SM 465 trans.......help?

Discussion in 'General Discussion' started by pistolwretch, Dec 9, 2018.

  1. pistolwretch

    pistolwretch Dremel jockey Supporting Addict

    Aug 26, 2011
    I'm having some problems.
    Anyone here familiar with these?
     
  2. HannibalMontana

    HannibalMontana Well-Known Member

    95
    Apr 30, 2016
    Transmissions aren’t my specialty, but what’s going on with it?


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  3. 1911fanatic

    1911fanatic Well-Known Member

    Nov 27, 2011
    Me neither. But I’m all about learning.


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  4. Apollo99

    Apollo99 Well-Known Member

    858
    Jun 26, 2017
    Oh I had one of those Muncie monsters in a one ton, after a hard life, (the tranny not me), I had to hold it in third gear or it would pop out. mine had a provision for a PTO. That thing was a tough old stump puller.
     
  5. Stromburg

    Stromburg Well-Known Member

    963
    Nov 6, 2015
    The good old SM465 is a solid (almost) bullet proof tranny, there are millions of them out there, GM used them in almost every 1/2 ton-1ton trucks from the late 60’s till the early 90’s. I’ve been running one in my Jeep for 23yrs without a lick of trouble and I abuse the sh** out of it.

    One of the common problems is popping out of 3rd gear due to bad detent springs in the shifter and the syncros, I’ve always felt that worn out detent springs caused that heavy shifter to put unwanted force against the syncros and causing them to wear out.

    Another common problem was the front input shaft bearing failure which was usually caused by a bad pilot bushing/bearing at the back of the crank.

    These tranny’s can be rebuilt fairly easy by any backyard mechanic for around $100 and a wrecking yard replacement should be cheap and easy to find. If it’s out of a 4x4 you’ll need to be year specific to make sure you get the correct output shaft for your transfer case, I can’t remember what year GM switched from the NP205 transfer case to the NP208 or 203 (can’t remember)
     
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  6. David R

    David R Well-Known Member

    384
    Oct 7, 2018
    Yes, what is it doing?

    David
     
  7. pistolwretch

    pistolwretch Dremel jockey Supporting Addict

    Aug 26, 2011
    It used to pop out of 3rd, but strangely that stopped.
    Now it's difficult sometimes to get into 3rd especially when downshifting, but
    double clutching takes care of that.
    Big problem now is it doesn't always like to go from neutral into 2nd.
    I don't have the ability to remove, repair or replace myself.
    The shifter has a LOT of play. I know that can be corrected via removing the top
    cover while in the vehicle.
    My question is can I improve the neutral to 2nd shift from the top without removing
    the trans from my truck.
     
  8. HannibalMontana

    HannibalMontana Well-Known Member

    95
    Apr 30, 2016
    From memory those don’t have a removeable shift tower like more modern transmissions. You have to remove the trans and split the case to do any work I’m pretty sure.

    If it’s not going into gear from neutral when stopped you may have a clutch not disengaging as well. If the trans comes out it would be prudent to go ahead and throw a disc and pressure plate in it, check clutch linkage and throwout bearing and machine the flywheel unless you know the status of the current ones.

    ETA: those have a release ring for the shifter. You may be able to get a bushing kit for it and solve your problems.


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    Last edited: Dec 10, 2018
  9. deadguy

    deadguy Charlie Daniels Supporting Addict

    Sep 7, 2011
    Praying for the Chebbie.
     
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  10. livinthelife

    livinthelife Well-Known Member

    Jul 30, 2015
    Chuck if you need a shop to work out of my pop is just down the road.
     
  11. Capthobo

    Capthobo NRA Endowment member Supporting Addict

    Nov 9, 2016
    Sounds like shifter fork slop. Possible to correct from top cover and shifter fork replacement.
     
  12. oatbill

    oatbill Well-Known Member

    127
    Jan 25, 2016
    I'm far from an expert but sounds like the cluster gear would need some attention, so I would think you'd have to get into it.
     
  13. David R

    David R Well-Known Member

    384
    Oct 7, 2018
    Is it a Hydraulic operated clutch? This could make shifting difficult and hard to get into gear. If you push the clutch ALL the way to the floor will it go in first or reverse with out grinding?

    Ck fluid in clutch reservoir. If low it will need bleeding.

    Above has nothing to do with dropping out of 3rd.

    Does it jump out of any gear if you let off the gas real fast?
     
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  14. Stromburg

    Stromburg Well-Known Member

    963
    Nov 6, 2015
    I know I’ve seen pics you’ve posted of your truck but can’t remember what year it is, I’m thinking 70’s which would be mechanical clutch linkage, if so....the first thing I’d do is make sure the clutch linkage is adjusted correctly, basically making sure your clutch is disengaging completely when the pedal is fully depressed.

    If that doesn’t work, I would try replacing or rebuilding the shifter itself, it’s really easy to remove as long as the opening in your floor board is big enough.

    Here’s a picture I just took of mine
    I have the channel locks placed on the dust cover that can be removed by pressing down then rotate counter clockwise then the shifter can be remove but........I would take the entire shift assembly out as a unit so you can inspect and/or work on it, with the top off you’ll be able to see everything.
    I’ll need to check my manuals but I believe to get the top off the tranny you’ll need to shift it into reverse.
    F7C7666B-1D26-47D5-9B44-D0B9271E068C.jpeg
    Here’s a picture of a different trans (NP435) but it basically looks the same
    Just remove all the bolts and lift the top off
    82F82036-DE75-4D77-80D2-A7EDDF783016.jpeg

    Here’s what yours will look like with the trans tunnel removed, as you can see there is plenty of room to get the shifter/cover off
    6D7F097C-46EE-4078-A2FC-37F1BA2893FC.jpeg
     
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  15. David R

    David R Well-Known Member

    384
    Oct 7, 2018
    I would like to figure out what is wrong before doing repairs.

    Does it grind going into first or reverse?


    David
     

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