 "Fully Optioned" SC3800 Riviera
    70 GS 455 Stage1, TSP 470, 602 HP@ 5900, 589 TQ @ 4900
    TA Hyd Roller Cam, 230*/238*, 112, .544"/.577" lift, 4-7 swap
    MSD Digital 6+, Ignitionman Distributor w/MSD trigger
    1967 BT Switchpitch ST-400, Gear Vendors OD
    with TSP 3200/1800 converter
    AED 1000 HO Carb, 800 CFM 7042240 Quadrajet
    8.5 10 bolt, 3.73's
    11.67 @ 115.49 MPH
    Larrymta@verizon.net, GSCA #291
    BPG # 1063
    N.E. GS/GN Club Assistant Director

  10. #10
    Join Date
    Mar 2008
    Location
    Denver
    Posts
    641

    Default Re: TH400 governor mod

    I did the mod and now it shifts at 4800 rpm. Much better, but now I'm not sure if I should raise the speed a bit more because I found my dyno sheets and it makes more hp and torque above the 5200 prm factory redline. My dyno sheet goes all the way to 5800 rpm. If a raise the shift point then I can put the engien back in the fat part of the torque curve on the 1-2 shift and the 2-3 shift.

  11. #11
    Join Date
    Feb 2002
    Location
    Oakland Gardens, N.Y.
    Posts
    21,569

    Default Re: TH400 governor mod

    Quote Originally Posted by N360LL View Post
    I did the mod and now it shifts at 4800 rpm. Much better, but now I'm not sure if I should raise the speed a bit more because I found my dyno sheets and it makes more hp and torque above the 5200 prm factory redline. My dyno sheet goes all the way to 5800 rpm. If a raise the shift point then I can put the engien back in the fat part of the torque curve on the 1-2 shift and the 2-3 shift.
    The stock Stage 1 shifted at 5200 RPM. Raise it. I have my 1-2 at 5500, and my 2-3 at 5400
    Larry
    1998 "Fully Optioned" SC3800 Riviera
    70 GS 455 Stage1, TSP 470, 602 HP@ 5900, 589 TQ @ 4900
    TA Hyd Roller Cam, 230*/238*, 112, .544"/.577" lift, 4-7 swap
    MSD Digital 6+, Ignitionman Distributor w/MSD trigger
    1967 BT Switchpitch ST-400, Gear Vendors OD
    with TSP 3200/1800 converter
    AED 1000 HO Carb, 800 CFM 7042240 Quadrajet
    8.5 10 bolt, 3.73's
    11.67 @ 115.49 MPH
    Larrymta@verizon.net, GSCA #291
    BPG # 1063
    N.E. GS/GN Club Assistant Director

  12. #12
    Join Date
    Sep 2004
    Location
    Michigan, USA
    Posts
    14,967

    Default Re: TH400 governor mod

    Experimentation with shift points at the track is the best way to figure this out, then modify the governor accordingly.

    Devon
    Fuel & Brake Systems Engineer
    "I can live with doubt and uncertainty and not knowing. I think it's much more interesting to live not knowing than to have answers which might be wrong." - Feynman
    "Good data is precious. The problem I have is when some damned fool fails to use it properly." - Slingerland

 

 

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