1 ton full floater versus semi floater

[John Cunningham]

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?

 

[98chevy2500SS]

Having a 350 vs 454/6.5TD sometimes made all the difference. Most 1 tons I see have full floaters.

I have been told if the truck has a 350, it will have a semi floater, full floater as an option. If I has a 6.5TD or 454, it will have a full floater standard. This in 3/4 tons, it may apply to 1 tons too, but I am not sure. I thought one tons usually got a full floater no matter what engine it had, but I could be wrong.

2WD vs 4WD full floating rear ends shouldn't be any different IIRC. Spring placement is the exact same as I converted my truck from having a 10 bolt, to the 14 bolt semi floating rear end, so a full floater will work.

I would put in a full floater though if I were you anyway, just because they are a more desirable rear end than a semi floater. I've got a semi floater in my 98 2500 and I am wanting to upgrade it to the GMT800 Duramax rear end w/ disc brakes, might be something to look into if you want your truck to be stronger. All GMT400 rear ends are interchangeable if you decide you don't want to modify anything, the GMT400 full floater will be a direct swap into your one ton with no modification.

 

[John Cunningham]

Having a 350 vs 454/6.5TD sometimes made all the difference. Most 1 tons I see have full floaters.

I have been told if the truck has a 350, it will have a semi floater, full floater as an option. If I has a 6.5TD or 454, it will have a full floater standard. This in 3/4 tons, it may apply to 1 tons too, but I am not sure. I thought one tons usually got a full floater no matter what engine it had, but I could be wrong.

I would put in a full floater though if I were you anyway, just because they are a more desirable rear end than a semi floater. I've got a semi floater in my 98 2500 and I am wanting to upgrade it to the GMT800 Duramax rear end w/ disc brakes, might be something to look into if you want your truck to be stronger. All GMT400 rear ends are interchangeable if you decide you don't want to modify anything, the GMT400 full floater will be a direct swap into your one ton with no modification.

Thanks......Yes I do have a 7.4 and I think it was a screw up from the factory because this truck has never been touched...it could be in a museum.
I am wondering what to do because I dont want to start welding spring perches etc....seems easy to find a gmt800 full floater but I do not know if there are any complications with this swap? Do you? LIke length and mounts etc

 

[454cid]

2wd vs. 4wd will have a different width, I'm told.

Somebody probably swapped the axle after the warranty. They don't normally go bad, but I'm sure there is the exception. My transfercase cracked at about 20K miles, so defects happen.

 

[letitsnow]

If you are going to swap rear ends, and want disc brakes - I would for sure get a gmt800 ff. Have somebody weld the spring perches on and be done.

 

[JayMB]

FYI the cab/chassis K3500 has a different frame spacing (closer together, oddly enough) than the other trucks - so not "all" rear ends are interchangeable on GMT400s, but almost.

I have a GMT800 AAM1050 (newer 14-bolt with disc brakes) on a K2500 GMT400 Suburban originally equipped with a 9.5sf. The spring perches needed to be moved about 1" outwards on either side on the AAM1050 IIRC. The shock mounts were different so swap yours over or go aftermarket. The U-joint is a 1410 vs a 1350 on the stock axle. You'll need an adapter u-joint or a new driveshaft. Worth noting is that the end of the pinion on the bigger axle sits closer to the transmission than on the smaller axle, so you may need a shorter driveshaft or it'll bottom out in the transmission/t-case tail-housing when you hit a huge bump fully loaded. Mine was lifted a bit so the stock driveshaft length ended up being fine. The e-brake cables are different, so use mostly gmt-800 parts up to the cable that goes to the pedal. You'll probably want to do something like a proportioning valve to stop your new better rear brakes from locking up really easy when stopping.

 

[evilunclegrimace]

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.

 

[evilunclegrimace]

FYI the cab/chassis K3500 has a different frame spacing (closer together, oddly enough) than the other trucks - so not "all" rear ends are interchangeable on GMT400

Only if it is dual rear wheel

 

[98chevy2500SS]

2wd vs. 4wd will have a different width, I'm told.

I did not know that, thanks for correcting me.

 

[evilunclegrimace]

Having a 350 vs 454/6.5TD sometimes made all the difference. Most 1 tons I see have full floaters.

I have been told if the truck has a 350, it will have a semi floater, full floater as an option. If I has a 6.5TD or 454, it will have a full floater standard. This in 3/4 tons, it may apply to 1 tons too, but I am not sure. I thought one tons usually got a full floater no matter what engine it had, but I could be wrong.

2WD vs 4WD full floating rear ends shouldn't be any different IIRC. Spring placement is the exact same as I converted my truck from having a 10 bolt, to the 14 bolt semi floating rear end, so a full floater will work.

I would put in a full floater though if I were you anyway, just because they are a more desirable rear end than a semi floater. I've got a semi floater in my 98 2500 and I am wanting to upgrade it to the GMT800 Duramax rear end w/ disc brakes, might be something to look into if you want your truck to be stronger. All GMT400 rear ends are interchangeable if you decide you don't want to modify anything, the GMT400 full floater will be a direct swap into your one ton with no modification.

You are contradicting your self, first you state that 350 engine equipped trucks get a semi float and that 7.4/ 6.5 equipped trucks got a full float diff and then you state that all one tons got a full float no matter what. Differential size was an option in the early years, you could get what you ordered.