Wanting to compare some cheap 4 spider against a TRE 4 spider?

 

Is someone is lathing down a factory 2 spider cross shaft and claiming it is as strong as the cross shaft that TRE uses?

 

1. When they cut through the hard nickel chrome plating it ruins the tribology so it'll gall up and seize the spider gears. Why do you think Mitsubishi went through the trouble of plating this part in the first place?

 

 

2. They lathe through the case hardening and find themselves going from 60HRC back down to 40HRC.  This will severely weaken the cross shaft.

 

3. This newly made cross shaft posts now has a 20 point of hardness difference between it and the spider gear.  This will certainly gall up and seize.

 

 

4. Are they leaving any sort of corner radius on these posts or just leaving that corner sharp so you have a stress riser?

 

5. In any case they are still relying on the 2 longer posts on the cross shaft to transmit all the force.  Take a look at any center diff housing where the two longer posts make contact with the center diff housing and you'll see where the post dent the fuck out the housing.  This is bad.  Why?  Because the cross shaft is no longer running square to the center diff housing. The cross shaft can rotate a few degrees off in one direction and this is a problem because the spider gears rest against the center diff housing. The end result is the spider gears galling up where they run on the cross shaft posts and where they run against the center diff housing.  The thrust washers wear out and the backlash becomes too much which increases the tip loading on the spider gears.  Not to mention the softer cross shaft posts aren't doing shit because they've worn down immediately and that's just the cross shaft.

 

Let's talk about the center diff.

 

Are they using a manual Bridgeport mill to machine the center diff housing to make room for the additional spider gears?

 

 

1. This is the typical machine finish of a cheap 4 spider center diff. A manual mill is not going to do the job precisely enough because it doesn't have the rigidity to mill the walls flat. Sure you could try but you'll need to make a clean up pass or two with a finishing end mill but you still have the problem of accuracy. Use the right tool for the right job!

 

2. How are they indicating the center diff housing?  Are they finding true center from the I.D. or just finding one wall and "going for it"? Are they averaging the two to make sure that Mitsubishi machined the housing off center? Are they machining just two walls or are they taking a skim-cut to make sure that all 4 walls are perpendicular to one another? How do they expect the loading on the gears to be evenly placed if the housing is not machined correctly?  If the walls are square to the cross shaft the spider gears will gall up and seize.

 

 

3. I've seen way to many center diffs machined out with an endmill that lacks any sort of corner radius.  That sharp corner leaves a huge stress riser that can cause the center diff housing to break and if you search you'll find this to be the case.

 

4. Do they drill oil outlets that allow metal fragments to escape?  If they didn't it'll wear out the center diff housing.

 

5. Is the center diff housing deburred after it was machined or do they leave them so the backlash won't be set correctly?

6. Do they shot peen the housing afterwards?  This bullshit about shot peening not doing anything is fucking stupid and people should do their own research the how's & why's of shot peening and how it makes the part stronger while improving lubrication instead of believing the loudmouthed arm chair experts on some forum.

Here's what TRE is doing:

1. We start with a new cross shaft. It's a 4 post cross shaft.  This has twice the load bearing points when compared to any other cross shaft on the market.  This keeps the diff housing from getting all pounded out of square.

 

2. The new cross shaft is forged, heat treated and has large corner radius for strength. It's 60HRC and it's also shot peened.  Not one has been broken and we've used them for years.

 

3. Your center diff is magnafluxed. This is done to make sure we aren't starting with some junk that has cracked gear teeth.

 

4. The center diff is lathed to square up the housing so it'll get machined properly. I have yet to see anyone do this correctly and it shows in their work.

 

5. The center diff is set up in the CNC. I can machine the housing with accuracy of better than 0.0005" and it's done correctly, milling all 4 sides and the finish is actually better than a new part.  When it is milled the housing is actually trued-up better than the work that Mitsubishi did and the gears are more evenly loaded. This keeps the spider gears from breaking or wearing unevenly.

 

 

6. I leave more meat in the housing at the bottom side. This keeps the housing strong so it doesn't spit.

 

7. The endmills have a .060" corner radius, reducing stress risers in the housing.

 

8. I mill out the housing in such a manner that I can true-up the walls and cross shaft slots. This is beneficial as it repairs worn out pounded housings.  Most center diff housings can be salvaged.

 

9.  I also mill openings so the oil can get in and the metal fragments can't build up.

 

10. The housing is checked with a go-no-go gage, checking my work.  You only need to make a mistake once to learn how to do it right.

 

11. The housing is deburred and then shot peened.  This improved overall strength of the outer gear. The housing is shot peened inside to improve oil retention which reduces wear to the housing.

12. I've seen just about every attempt to machine a center diff and I feel that what I'm offering is the best. You can find cheaper pricing but the work is not being done correctly and they are simply using the stock cross shaft.