The Stovebolt Site Forums The Shop Area Engine Shop 2.73 rear end, and rear springs

Two questions here. First,my 57 has a 3.36 rearend from a GM A-body. Engine/trans is 350/ MY6. I would like to change the rearend to a 2.73 for better gas mileage. I have done some research and discovered that the 2.73 was in a number of vehicles including Nova, Blazer, and others. The issue that concerns me is width of the unit. I am running 8" rallye wheels, and if I load the truck, the tires rub on the inside of the fenders. Is there a particular 2.73 application that is narrower than others? Second, my truck suspension is original configuration, and has a nose-up stance. That, and the fact that any sort of load causes the bed to settle way down, indicates weak springs--I expect they are original to the truck. I have heard of re-arching the springs, but is that any better or cheaper than buying new ones ?

Sounds like the springs are shot. Rearching them will help, or at least for a while. Rearched springs have a tendacy to eventually settle back down to where they were to begin with. For the cost, you would be ahead getting new springs. Replace the shocks at the same time.
On the rearend, I would advise against the 2.73 gear, given the transmission you're running. It's too high of a ratio. You'll find that you'll lose gas mileage, especially in traffic, as there's not enough gear to get the truck rolling. With the rear gear and trans you currently have, your final drive is approximatly 2.36:1, with a 2.73, it'll be 1.9:1. Great for a high speed highway cruiser with a torquey big block, not so great with a smallblock. It'll get the engine below it's ideal powerband, which will kill the mileage.

G-bodies and S-10's have 2.73's. I had a 2.73 rear from a V8 Monza in my Opel GT. The upside, light car and I could get 32mpg. The down side, I had to red-line it in 2nd through the traps against the rev limiter. Shifting into 3rd made me slower.

The car only weighed 2100# with 330hp. It needed better gearing. A truck with more weight and less power will be not as stellar at acceleration.

I would not recommend anything less than a 3.08 with plenty of torque, or a 3:42 with an SBC and the trans you have.

Thanks, guys. New springs definitely, new rearend, maybe. My 350 has incredible low-end torque. Most of my driving is in OD, and Iwould like the RPMs at 65-70 to be in the 2000-2300 range. I know the acceleration will be un-stellar, but am more concerned with fuel economy. BTW, I'm running a 4GC square bore w/ manual choke.

Assuming a stock tire, which was 27" in diameter for the TF trucks, in 4th gear (.71 overdrive) and a 3.36 rear gear, you should only be turning about 2073 rpm at 70 mph. With the 2.73, you only be turning 1681.
With my setup, I'm running a 3 speed w/B-W overdrive and 30" tires. Rear gear is stock 3.90. At 70 mph, I'm only turning 1850 rpm.

i have a nova 2.73 on my 54 with a 235/6 and it runs just fine in 4th and 5th at highway speeds but on hill it needs the 4th. on take off it does ok but around town driving is better in third. mileage in town stinks, 12-13 but on the trip to KC i averaged 20mpg and got a high of 23.5 at 70 mph. you can put over load springs on the leaf spring pretty cheap. ron