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
Jul 15, 2010 | 06:20 PM
#46
Newbie
Joined: Apr 2010
Posts: 41
Likes: 0
From: SJ
It's a bodge because it's not addressing the cause of the problem, the gears picking up on the pins. The only way to solve the problem is to fit pins that have the correct tolerance and coatings.
You said you stripped the box and checked for wear. How can you see the wear on the pins if you cannot remove them? That's the ony way to see. Guaranteed there will be wear on the pins and gears causing friction and heat, and also distributing small particles of metal which will be floating around in the oil of the gearbox, accentuating wear on all the other components. And the more wear there is, the worse it will get, and the quicker it will wear.
I'm trying to help you here, I'm not having a go at you
I have a lot of experience as an engineer in the Aero industry, and my hobby and passion is Evo's. I only post facts from my own findings and experience, not conjecture, rumours or BS.
Check out the Evo I built Here to see what I normally do in my spare time
You said you stripped the box and checked for wear. How can you see the wear on the pins if you cannot remove them? That's the ony way to see. Guaranteed there will be wear on the pins and gears causing friction and heat, and also distributing small particles of metal which will be floating around in the oil of the gearbox, accentuating wear on all the other components. And the more wear there is, the worse it will get, and the quicker it will wear.
I'm trying to help you here, I'm not having a go at you
I have a lot of experience as an engineer in the Aero industry, and my hobby and passion is Evo's. I only post facts from my own findings and experience, not conjecture, rumours or BS.Check out the Evo I built Here to see what I normally do in my spare time
so what pins do you suggest going with? which one has the right clearance and coating?
Jul 17, 2010 | 01:47 PM
#47
Jul 17, 2010 | 10:10 PM
#48
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. With adequate lubrication there shouldn't be a problem, but if starved, 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.
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. With adequate lubrication there shouldn't be a problem, but if starved, 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.
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.
I was guessing that the pins and shafts on pre-evo-X are the same as on evo-Xs and the failures were due to the design and heat distribution. Wouldn't it be cheaper to produce them all the same as opposed to making a different design, part number inventory, etc? But I guess, Mitsu figured therwise.
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.
). So harder pins will pick up on gears if there's some degree of wobbling there.I agree with your recommendation, but it's like saying that if you find a right pill, you'll live forever. Sounds good, but good luck finding that pill.
So far there only shep/buschur pins that are available on the market and so far there has not been any reports of them breaking. I hope it stays like that.
I also have shep pins in my diff and after 1000 miles I inspected the state of this pins and they still show signs of wear:
And this is because there still some movement there. Very tiny but still there is some free play.
So I wend ahead and welded them up with a laser to stop the movement. I hope that this now eliminated any possibility of them breaking in the future.
BTW a guy on Evo X forums posted a picture of his stock pins after 25K miles and they looked like new. He says that he launches and doesn't babysit his car. On the other hand I already broke two diffs in just 10K miles. Go figure.
Jul 18, 2010 | 05:40 AM
#49
) is the key, and it's not so much the wobbling and clearance of the gear to the pin shaft dia that causes the problem, although it doesn't help, but two parts running together of the same hardness.So far there only shep/buschur pins that are available on the market and so far there has not been any reports of them breaking. I hope it stays like that.
I also have shep pins in my diff and after 1000 miles I inspected the state of this pins and they still show signs of wear:
And this is because there still some movement there. Very tiny but still there is some free play.
So I wend ahead and welded them up with a laser to stop the movement. I hope that this now eliminated any possibility of them breaking in the future.
BTW a guy on Evo X forums posted a picture of his stock pins after 25K miles and they looked like new. He says that he launches and doesn't babysit his car. On the other hand I already broke two diffs in just 10K miles. Go figure.
I also have shep pins in my diff and after 1000 miles I inspected the state of this pins and they still show signs of wear:
And this is because there still some movement there. Very tiny but still there is some free play.
So I wend ahead and welded them up with a laser to stop the movement. I hope that this now eliminated any possibility of them breaking in the future.
BTW a guy on Evo X forums posted a picture of his stock pins after 25K miles and they looked like new. He says that he launches and doesn't babysit his car. On the other hand I already broke two diffs in just 10K miles. Go figure.
