The Stovebolt Site Forums The Shop Area Engine Shop Differential or Rear End swap?

Hello! I have a '61 chevrolet C20, I'm trying to get interstate travel out of it. It's to my understanding I have a 4.57:1 pinion differential and I would like a 3.5 (or similar) ratio. It seems i can put a '73-'87 3/4 or 1 ton 14 bolt rear end in it, would that be the right thing to do? I would like an 8-lug axle if I were to chose the rear end, so I can keep the wheels I have. I've measured it out and I'm near positive I have the 3 inches to spare with these wheels. If I were to load it up though, I'm not so sure. I'd love a C10 positraction differential if those are available in that ratio and compatible with my truck. I don't do much towing with it. It's a daily driver, but it isnt very practical as is. I believe I have the skill at this point to do a rear end swap If it isn't ridiculous. Any additional info you think I need would be welcomed of course. Thanks for the advice in advance!

Just a thought here... It is easier to swap the transmission than it is to swap the rear end. You don't mention what engine or transmission you have, but I'll assume you have a sm420 granny low 4 speed. Changing to a 4 speed OD transmission like the my6 (a chevy version of the A833) or even an NV4500 5 speed will give you an effective final drive ratio of 3.34:1.

Anyway if you had 29 inch tall tires, and the 27% OD either of those transmissions offer, 70 mph would be about 2700rpm. instead of 3700 rpm without the OD.

First I don't much about the different rear axles, 12 bolt, 14 bolt,etc.

I was told by someone at a swap meet last weekend that they had put an Eaton pumpkin in a 14 bolt rear axle. The only problem they had was to swap the axles because of the splines. If the reverse could be done, 14 bolt pumpkin in an Eaton rear axle, that would make more rear axle ratios available for the Eaton.

Larry

swingdaddy- I do have the granny low 4 speed and a 235.. my tires are 31" so I'm fine there. I'll look into those now too.. The truck's top speed is 70mph right now, and that's pushing it.

LG- That sounds like what I thought I'd be doing, I'll see about that right after these transmissions.

Thanks you very much

Im not finding anything for the MY6, could i use the A833?

Nevermind, you've given this info before! I'll just browse the site on NV4500

You can put a locker from a 14 bolt into an Eaton but you have to use the 14 bolt axle shafts and spiders. You have to stick with the Eaton ring and pinion and carrier though. Other than that nothing else is compatible. The Eaton has the drop out style center section like a Ford 9", the 14 bolt does not. (Salisbury type)

Thanks Ghostrider, Thought something was left out, or someone would have done already.

Larry

I have done NV4500 swaps, never in a 61, but it shouldn't be that much different than in the 59 GMC I am currently driving.

PM me if you have some specefic questions about the swap that I might be able to answer.
John