Quick Shift

Discussion in 'The "Juice Box"' started by IlliniGSX, Jul 31, 2018.

  1. IlliniGSX

    IlliniGSX GSX #401

    I have a 70 GSX, it has a strong Stage 1 engine built by Mike Phillips and it has a freshly rebuilt TH 400 with a 1700 stall converter. My problem is at full throttle it shifts out of second gear almost as soon as it shifts into second gear really slowing the car down. What is wrong and how do I fix it. I am guessing the governor springs from what I have read.

    Thanks Jim

    BRUCE ROE Well-Known Member

    I have had such issues with Buick TH400s, fixed them by modifying the governor as
    has been described may times. I see modulator adjustments as more for shift
    harshness. Bruce Roe
  3. Ken Warner

    Ken Warner Stand-up Philosopher

    Curious how this plays out. I was always told the governor impacts WOT shift points. The hand full of TH400s I've dealt with through the years including my old one would roll right into 3rd gear crossing an intersection. Even with a red stripe modulator most engines with a cam of any sort are low enough on vacuum that they just shift prematurely.
  4. Jim Weise

    Jim Weise EFI/DIS 482

    Lighten the outer weight on the governor to extend your part throttle upshifts. The Stage 1 BB trans governor had 1 42 gram outer weight and 1 43 gram outer, with 9 and 10 gram inner weights.

    I recently fixed this issue in a local guy's 71 Stage 1, it would be in 3rd gear in an intersection just about. All I did was take one gram off the outer weights, it had a big car governor in it, with 44g outer weights.

    Outer weights work with the modulator and shift valve springs for part throttle upshifts, the inner weights control the WOT shift timing, in conjunction with detent pressure.

    Playing with the springs between the inner and outer weights will help you get the 1-2 and 2-3 shifts to happen at or near the same rpm, under WOT.

    The modulator adjustment is more about matching shifts to load, so it shifts just at the right time, there is not a lot of adjustment available there.. couple hundred rpm at the most.. have to get the governor right first.

    matt68gs400 and Bigpig455 like this.
  5. IlliniGSX

    IlliniGSX GSX #401

    Thanks for the feedback. Is this something most transmission shops can tackle? I have never worked on a transmission so I do not think I will attempt working on the governor.

    Thanks Again
  6. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    This is the kit I use.


    It takes some trial and error, and road testing:) not sure you want a trans shop guy driving your car like that:D. The governor is easy to remove, it is behind the square cover held on by 4 bolts, passenger side of the transmission. You lose a small amount of fluid with each try. The stock governor uses axles with flattened ends, you clip them off. The kit comes with replacement axles that use small E clips. That way, it is easy to disassemble the governor to change weights. The fun part is road testing. You need to make a full throttle 1-2 shift and observe the results. Change 1 weight at a time and evaluate the results. The weights get you in the ball park, the springs bring the 1-2, and 2-3 shifts closer together or further apart. I have found the best way to check the 2-3 shift is to get up on a highway with less traffic. (early morning or late night). Nail it at 60 MPH, it should downshift to 2nd, then wait for the full throttle upshift.
    Last edited: Aug 1, 2018
  7. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    There is also this way. You lighten the inner weights by grinding on them. Only problem is you can't go back if you go too far.:)

    matt68gs400 likes this.

    BRUCE ROE Well-Known Member

    It takes me days of trial and error to get it right. Best to learn to do it
    yourself. Keep good records of each mod, so you don't forget where and
    how you got there. I put the original governor aside and grind on a spare.
    Bruce Roe
  9. TexasT

    TexasT Texas, where are you from

    Can if you have a welder.
  10. 72STAGE1

    72STAGE1 Runnin' with the Devil

    IMO if your motor is BUILT over stock you need more stall also, a 2500 stall would help the BO tremendously, 1700 is stock and pretty low.
  11. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    Ahhh, OK.:D:D
  12. TexasT

    TexasT Texas, where are you from

    When you push the envelope, it helps to have industrial tape in case it rips. And yes the 2004r is not easy to get it to shift where you want either. And the gov isn't near as convenient.
    I am excited to try a TH400 overhaul but I have some other projects ahead of that.
  13. IlliniGSX

    IlliniGSX GSX #401

    Adjusting the shift point may be a fun learning experience. At what rpm would I want the shift to occur, 5000? Will changing the shift point from 2 to 3 affect the 1 to 2 shift point also? The booklet I got from Mike when he built the engine says the power band is 3600 to 5100 with a 5500 red line.
    Thanks Jim
  14. Bens99gtp

    Bens99gtp Well-Known Member

    Make sure the actual valve that moves when the weights do isn't stuck, when you pull the gov and sit in on the table with the gear up look through the slots you will see a valve inside there......squeeze the weights in valve should drop, pull the out valve should rise.........if the valve is stuck up it will not matter what you do to the gov.

    Up shifts occur in transmissions when gov overcomes throttle pressure.
    Also make sure your throttle valve isn't stuck either.

    Normally in vehicles with less vacuum......aka built motors with bigger cams......because of the lower vacuum normally shifts are later.........low manifold vacuum doesn't pull on the modulator diaphragm as much causing later part/light throttle shift..

    They make adjustable modulators but this is normally used to get higher wot shifts too.......by turn the adjustment in you are preloading the spring in the modulator more making gov pressure have to go higher to push on the other side of the shift valve more b4 it can move it.

    If you can find one the gov from the transmission behind the 90s as pickup trucks had some of the lightest weights gm ever used. Those trucks had a real issue with stack shifting......when it goes right through the gears too fast.

    On normal light throttle driving you should want the 1-2 shift about 15mph and the 2-3 near 30mph.

    Jim nice to know those weights, I have never measured them b4 just ground weights down to get the part throttle shift where I wanted then used the modulator to help control wot.

    Yet another case where 1 gram matter alot
  15. Bigpig455

    Bigpig455 Fastest of the slow....

    Years ago I wrote up a recipe for a 5300 RPM TH400 governor, it should be on here somewhere. I looked all over the internet for what was working for other people, took the best of each and compared against a stock BB Stage 1 governor. The big mistake people make is using total weight to measure by as opposed to nose weight..
    matt68gs400 likes this.
  16. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    The stock 70 Stage 1 shifted out of 1st at WOT at around 5300. I would aim for that. Change 1 weight at a time and evaluate.
    72STAGE1 likes this.
  17. johnriv67

    johnriv67 Well-Known Member

    Very helpful....
  18. matt68gs400

    matt68gs400 Well-Known Member

    Does anyone sell just springs? I don't mind messing around with $5 worth of springs and grinding some inner weights. $80 for a kit when you need $5 in springs is a little steep.
  19. IlliniGSX

    IlliniGSX GSX #401

    Guys, I am getting ready to adjust the governor and found a weight a spring kit for $46 on Ebay. It is branded Shift Technology Products but appears to be the same components as the BM kit. Any one use one of these? Also I have a spare governor out of a Electra 225 transmission. So I would like to make a change in it before installation any suggestions on a weight and spring combination that will get my shift point close to 5300 or at least to a good starting point. The car is a 70 GSX, original transmission with a 1700 rpm stall converter and a almost stock 455 Stage 1 that made 410 hp and 515 ft lb of torque.
  20. matt68gs400

    matt68gs400 Well-Known Member

    What does it shift at now?

    Just grind the Outer corners off the weights, maybe a triangle about a 1/4” or less on each side. Start small. Be patient. You get too aggressive and you’re screwed.

    There’s no one size fits all. I used Rhett’s combo and mine shifted too high.

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