3/4 ton without full float axle

[kipps]

How common is this?

My '87 v20 is the heavy 3/4 ton, with 13" brakes and a 8600 lb. rating. Surprisingly, it also has these semi-floaters. What was the point, cost savings? Was the same truck available with full-float and semi-float?

[Matt Man]

I thought the higher gvwr c20/k20's got the full float axle.

[mongocanfly]

The 91 suburban I parted out had the semifloat 14b..
I assume it was all about cost savings.....Keith S. may have the answer to that..

[Ziegelsteinfaust]

It was in part for better mpg since it is like 1/2 the weight of the FF. Dana made the D61 for the same issue. While Ford dropped the ball with the Sterling 10.5 sf.

It is a good rear end, and that are stronger then a ford 9 inch. With not much weight added, and the same hp to draw.

Every C20 I have built has gotten one.

[toddoky]

When GM first started using the semi-floating 14-bolt in C20's the early 80's the only way you could get the full-floating 14-bolt was with a 454 BB engine. I don't know if they continued that into the later 80's models or dropped the full-floater all together on the C20's.

[tucsonjwt]

toddoky sounds right. My 83 C20 454 has a full floater.

[jocko]

kipps, all V20s in 87 received a SF rear axle. Std V20 received the 5700# SF, whereas the V20-C6P received the 6000# SF (your case, if by heavy 3/4, you mean C6P).

In 87, all R/V30s and R20 bonus/crew cabs received the 7500# FF, regardless of engine size.
R20 conv cabs optioned with a 454 also received the 7500# FF.

[kipps]

Does anyone have any input on the relative strength of this axle? Is it appreciably weaker than the 14 bolt full floater? What does it take to break it?

[mongocanfly]

I just tore mine down for a gear swap and trutrak upgrade..ill have to say its very beefy looking inside...the only limiting factors I could see with it was the ol gov-lok and c-clips...ring gear is 9.5" so id say it on the same level as a 9in ford..pinion only has inboard and outboard bearing where a FF has the 3rd bearing...axles look plenty strong as well

[csdineley]

My 87 R20 c6p #8600 also came from the factory with a 14sf. I did swap it out for a 14ff. But that was more just for the different gears then anything else. Ironically I'm now changing the gears in the 14ff to the same the 14sf came with.

[1976gmc20]

To me, a 3/4 ton ain't a 3/4 ton unless it is 8 lug full float.

[dajn]

Originally Posted by jocko

kipps, all V20s in 87 received a SF rear axle. Std V20 received the 5700# SF, whereas the V20-C6P received the 6000# SF (your case, if by heavy 3/4, you mean C6P).

In 87, all R/V30s and R20 bonus/crew cabs received the 7500# FF, regardless of engine size.
R20 conv cabs optioned with a 454 also received the 7500# FF.

My 87 v20 has the full float. So are you saying someone swapped out the semi float? I believe you if you say that's what happened. Just curious.

[jocko]

Originally Posted by dajn

My 87 v20 has the full float. So are you saying someone swapped out the semi float? I believe you if you say that's what happened. Just curious.

That would be my take on it - but you never really know. All the factory documentation I looked at indicates no V20s got the FF, but there could always be an exception.

[Ziegelsteinfaust]

Originally Posted by kipps

Does anyone have any input on the relative strength of this axle? Is it appreciably weaker than the 14 bolt full floater? What does it take to break it?

I have put almost 600/600 HP/tq from a 496 big block through one. Only mod was done was a rebuild, and a Detroit locker. I had the truck for only a couple months, but I beat on it like it owed me money. Plus there are still cromo axle shafts, and higher spline count axles.

The guy I sold it too sent me some pics after he had it painted. Basically telling me how much he still loved the truck.