Car 12 bolt in C20?

[lts70]

I have been helping my boy convert his 68 C20 to a 5lug C10. We have the front finished but have not been able to find a 5lug rear end for his trailing arm truck. We did find a 12 bolt car rear end out of a Nova. The rear end has a code stamped in it of BM03414G2. It came out of a V8 car I believe a 1968 as well. I think it is a 3.31 open rear.

Has anyone used something like this in our trucks? Looking for PROs AND Cons.
Like width, Bakes, strength, ect.

[HotWheelsFan]

5 lug bolt pattern on a Nova would be a 5 on 4.75" pattern and 1/2 ton trucks use 5 on 5" pattern for the rims. Some full size GM B-body vehicles also use the truck 5 on 5" pattern.

I have had to carry 2 spares due to putting truck rotors on the front of a early Monte Carlo I had.

[HO455]

It would be much less work to buy a pair of 5 lug conversion axles and install them instead of changing the mounts on the car axle and dealing with the differences in the axle lengths and possible differences in the U-joints.

You would need an long adjustable track/Panhard Bar on the coil spring truck. Which is not a bad idea especially for lowered trucks. But it would be an additional cost.

Selling the 12 bolt Nova rear end would pay for the conversion axles. There is no real differences in strength of the two in stock configuration. There will be larger drum brakes available for the truck rear end, unless you get extremely lucky and find some station wagon drums and backing plates.

I'm not endorsing the products below just showing examples. There are lots of threads on both just do some searches.

https://www.summitracing.com/parts/c...CABEgIdJPD_BwE

https://www.holley.com/products/rest...DqVx9pIxdylQLY

[RustyPile]

Originally Posted by HO455

It would be much less work to buy a pair of 5 lug conversion axles and install them instead of changing the mounts on the car axle and dealing with the differences in the axle lengths and possible differences in the U-joints.

You would need an long adjustable track/Panhard Bar on the coil spring truck. Which is not a bad idea especially for lowered trucks. But it would be an additional cost.

Selling the 12 bolt Nova rear end would pay for the conversion axles. There is no real differences in strength of the two in stock configuration. There will be larger drum brakes available for the truck rear end, unless you get extremely lucky and find some station wagon drums and backing plates.

I'm not endorsing the products below just showing examples. There are lots of threads on both just do some searches.

https://www.summitracing.com/parts/c...CABEgIdJPD_BwE

https://www.holley.com/products/rest...DqVx9pIxdylQLY

Maybe I'm confused about your proposal.. But as I understand it, his C/20 has a 3/4 ton rearend. those "conversion axles" will not fit a C/20 housing.. They are designed to "convert" 6 lug 1/2 ton rears to 5 lug....

[lts70]

That is correct. I do not currently have an axle that will accept five lug inner axles. The axle that we removed is an eight lug corporate full floater.

If there is anyone in the Idaho/Utah area with an axle let me know. Trying to get this beast back on the road.

When I search out the 12 car rear end, it’s everyone from the car side putting the truck axle in the cars, not vice versa. But I figured if it worked going that way, the car axle might work well in the truck

[1967GMCC20]

Axle bearings should tell the story. 12 bolt car rear ends are hardly capable for performance work, and unsuitable for load carrying strength.
I would search for the correct truck rear axle. Dana 60s are common.

[MikeB]

You might want to keep the current rear end, unless the gear ratio is too low, and call Currie or Strange to see if they can fix you up with 5-on-5 axles. I know very little about C20s, so I could be out in left field with that idea!

Edit: Just occurred to me that C20 backing plates and brake shoes may be larger diameter and won't work with C10 5-on-5 drums. In that case your best solution would be a 71-72 C10 rear end. The 69 housing and axles were shorter, and the 70 still had 6 lugs.

Another edit: That's not say the 69 won't work. My 69 C10 has the stock rear end with axles re-drilled for 5-on-5. With 73-87 8" rally wheels and 255-70 tires, the wheels no longer look too far inboard when viewed from the rear, like it did with the original wheels and tires. I haven't looked it up, but I think 67-68 C10s (and maybe earlier) had the same rear end dimensions as the 69.

[72c20customcamper]

May be a stupid question but why are you changing it to a 5 lug ?

[HO455]

Originally Posted by RustyPile

Maybe I'm confused about your proposal.. But as I understand it, his C/20 has a 3/4 ton rearend. those "conversion axles" will not fit a C/20 housing.. They are designed to "convert" 6 lug 1/2 ton rears to 5 lug....

My bad I somehow missed the C20 in the original post. Dhoo! Sorry for adding confusion.

This might be an option. Hard to tell if it is 6 lug or not. If the rest the tailgate is in as good shape as what's in the picture it would pay for the whole tailer.

https://boise.craigslist.org/tro/d/c...756735252.html

[RustyPile]

Any C/10 rearend from '67 - '72, regardless of its length will bolt right up under your truck.. If you want 5 X 5 lug pattern, then any '71 - '72 is your choice.. Maybe it's just a regional thing, but those '67 - '72 trucks are everywhere in my part of Texas... If you want to make the trip, I can have one of those rearends in your hands first thing Monday morning...

[MySons68C20]

Originally Posted by RustyPile

Any C/10 rearend from '67 - '72, regardless of its length will bolt right up under your truck.. If you want 5 X 5 lug pattern, then any '71 - '72 is your choice.. Maybe it's just a regional thing, but those '67 - '72 trucks are everywhere in my part of Texas... If you want to make the trip, I can have one of those rearends in your hands first thing Monday morning...

This is exactly what I did with the C20..... 67 truck diff, new 5 X 5 axles, Eaton posi with 3.42 Yukon ring & pinion etc. Everything fit perfect.

[Daves70]

If your c20 has leaf springs, ( most do) then get a rear end out of a square body. 12 bolt truck rearends are pretty strong and were available into the early 80's.