K1500 8.25 to 9.25 swap

[Gobistro00]

So to all that have told me it cant be done" In your Face! Lol thanks for sharing, I'm in the process of this as well, from my measurements I don't feel that I'm going to have quite as many issues, I have 6" lift - pro comp? I shaved a peace off frame on driver side because the 92.5 is fatter, but it looks like whoever originally put the lift on the truck shave the fins on the driver side of the 8.25 diff for it to fit, I didn't want to do anything to weaken it, I'll send a photo of what I did if I can figure out how, my donors from a 2004 2500 HD, I wish it was angled on the passenger side mount because I'd be In Like Flint, remind me to remind appears that it's going to bolt in if I altered that bracket hanging down for the passenger side. We'll see, my question for you is, what about the actuator? I've ls 4l80e swapped Holley wiring, can't find a cable actuated for it, need to figure that part out before I carry on ,I haven't done anything thiats keeping me from going back or sas if I win the lottery. Thanks

Sorry for late reply, I used the stock actuator that came with the diff, everything engages fine, used my front lockers about a dozen times too and have had 0 issues, no signs of wear anywhere

 

[offroadtahoe]

to convert to a 9.25 on a stock or cranked 3" lift truck

I'm sure you can use a diff drop kit and modify it,I tried it but you would have to shave the side fins a little bit,and it just hangs too low since its already bigger.i didn't like this route,It drops it 2"

I have a k3500 and k1500 stuffed the 8.25 in the k3500 to check the differences.
The only difference is the driver side top.everything else is the same,tried both,the lower one is the one to use and change the other,for cv spindle to not hit frame/ lca bolt

the bolt in passenger side a-arms stay the same for their frame,

to fit the 9.25 in the stock location.
#1 cut the drivers lower side mounting tab,you need to replicate the stock but make a bolt in version,or you wont be able to get it in

#2 you need to grind the corner of the drivers motor mount frame,not by much can't even tell but the middle of the diff won't clear you and won't be able to get the rear lower bolt in.

#3 the A-arm bolt's that hold the diff need to be drilled to the next size of the 9.25 bolts then use the 8.25 bolts now its wide enough and will bolt up.

#4 the top driver side is going to have to be custom made,check the pics.

 

[spooledyou08]

to convert to a 9.25 on a stock or cranked 3" lift truck

I'm sure you can use a diff drop kit and modify it,I tried it but you would have to shave the side fins a little bit,and it just hangs too low since its already bigger.i didn't like this route,It drops it 2"

I have a k3500 and k1500 stuffed the 8.25 in the k3500 to check the differences.
The only difference is the driver side top.everything else is the same,tried both,the lower one is the one to use and change the other,for cv spindle to not hit frame/ lca bolt

the bolt in passenger side a-arms stay the same for their frame,

to fit the 9.25 in the stock location.
#1 cut the drivers lower side mounting tab,you need to replicate the stock but make a bolt in version,or you wont be able to get it in

#2 you need to grind the corner of the drivers motor mount frame,not by much can't even tell but the middle of the diff won't clear you and won't be able to get the rear lower bolt in.

#3 the A-arm bolt's that hold the diff need to be drilled to the next size of the 9.25 bolts then use the 8.25 bolts now its wide enough and will bolt up.

#4 the top driver side is going to have to be custom made,check the pics.

Sorry if I missed the info, but what cv axles would you use if it was stock or cranked? And are you saying a lift kit makes it more difficult due to the CV axle length because of the differential drop?

This is a swap I’m very interested in if I can retain the 1/2 ton hubs and bolt pattern.

Thanks for the info!

 

[offroadtahoe]

sorry i should have added,i made my own thread with the cv axle info and updated pics. https://www.gmt400.com/threads/9-25-ifs-conversion-0-3-lift.60583/#post-1284970

for stock or cranked 0-3" the stock 9.25 cv's fit
keeps 6 lug.

yes it does,after testing my stock 9.25 cv setup i can see how,lift kits where your cranked 6" and not true 6" diff dropped,if you decrank you wouldn't have to shorten your cv axles,

LCA's in a straight postion with 9.25 cv's have plenty of space.the second you start cranking the lower control arms come down,at a point you instantly start losing space,
now imagine the cranking going a few inches more then stock 0-3"..even .5 past the 3" mark its diff drop,this is why you will have to shorten axles.

 

[spooledyou08]

sorry i should have added,i made my own thread with the cv axle info and updated pics. https://www.gmt400.com/threads/9-25-ifs-conversion-0-3-lift.60583/#post-1284970

for stock or cranked 0-3" the stock 9.25 cv's fit
keeps 6 lug.

yes it does,after testing my stock 9.25 cv setup i can see how,lift kits where your cranked 6" and not true 6" diff dropped,if you decrank you wouldn't have to shorten your cv axles,

LCA's in a straight postion with 9.25 cv's have plenty of space.the second you start cranking the lower control arms come down,at a point you instantly start losing space,
now imagine the cranking going a few inches more then stock 0-3"..even .5 past the 3" mark its diff drop,this is why you will have to shorten axles.

Thanks for the info. Does the 9.25 differential require front drive shaft modifications due to its size difference, or are the yoke to transfer case distance the same?

 

[Supercharged111]

Thanks for the info. Does the 9.25 differential require front drive shaft modifications due to its size difference, or are the yoke to transfer case distance the same?

