Picked up a Saginaw 4 speed

Discussion in 'U-shift em' started by 68Rivi_In_Cali, Dec 26, 2019.

  1. 68Rivi_In_Cali

    68Rivi_In_Cali Well-Known Member

    On my quest to track down parts for the manual swap, I ran across a 4 Speed Saginaw that had been rebuilt 8 months ago. It was in a stout 69 C10 that was coverted to automatic.

    Is this a decent transmission? Would it work with my 350 and future 3.42 posi rear?

    I am completely new to 4 speeds, I picked it up for $300 figured it's already rebuilt.

    After research:
    3 Lines (grooves) 3.50 2.47 1.65 1.00

    I just have not heard of these much in Buicks. I am still thinking of looking at an M20 if I run across one.

    Would the Saginaw be fine behind the 350 and future 455?

  2. tubecatgs

    tubecatgs Finally a 4 speed......

    My buddy has a saginaw 4 speed in his '72 chevelle 350 built to about 300 hp if that helps. My car 72 skylark convertible 350 had a saginaw 3 speed (3 on the tree) when i got it. If i remember they are a lot heavier than the aluminum Muncies.
    68Rivi_In_Cali likes this.
  3. 68Rivi_In_Cali

    68Rivi_In_Cali Well-Known Member

    Okay sounds like a decent transmission. I have a couple of upgrades on the 350 at the moment. Stock bottom end, with a cam, ported heads, headers and aluminum intake. In sure I'm not breaking the 300hp range and if I am, probably not by much, it was about 235 to the rear wheels before the headers.

    Definitely feels heavier. Hopefully the shifters I have will work with it. I just want to row some gears while I build the 455.

    The gentleman I bought it from had receipts for a rebuild. He had 2 splines replaced and the trans resealed.

    I will be adding the 3.42 posi and have 15x8 wheels with 275s on the rear, hopefully it doesn't put too much stress on the Saginaw
  4. Dwayne B

    Dwayne B Well-Known Member

    I have A Saginaw 4 speed I'm going to install in my skylark this winter, mine doesn't have any lines on the input shaft 2.80 first gear.
    I have A saginaw in my 72 nova and I have miss treated it and it took it.
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  5. philbquick

    philbquick Founders Club Member

    That ratio would be great with a 2.73 or 2,56 rear. It's not the strongest Saginaw made, I wouldn't put much more than 250 hp through it. The strongest Saginaw has the 2.54 1st gear ratio which would be good for 300 - 325 hp.
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  6. Mart

    Mart Gold level member

    Saginaw are iron case, Muncie are aluminum.
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  7. philbquick

    philbquick Founders Club Member

    No lines could be 2.54 or 2.85 first, that's the strongest saginaw they made.
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  8. Dwayne B

    Dwayne B Well-Known Member

    If I can remember right, no lines is A 2.80 or 2.85 and 1 line is 2.54 .
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  9. 68Rivi_In_Cali

    68Rivi_In_Cali Well-Known Member

    Awe man, I have the 3.50 ratio, so I'm guessing it's the weaker one. Would the 3.42 rear gear make it less drivable? Or just launch harder?

    I currently have the 2.56 open rear

    The gentleman that had it was pushing 420hp probably not as much torque but still.
  10. gsgnnut

    gsgnnut Well-Known Member

    Bolt it in and send it!
    68Rivi_In_Cali likes this.
  11. Golden Oldie 65

    Golden Oldie 65 Well-Known Member

    It'll likely hold up behind your 350 but with the 3.42 rear gear the combo will have a pretty short 1st gear. A friend of mine had one behind a 396 in a Nova for years and he beat the crap out of that car. It held up for years before he finally blew it up. For now I'd go ahead and use it and keep your eyes open for a Muncie or another Saginaw with a 2.54 1st gear to swap in when you do the 3.42 swap.
  12. 436'd Skylark

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

    It'll drive like a dump truck.

    Despite the iron case the Saginaw 4 speeds are weaker than a muncie or a T10. It'll work sure thing, but I would not expect much out of it. If you're not in dire need of transportation I'd keep shopping . Especially with those ratios.
  13. 68Rivi_In_Cali

    68Rivi_In_Cali Well-Known Member

    Aw man -_- I supposed I can sell the Saginaw

    There's an M20 a few miles from me but the gentleman wants $600 and he has a T10 as well for $700. I might have to go with one of those then. Which one should I go with? I am thinking the M20.
  14. wkillgs

    wkillgs Gold Level Contributor

    Your 'starting ratio' is the first gear ratio * rear end ratio....in your case, 3.5 * 2.56= 8.96. That's your ratio 'off the line' . That's in the ballpark of 9-10:1 that is desired. PLUS you will have a great ratio for highway use.

    A 2.54 Muncie with a 3.42 rear gives a 8.67 starting ratio, which is pretty darn close to the Saginaw/2.54 rear combo.

    Your ideal trans and rear ratios will depend on how much highway driving you plan to do. Other options (for highway use) include a 5 speed trans or a gear vendors overdrive.

    Trannys with steep first gear ratios have lower torque ratings than the same trans with a low (numerical) ratio. I wouldn't worry too much about the torque rating, just put it in and drive the damn thing!
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  15. 68Rivi_In_Cali

    68Rivi_In_Cali Well-Known Member

    Thanks! That makes sense. I do drive my car's a lot. The 2.56 rear has been great on the highway but very slow off the line. I wanted to be able to light the tires up some.

    Looks like the M20 with the 3.42 rear is going to be a good all around combo.

    I think I will just swap in the Saginaw and run it with the 2.56 to see how it feels while I build up the 455. I sourced an M20 near by as well.
    wkillgs likes this.

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