New truck 72 C20 4x4

[mattwhiteyanks1]

Finally got my old man to sell me his 1972 c20 4x4. I'd love to share pics but can't seem to figure out how to do it on here. Anyways, my question for now....has anyone ever swapped a late model rear end into one of these trucks? I want to swap a 3/4 ton rear end out of a 2000 and up truck. Leaf springs and all. Thanks guys

[swamp rat]

If its a 4X4 its a K20 not a C20, it probably has an emblem on the side that says Custom?

There has been a lot of rear end swaps but most involve moving the spring perches on the axle. cant tell you the width differences between what you have (I assume its an Eaton) and the 2000.

You could post this question in the 4X4 section and maybe get more reply's. Also learn to use the advanced search function once you know what axle you want to swap, it may bring up some relevant threads.

[mattwhiteyanks1]

Thanks I appreciate the help. Not sure why I said "c20". I don't think it has any badges on the sides if I remember correctly. I used to be on this forum quite a bit whike I was deep into a 70 c10 I was building for my grandfather (it's still a work in progress). I never had issues loading pictures, but I dont see that option now.

[franken]

Why swap? Disk brakes? Disks in the rear are more to say, look I have rear disks than actual braking effectiveness. ~75% of braking happens in front.
Spring perches won't be the same, the WMS is wider, and the shock location is different.

[mattwhiteyanks1]

I like the looks and function of disc. As well as ease of maintenance. As for the swap, I can get a locking diff in a newer rear end from the factory. It'd also give me a complete disc brake including an e brake set up without mixing small parts and brackets. And I'll actually use the truck for occasional hauling and pulling a gooseneck trailer. I'd rather have leaf springs and build a ladder bar set up for it. I know it won't just bolt over but I was just curious to see if v anyone had done it before. I know I'm not the only one that appreciates late model engineering. It's not always "best" but there can be significant benefits. What is "WMS"?

[57taskforce]

Wheel Mount Surface. Basically the width of the rear end. Beware that the G80 gov lock portion of the late model rear ends are pretty weak. That factory locker didn't last long in a s-10 I had or in my k2500 suburban or k2500 Silverado either. In my opinion they are useless. The gears will be fine when the gov lock goes out but you will have no factory locker.
The latemodel disks are nice to maintain. However, I'm not convinced they add much in the way of braking performance. The one big advantage is heat dissipation.

[mattwhiteyanks1]

I like the heat dissapation, the simplicity, as well as they don fall off (performance wise) when wet or covered in mud. Not that drums are bad, I just prefer disc all around. Id also like a bit more confidence than the factory set up provides (as im swapping the motor with a few more ponies).You don't know what the width difference is by chance do you?

[jocko]

To post pics, click "go advanced" then click on the little paper clip. Browse and add up to 5, then upload, then close, they'll be displayed.

I too thought I'd prefer rear disks, until I completely redid my stock 3/4 braking system. Disk/Drum combo worked like a champ (vast improvement over the worn system) and whenever I needed parts, I'd just look up what the truck was, 72 C20, not 72 C20kenstein. Much simpler. I'm not seeing the benefit of the swap (when you con sider the cost and effort of install - minimal gains).

[mattwhiteyanks1]

Let's try these pics. I know I mentioned it being a daily driver, but it will be around 560-580hp. Not gonna be a race truck by any means. Just a fun driver that I can use for work when I need it. If I were to retain the stock axle, what's the best 8lug disc kit for it?

[mattwhiteyanks1]

Ok, I'm going to sound really dumb as I've not really paid much attention to the truck in several years. I just mentioned to my dad that I'd like to buy the truck if he ever wanted to sell it. Biggest reasons being, it's been in our family forever. It's a cool somewhat rare truck. It's 4x4. I love these trucks. I just realized, it looks like (in the pictures i have. Its still at my dads shop till i can pick it up in a couple days.) Its a 6 lug truck. That'd make it a k10 wouldn't it? 350 with a 4spd. This whole time I was thinking it was a 3/4 ton truck. Not that it matters, but now I'm confused ha. Go ahead and figure that I'm an idiot now....anybody straighten this out?

