First post Changing 3/4 ton rear end to half ton rear end
 

Need Help. Have a 66 C20 with 8 lug rear axle, would like to change to 5 lug 1/2 ton rear axle. Anyone have a list of donor vehicles for easiest swap on coil spring truck?

Re: First post Changing 3/4 ton rear end to half ton rear end
 

One, the rear u-joint is different size.

Second, the pinion on the 3/4 ton is longer.

Re: First post Changing 3/4 ton rear end to half ton rear end
 

Welcome to the site. I guess it's not as simple as just swapping the rear, which you may already know. Does your c20 have coil springs or leaf? Let's assume it has coils. You would need a '71 or '72 rear to be coil spring ready with 5-lug. '70 will have 6 lugs but axle shafts are interchangeable with 71/72... and later 12-bolt? Maybe someone else knows about post-72 better.

Re: First post Changing 3/4 ton rear end to half ton rear end
 

Moser lists all 70 rear ends to be same width as 71 and 72, and 73 and up. I've never heard much here about all 70 diff housings being same width...anyone???

I'm the one that's waiting for someone to come up with a 70 C-10 that has factory disc brakes. I had a thread about it. Might be a very limited option...back to topic...

C20, it would be best to fins a 71 or 72 diff with the 5 lug axles. You might be able to buy a combination U-joint to adapt your current drive shaft to the 1/2 ton diff...IF, IF the length of the drive shaft doesn't need to be altered... I don't know about that...

Re: First post Changing 3/4 ton rear end to half ton rear end
 

To the best of my knowledge '70 rears are same width as 71/72. This issue with the u-joint differences can be remedied by using a driveshaft out of a longbed C/10. Or, when you have the C/20 driveshaft lengthened it may be possible to replace the back yoke with the right size...or do the conversion joint.

Are you saying you have or have seen a '70 with 5-lugs and disc brakes? I haven't personally verified it yet, but I have known a father and son who deal in old trucks I've known a long time who offered me a '70 shortbed chassis with title and such that is 5-lug. They both know this is not supposed to be and they are convinced it is all factory original. I hope to see it and another chassis I really want before too long. I'm curious to see this for myself.

Re: First post Changing 3/4 ton rear end to half ton rear end
 

I started a thread about 70's with disc brakes, you mentioned the truck offered to you in it. I sold auto parts back in 80's and 90's.

Had a customer that wanted front brake PADS for his 70, had been all over town, everyone wanted to sell him shoes. He was pretty huffy acting when he asked me for the parts. I calmly told him that disc brakes were listed in MY catalog as an option, no big deal.....he said he'd be doing business at my store from then on. Not sure I ever saw him again. Wish I had gotten to know him. Many times I went to customers house after work to help them figure out how to repair their vehicle. Yeah, I sold a lot of parts, in my day. Folks would look to see if my car was at store before they turned in the drive way. Not bragging. Think about it, how many bad experiences have you had at a parts store??? Likely most of them were bad, unless you found someone that knew their job, and tried to genuinely help you.......

I've had my 68 since 1980, had gained knowledge of these models. My parts book showed 1970 that disc was an option. May have been something GM did in 70, possibly started using 71 parts early. Have not had any positive's her on 70 disc brake pickups...oh, well