I have the original saginaw 4-speed with an estimated 375-390 HP... I've heard that it wont last long... is this true? (10 bolt) (3.73 rear)

If you drive it REAL easy it could last a long time...if you hammer on it...not very long.

It's torque that kills drive train parts. My brothers old Nova SS came with a 275HP 327 and a Saginaw. He couldn't break it but it always had street tires and an open rear end. If the trans isn't worn out and you don't ever power shift it it might work just fine.

It will break very quickly. 3 of mine did, and I don't have 390 HP.

Good luck,
Tim

I'm running about 300hp in the '67 with the Sag. I'll grab second every now and then, so far so good.

thanks for the info... so pretty much if i'm gonna drive it around town on the weekends i'm ok, but if I want to run it at the strip or eat up some cars on the street I need something stronger.... I like the 4-speed though... does the muncie have the same gearing ratio?

What year is your saginaw? I know the a 67 Muncie m20 (not close ratio m21 & rock crusher) and 67 Saginaw are geared fairly close.

Saginaw 1st-2.54 2nd-1.80 3rd-1.44 4th-1.0 (direct)

Muncie m20 1st-2.52 2nd-1.88 3rd-1.46 4th-direct

If you have 375-390 HP you had better take it REAL EASY with the Saginaw.

Its the original 68 tranny... I thought about taking it out because the numbers match and it IS original... also the block I should have boxed up cause the #'s match (and the block only had 76'000 miles on it), but I rebuilt it, this was the weaker 68 327 (with the saginaw and only a double barrel carb)

I'd yank it.

I did flog my sag 3-speed a dozen times at the track, but my car was only pushing 300 hp.

Mothball it since it's original.

The 68 Saginaw has the same gearing as my earlier post but it is the better "second design" which started production in late 67.

There was a saginaw 4 speed in my 67 when I bought it. It wasn't the original tranny, it came from out of a 69. It worked fine until I pulled it out to install the "original" (very long story), rebuilt Muncie tranny, but I wasn't pushing any where near what you are. (Maybe 250 to 275 HP tops in a modified 283 motor out of a 62 Impala. = not a whole lot of torque).


The gearing is very similar, but the muncie M20 holds up to alot more abuse, but not as much as a M22. There aren't a lot of original Saginaws still functioning, which is something for you to add into the mix of whether to leave it in or pull it out and save it. If it were me, with 390HP, a 2.54 1st gear and 3.73 rear end gears I would pull it and put something that is going to take more abuse

I've got 190K on my original Saginaw 4 speed behind a variety of small blocks 327/275 and 327/365. Right now it is attached to a 302. All of these are fairly low torque engines.

No problems but I do baby it. No clutch popping and no speed shifts.

I have the 3.11 Sag behind a very mild 350 in a posi-equipped '72 Nova, which originally came with the 2.54 version. I don't baby it, but I use a stock clutch, & I don't dump the clutch from a dead stop. Rarely, anyway. The only trouble I've had was the original lost a tooth from the 1st-gear section of the countershaft for some reason (it fell off while parked!?), & the newer one got full of water & wouldn't shift right. Works better with 90W for some reason. :rolleyes: I had a Muncie in another car (230cid)& it ate synchronizer keys regularly.

i had a 4spd saginaw with around 380hp, i stripped all teeth off third and chunked up the cluster. One to many hard shifts? Not sure on miliage, trans looked clean minus metal shavings. My is a 10 bolt a 3.73 ratio with an open differential. I rebult a used muncie, m-21 close ratio, happy with the transmission but I now need to do something with the rearend

Imho, a Sag. will last a goodly time if you don't hook!!!

A buddy of mine had one behind a built up BB, I forget what he said it's first gear ratio was?? something like a 3.27 or 3.44. It was out of a small car like a Vega. He hunted it up after considering several tranny's just for the very low first gear to get moving...

Anyway, he said he was in low just long enough to roll out AND spin and was gone!!

I figure that was the only reason it lived..

If you check tranny strengths vs first gear ratio's, you will see where a Muncie M-21 with a 2.20 first gear is about 425 to 450 T or so(?) and the big, MOPAR A833, with a 3.07 first gear OD four speed is 275 T...

I looked into this a lot trying to figure out a way to put one of the big, older, regular four-speed OD trannies like the big MOPAR A833 or Ford Top-Loader "RUG" behind my 496 to get better mileage and to mostly slow the rpm's down to hold engine wear down..

The new M-21 OD geared Italian Super-case Muncie is a good idea but pricey, imho for a "FIX" vs a cure if you don't want to really go a Tremac or 6-speed tranny as well as change your rearend gears for a better overall match.

pdq67