GMC Truck Forum banner

1 - 20 of 249 Posts

·
Registered
Joined
·
6,189 Posts
Discussion Starter #1 (Edited)
Ultimate IFS Build Thread: Locked AAM 9.25 With Hydro Assist!

Here you will find the conversion of my 2000 Z71 from a 8.25 to an AAM 9.25 front IFS chunk, complete with an Eaton Elocker, custom CVs, and hydro assist steering.

There are a variety of reasons I chose to stay with IFS. For the type of swamp wheeling I do, it works very well. Massive ground clearance, very little unsprung weight. Aesthetics was also a consideration. I just think IFS trucks with cranked up torsion bars and the angularity of the a-arms looks impressive along with a set of super swampers. Not to mention, beam axles are for scenesters. Just kidding.

The conversion itself is not as complicated as it seems. I would like to take a moment to clear up some misconceptions about a 9.25 differential fitting in a 1500 truck. For years Dark Eternal preached on this board about how radically different the mounting locations were, and that they were all atleast 1" further apart. NO. That is not the case at all with NBS trucks! The 8.25 and 9.25 share many of the same features. The rear mount is identical, along with the passenger mount. Yes, it is roughly 2.5" wider, but that is stub shaft to stub shaft. Only the front mount needs modification.

All of the problems of the differential being larger are easily solved by a set of custom CV shafts. The differential flanges of the 9.25 are 6 lug, just like on the 8.25, but they are about .25" larger. Once again, easily solved by the custom CVs. Take a stub shaft for a 1500 truck, differential mounting flange from a 2500 truck, and mend them together with a custom link shaft, using all factory GM hardware. Easy. Yes, everything else is 1500 hardware, but it is more than rugged enough for what I will be using it for.

Please feel free to ask questions, send hate mail, etc. Thanks for looking. :)



Here is how I use the truck:

DSCF0589_edited.jpg


DSCF0598_edited-2.jpg


Left to Right: Factory GM GL torsion bars, 1500 CVs, 8.25 IFS chunk, 9.25 IFS chunk. While the 9.25 differential housing itself is still aluminum, it is substaintially stronger than the 8.25 and has a steel axle tube, which is prone to grenading on the 8.25.

DSC01067_edited.jpg


Eaton Elocker. The switch button is roughly the same size of the 12V receptical, where it will be mounted for a factory look.

DSC01063_edited.jpg


Motive 4.56 gear set and master install to match the the rear.

DSC01061_edited.jpg


DSC01062_edited.jpg


This tool makes taking the steering centerlink off a breeze. I had to purchase it online because they no longer rent it at the auto parts stores anymore, it appears.

DSC01059_edited.jpg


Removal of the front differential ear. It needs to be moved back roughly 2" for proper clearance for the steering center link. Welding cast aluminum is expensive, and doesn't leave much room for error as I am in uncharted waters here. So I ordered a bracket from Cognito that replaces the ear if one was to cut it off for a knuckle lift, for example. It is much easier to mess with steel than cast aluminum in situations like this.

DSC01064_edited.jpg


DSC01065_edited.jpg


CV stub shaft. I put these in the hub so I can still daily drive the truck and mess with the differential at the same time. The wheel will fall off if you try to drive without it.

DSC01066_edited.jpg


Disassembly of the 9.25 IFS chunk. The 9.25 differential is quite heavy as you might imagine. Since I will be lifting it up into place myself and probably removing it multiple times, I removed all of the internals to make it lighter for figuring out the geometry of the mounting locations.

DSC01069_edited.jpg


Removal of the pinion. There are many was to do this, but I like to use a gear puller that can be used for unloading torsion bars. Once the pinion nut is loose, I take about a 4' length of 4x4 cypress, stand up the differential, and pile drive the 4x4 into the top of the pinion. Usually one or two good whacks does the trick.

DSC01073_edited.jpg


The replacement Cognito differential ear. This takes a lot of guesswork out of the conversion.

DSC01071_edited.jpg


Removal of the pinion nut.

DSC01072_edited.jpg
 

·
Swamper Brotherhood
Joined
·
3,892 Posts
Ben... I cant see the pics at work but its amazing that you are doing it.

Your truck is gunna be a hoss now!
 

·
Swamper Brotherhood
Joined
·
3,892 Posts
I am interested in how the hydro assist will be mounted.

If you need a hand holla at me.
 

·
Registered
Joined
·
4,159 Posts
good deal man, I am hoping to do this eventually with my big truck as well, more just because I can rather than need. Regardless, its great you are going ahead and getting it figured out, haterz gonna hate but rock on man.

also, what are you doing for the hydro-assist? I have been thinking another thing I would really like to do is beef up the steering system. Cognito tie-rods, idler/pitman braces and the idler mount should help a lot but the actual power steering system could use a boost too, im sure my pump hates me.
 

·
Bayou Surface Drive, LLC
Joined
·
7,077 Posts
Will the stock centerlink be in tact? With it in tact I can see hydro assist working because for the ram to receive pressure the steering gearbox needs to have resistance on it do to it's design. I am eager to see your progress. Kudos for your experimenting ben.
 

·
Registered
Joined
·
6,189 Posts
Discussion Starter #13
also, what are you doing for the hydro-assist? I have been thinking another thing I would really like to do is beef up the steering system. Cognito tie-rods, idler/pitman braces and the idler mount should help a lot but the actual power steering system could use a boost too, im sure my pump hates me.
The truck has Cognito UCAs and tie rods. ORU makes a kit now for 2500 IFS trucks, in which I will base the geometry on. The stock steering center link will be utilized, along with additional support. Cognito TREs are prone to bending, so they will be sleeved like the Duramax pulling trucks you see.
 

·
haz 12"s!
Joined
·
4,533 Posts
You are my fucking hero! Its about time someone did this. I would have a long time ago if I didnt need my junk to drive so much.

Any ballpark of a price for the swap?
 

·
Bad Luck is all i got.
Joined
·
1,483 Posts
This has the signs of being an epic mod. Keep up the good work looking forward to updates.

Its a damn shame some of these last builds are so far away id love to get in on the wrenching.
 

·
GMFS Enforcer
Joined
·
3,568 Posts
Tear it up man! Way to go outside the box. BTW, just throwing this out there, did you ever think of making your tie rods using heims and solid bar stock? It would much easier on the wallet.
 
1 - 20 of 249 Posts
Top