[mattwhiteyanks1]

Just checked the vin. It's a 1/2 ton 4x4. Well, I guess that's that. I'm not sure why I thought it was a 3/4 ton truck.

[68350]

looks like a pretty solid half ton. i see it has factory cab lights too. I would think you could just add discs to the 12 bolt out back. or you could swap over to 3/4 ton suspension if thats really what you want, but just remember the 3/4 ton frames are beefier than half tons. My 496 makes 555 hp and the 12 bolt has been working good so far. I would think the weak link in the entire system will be the dana 44 front (if you plan on beating on it in 4wd)

[swamp rat]

1/2T all the way. 6 lug is heavy 1/2T

[57taskforce]

Originally Posted by 68350

looks like a pretty solid half ton. i see it has factory cab lights too. I would think you could just add discs to the 12 bolt out back. or you could swap over to 3/4 ton suspension if thats really what you want, but just remember the 3/4 ton frames are beefier than half tons. My 496 makes 555 hp and the 12 bolt has been working good so far. I would think the weak link in the entire system will be the dana 44 front (if you plan on beating on it in 4wd)

I beg to differ on the difference in frames assuming we are talking about long bed trucks:
Read sstims posts in this thread.
http://67-72chevytrucks.com/vboard/s...d.php?t=659340

[68350]

I love this board for learning stuff. I was always under the impression they were different.

[mattwhiteyanks1]

I guess I figured it was a 3/4 ton truck because of the marker lights on the top. Most 1/2 ton trucks don't have marker lights. I'm going to check the rear end today and add that to the equation. I was expecting the 14 bolt, but we'll see.

[mattwhiteyanks1]

While I've got a bit before I can go out and check the axle. There were no 67-72 6 lug trucks from the factory right? 5 on the 1/2 tons and 8 on the heavier. Somebody has swapped these somewhere down the line?

[mattwhiteyanks1]

Originally Posted by swamp rat

1/2T all the way. 6 lug is heavy 1/2T

They made a "heavy 1/2 ton"? What are the differences?

[57taskforce]

Originally Posted by mattwhiteyanks1

While I've got a bit before I can go out and check the axle. There were no 67-72 6 lug trucks from the factory right? 5 on the 1/2 tons and 8 on the heavier. Somebody has swapped these somewhere down the line?

67-70 all half ton were 6 lug. 71-72 2 wheel drive= 5 lug. 71-72 4x4=6 lug. All 3/4 & 1 ton were 8 lug.

Originally Posted by 68350

I love this board for learning stuff. I was always under the impression they were different.

I hear you! I actually discovered they were the same on accident, and started doing some research here to confirm it

[Joesjunk]

All 1/2 ton 4x4 trucks are 6 lug.

1/2 ton 2wd trucks were 6 lug until 1970, then went to 5 lug in 1971

What you have looks like a normal 1/2 ton 4x4. Roof marker light could have been ordered on any truck. It will list them on the SPID on the inside of the glove box door

And it should have a 12 bolt rear axle, not a 14 bolt

Cool truck regardless, just clean it up, get it running and driving and enjoy it.

[mattwhiteyanks1]

Just got back in from looking it over. It is without a doubt, a half ton truck. Granted, it's not been driven in over a year, and even before that it wasn't driven much at all. I can't believe most of us thought it was a 3/4 ton. I never paid much attention to it. Sounds dumb since I bought it and didnt actually know, but this truck has so much sentimental value, it doesn't matter. I am glad to have the 4x4 and 4 spd manual. Can anybody tell me which 4spd it is?

[68350]

Should be a sm465

[mattwhiteyanks1]

Thanks. Pros and cons? Advised upgrades or changes?

[mattwhiteyanks1]

I've been building 70 c10 for my grandfather, but I've already got an ls motor in it and a 4l80e. 2wd truck. I've not done a lot with these trucks aside from these two.

[68350]

465 is a good transmission. If you plan on putting a 550+ hp motor in it, i would ditch the 465 tho. But as far as everday driving they work very well. They are essentially a 3 speed with granny low. I rarely used 1st in my 71 gmc. They are not a hot rod transmission by any means