axle difference in 1988-1998

[nolli69]

so ive got a 1988 k3500, and the rear end decided to eat the g80 spider gears. its a 9.5 inch sf 14 bolt 3.73 geared. I was just going to upgrade it to the 10.5 ff 14 bolt, but im getting conflicting info online that the axles im looking at fit 90-98 gmt400's, so my question is whats the difference between the 88-89 and the 90-98 axles? I did a few searches on here and my search strings didn't bring up any helpful info, maybe I do not know the proper keyword. thanks for help in advance.

 

[someotherguy]

If your '88 K3500 is a squarebody (73-87 body), you'll need a rear out of another squarebody. Mounts are different once it gets into GMT400 body style (88-98 body)

Richard

 

[nolli69]

No it's a gmt400. 88-98 body style k3500.

 

[skylark]

The other conflicting info would be regarding 10 bolt rear ends. The 88-89 had 28 spline axles and the 90-98 has 30 splines.

 

[Chewy1576]

I just swapped my 1990 14b SF for a 1998 14b FF. Bolted right in.

 

[Supercharged111]

Don't forget about u joints, you may require a crossover joint.

 

[ncnichol]

so ive got a 1988 k3500, and the rear end decided to eat the g80 spider gears. its a 9.5 inch sf 14 bolt 3.73 geared. I was just going to upgrade it to the 10.5 ff 14 bolt, but im getting conflicting info online that the axles im looking at fit 90-98 gmt400's, so my question is whats the difference between the 88-89 and the 90-98 axles? I did a few searches on here and my search strings didn't bring up any helpful info, maybe I do not know the proper keyword. thanks for help in advance.

If your '88 K3500 is a squarebody (73-87 body), you'll need a rear out of another squarebody. Mounts are different once it gets into GMT400 body style (88-98 body)

Richard

So I've got an 81 square body with the s/f 14 blt. I want to go with the bigger full floater and i happen to have a complete unit just sitting here but its out of a 2004 h/d 2500. Be nice to use because it also has disc brakes. Do you know what the difference is ? I also have a 89 2wd 1500 with 5 blt axles that has very high miles and i have a 2002 2wd 1500 parts truck with 6 blt axles. Do you know if the 5 blt 1998 axles will fit in the 2002 housing?

 

[Chewy1576]

So I've got an 81 square body with the s/f 14 blt. I want to go with the bigger full floater and i happen to have a complete unit just sitting here but its out of a 2004 h/d 2500. Be nice to use because it also has disc brakes. Do you know what the difference is ?

Measure the spring perch width and shock mounts to compare between the axles. Although, I think that the square bodies had a different frame than the GMT400s, so the spring perches will be different widths. You could always cut them off and reweld in the correct location.


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[ncnichol]

Measure the spring perch width and shock mounts to compare between the axles. Although, I think that the square bodies had a different frame than the GMT400s, so the spring perches will be different widths. You could always cut them off and reweld in the correct location.


Sent from my iPhone using Tapatalk

I was kinda thinking the same thing. I haven't acually measured yet but even if i have to move mounts it'll be worth it. Thx

 

[someotherguy]

Any time you're attempting to swap axles between different body styles you will find the mounts are different, often including the shock mounts. It's just about never a direct swap. Also pay very close attention to overall width of the wheel mounting surfaces. You will also likely find that the U-joint is not the same, and you should also double-check that the driveshaft length won't be affected because of different distance from transmission yoke to pinion yoke (or carrier bearing in case of 2 piece shaft) - swapping different types of differentials the pinion yoke is not always in the same place, and if it's different enough, the slip yoke up front or at the carrier bearing may not have enough slack to allow for the difference.

Just some gotchas to look out for.

Richard