The Stovebolt Site Forums The Parking Lot Big Bolts Two speed real axle

Did chevy ever make a 2 speed rear axle like the internationals for their larger trucks?

Well I don't think Chevy actually made it, but a 2-speed axle was an option in the bigger trucks.

I would assume you know that a two speed gives you a slow and slower rear ratio.
Some people think you can go faster if you have a two speed rear, not so. If you swap a two speed where you had a single you are most likely swapping to a lower, slower on the road, ratio.

Got two speed rears on both my '48 2t. chevy dumps. Even have decals on the dash with instructions. Looks factory to me.

Chevrolet first offered a 2 spd. axle in 1939.

Grigg:

So a two speed axle won't add a higher ratio to 6:16 differential gears? You're right, I thought that would add taller gears for faster highway speeds.

Dale in Iowa,

I have never seen a two speed rear end offer any other choices than...the ratio allowed by the ring and pinion, and one lower. If you can install a auxiliary transmission (brownie), you can get a overdrive ratio.

Stuart

Dale - the 2 speed would be about 6.40 and 8.72

Bill

Dale in Iowa,

I might using the term "lower" incorrectly. When I think of a low gear, I guess it really is a "high" ratio. So the two speed will give you the ratio of the installed ring and pinion, and a optional higher ratio, which will result in a slower speed, but more torque! Clear as mud.

Stuart

Here is some additional technical specifications on the single and two-speed rear axles for the medium duty trucks...

When I got my '57 Fire Truck it had a 7.17:1 single speed rear and had a top speed of about 53 mph. It has an 18,000 pound Eaton rear, so I found a 2-speed pumpkin (that fit my housing) that had a higher high ratio and a lower low 6.14/8.36:1. I added 10 mph on the top side and have a deeper low for pulling (Granny and 'Low Rear' will pull a house down). I drive it like a 6-speed, set the rear to 'low rear' and work up to 5th low then shift the rear to 'high'...I'm very happy with the results. When we convoy to truck shows I never hear I'm holding the group back...I'm usually out in front leading the way!

Mike B

Hey Big Dogs, I wonder if you can help me out. I have a '57 3600 one ton dump and the little dogs only have half and three quarter trucks so I come to you my Big Dog brothers with a question about rear ends. My GM 10 bolt 11 inch is geared so stinkin' low (probably 4.57) it's cruel. At 50 mph that 350 engine is really whirlin'. This thing has power aplenty; I just hauled 4000 lbs, taking off in second gear no problem. I'm told they don't make aftermkt gears for this thing. I can hang an aftermkt overdrive where the carrier bearing sits for only 3k!!! Any thoughts about a two speed axle???? or other solutions to my screaming dilema???????

Skip,
Try posting a new topic with your questions, I am sure you will get more responses than tacking on the end of this one.
Grigg

Dude (I'm from California), Thanks!