GMT800 9.25 IFS axle only swap?

[KansasOBS]

Hey all,

Searched about a bit, but didnt come across much.

Working on a 98 K3500 dually project, and robbing some parts from a donor 04 2500HD along the way. Anyhow I noticed it looks like AAM or whoever beefed up the cases on the GMT800 IFS a fair bit. Aside from the brackets that are bolted to the axle, it looks to be the same mounting otherwise. I also found newer style case halfs that said they fit the gmt400 and gmt800 years. Anyone done the swap, or know of some complications I'm missing? The actuator wiring is a non issue.

Swamped with actual jobby job work to be working on the truck lately, but I'll have to split one of the cases open to swap to 5.38's. Might save me some time from pulling the 2500HD axle, if someone has a definite "no, youre stupid, that doesnt work".

 

[KansasOBS]

Just thought I'd throw this out there, incase anyone else might be searching for info. The axle tube is different, but everything else is interchangeable it seems. Just have to swap it over. GM made some parts better, and some parts worse. The NBS pass side axle flange has holes near the center, so it rusts inside, kinda dumb.

The case looks like it will fit, and at least 20% stronger. Its quite a bit thicker, more splines, and bigger around the gears. I haven't thrown it in there yet, debating if I want to gear swap now or later, and I'm going to cut the section of the frame off, and weld in a plate at the spot that RCX tells a person to cut their diff, so I don't have to cut the NBS one. Truck has their 6" lift kit.

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[offroadtahoe]

Awesome,This is what i was talking about in my thread https://www.gmt400.com/threads/9-25-ifs-conversion-0-3-lift.60583/ post #9

summed up
88-96 9.25 has the least aluminum reinforcement
97+ of Gmt400's have this little aluminum reinforcement on two ends.and have upgraded mount bushing's
98-99 silverado gmt800,has the same aluminum casing as Duramax and is the strongest

 

[KansasOBS]

88-96 9.25 has the least aluminum reinforcement
97+ of Gmt400's have this little aluminum reinforcement on two ends.and have upgraded mount bushing's
98-99 silverado gmt800,has the same aluminum casing as Duramax and is the strongest

Yeah man, you got it. I didn't notice that much difference between the 96 and 98 as far as strength, but I don't doubt you spotted some differences. I had a 96/97 (mystery donor), a 98, and an 04 HD to build from. The "duramax" terminology has amused me a little. The donor I used had the HD IFS, and the HD transfer case, but I havent been super impressed with the Tcase over what was in the 96 K3500, it didnt have a slip yoke in the back, and I dont think they had the pump rub problems. I didnt have a rear shaft, and the one I came across out of an OBS worked with the newer Tcase, so thats why it got used.

The 96 axles actually had little shields on the inside of the flange to help protect the passenger side tube/seal, and the carrier adjuster on the left/driver side was made a little different with a lip for the shield. The carrier adjuster for the 98 was the same as the 04. I put the 96 axles, axle tube, and carrier adjuster in the 04. The fork for the axle engagement was better in the 04, but it doesn't hit the switch that the 96 axle tube has, if that is important to someone. Another reason for going with the 96 axle tube was for a posi-lok if I decided to run one. Pretty sure its built for the extra length of the actuator boss.

Its all in and been working good so far. Ive been led to believe a 9.5 semi float locker will fit in these, and a H2 right/passenger axle shaft can be used to eliminate the axle lock/actuator if someone desires. Part of me wishes I had tried the locker, but didnt have the $350 at the time for one.