Saginaw box

[Valencia]

Can anybody decifer what this sagbox came out of originally
GM4 3925656 extension housing
52 om 386042
cheers

[Innuendo]

You mean Saginaw. You can pretty much guarantee late 60's.

[Alien DNA]

^ Fixed

[Innuendo]

The Saginaw was a general GM 4 speed box used between 1968-75.
Basically it was the Yankee version of our all syncro 3 and 4 speeds M15/M20/M21 etc.

saginaw_4_speed.jpg

[HK1837]

As above the Saginaw was a 1950's-1960's product, started life as a 3spd just like the aussie box did. Used behind small V8 and 6cyl. Became a 4spd in the later 60's. High power engines used the 3spd and 4spd Muncies. The 4spd Saginaw and Muncie replaced the T10 (which itself was a modified T85 3spd). Once big power big blocks finished the Muncie was shelved and GM used the T10 again now made by Borg Warner.

Gene, does the Saginaw you have, have a side shifter mount like the photo above or does it have a smooth extension housing? Holden used the Saginaw in lots of applications:

HK-HT 6cyl HD option.
HK-HG standard 4spd in commercials.
HK 307 and 327.
HT-HG standard V8 4spd manual.
HT-HG 350.

There were 2 x different ratios, but the boxes were identical externally (no longer input shafts for V8, that silly idea is a Holden anomoly).

[Dr Terry]

The 4spd Saginaw and Muncie replaced the T10 (which itself was a modified T85 3spd). Once big power big blocks finished the Muncie was shelved and GM used the T10 again now made by Borg Warner.

The T10 was always made by Borg Warner. It was the 4-sp of choice for GM, Ford & Chrysler in the USA, before the advent of their own Saginaws, Muncies, Top Loaders & New Process gearboxes.

The later financial structure is a bit hazy, but basically Borg Warner took over the Muncie factory (or GM took control of BW, whatever), but the end result was that the best features of the Muncie & BW T10 were combined to become the 'Super T10'.

The Super T10 was arguably the best US 4-sp of the era, with both Holden & Ford using it behind their respective engines in the later Group C time.

Dr Terry

[Valencia]

Byron it does have the smooth extension housing and
a) been told it has the 2.54 ratio i think i got that right same as the XU1 box
b) been told it came out of a commercial vehicle
only going what i have been told

[HK1837]

I had heard Terry that GM ceased using the Muncie (in M22 form anyway) as hipo big blocks and engines like the 1970 LT1 dissapeared in production cars. They went back to the T10 as it was strong enough for what thy had, but never rated high enough for big engines.

I thought GM developed the T10 with Borg Warner for the 1957 Corvette, and then BW used it elsewhere once GM started their own production of boxes. I knew BW was involved from the start, but GM were heavily involved?

[HK1837]

2.54:1 1st gear is the M21 version used in V8 HK-HG applications and also on 6cyl HK passenger vehicles as a heavy duty option. The M22 version (2.85:1 1st) was standard on HK-HT commercials when a 4spd selected, also optional on HT GTS. If you have an M21 out of a commercial it'll be from a HK 307 or a HT-HG 253 or 308.