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

Hi

Will a 55 (2nd) 5000 series rear axle interchange with a 59 5000 rear axle. I know of a 2 speed 55 axle so I want to know if I can bolt it to my 59? Is it still 6-8.75 lug pattern on a 55?

Cheers Dyna

55 manual - yes the bolt pattern will be the same .... what will a 2 speed axle gain you? do you know the ratios of your original and those of the 2 speed? plan on hauling heavy loads? is the axle you have bad in some way?

Bill

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

that would be 7.20 or 6.17, and I wouldn't rule out the 6.17 until you cheack what's in the actual vehicle - also what ratios are actually in the 2 speed .... is even 5.83 enough different from 6.17 to be worth the work involved?

Bill

Bill,

The 6.17 is in a 4000 series, the 5000 never had the Chevy 6.17, the 7.17 I'm referring to is the optional Eaton. Sorry to say the Chevy 6.17 axle is the 1-1/2 ton so I'm pretty sure I could not fit that on a 5000 2-ton.

Cheers Dyna

never say never when discussing 50 year old trucks, back then absolutely anything made could have been ordered .... the difference in the 4000 and 5000 series GVW ratings is in the front and rear suspension and wheels and tires, and not much real difference from 55.2-59 ... you really should confirm what the truck actually has before planning on major changes for minor advantage

Bill

Bill,

I will check it but it looks like the std axle in 59 was a 7.20 but hey as you say you never now. Is there a tag or marking I can have Matt checking?

Are there later lower ratio 2-ton axles with 6-8.75 bolt pattern and about the same width that will fit the 5000?

Cheers Dyna