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Thread: M5r2 major shift problems

  1. #1
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    May 2018
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    M5r2 major shift problems

    Just got a 90 SC in Feb. Put a clutch kit, master cylinder, clutch line, and slave still has terrible grind in all gears as if the transmission isn't slowing down when clutch is depressed. Personally I thing it's either syncros or blockers anyone know of anything different worth trying?

  2. #2
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    Transmission not slowing down on input when clutch is depressed? That's either the clutch bad (as in not disengaging properly; could be linkage, could be air in the hydraulics, could be needs to be shimmed, etc.), or the pilot bearing bad dragging on the input shaft.

    Not much else there.

    If all is new, my next question is, "How much did you shim the pressure plate to match the resurfaced flywheel?"

    RwP

  3. #3
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    If you're sitting still with the clutch pedal pushed in, does the car creep forward? If not, how far up does the pedal go before it starts to pull forward?
    90 5spd, best ever E.T. 12.250
    best ever 1/4mi speed 112.89 mph
    Current dyno tune 383.54 rwhp 418.88 rwt

  4. #4
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    Make sure you are getting adequate pedal and slave travel. You should feel the diaphragm overcenter about 1/2-2/3 travel down. If not, then make sure your pedal to master pushrod pin/connection isn't damaged or worn out, and if it's good and tight, then most likely you still have air in the line. Bleeding can be a bit of a pain, with 30-50 pedal presses between bleeding. Generally makes my legs (both of them) sore.

    If you have good diaphragm feel and hence appropriate travel (about 3/4" at the slave), then it's most likely a bad disc. Yes, I have gotten them bad right out of the box, but usually it's something that happens more over time. Basically a disc that is slightly warped will drag and there is nothing you can do other than throw it away and get another one.
    Quote Originally Posted by Miller View Post
    Ya thats why i tape mine down. People think its bc i dont have a moonroof seal (which is true) but its really to keep my roof from ripping off .
    Email me here.

  5. #5
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    Clutch dragging

    Or the disc is in backwards ?
    Hard to believe I know, but I
    usually see 1 a year come in to
    our shop with those symptoms
    (all makes)

  6. #6
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    Quote Originally Posted by RalphP View Post
    Transmission not slowing down on input when clutch is depressed? That's either the clutch bad (as in not disengaging properly; could be linkage, could be air in the hydraulics, could be needs to be shimmed, etc.), or the pilot bearing bad dragging on the input shaft.

    Not much else there.

    If all is new, my next question is, "How much did you shim the pressure plate to match the resurfaced flywheel?"

    RwP
    I didn't resurface the flywheel didn't see any scaring on the flywheel

  7. #7
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    Quote Originally Posted by Mike Puckett View Post
    If you're sitting still with the clutch pedal pushed in, does the car creep forward? If not, how far up does the pedal go before it starts to pull forward?
    It doesn't creep forward what soever I even lifted the rear and tried to it with no weight on the rear tires and doesn't try to turn the tires with it in any gear with clutch depressed

  8. #8
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    Quote Originally Posted by DOUG H View Post
    Or the disc is in backwards ?
    Hard to believe I know, but I
    usually see 1 a year come in to
    our shop with those symptoms
    (all makes)

    I put the disc in same way old on came out hard to explain but one side of the disc has the springs in the center that protrude further outward that side is facing the pressure plate

  9. #9
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    Also I should have mentioned that this issue was present before I replaced the clutch and everything else it was the reason why I replaced all of this trying to correct the problem

  10. #10
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    Quote Originally Posted by XR7 Dave View Post
    Bleeding can be a bit of a pain, with 30-50 pedal presses between bleeding. Generally makes my legs (both of them) sore.
    Guess I shouldn't say then that all I ever did to bleed mine was just use it.. The reason I didn't was the soft aluminum bleeder screw snapped off, so I had no good choice in the matter. I wasnt about to pull it the whole tranmission out to extract the stub. But with the slave being below the line, air bubbles just naturally went up and out over time. So it sort of just fixed itself.

  11. #11
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    Mine is grinding enough to not drive the car I fear that if the transmission isn't already shot then it would be if I drove it like it is now. My father was saying he thought it would most likely be syncros is that a possibility in my case I'm not very familiar with the inner workings of the transmission. When I shift if I do it ridiculously slow I can feel the transmission spin and slow to a stop.