The 6mm retaining pins are made of normal steel, and even in the earlier boxes without problems they always have very small marks on them, but this isn't a problem and they never have any proper wear.
With the new main pin I've designed, as well as the coating and better tolerances, the oiling system is improved, and the pin designed for better support of the gear. I will change the 6mm retaining pins aswell, from the standard mild steel items, to 6mm silver steel dowels, not really needed, but for the extra small expense, belt and braces.
Another thing to think about aswell is once the main diff pins wear and pick-up on the gear, there is damage to both. I've also found that due to the extra torque and loading on the pin caused by this pick-up, wear to the diff housing is caused (where the outer part of the pins sits) and wear to the central inner block (Where the inner part of the diff pin sits) Due to this, if you just replace the pins with another of same diameter, there would be play where the pins are supported inner and outer, and also the damaged part of the gear may cause damage to the new pin. Because of this the new diff pins need to be slightly oversize and the gear needs to be re-ground to suit and the diff casing and inner block need to be reamed to suit the new bigger pin.
Sep 5, 2010 | 11:14 AM
#50
Evolving Member
Joined: Jun 2008
Posts: 146
Likes: 0
From: Romania
I have 2008 USDM Evo X and the car have 14k miles on it, the car is modified approx. 400hp and I have over 150 launches and street hard driven with some drifts.
since a few months the transmission started to make some noise (nothing broken yet), first time I tought it is the engne mounts from launches.
Here in this movie you can hear the transmission noise at 0:45 http://www.youtube.com/watch?v=BglHcHLXo1U
then I have another transmission noise since a few days, after I drive hard the car then I want to park it and turn the wheels then driving in reverse at the rear wheels there is a noise cracking noise (4-5 times) just like when you driver over small rocks and they break. (I think the LSD is making this noise). After that there is no noise for a while.
since a few months the transmission started to make some noise (nothing broken yet), first time I tought it is the engne mounts from launches.
Here in this movie you can hear the transmission noise at 0:45 http://www.youtube.com/watch?v=BglHcHLXo1U
then I have another transmission noise since a few days, after I drive hard the car then I want to park it and turn the wheels then driving in reverse at the rear wheels there is a noise cracking noise (4-5 times) just like when you driver over small rocks and they break. (I think the LSD is making this noise). After that there is no noise for a while.
Sep 5, 2010 | 01:36 PM
#51
Newbie
Joined: Apr 2009
Posts: 30
Likes: 0
From: Roundlake, Illinois
I had my pins go out at 9000miles last year with a few launches. And I got it warranty by mitsu and they replaced them with the stock pins again My car has almost 30K now no problems but I still want to replace the pins just for safety. I haven't really changed my driving style and I don't know what caused it to brake so fast.
Last edited by evo=ms3killa; Sep 6, 2010 at 08:32 AM.
Sep 7, 2010 | 07:43 PM
#54
I'm hoping. I'm at 47k on stock clutch so hopefully I won't have center diff. pin problems either. I've scrapped big power plans because of all of this crap, though. Mitsu lost my respect by cutting all of these costs. Not the same car as the earlier Evo's.
Sep 8, 2010 | 07:00 AM
#56
With the new main pin I've designed, as well as the coating and better tolerances, the oiling system is improved, and the pin designed for better support of the gear. I will change the 6mm retaining pins aswell, from the standard mild steel items, to 6mm silver steel dowels, not really needed, but for the extra small expense, belt and braces.
Sep 8, 2010 | 03:20 PM
#57
Sep 14, 2010 | 05:32 PM
#58
Evolving Member
Joined: Jun 2008
Posts: 146
Likes: 0
From: Romania
Well I think it happened to me, I'm not sure yet 
, please read my post https://www.evolutionm.net/forums/ev...nsimssion.html
I have just read this post 3 days ago and I tought it won't happen to me...
, please read my post https://www.evolutionm.net/forums/ev...nsimssion.htmlI have just read this post 3 days ago and I tought it won't happen to me...
Last edited by GTR2009; Sep 14, 2010 at 05:41 PM.
Sep 23, 2010 | 07:28 AM
#59
