MY GN's Transmission is Acting Stupid. Suggestions?

Discussion in 'The "Juice Box"' started by 2manybuicks, Oct 13, 2021.

  1. 2manybuicks

    2manybuicks Founders Club Member

    Original owner car, as close to bone stock as I can keep it. The transmission was never out until a year ago when I had it rebuilt by a local shop of good repute.

    After a year it developed the following problems:
    -- Up-shifts into overdrive at about 15 mph.
    -- Down shifts out of overdrive at about the same speed, maybe lower.

    So it is fine on the highway, but completely undrivable around town.

    It is the correct original numbers-matching transmission. Dropped the pan and verified that it has the original GN valve body. Did not check the governor yet but doubt it got swapped -- tranny shop said the original valve body and governor were retained.

    Tranny shop had no ideas, plus out of warranty. They finally gave up.

    Another tranny shop messed with it. My mechanic paid them, but they could never solve it either and finally gave him his money back and told him to never come back. At least not with my car.

    The speedo reads low; guy at a speedo shop says it is just fine.

  2. brucer

    brucer Well-Known Member

    Pressure switches? 4th gear pressure switch affects OD engagement.
    Last edited: Oct 13, 2021
  3. breakinbuick11

    breakinbuick11 Platinum Level Contributor

    I’m not of much help to diagnose, but curious if the trans still does the same thing in just “drive”?
  4. TexasT

    TexasT Texas, where are you from

    What did you do to verify the unit was the brf vb?
    How is the tv cable adjusted? Should be tight at wot(do this with the engine off).
    Might need to drop pan to verify that the tv is fully applied at wot.
    Hopefully this "reputable" shop didn't fool with that vb but from the symptoms it might have been pulled apart and got some springs or other parts mixed up. Was there a "shift kit" or anything like that installed?
  5. 2manybuicks

    2manybuicks Founders Club Member

    BRF trans should have a valve body with a purple stripe. It does indeed have a purple stripe.

    Shift kit issue worries me.

    F'd upped reassembly? Dunno.
  6. Matt Knutson

    Matt Knutson Well-Known Member

    I don't have answers about your transmission, but, what sort of shop "gives up" on trouble shooting a problem?

    You may want to locate a "real" transmission shop and have it gone thru again - if the easy external adjustments can't or won't remedy the issue.
    1973gs and sean Buick 76 like this.
  7. 2manybuicks

    2manybuicks Founders Club Member

    Dude, they are both real transmission shops. I guess they finally decided it wasn't the transmission and that they had done all they could. Heck, the GN specialist I know even says he can't help me and has no real ideas.

    Speedo guy says he can build a transducer setup of some sort -- says he has done it twice before. Sounds nutty to me.
  8. 436'd Skylark

    436'd Skylark Sweet Fancy Moses!!!!!

    Well there is no computer input to the 200 4r besides the locking converter. So that leaves the transmission as the problem. If you think the converter might be locking or unlocking sporadically simply unplug it to rule it out. The trans will shift the same with it unplugged..
    Mark Demko likes this.
  9. Jim Weise

    Jim Weise EFI/DIS 482


    So I gather from what your saying, it worked fine after the rebuild, but this issue just cropped up.. how much has it been driven, between the time of rebuild, and the start of the problem.

    When you say it's in OD at 15mph, do you mean it's actually shifted 3 times? Or are we dealing with a converter clutch that is locking up in second gear, which can happen in the 200.. Lock the converter clutch up in second, and ya, it's undriveable at low speeds around town, that's for sure.

    If your unsure of the above.. then take the car out, and shift it manually.. if the converter is locking up when it goes into second gear, then you have a wiring issue, or a 4th gear switch failure. Most likely a wiring issue...

    Your next step in the diagnosis would be to unplug the connector on the side of the trans.. see if it now drives normally, other than no converter lockup..

    I would assume that any professional trans technician would have done this right away, in the initial test drive .. but you never know, there are a lot a folks out there masquerading as professionals these days.

    That's the start here..

    Now if it shifts from 1st to 4th, then you have a valve body issue.. 2/3 and 3/4 shift valves are stuck in the upshifted position.. this would be unusual, but possible.

    Report back after a manual shifting test drive.

    David Cooke, 1973gs and timesublime like this.
  10. sean Buick 76

    sean Buick 76 Buick Nut Staff Member

    I would check the line pressures. The TV cable would be the first place I looked on the 200
  11. gsgns4me

    gsgns4me Well-Known Member

    As far as the speedo goes, I have seen the plastic gears "apple core". Worn enough to cause problems, but not enough to keep the speedo from getting some input.
  12. Mark Demko

    Mark Demko Well-Known Member

    I say its the TCC solenoid
    Every issue you describe, short shifting, 1 2 3 lockup chug chug chug points to a bad TCC solenoid.
    Coming to a stop does the engine lug down then recover like a manual trans pushing the clutch pedal in right before you come to a stop?
    Plus you said it was fine for a year, and it just started doing this.
    Also a bad TCC solenoid usually waits till the trans is hot.
  13. 2manybuicks

    2manybuicks Founders Club Member

    I got a little more info, and it turns out
    Matt was evidently close to the mark with this comment.

    Talking w my mechanic, and he clarified just what happened:

    My mechanic took it the 2nd transmission shop, and they were having trouble with it. Well, my mechanic knew someone who was very familiar with GNs and put him in touch with the shop. Dunno what happened, who said what, but the GN guy explaining much of what Jim Weise posted must have been too much for the trans shop guy, because the next day is when he gave my mechanic his money back and told him to go away...

    Proceeding next week according to comments received. Thanks to all who chimed in.
    Mark Demko likes this.
  14. 436'd Skylark

    436'd Skylark Sweet Fancy Moses!!!!!

    It's easy to diagnose the clutch- there is a plug going into the trans near the pan rail. It's a 3 or 4 wire square plug, simply unplug it and go for a ride. It'll take 5 minutes to do. Report back!
  15. Mark Demko

    Mark Demko Well-Known Member

    OMG, sounds like a bunch of women who love drama:p:p:p
    Just do what Joe above said;)

Share This Page