1 ton full floater versus semi floater

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JayMB

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Ah, ok. Thanks for pointing out that the frame is skinnier on the dually cab & chassis trucks. The one I put a tape measure on was already torn down to just the frame. Makes sense.

Also to anyone curious, the GMT800 AAM1050 is about 1.5" longer hub face to hub face than a 4x4 GMT400 9.5sf. Which is kinda nice since the rear wheels always looked excessively "tucked-under" at the back. I realize this is by design but I like the way it looks now better.

The reason I swapped my 9.5sf for a 14FF is because I needed new drums and they are expensive. I also wanted a locker (g80) in the back. I bought a complete GMT800 AAM1050 with 65,000 KM on it (so like 38,000 Miles) for $700 Canadian. I come from big trucks, two bearings is better than one and any design where I broken axle shaft can lead to a flying wheel is not my first choice. I wouldn't swap axles for no reason but a 14ff in place of a 10 bolt is a worthwhile swap any day. Less so on a 14sf but hey it's the owners' money so whatever. Still better than $45,000 for a new crappy truck with a 4 cylinder.
 

98chevy2500SS

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Ah, ok. Thanks for pointing out that the frame is skinnier on the dually cab & chassis trucks. The one I put a tape measure on was already torn down to just the frame. Makes sense.

Also to anyone curious, the GMT800 AAM1050 is about 1.5" longer hub face to hub face than a 4x4 GMT400 9.5sf. Which is kinda nice since the rear wheels always looked excessively "tucked-under" at the back. I realize this is by design but I like the way it looks now better.

The reason I swapped my 9.5sf for a 14FF is because I needed new drums and they are expensive. I also wanted a locker (g80) in the back. I bought a complete GMT800 AAM1050 with 65,000 KM on it (so like 38,000 Miles) for $700 Canadian. I come from big trucks, two bearings is better than one and any design where I broken axle shaft can lead to a flying wheel is not my first choice. I wouldn't swap axles for no reason but a 14ff in place of a 10 bolt is a worthwhile swap any day. Less so on a 14sf but hey it's the owners' money so whatever. Still better than $45,000 for a new crappy truck with a 4 cylinder.
Thanks for the info! Can't wait to swap to a GMT800 FF soon. :D

And yes, still better than buying an expensive new truck when these trucks were made to last a long time.
 

454cid

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I have a GMT800 AAM1050 (newer 14-bolt with disc brakes)...

It's just a later 14BFF.... AAM has made them since March of 1994. The GMT800 just demanded a revamp just like the change from Squarebody to GMT-400 did. "AAM1050" actually makes me think of the Dodge axle, even if AAM may use that terminology.
 

JayMB

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I didn't mean to imply that the AAM1050 is in any way superior to "ye old 14ff". You're right, they're practically the same. Even used a rear diff cover for a 14ff on mine. Needed metric bolts though, so that's a difference. I was just trying to differentiate the AAM1050/14ff that only comes behind a 6.0L in the GMT800 trucks from the " Duramax axle" AAM1150 which is different. You're 100% correct. Execept I thought AAM started in '01 but whatever.
 

John Cunningham

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Guys, this whole semi vs full floater is getting out of hand. For ***** sake, either of these diffs will work just fine. I have a 1988 K 3500 with a 9.5 semi float and a g 80 with 250,000 plus miles on it and it works just fine. All of you are looking for a problem that does not exist. If you abuse the diff it will break, it does not matter if it is semi or full float. I am a retired GM truck tech and have seen more of these than most of you will see in your life unless you have worked on them for the last 30 years. All of them will break at some time if you use them incorrectly.
I see people on this forum posting about their diff breaking, blowing up grenadeing or over loading etc. The majority of the times it is due to abuse, drifting, power breaking, spinning the wheels on take off, doing doughnuts in the dirt or snow with a G80. If you use the diff out side of its design parameters it will break sooner or later.

You have to remember that MOST people do not abuse their trucks on a regular basis AND that GM designed these trucks to appeal to the MAJORITY of consumers and these consumers want a vehicle that is comfortable to drive with NO harsh quality's. There is a reason that the after market exists.
Let me give you some of insight because your not telling the entire story....lets get to the truth......Here is a question for you now: Why did GM bother building a full floater if a semi will work just fine?
here in lies the reason....First off the ring gear is 1 inch larger and dia and now there are two bearings supporting weight. If you were to say brake an axle with a truck camper on top of your truck you will surly be in a world of hurt driving down the hwy at 60MPH...your axle will come out along with the tire causing a possible serious accident for you and innocent victims...........now if your not going to ever load your truck thats a different matter.........this is more about safety and nobody wants to take a chance with your loved ones in a truck under any condition...........GM did this for a reason so your method of reasoning does not hold water period.....
 

evilunclegrimace

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Let me give you some of insight because your not telling the entire story....lets get to the truth......Here is a question for you now: Why did GM bother building a full floater if a semi will work just fine?
here in lies the reason....First off the ring gear is 1 inch larger and dia and now there are two bearings supporting weight. If you were to say brake an axle with a truck camper on top of your truck you will surly be in a world of hurt driving down the hwy at 60MPH...your axle will come out along with the tire causing a possible serious accident for you and innocent victims...........now if your not going to ever load your truck thats a different matter.........this is more about safety and nobody wants to take a chance with your loved ones in a truck under any condition...........GM did this for a reason so your method of reasoning does not hold water period.....


I am aware of the reasoning behind the semi vs full float diff. The reason that GM offered a full float diff is that the full float has the ability to carry more weight and you can get a numerically higher diff ratio for more torque. The full float also has a better pinion bearing setup, But like I stated either diff will work IF IT IS NOT ABUSED. over loading is abuse period.

