Inliners International Forums General Discussion Drive Train Trans help

I have a 78 chevy G20 292 three speed colum shift that I just changed the rear in. I went from the stock 3.42 to a 2.73 in a effort to get better gas milage. It works great on the highway. But now I have another problem. Specifically first gear is to high. Can anyone tell me what the gear ratio is in this trans and what four speed trans I can put in to get a lower first gear. I'm not looking for a stump puller in the 6 or 7 range just something in the threes with a good spread between gears. I climb a fair amount of hills in this area and would like something that I don't have to shift two or three times before I get to the top.

A saginaw transmission with two grooves on the input shaft should do what you want, it has a 3.11 first gear. Ratios are (1234) 3.11 2.20 1.47 1.00 .

A three groove transmission would give you a 3.50 first gear, which would be lower than your present setup but you may want that.

Most 3-speeds have a 2.54 first gear, so with the 4 speed and the 2.73 axle 1st gear of the saginaw would be very close to 1st gear of the old 3 speed with the 3.42 axle.

Thanks for the info on the trans. Now all I have to do is find one. Any ideas on what the casting numbers would be and what truck/car I would find that trans in?

I can't give you casting numbers but I can tell you the 3.11 first gear Saginaw trans was used in 4 and 6 cylinder cars from GM, mostly like the Chevy Vega, Monza, and similar bodied Pontiacs of the 70's and early 80's.
The 8 cylinder version of the Saginaw had @ 2.54 first gear and is more commonly found in G bodies like the El Caminos until 1981 and in the F body cars, Camaros & Firebirds.

If you are lucky enough to find one still in the vehicle this may make it easier to know which trans it is.

It's really easier to figure out which tranny is when it isn't installed, because the grooves are on the input shaft.

From Patrick's catalog (thanks Jack):
No grooves = 2.85 1st gear
1 groove = 2.54
2 groove = 3.11
3 groove = 3.50


I have a pristine Sag 3 groove that I paid $50 for out of a guy's garage sale.

If it has a cast iron case, and the reverse shift lever is in the tail housing, it is a 4 speed saginaw.

All 4 speed Saginaws have the 3 shift arm pins coming out of the side cover.

Muncies and BW T10 4 speeds have only the forward gear pins in the side covers. On both makes the reverse gear pin is located in the tailshaft housings.

Saginaws are all cast iron from end to end, Muncies are all aluminum except for the spacer plate between the main case and the tailhousing, and the T10's vary in materials depending on when they were built and by who - original Borg Warner or the currently made Richmond T10.

Don't get sucked into paying a high price for a Saginaw 4spd. Muncies and Borg Warner T10's are high priced any more, but the Saginaw was considered a light duty transmission, and was always cheap because of it. I don't think you can tear one up with an inline though, unless you are doing some serious drag racing. I ran one with an OD built on for probably 8 or 10 years behind an HP 400 small block Chevy in a 5000# 4WD Ford PU and never broke it. If you are patient, you should be able to find one any where from free to no more than $100. Joe

One other comment that goes along with what Joe posted. The Saginaws were not considered desireable so the price for a used one was pretty cheap as he said. Because of this when one needed to be rebuilt or repaired they usually got tossed in favor of a used unit from a salvage yard for about 1/3 to 1/2 the cost of an overhaul.

Just be careful when you are shopping for a Saginaw and keep in mind that it might have been removed because it needed repairs. The typical failure on them was the snap rings and wave washer on the 1 - 2 synchro hub would break and the hubs would then slide enough back and forth to crash into the shoulders of the mainshaft gears for 1 & 2. If driven long enough this way the trans also needed a new first and / or second gear and complete synchro hub assy, in addition to the regular overhaul kit.

The last one I repaired cost $155 for the o/h kit and another $125 for a first gear and a hub. This is in a numbers matching car so a different tranny wasn't an option.

Don't be afraid of a Saginaw, just be careful what you buy and what you pay.

For all sorts of 4, 5, and 6 speed info and tech go to www.gearzone.net