View Poll Results: Center diff pins
No issues
139
79.89%
Upgraded prior to pins breaking
11
6.32%
Pins backed out no tranny failure
8
4.60%
Pins backed out w/ tranny failure
16
9.20%
Voters: 174. You may not vote on this poll
Center Diff Pins
What I have detailed are the facts. I have removed and inspected the centre diff components in minute detail. I have hardness tested all the components, measured all clearances, and compared the design and tolerances to the centre diffs from earlier Evo's 4-8 (which don't have any problem), and are near identical in design, but with different material specifications.
The wear on the big pins is a combination of too large a clearance, but mainly caused by the lack of a special hard coating on the pins. The hardness of the pins is 55 rockwell C scale, and the gears around 60. Any engineer worth his salt (and I've been one for 27yrs) will know not to run two surfaces together with similar harness. And this is what has been done, the gears and pins pick-up which causes damage to both and a torque on the main pin which then damages the small retaining pin. This then accentuates the wear.
The pins from the earlier boxes which suffer no problems have an extremely hard ceramic coating with a very low coefficient of friction (0.65) which means even with a lack of oil, the gear will not pick-up on the pin. It looks like Mitsubishi have cut costs and omitted the coating which has caused this problem.
The strength of the components have nothing to do with it, it's the hardness that counts. If you put two components together with differing harnesses, the least hard will wear, but they will not pick-up on each other, which is something completely different, and the components picking-up causes a big torque load on the main pin.
If you replace the pin with one which has the correct tolerances and coatings, you don't need to do anything else. As I said before, earlier boxes have a near identical design and have no problems. I've stripped 15 year old boxes which have only miniscule wear of the pins and absolutely no pick-up. Any welding is a bodge, pure and simple.
The wear on the big pins is a combination of too large a clearance, but mainly caused by the lack of a special hard coating on the pins. The hardness of the pins is 55 rockwell C scale, and the gears around 60. Any engineer worth his salt (and I've been one for 27yrs) will know not to run two surfaces together with similar harness. And this is what has been done, the gears and pins pick-up which causes damage to both and a torque on the main pin which then damages the small retaining pin. This then accentuates the wear.
The pins from the earlier boxes which suffer no problems have an extremely hard ceramic coating with a very low coefficient of friction (0.65) which means even with a lack of oil, the gear will not pick-up on the pin. It looks like Mitsubishi have cut costs and omitted the coating which has caused this problem.
The strength of the components have nothing to do with it, it's the hardness that counts. If you put two components together with differing harnesses, the least hard will wear, but they will not pick-up on each other, which is something completely different, and the components picking-up causes a big torque load on the main pin.
If you replace the pin with one which has the correct tolerances and coatings, you don't need to do anything else. As I said before, earlier boxes have a near identical design and have no problems. I've stripped 15 year old boxes which have only miniscule wear of the pins and absolutely no pick-up. Any welding is a bodge, pure and simple.
Last edited by olo; Sep 13, 2011 at 09:31 AM.
Evolving Member
Joined: Oct 2010
Posts: 130
Likes: 0
From: lethbridge, ab, canada
2008 GSR w/33k miles, exactly 2 years old (purchased 09/09), AP intake & CNT catless turboback & ACT ME1HDSS & Streetlite
Pin let loose, blew hole in case, spider gears rattled around and metal shards made it into the transmission too. Warranty is being denied currently due to "misuse or neglect" so they dont even know why to deny me. I'm in talks now using my new found knowledge of the diff pin weakness and lack of proper oiling.
Pin let loose, blew hole in case, spider gears rattled around and metal shards made it into the transmission too. Warranty is being denied currently due to "misuse or neglect" so they dont even know why to deny me. I'm in talks now using my new found knowledge of the diff pin weakness and lack of proper oiling.
I didn't have issues, but was ready to upgrade before I sold the car. I learned that if you ask too much from the stock parts, they will break. Now I have a shep trans for sale if anyone wants to take the easy way out and not have their car down for months.
https://www.evolutionm.net/forums/sa...ml#post9725118
https://www.evolutionm.net/forums/sa...ml#post9725118
Newbie
Joined: Nov 2011
Posts: 8
Likes: 0
From: Oxnard Ca
Now I have to ask this. Well I just recently bought my evo x. I bought a 2008 with 65xxx miles.
Now i am just trying to find out if I have anything to look out for?
All this is scary info to hear and hope it doesn't happen to me.
Now i am just trying to find out if I have anything to look out for?
All this is scary info to hear and hope it doesn't happen to me.
Evolving Member
Joined: Mar 2009
Posts: 106
Likes: 1
From: ROMANIA
My gearbox had a problem.
Pins broke, and a bolt came out of his place.
So I broke a lot of parts. Now I am forced to buy parts and repair.
I have to buy all the pieces of picture and all the screws holding the differential crown.
Last edited by Malaxa; Nov 19, 2011 at 05:15 AM.
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