The Stovebolt Site Forums The Parking Lot Big Bolts 55 to 59 rear axle interchange?

Thanks for the info Bill,

Well if I got it right a 55 speed (5000) is either 5.83/7.95 or 6.40/8.72, while the std axle on a 59 5000 is 7.20 possibly 7.17. I know everyone is saying a 2 speed rear is for the lower (higher numerical) gearing at heavy load and don't give you an “overdrive” but I'm sorry 5.83 or 6.40 is a lot higher gearing (lower numerical) than 7.20.

With 8R22.5 and 7.20 axle you will get 3200 RPM's at 50mph while a 6.40 axle will give 2800 RPM and a 5.83 only 2500 RPM

With 10R22.5 and 7.20 axle it's 3000 RPM's at 50mph while a 6.40 axle will give 2600 and the 5.83 will give 2400.

You should be able to cruise at a comfortable 60mph at 3200 with a 10R22.5 tires and a 6.40 rearend – think that should be doable especially if you fake a 350 or 400 to look like a 283. Sometimes I will actually have a pretty heavy load, one car on the truck and one on a trailer behind it and we aint talking new tin cans but old American iron (Cadillacs, Buick etc), so yes it might be nice have a two speed for that reason too.

Cheers Dyna