Opinions on H3 Differential Drop Spacer

[amrg]

This subject is currently being raised/re-raised on another forum, but it mainly ended up as a heated discussion between two people on either side of the argument. So I thought Id raise it here to get a constructive discussion.

The colorado/canyon guys on 355 nation have been doing this mod for several years now. Its a spacer thats installed at the 4 bolts that hold the 2 differential side brackets, allowing you to lower the differential abit which reduces the angles at the CV joints. Only that part of the differential is lowered, the part held at the CM remains where it is (although the diff is no longer straight above it, but at a slight angle). The colorado guys have the spacers at certains lengths, 1/2, 3/4 and 1" spacers. Depending on what size you get, they may or may not affect clearance under the skid.

The way I see it, its good for the CVs. Whats the bad thing about it?

here is a link to the colorado guys:

http://coloradofans.com/forums/88-m...ing-front-differental-after-tb-crank-mmp.html

 

[4speedfunk]

Thats sort of an "apples to oranges" comparison. While the C/C & H3 share the same basic front axle...the axle housing mounts to the frame in a completely different manner. The C/C guys can space down the housing from the frame, because they don't have the crossmember situation that we do. The C/C axle is hung entirely by the (4) bolts at the frame rails. The H3 is hung by (2) bolts at the frame rails, and cradled underneath by (1) bolt and bushing at the crossmember. So...this mod won't be quite as easy on the H3. You will most likely need to cut & weld your crossmember to get the drop you want.

Dropping the center of the axle like this can get you flatter angles at the half-shafts....but it increases the angle at the front driveshaft. So, IMO...its a wash. The stock front driveshaft on these chassis's is total junk anyway, and the CV boot on the rear end of it cannot handle the increased angle very well. The CV joint itself does okay...but that little boot & cup that surrounds it, is prone to ripping and flinging the lube out, if you increase the angle too much. This is a very common problem with Rancho & TC kits, for the same reason.

Unless you have tire-rubbing issues...I don't see the point of a crossmember drop. It can increase your break-over clearance but, it will actually cost you some center clearance at the axle itself. A stock H3 with a proper t-bar crank (23.5") has fantastic axle clearance, and I would never trade that off for flatter half-shafts. IMO...its one of the advantages of running an IFS. But there is a fine line between "too much crank" and "flat half-shafts"...and I see a lot of H3 guys running way too much crank (and half-shaft angle). I think the H3 half-shafts are pretty robust and they don't seem to have a problem running at higher angles but there are limits. Another downside of doing a crossmember drop, is that your steering system will be stretched to the max. The Rancho & TC kits address this problem by including equal-distance dropped knuckles. You're not going to get that with a home-built diff drop...so you'll have to un-thread your tie-rods about 3-turns and run them at steeper angles. Probably not a good idea.

If you want to run totally flat half-shafts...you should leave it stock...look into a Rancho kit....or chop it all off and go solid axle (they're always flat!).

 

[06 H3]

I did the drop spacer with mine years ago and did a whole write up on why it didn't go well

 

[06 H3]

Ill find it hold on....or rewrite it.

 

[06 H3]

Ill just rewrite it...

The first time I broke my diff I had diff drop spacers in. They would be ok if the rear crossmember drops too, but it doesnt in the kit I had. Basically you drop the front diff by spacers by the front 2 bushings but not the rear crossmember. With that being the case the diff on the back crossmember is trying to pushing up. At the time we didnt have any crossmember bushing solutions so it put stress on the stock bushing and it couldnt handle it. Eventually leading to the diff to bouncing around and while the other 2 pieces of a 3 piece diff being stationary the back piece wasnt with a broken diff bushing. It causes flex and movement in the diff and BAM, your diff says see you later.

So the real question is, can a new crossmember bushing design handle the force of the back end of the diff trying to push up? I am not sure and even if it can it still isnt "right" geometry of how the diff wants to sit. The right way would to be cut the back crossmember and weld in a 1/2in piece to drop that too, or 3/4in or 1in all depending on how much the front bushings drop.

 

[alrock]

I'm with 4speed. I picked up some spacers a long time ago and ended up not installing them for the reasons that 4speed stated.

The CV angles are not bad unless you really raise the height of the front end and then you've got a problem with tie rod angles and the inner tie rod ends will fail prematurely due to the angles and increased wear and tear.

Pros:
flatter CVs

Cons:
increased tie rod angles (if you crank up the torsions enough that you need the spacers in the first place)
increased drive shaft angle (partially cured if you get an aftermarket drive shaft)
crossmember issues (either modify the crossmember or have the diff improperly mated to the crossmember)

Net results for me? 130,000 and I haven't broken a CV on the H3. Keeping the front end at a reasonable height is what has worked for me, 23.35" from hub center to fender lip

 

[CaseyS]

06H3, what size drop bushings did you run? It looks like my motor mounts have settled a bt and the oil pan is contacting the front axle tube. I'm looking for an easy solution to push the diff down slightly. I'm considering doing 1/2" spacers along with slotting the frame holes slightly to give me just a bit of drop on the crossmember to help it out.

 

[06 H3]

They were about 1/2 to 3/4 of a inch. I can see if I still have them to get a measurement. You can do it cheaply with grade 8 washers. I would just put something out back to address that issue. If the front goes down the rear wants to go up so possibly add washers in between the back one so the bushing can still compress