Swap 8.5 IFS for 9.25?

[89RCLB]

Father/son project, a lot of experience gained...sounds like a success

 

[98chevy2500SS]

Yeah it was a father/son project, learned a lot more about these trucks for sure.

Truck's doing pretty good so far, been checking brakes and stuff after we did this to make sure everything is working properly. Just need to figure out why my steering is still not straight, oh well, going to be ordering some GMT800 aluminum rims and going to get it professionally done after I get them installed, hoping if that helps. Even as a half-ton it pulled to the right.

 

[White96k2500]

Ok, got pics, sorry that I don't have the front diff relocation mount photographed, I will get that sometime, it's been raining here quite a bit to get under the truck on a wet cement pad lol.

Now, here is the driver's side front mount, we had to cut it and move it upwards, since the 3/4 ton frames are indeed taller:

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Next we have the whole driver's side assembly, got a picture of the best I could:

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Here is the bottom shock relocation mount, since we got 3/4 ton 7200GVW shocks, couldn't find any brand new 8600GVW shocks for it, they mostly have stuff for half-tons. But trust me, these shocks are great:

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Here is the passenger side setup, sorta:

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Like I said, the lower control arms bolt right up. No problem there, and to be clear, the keys for the torsion bars are the same, 3/4 ton, half-ton, exact same. We were reading that they were different, but when we placed them side by side, they looked identical. We used the 3/4 ton one's no doubt, since we had to cut the other keys out. Rust, gotta love it.

Now here is how far we moved it up on each side:

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We just put a piece of sheet metal behind the bracket so that it's enclosed. Now, I made mistake earlier saying that you have to move the front mount forward... DON'T!!! That will give you negative camber and you want positive camber. The rear mount is the one you have to move; you will have to move back.

After you have cut the front mount, moved it upward, and welded it all back together, I recommend putting the upper control arm in the front mount, and with the rear mount cut off the frame, put the mount in the control arm link and see where you have to weld. Align it. Try to make sure you measure the front mount how far you moved it, you will want them the same height. I recommend spot welding the rear mount, then remove the upper control arm to finish off welding.

Woof! Lots of typing, lol, if you guys need more pics, just holler and I can get you some as soon as I can!

One thing we learned after doing this is that, we will NEVER do this again! lol, just easier to buy a 3/4 ton truck to be honest, but you don't see a 3/4 ton ECSB too often, which I think are pretty cool to see.

that is exactly why i want to keep my truck I haven’t seen another ECSB except photos online but never around where i live in NC

 

[Supercharged111]

Well guys, conversion complete!!! Took us a little under a month of weekends and it's finally finished. Took us mid August through the last week of August.

You will need to look at a 3/4 ton front mounts closely, basically look at a 3/4 ton very closely in general <-- I CANNOT STRESS THIS ENOUGH. Both mounts will need to be positioned back and up, since the 3/4 ton frames are indeed taller. For the front diff, you will need to add an extension on the bottom bolt where the skid plate mounts in the back, it will need to be about an inch or two lower since the diff is bigger and goes farther south. Lower control arms bolt right in to the existing holes and so should everything else. You will need a 1/2 ton to 3/4 conversion u-joint for the rear end, since the 3/4 used a bigger u-joint. Front drive shaft will need to be shortened since the 4L80E's where longer, so they could use the length, the 4L60E is not long enough, so you will need to have that drive shaft shortened. I know I am forgetting things, if anyone wants to ask me anything about this project, I will be gladly happy to answer to my best ability!!! Oh, before I forget, be sure to lube everything up before installing --> antiseize stuff. If you want, paint every part you take off a 3/4 ton (except front diff., doesn't need it before installing - I highly recommend.

So you're saying 3 of the 4 bolts line right up on the front diff itself? Because I'm pretty sure 1500 half shafts bolt right up to a 9.5" diff. I kept the 9.5" front diff from the wrecked dually that I junked in hopes of finding the time and motivation to tackle this one day, but I'm not sure I really need the 8 lugs. Or at least if I could tackle it in 2 pieces that would lighten the load.

 

[98chevy2500SS]

Are you talking about half-shaft as in CV axle or the front drive shaft? I don't remember if the half-ton CV's fit on the 9.5" diff, thought they did, but I could be wrong, I just used the ones that came off the parts truck, since they were bigger and thicker. The drive shaft will fit in the 9.5" diff, just needs to be shortened. We had tried to fit the one that came out of the parts truck, but wouldn't fit. Did the one tons and 3/4 tons use the same front diff? If they did, it should bolt right up, except the lower diff mount/skid plate mount, which needs modifying.

 

[Supercharged111]

Since I have the 4L80 the regular shaft should be fine, right? Man all this time I thought it was just the top front driver's mount that lined right up.

 

[98chevy2500SS]

I think it will work, because with the 60E it has to be shortened, for the 80E it should be fine. Just looked up the difference between the 60E and 80E: 60E is 23.5" long, whereas the 80E is 26.4" long, so that makes sense why the stock front shaft didn't work for us. Source: https://mechanicbase.com/transmission/4l60e-vs-4l80e-differences/