The Stovebolt Site Forums The Shop Area Engine Shop Rear end ratio

The donor rear axle for my 49 Sub is out of an 84 GMC half ton pickup. My local Chevy dealer read the numbers stamped on the axle tube and and after looking it up told me that the ratio is 2.73. The engine and transmission combination is 283/TH350. Does anyone know what kind of mileage I might expect with this combination? Also is this indeed an even workable combination. Thanks for any info bolters!

Back before the days of super-high ratio overdrive transmissions and high-geared rear ends, that was considered to be a very high-speed rear end. I remember driving a 58 Chevy Delray with a 3.70 gear, and when I switched to a 3.34, I thought I had a high-speed rig! Your 2.73 ought to work well, and give you good cruising speed, and also good acceleration. Unless the 283 has a radical camshaft and/or a big 4-barrel, I'd expect gas mileage in the high teens or low 20's. Go for it!
Jerry

I agree. It will be a great cruiser unless you
pull a large trailor or run very big tires.

I have 3.08 gears in my Suburban with a 270 and a 4-speed. Great unless I try to pull a loaded trailer.

I have a 2.29 rear out of a Monte Carlo that was a 305/350 combo. That car weighed about the same as my '54 Chevy pickup. Though it sure wasn't a race car, the car performed fine. The rear and possibly engine transmission may go in my '54.

Old Sub,Wrench and Jerry. Thanks much for answering my question on ratios and mileage. Do any of you see a problem with occasionally pulling an 18' camper with this setup?

No problem as long as you're not in a hurry and don't need to climb any big hills....

That 283 doesn,t have a lot of torque. It would
be constantly downshifting on hills. I dont think
it would be a very comfortable ride.

My '89 Suburban has 350EFI/TH700R4/3.08. I thought it was a pooch so I massaged a few things in the engine. It's no barn burner, but it is much nicer to drive now. Sounds better too. Also added a rear anti-sway kit and huge trans cooler.

I pulled the '47 ton dually panel, on a trailer, (total weight approx 7500 lbs) 600 miles to get it home. It worked it, but I just stayed out of OD, kept it down to 55mph and avoided stopping where I had to take off headed uphill. The 1/2 ton suspension caused me more stress than the powertrain. It was definitely floating. The key is to take it easy.

If you don't like the way it pulls your trailer, think about adding some snort to the 283. Or better yet, look around for a 350. That 283 should sell for enough to pay for one.

You could also consider regearing that 2.73 to a 3.23 or 3.54. A ring and pinion isn't all that much, but the GM rear ends are a little tougher for an amateur to get set up right, so you might want to get a pro to mic it all out and do the final adjustments.

BTW, The fuel mileage actually improved with the modifications I made to the 350. Best I ever got was 18 mpg highway. I hope I can get the panel set up so well!

I agree with Wrenchbender. A 2.73 axle is too tall for a stock 283 in your Suburban unless you only plan to use it for unloaded highway cruising with small (<= 28") tires. I am certain you will be very unhappy with it's towing performance, esp. with an 18' camper. The 3.73 and 4.11 axles were common factory ratios on these trucks for good reason. Its a matter on how you plan to use it: Sunday cruiser or daily driver.

Hey everybody many thanks for the education on engines, transmissions and rear end ratios. Whenever I ask the bolters I always get the feedback I need. What a great site. Now if I could just learn how to post some pictures. Weeds