Good Conversion Tranny?

Discussion in 'U-shift em' started by MattRush10, Jun 25, 2009.

  1. MattRush10

    MattRush10 Buick Fanatic In Training

    I am just wondering into the land of converting my auto into a 4 speed... What do you guys recomend for starters... What are key things to remember... What should I stay away from... and about (I don't need an exact price, just in the ball park) how much would this run me?

    Would a used/rebuilt 4 speed be any good, or should it be brand new? (pricy, I know)

    Just to let you guys know, I am not the most educated person when it comes to trannys, nor do I claim I am. haha Thanks for the help, guys!
     
  2. KFD

    KFD Well-Known Member

    So what I have figured out so far about the Auto/4-speed conversion is this so far, here are some of the obvious ones, pedal setup, steering column, shifter hump, radiator (or just put plugs where the cooling lines go). The speedo (if it can be found). The underdash wiring might be a little different for the clutch switch/reverse/neutral safety switch, but I am not sure on that... Anybody else here think of what I am missing?
     
  3. flynbuick

    flynbuick Guest

    It will usually run $3000-4000.
     
  4. 69 wag

    69 wag 69 wag

    also, your crank may not be drilled for a pilot bushing. the hole may be there but a pilot bushing won't fit. dick millar makes one that fits into the torq recess of the crank but i don't know if it's concentric. mine got chewed up after a few hundred miles. dialing in my bellhousing might have helped. they are about 1,75 inches in diameter and 3/8 thick. After reading and doing the conversion i believe cranks are different in the back between auto and manual trans applications from factory. maybe im wrong. i went from a turbo 400 to a tremec 5speed. definately more fun to drive. i've since had my crank properly drilled for a pilot bushing as the ,motor has since been out.
    good luck pete
     
  5. poison heart

    poison heart Well-Known Member

    You don't have to plug the holes in the radiator. You can just leave them.

    I wouldn't get a saginaw, they're supposed to be the weakest of the GM 4 speeds. Just get a Muncie M20. You can find a good, clean used one for 500-700$

    I don't know about your car but a bellhousing and flywheel will usually cost you maybe $400 max. A performance clutch kit another $300 or so. Might have to modify your cross member/driveshaft. You'll have to get a nuetral safetly switch or just wire up a switch (I hid a toggle switch on mine so you can't start it unless the switch is on).
     
  6. MattRush10

    MattRush10 Buick Fanatic In Training

    I'm wanting to put it in my 72 Lark. It has the 350 and the TH350 tranny, everything is stock right now. Where do you suggest I should look for the M20? Ebay? Here?
     
  7. MattRush10

    MattRush10 Buick Fanatic In Training

    And what is significant about the numbers on the housings?
     
  8. poison heart

    poison heart Well-Known Member

    I would watch ebay and craigslist. If you inspect one in person I would look for worn input and output shafts, some play is OK but excessive is bad.

    Since you have a 350 tranny I would look for a pre 1970 M20 since they have the smaller output shaft like your 350 has. The 1970 and up M20s have a 26 spline input and bit output shaft like the th400s and M21 and M22, That way you won't have to change the yoke on your driveshaft
     
  9. MattRush10

    MattRush10 Buick Fanatic In Training

    Ok good, because the pre 1970 M20's seem to be all I can find!
     
  10. wormwood

    wormwood Dare to be different

    make sure that this is what you want. if you are going to spend big bucks anyway, might as well look for a 5 or 6 speed. the new tremec and richmond transmissions are far superior to the old muncie and saginaw, (plus a 5 or 6 speed definitly add a cool factor)
     
  11. poison heart

    poison heart Well-Known Member

    But there's no factor like the old school factor in my book. I wouldn't trade that old school Muncie 4 speed for anything
     
  12. MattRush10

    MattRush10 Buick Fanatic In Training

    I definitely agree. The four speed is what I want, because I want it to be exactly how it was back in 72.
     
  13. MattRush10

    MattRush10 Buick Fanatic In Training

    I was just thinking about my situation and I was wondering what you guys think- should I keep my turbo 350 tranny after I buy the 4-speed? Or should I sell it or trade for the 4-speed?
     
  14. flynbuick

    flynbuick Guest


    No the 70 model year also has the course (10) input spline shaft. The fine spline I recall started with the 71 model year.
     
  15. MattRush10

    MattRush10 Buick Fanatic In Training

    Alright, so I'm still trying to decide if this is worth doing. I am trying to figure out what I'll need, and the cost. And please keep in mind that I don't know a lot about transmissions. Here is what I know I'll need.
    For the auto to 4-speed conversion:
    Pre 1970 Muncie 4-speed (obviously)
    Clutch pedal
    Shifter

    A Few Q's
    Will there be anything else clutch wise that I'll need to buy, or is that part of the tranny?
    Can I keep the steering column I have right now, just take the shifter off?
    Will I need some sort of adapter so the tranny will fit the SBB?:Do No:

    Anything else? I know I'm most likely missing something, or multiple things. Please tell me what. And thanks to all for helping this transmission illiterate.
     
  16. racenu

    racenu Well-Known Member

    drive an old school 4 gear car, then drive a newer car with a 5 or 6 speed before you set your heart on something. just my 2 bits.
     
  17. MattRush10

    MattRush10 Buick Fanatic In Training

    I know the four speed isn't as "cool" or up to date as the new tremec 5 and 6 speeds. I have driven a four speed, and that's what I want. All the 5 and 6 speeds seem to be more expensive anyway. And I like the 4 speed because that is what was in the cars back in 72.
     
  18. racenu

    racenu Well-Known Member

    then your on the right track to a happy ride....cheers, Gord
     
  19. 73-462GS

    73-462GS GS Mike

    Keep the automatic,you will be putting it back in the car in my opinion. Peace, Mike D.
     
  20. raminc

    raminc Well-Known Member

    I believe you can use a Super T-10 and a TH400 Yoke. You won't have to modidy the crossmember or drive shaft.
     

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