  12. #12
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    Quote Originally Posted by 35th View Post
    Mine is grinding enough to not drive the car I fear that if the transmission isn't already shot then it would be if I drove it like it is now. My father was saying he thought it would most likely be syncros is that a possibility in my case I'm not very familiar with the inner workings of the transmission. When I shift if I do it ridiculously slow I can feel the transmission spin and slow to a stop.
    All gears you say? Its kind of unusual for all the "synchros" to have that occur. Usually gear 1 is the first to go, then 2 and 3. The higher gears usually don't wear so fast due to not being used so much.

    OK, so some terminology for you. The syncho in the M5r2 is a set of parts. Its a slider ring, with grooves with pointy tips, that get pushed past a blocker ring. The blocker ring is what "grabs and stops" the input shaft from spinning.. then the slider can move past it to latch onto the gear and thus.. lock it to the input shaft. The blockers are the part that the heavy work. They do wear out. If they don't engage, the slider teeth skip against the gear teeth and thats the grind. If it goes on, the teeth will get dulled and then it will always shift poorly.

    So if you're having grinding, you most likely have worn blockers, but you can also have dulled sliders and dulled gear teeth. About the only way to know is to take the top cover off and inspect them. Search for a diagram of the m5r2 inner working to see how it goes together.
    Last edited by TbirdSCFan; 05-04-2018 at 07:05 PM.

  13. #13
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    Ok. So I watched a few videos about manual transmissions in general. It seems to me that the blocker really only slows the output shaft and that the clutch disc slows the input shaft is that correct? If it is then my problem would have to be something to do with the clutch disk itself being that the car is stationary when I'm trying to shift into 1st and it still grinds. So in theory if the car isn't rolling and the clutch disk was working properly then it would still shift correctly even with worn blockers. I'm not 100% sure my way of thinking is correct but that's how I'm understanding it so far. Do you know if that's correct or false? By the way I wanted to thank everyone on here for helping me I'm sure you all have better things to do but I really appreciate it

  14. #14
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    I rebuilt an M5R2 for someone a few years ago that had been rebuilt before. They had put 90 weight gear lube in it and every blocker was half stripped of lining. Usually 1st and 4th don't look too bad but it is possible that they could all be bad. You'll need to pull it and open it up to find out. I strongly suspect that it needs blockers. And yes, I have plenty of CF sets left in stock.
    90 5spd, best ever E.T. 12.250
    best ever 1/4mi speed 112.89 mph
    Current dyno tune 383.54 rwhp 418.88 rwt

  15. #15
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    Quote Originally Posted by 35th View Post
    Ok. So I watched a few videos about manual transmissions in general. It seems to me that the blocker really only slows the output shaft and that the clutch disc slows the input shaft is that correct?
    With the clutch pedal pressed and the disc dis-engaged from both the flywheel and the pressure plate, everything associated with the disc is allowed to spin at a different rate from the crank. There can be multiple causes, or just one...

    The blocker ring is actually a 'cone clutch' - it's job is to attempt to match rotational speed of two gears, grabbing one to temporarily spin it (vs. stopping it, assuming the vehicle is in motion, where a stop of the input shaft would only happen if the vehicle was at rest, in gear with clutch pedal depressed...your complaint seems to surround while driving/in motion, so...), at the same speed as the other so the two are in sync when a shift occurs. The shafts are along for the ride. I'd not be surprised in some examples to find the input shaft in motion to some degree (slight) even with the trans in neutral, clutch pedal pressed and the vehicle at rest.

    Example video here: https://www.youtube.com/watch?v=0Bqs-oHBBQk

    But yes, as noted, I'd generally suspect blockers/synchros, and the tip about 90w being a culprit/root cause should be taken seriously, I think. Otherwise, look into bent shafts, mis-aligned case bearings, bent center plate/disc, worn input shaft where the disc slides on it, did you grease the pilot before installing, mismatched parts, etc. Was the trans allowed to hang without being bolted to the engine? Was force needed to mate it up? Was it pulled in using the bolts or was it mated up clean without a fight?

    Good luck.

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