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SM465 problem or Clutch bad?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by 4x4x454, Oct 24, 2001.

  1. 4x4x454

    4x4x454 Registered Member

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    Hello... As a relatively new person, this is my first post here. I have a problem with a "new" project truck I recently bought. It's a '79 Chevy with the SM465 manual transmission. This is also the first stick shift I've ever owned. I've noticed that often, the tranny grinds when I put it into gear, even through the clutch is all the way to the floor, mostly when going into Low 1st or Reverse. After a few seconds of still holding the clutch in, and trying again, it'll then almost always go into gear ok, no grinding. This surprised (scared) the crap out of me the first few times. Another thing I noticed is that when taking off in 1st gear, there's a point where the truck will shimmy and jerk somewhat, then smoothen out, at about 1/3-way through releasing the clutch. It only lasts for a couple seconds, then is ok. I changed the gear oil, and that hasn't seemed to help any. Anyways, being that this is the first manual tranny truck I've ever had to deal with, I was wondering if anyone has some suggestions as to what the problem might be?.?. Tranny problem, or maybe the clutch?.?. Both?.?. Any insight or help would be greatly appreciated. Thanks!!
     
  2. TXsizeK5

    TXsizeK5 1/2 ton status

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    I'm guessing yours is the Sm465... with the
    L 2
    |-|-|
    1 3 R
    Pattern... dont use low on the street. just stick it dirrectly in 1st and it wont grind... grining is normal in low sometimes and in reverse b/c the tranny is keeping you from sticking it into gear and messing something up if your over reving or something. What i normally do before i go into reverse or low is shift if into 2nd and leave it there for a second and then putting it in reverse or low
    The other thing about the truck shaking... is your probably taking your foot off the clutch too fast.. let it off smoothly and keep it at the cathcing point for a few seocnds and let it off more smoothly, nice and slow
    Hope this helps.. this is what ive learned dirving a Sm465 as my first manual transmission vehicle ive owned.. ive had it about 2 monjths, its been all good.

    6in 87' K5 w/ 35" BFG muds.
    305/Sm465/ NP208
    Kn, 4.56's.
    next... off with the cat's and a single inlet dual outlet flowmaster with 4" tips =D
     
  3. HarryH3

    HarryH3 1 ton status Author

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    Granny low and reverse have no syncros in a 465 tranny. To shift into one of those gears without grinding, press the clutch, shift into any of the gears that are syncronized and then shift into granny low or reverse, then engage the clutch. This has worked great on 2 different 465 K5's that I've owned in the past. [​IMG]

    <font color=black>HarryH3 - '75 K5</font color=black>
    <a target="_blank" href=http://www.angelfire.com/super/ThunderTruck>www.angelfire.com/super/ThunderTruck</a>
    It's a great day to be alive...
     
  4. RedDwarf

    RedDwarf 1/2 ton status

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    Yup, he's right.

    Sometimes you will do this and it still won't go into gear. Keep pressure on the shifter while slowly letting out on the clutch. The gears will line up and it'll go in. You will get used to this pretty quick.

    Still Poundin' "pavment" after all these years!!! [​IMG]
     
  5. BlueBlazer

    BlueBlazer 1/2 ton status

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    Did you say that it does it in 1st too. If so, youre clutch pedal may need to be adjusted. Basically what could be happening is youre pushing the pedal to the floor but its not disengaging the clutch all the way causing the grind.

    82 K5, 6.2L Diesel, sm465, np205, 14 bolt welded, 8 lug 10 bolt lock right, 410 gears, 35" Mud Kings
    SPEAK SOFTLY AND DRIVE A BIG TRUCK
     
  6. HarryH3

    HarryH3 1 ton status Author

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    That depends on your definition of "first". Some trucks showed a shift pattern of 1-2-3-4-R, while others showed L-1-2-3-R. Granny low ("1" in the first shift pattern and "L" in the second shift pattern) has no syncros and will usually grind if you try to shift directly into that gear.

    I guess they had to come up with the L-1-2-3-R shift pattern to help folks understand that granny low isn't required for everyday, around town driving. [​IMG]

    <font color=black>HarryH3 - '75 K5</font color=black>
    <a target="_blank" href=http://www.angelfire.com/super/ThunderTruck>www.angelfire.com/super/ThunderTruck</a>
    It's a great day to be alive...
     
