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Old 02-12-2014, 12:47 AM
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Saginaw 4 speed transmission

I have a '64 Nova w/ a 406 ci small block, about 375 HP. Will the Saginaw 4 speed from a 60's era Firebird hold up for street use and the occasional 1/4 mile run?
Thx

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Old 02-12-2014, 03:56 AM
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For a while.......not the strongest trans in the world, they have a great 1st gear ratio
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Old 02-12-2014, 07:13 AM
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If you come out of the hole like Aunt Ethel, for awhile maybe. There are several 1st gear ratio Saginaws. The lower the number for 1st gear, the stronger it will be (marginally). Stick the trans in first, turn the OUTPUT ten times and cound the number of times the input goes around. 25 times would be 2.5; 27 would be 2.7 for example. If you decide to go to a T10 or Muncie later, remember that the shifter linkage is different from the Sag to the T10/Muncie.
Keep street tires on it; and if you do go quarter mile, no wicked burnouts, no slicks and have a friend with a trailer just in case. Enjoy it!
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Old 02-12-2014, 09:28 AM
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I've broken every ratio of Saginaw, but they always got me back home.
Here's a pic of one with a faceplated 3rd gear...



I ran them into the mid 6's in the 1/8th with radials for a couple years at 2525lbs, the track was about 85mi away. Never needed a trailer, but there were times that i needed earplugs for the drive home!
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Old 02-12-2014, 10:42 AM
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Input shaft ring count.
No grooves= 19 tooth input, 2.84 low, 2.01 2nd, 1.35 3rd, (all had 1:1 4th)
One groove= 19 tooth input, 2.54 low, 1.81 2nd, 1.44 3rd
Two grooves= 18 tooth input, 3.11 low, 2.20 2nd, 1.47 3rd
Three grooves= 16 tooth input, 3.50 low, 2.47 2nd, 1.65 3rd
1" x 14 spline input= 16 tooth input, 3.50 low, 2.16 2nd, 1.45 3rd

I`ve always read that the 2.54 first gear set was the stronger of the trans due to gear set, but still wouldn`t use sticky tires, stronger that a T-5 anyways...
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Old 02-12-2014, 03:04 PM
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All the Saginaw gearsets (both 3 spd and 4 spd) use the same 29 tooth 1st gear that mates with the same 15 tooth gear that's machined onto the cluster (1.93 ratio).

The difference in the 2.54/2.84/3.11/3.50 1st gear ratio gearsets is not 1st gear itself (they are all the same), it's actually the input ratio at the front of the box. Here's the ratios at the front of the various gearsets...
...2.54 gearset 19 tooth input shaft, 25 tooth front cluster gear (1.32 ratio)
...2.84 gearset 19 tooth input shaft, 28 tooth front cluster gear (1.47 ratio)
...3.11 gearset 18 tooth input shaft, 29 tooth front cluster gear (1.61 ratio)
...3.50 gearset 16 tooth input shaft, 29 tooth front cluster gear (1.81 ratio)

2.54 gearset is stronger because it has less reduction between the input shaft and cluster. Basically, the input shaft torque into the cluster is only multiplied by a factor of 1.32 for the 2.54 gearset, vs a 3.50 gearset which multiplies the input shaft torque into the cluster by a factor of 1.81.

Let's assume that the weak point in the box is going to be the small 15 tooth gear on the cluster that mates with 1st gear (remember, all the Saginaw gearsets have the same 15 tooth gear).
...If we put 600ft/lbs into the input shaft of the 2.54 gearset, that small 15 tooth gear will see appx 792 ft/lbs.
...If we put 600ft/lbs into the input shaft of the 3.50 gearset, that small 15 tooth gear gear will see appx 1086 ft/lbs.

Looking at it from a different way...lets say the small gear's breaking point is 792 ft/lbs.
...with the 2.54 ratio gearset, we reach the failure point with 600ft/lbs of torque from the engine.
...with the 3.50 ratio gearset, we reach that same failure point with only 437ft/lbs of torque from the engine.

With all that being said, in my experience i have found that the weak point moves around a little depending on what ratio gearset you have.
...with the 2.54 ratio gearsets, the small 15 tooth gear on the cluster is what we always broke first.
...the 2.84 and 3.11 gearsets are pretty well balanced, may break the 15 tooth gear 1st, might break teeth off of the input shaft.
...with the 3.50 ratio gearsets, we always stripped the teeth off of the input shaft first.
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Old 02-12-2014, 06:14 PM
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Thanks Asir, you expland it much better than I did...
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Old 02-12-2014, 06:20 PM
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I had a 68 RS/SS Camaro with a built 396 BBC and a 4 speed Saginaw tranny and it held up fine even with 60's on the back. In fact, it was strong enough to hold up and snap the pinion shaft in the rearend while doing some wicked driving.
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Old 05-06-2014, 05:07 PM
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I have my saginaw tore down at the moment. I'm worried my 1-2 cam detent is bad...






It's bent right where the selector is, the 3-4 cam is straight as an arrow. I think its bad but can someone confirm this isn't by design?
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Old 05-07-2014, 06:43 AM
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I don't have a saginaw one to compare; but Muncie ones are flat.
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Old 05-07-2014, 09:56 AM
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I'd just flatten it out on the bench with a hammer.
I used to modify the Saginaw detent plates to more accurately define the shift fork positions and to change the detent locations when faceplated. I've never broke one (detent plate), even ones that were welded (built-up).
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Old 05-07-2014, 11:02 AM
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. OP had one post and never came back...

. Are you guys all sure your testimonials were with little Saginaws... and not Muncies?
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Old 05-07-2014, 11:39 AM
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Awesome thanks guys...I'll be straightening it out today.
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Old 05-07-2014, 12:49 PM
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Quote:
Originally Posted by BuzzLOL View Post
. OP had one post and never came back...

. Are you guys all sure your testimonials were with little Saginaws... and not Muncies?
I've broken way more than my fair share of Saginaws, but I did find them to be stronger than T5's. I even had a Saginaw main case that had the top cut out for test fitting the side cover / mainshaft assy, to make sure that the detent cams stopped the sliders where i wanted them to.
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Old 05-07-2014, 01:01 PM
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Quote:
Originally Posted by aisr View Post
I've broken way more than my fair share of Saginaws, but I did find them to be stronger than T5's.
. Did that include the WC T5's?
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