aam rear axle

[1tuff71]

Does anyone have any experience with the aam rear axle GM is using on their 1/2 ton trucks. I was thinking of replacing my c-clip 12 bolt and was wondering weather it would just be cheaper to put a eliminator kit on or find a newer aam axle and work with that. Will my wheels work with the newer axle? This truck is a trailer queen so strength is not too important but running the large tire/wheel combo I have worries me. Thanks

[Mike C]

The newer trucks 8.6" 10 bolt is probably a little stronger but not exponentially than the 12 bolt. It does have the same pinion shaft diameter of the 12 bolt car. IMO, the c-clip eliminator kit is a worthless addition. They leak and are NHRA legal but not the best choice.

A real upgrade in strength would be the 6 lug 9.5" 14 bolt that was used in the light duty 88 to 98 3/4 ton trucks and in some of the higher GVWR 1/2 ton trucks (extended cab Z71 for example. Not all of them but some.) It's still a c-clip axle, but the 33 spline axles are probably twice as strong as the 12 bolt.

If you really want to be stronger go 8 lug Suburban stuff. (9.5" 14 rear and 8.5" 10 bolt front) That's good for moderate offroad usage with 35" tires easy. No need for a 60/FF14 combo unless you wheel it hard with 37"+ tires But you'd have to buy new wheels with either of those...

Axle is about the only thing I never broke on a 12 bolt FWIW.

[1tuff71]

So I would have to change my wheels with the sf 14 bolt or will the 15" fit ? Maybe if I do a disc brake conv. ?? Not sure that's even an option. I haven't dug that deep yet. Thinking of giving the guys at ORD a call. They seem to be the gurus of GM trucks and I'm trying not to spend a ton of cash. So the c- clip kit is a leaker eh. Is this from personal experience or rumor ?

[Mike C]

I think the 15" wheel would fit on the 6 lug sf 14, but I can't guarantee that. I'm almost positive it would fit with a disc conversion on the back. The Z-71 may have come with 15" wheels in the beginning before going to 16's, but I don't know the years.

Your 15" would probably work with a disc conversion in the rear but would need to verify with kit manufacturer.

My 12 bolt has been broken at least 7 times. 35" tires, granny gear 4 speed, high miles, wheel hop, warped differential carrier, weird backfire while turning it off and letting the clutch out. (That was the first one on my dad in something like 1980). If you aren't planning on driving hard or 100's of thousand miles (my Jimmy has 350,000 miles on it) I wouldn't worry about it.

And when you do break it, I would seriously consider 8 lug axles but that does mean new wheels and tires. Eventually tires have to be replaced (and if you are worrying about broken axles on a street truck, you should REALLY be worried about older tires coming apart which is way more likely.)

[1tuff71]

Is it possible to use everything from the backing plate out from a 12 bolt to the sf 14 bolt since their both GM pieces. Where did the c-clip elim. kit leak from ? Save me from new wheels/tires.

[obijuan]

15 inch wheels should clear just fine. The 14sf 6 lug also uses 14mm studs. I'd drill out the front to match.
I do think 10 bolt backing stuff matches, but unsure of 12 bolt. Just run with the same brakes.

[Mike C]

I think the center pilot on the SF 14 is smaller diameter like the 5 lug setup so I don't see using the 12 bolt brakes. But the SF 14 should have bigger, better brakes. I did use my original parking brake cable on my 14 so no mods to that were needed. I cut off the original perches and reused them because it's a 3.25" tube axle and not 3". I don't like the newer style shock mounts so I used a set cut from a junk 12 bolt and rotated them where they don't hang below the axle tube for max clearance offroad.