  7. BlueBlazer

    BlueBlazer 1/2 ton status

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    I see what youre saying, but I just reread his post and he said low AND first it grinds which leads me to believe it may be a simple clutch adjustment. If not, possibly a badly warped flywheel that grabs the clutch as it comes around which would explain the shaking that he experiences.

    82 K5, 6.2L Diesel, sm465, np205, 14 bolt welded, 8 lug 10 bolt lock right, 410 gears, 35" Mud Kings
    SPEAK SOFTLY AND DRIVE A BIG TRUCK
     
  8. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    The shaking could be clutch chatter...

    Rene

    <font color=green>Dyslexics of the world...UNTIE!</font color=green>
    <a target="_blank" href=http://coloradok5.com/gallery/project_T2> tRusty pics...</a>
     
  9. POWERMAD

    POWERMAD 1/2 ton status

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    That is what I was thinking.


    <font color=green> Too bad ignorance isn't painful </font color=green>
     
  10. 4x4x454

    4x4x454 Registered Member

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    I want to thank everyone for their input and suggestions. I'm surprised at the response, in less than a day! What an awesome group you guys here are... impressive. Taking your replies into consideration, I took it out for a drive today. From standstills, I shifted it into 2nd for a second, before shifting into L, 1, or R, and that pretty much eliminated the grinding problem, and made it slip into gear easier. I also tried to be more patient, and slower when shifting, rather than a quick "clutch-shift-go!" As for the shimmy-jerking that it does when letting off the clutch, I tried letting it out really really slow, and that made it worse... it felt like I was in a Ford, doing a burnout, with real bad wheelhop. It seems like it does it through a very narrow range when letting off the clutch... maybe an inch or so of travel within the entire range. And when it happens, the truck's already rolling by then. The only thing that seems to help is if I carefully let out the clutch, while not giving it any gas... letting it idle low, hopefully not stalling, until the clutch is about 3/4 of the way out, truck rolling, and then giving it gas. Does this seem like normal operation, or something messed up here? I just picked up a repair manual for it, and will look into clutch/pedal adjustment this weekend. It's a little tough getting used to driving this beast, but I think I got the grinding under control... just worried about the jerking. Thanks again to all, I really appreciate it.
     
  11. TXsizeK5

    TXsizeK5 1/2 ton status

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    Well if you let it out of the "catch zone" too fast it will jerk around and hop etc. Try finding the catch point.. rev it up to like 2k and let off the clutch slowly untill it feels like the truck is engaging or starting to roll, then leave the clutch at that point for a few seconds and when your rolling faster let off the clutch slowly and completely. Taking off i usually rev to less than 2k and let it catch and go. In traffic you can slowly slowly let off the clutch untill it catches and you can roll without using the gas.

    6in 87' K5 w/ 35" BFG muds.
    305/Sm465/ NP208
    Kn, 4.56's.
    next... off with the cat's and a single inlet dual outlet flowmaster with 4" tips =D
     
  12. ArrowheadK5

    ArrowheadK5 1/2 ton status

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    I just got an 87 K20 and it acts exactly like you described it, it seems like teh range where the cluch engages is very small. Howeverm the only other stick I've driven was an 82 F250 and it was the same way. (oh yeah, also a 64 chev dump truck, very different...) I thought it was simply a matter of practice and experience. If there's something to make it easier, let us know!![​IMG]
    About this board being the greatest, yeah, I agree. I don't post at any other lists any more, because they get NO traffic compared to this one. What a great org.!

    The tree of liberty must be refreshed from time to time with the blood of patriots and tyrants.
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  13. 84_Chevy_K10

    84_Chevy_K10 Banned

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    Sounds like the rear main leaked all over the clutch to me.

    Tim
    '84 Chevy K10, lifted, loud, fast, and 3/4 ton axles
     
  14. POWERMAD

    POWERMAD 1/2 ton status

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    I can dump mine in any RPM range and it is smooth.
    Or let it out easy and it is still smooth.
    It sounds like there is either oil on the clutch or the flywheel didn't get ground when the clutch was replaced.
    Either way it is not good.
    If it is getting real bad it will prolly break off the snout on the front bearing cover. The part that the throw out bearing slides on.
    That is what happened in the old shop truck.



    <font color=green> Too bad ignorance isn't painful </font color=green>
     

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