OP will have the for sure answer, but I think the yoke hangs farther back. Pairing this with a 4L80 swap negates the need to modify your front driveshaft for the additional length of the 4L80. I think.

 

[offroadtahoe]

Thanks for the info. Does the 9.25 differential require front drive shaft modifications due to its size difference, or are the yoke to transfer case distance the same?

if you have the collapse kind,it should push in enough to get the driveshaft in,if not it has to be shortened

 

[Timcook8]

Hey all! So as far as i know i only seen a couple of threads (like one or two) about completing a 9.25 front diff swap. Well i just completed my swap and its equipped with front ARB lockers. i will try to answer as many questions as i can since there isnt to many threads about this.

okay if youre planning on doing this swap please keep in mind your lift. If you have a rough country or full drop lift (lift that drops upper control arms) youll need to modify youre cv axles or shorten them. i recommend to have atleast a 4 inch lift for this swap. 3 inch lift is possible, but it will be very tight. anyways for a RC or any full drop lift, the lower drivers side mount on the diff will remain the same, the upper drivers side mount on the 9.25 will be shorten about 2-4 inches depending on whether you have a 4-6 inch lift. as for the passanger side mount, youre going to want to cut the mounts and reweld them or shorten it about a couple inches, thats probably the hardest part, what i did was measure the axle flanges on the diff from the lower drop crossmember and made sure both sides had the same distance from the rear lower crossmember drop bracket. once this is achieved youll need to make sure the upper diff mount wont interfere with the center link, itll be close, but as long as it doesnt touch youll be fine. as for the cv axles, you have 2 options, you can go to the junkyard and find original gm axles and shorten them, or you can order custom ones. reason that youll need original gm axles is because theyre splined an extra inch down and you can just remove c clips holding the tripod and slide the tripod all the way down to the end of splines and flush cut the excessive splines, then weld the tripod onto the splines so the tripod wont seperate from the splines at full droop. most or all after market cv axles are only splined where the bottom of the tripod sits, this makes it unable to be shortened. as for connectors everything will be the same, and itll be plug and play. if youre using a 9.25 axle from 2000-2007 itll be easier to modify passenger mount because itll be flat, the passenger mount on a 99- or lower is at an angle.

if youre using a knuckle style lift, this will be more convenient because the knuckles add about 2 inches of track width and youll be able to use your stock cv axles with spacers, youll also have more space to work with, and the diff will sit higher, as for knuckle lifts youll need 1.75 inch axle spacers for the cv axles, and youll need to have youre torsion keys at stock crank, because on knuckle lifts the diff sits a bit higher and your angles will be to sharp and cv axles will bind up. also youre going to have to cut upper drivers side mount and add a mount on the diff and bolt it to the front crossmember. if you have a 1 piece driveshaft youll need to get it shortened. if you have a2 piece driveshaft it should compress enough to bolt it up, the lower drivers side mount on the diff will remain the same and youll have to grind about 1/4 of an inch of the lower rear crossmember so the diff wont scrape with it, as for the lower front drivers side mount that connects to the front crossmember, youll need to get a 9.25 mount and move the mounting tabs on the front crossmember that connects to the diff and move it about 1.5 inches to the passenger side. (cut mounting tabs and reweld)

im probably forgetting more things so feel free to ask questions, i will post pictures tomorrow since its dark right now, and yes you can probably just slap a solid axle on the front, but id rather have a great riding ifs with a 9.25 front axle.


Edit: i should mention that i orginally attempted this with a rough country 4inch lift. but i didnt want to order custom cv axles, but its easier to install on the rough country because the rough country lowers the front diff way more than a knuckle lift

Doing this swap. Did you take the suspension over also or keep the 6 bolt hubs and control arms? I have a 6" Fabtech lift. Want to swap all of the 1 ton stuff over. Happy to buy aftermarket/performance components. Swapping to RTVs and looking at options for the 1ton arms etc. Curious what you did. Steering upgrades too. Will move to a 40" tire from the 37s also

 

[offroadtahoe]

Doing this swap. Did you take the suspension over also or keep the 6 bolt hubs and control arms? I have a 6" Fabtech lift. Want to swap all of the 1 ton stuff over. Happy to buy aftermarket/performance components. Swapping to RTVs and looking at options for the 1ton arms etc. Curious what you did. Steering upgrades too. Will move to a 40" tire from the 37s also

you can keep 6-bolt hub's the 9.25 cv's are bigger but are bolt in

And you can use your k1500 upper control arm,k2500-k3500 upper control arm's are wider at the mount's and would need the frame mounts cut/welded.

you can run any of the 3 different lower control arm's.(stamped steel bolt in ball joint) (forged end stamped steel) (forged control arm's)

as for the passanger side mount, youre going to want to cut the mounts and reweld them or shorten it about a couple inches,

I don't think this part is necessary but if you use a 9.25 diff with the axle flange extreme angle then yes.the only thing that need's messed with is drivers top mount.

 

[Timcook8]

you can keep 6-bolt hub's the 9.25 cv's are bigger but are bolt in

And you can use your k1500 upper control arm,k2500-k3500 upper control arm's are wider at the mount's and would need the frame mounts cut/welded.

you can run any of the 3 different lower control arm's.(stamped steel bolt in ball joint) (forged end stamped steel) (forged control arm's)

I don't think this part is necessary but if you use a 9.25 diff with the axle flange extreme angle then yes.the only thing that need's messed with is drivers top mount.

Thanks for the replies. Going to RCVs and looking for the beefiest control arms and steering components.