As to your not loading your truck reasoning, keep the load with in the design parameters and it will be very unlikely that you will have a problem. MY 88 K3500 has a 8600 GVW and that lets me carry about 3000 lbs. in the bed. Those are the design parameters for that setup and it works as designed. If I needed to carry more weight then yes a Full float diff would be needed.

The MAJORITY of people do not need the weight carrying capabilities of a full floating diff (including folks on this forum) but some like to go overboard with their trucks, like putting a lift kit on a truck that never leaves the pavement or putting a high horsepower engine in a truck that is used for a daily driver that has to follow the posted speed limit or even putting a full float diff in a truck that never comes close to being used to its load capabilities. And to be clear I am not saying that any of these mods are wrong/bad, we all like to personalize our trucks

Now to your argument that the axle will brake from over loading, the bearing would be the most common failure point due to overload regardless if is semi float or full float, most axles break from shock loading NOT overloading. I have seen more broken axles in full float diffs than I have in semi floats, I am not saying that it does not happen but it is rare, after all there are millions of these trucks on the road and most of them have 8.5 semi float diffs and these are overloaded on a daily basis pulling trailers, used in plow trucks used for landscape dump trucks ( with bed inserts) and you don't see the road side littered with them with axle/wheel assemblies missing.

So yes my reasoning does hold water.:waytogo:
 

letitsnow

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After tearinginto my rear end I relized I have a 1 ton K3500 semi float rear end....This is an unmolested truck so I am not sure how this rear came about on this truck.

I was going to install rear discs and thought how foolish not to have a full floating rearend in this truck for what I am going to use it for.

Carrying so much and or pulling so much weight could cause a serious accident with an axle come flying out if it broke and I have seen them brake.

2 outside bearing are better than 1 so why take a chance. I have a nice rear end 4:10 gear that is worthless to me because I am not going to use it...........I am looking for a full floater for this truck. I am not sure if the 4x4 has any bearing on the rear end selection.

I imagine the leaf spring placement is the same too....I was wondering if anybody has ever made this swap. I am not interested in a dually just a full floater instead of a single floater.

Especially if I carry a 3000 pound truck camper...those bearings will make a huge difference with two.

Can anybody tell me how I ended up with a semi float rear end in an unmolested K3500 97 silverado that has never been touched?

I dont even see an option for that rear end either...must have something to do with a camper option?
Any ideas?

After seeing your posts about this truck - I recommend that you sell it and buy something newer that will make you feel better about what you are doing. I am not saying that to be an ass, I just don't think that you are willing to put up with this trucks design. Get out your checkbook...
 

Supercharged111

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The GMT400 FF is a deceivingly underrated in the pickups, it's not the weak point. The spring pack is, that's why the cab and chassis trucks were rated 2000# higher on GVWR. These old trucks are still pretty capable. I carry a 5000# camper in mine with nothing more than a pair of airbags and the truck drives just fine, no feeling of an impending rollover and still enthusiastic to stop. Newer trucks have stronger frames and bigger brakes, but there's nothing black magic about how they carry more weight better and there's no reason you can't easily and safely get these trucks to do more than they were intended to do. You're just never going to be legal, but answer me this: when's the last time any of you were pulled over by a cop and questioned about your weight? Furthermore, back in the 90s there was no standard by which tow ratings were assigned.
 

John Cunningham

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After seeing your posts about this truck - I recommend that you sell it and buy something newer that will make you feel better about what you are doing. I am not saying that to be an ass, I just don't think that you are willing to put up with this trucks design. Get out your checkbook...

I wont sell the truck...........I am going to hang a quadrasteer rear end under it
 

John Cunningham

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I am aware of the reasoning behind the semi vs full float diff. The reason that GM offered a full float diff is that the full float has the ability to carry more weight and you can get a numerically higher diff ratio for more torque. The full float also has a better pinion bearing setup, But like I stated either diff will work IF IT IS NOT ABUSED. over loading is abuse period.

As to your not loading your truck reasoning, keep the load with in the design parameters and it will be very unlikely that you will have a problem. MY 88 K3500 has a 8600 GVW and that lets me carry about 3000 lbs. in the bed. Those are the design parameters for that setup and it works as designed. If I needed to carry more weight then yes a Full float diff would be needed.

The MAJORITY of people do not need the weight carrying capabilities of a full floating diff (including folks on this forum) but some like to go overboard with their trucks, like putting a lift kit on a truck that never leaves the pavement or putting a high horsepower engine in a truck that is used for a daily driver that has to follow the posted speed limit or even putting a full float diff in a truck that never comes close to being used to its load capabilities. And to be clear I am not saying that any of these mods are wrong/bad, we all like to personalize our trucks

Now to your argument that the axle will brake from over loading, the bearing would be the most common failure point due to overload regardless if is semi float or full float, most axles break from shock loading NOT overloading. I have seen more broken axles in full float diffs than I have in semi floats, I am not saying that it does not happen but it is rare, after all there are millions of these trucks on the road and most of them have 8.5 semi float diffs and these are overloaded on a daily basis pulling trailers, used in plow trucks used for landscape dump trucks ( with bed inserts) and you don't see the road side littered with them with axle/wheel assemblies missing.

So yes my reasoning does hold water.:waytogo:
Carrying more weight safe is the most important thing to me........thats why they put these rear ends under the truck...not because it was an engineering exercise or for fun...dont be critical of anybody who wants to do the right thing and tell everybody dont worry about it...
 
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