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Old 04-18-2011, 10:43 AM   #1
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Default M-SPEC MBX6T diffs destroyed after 4 tanks !

ok bought my second mbx6t mspec and after break in on the motor ( tank idled through and 2 tanks on track ) 2 heats and 1 main, both front and rear ring gears and pinions are totally roached! i noticed them clicking so i reshimmed both and toned down my break front and rear and still destroyed them. called mugen they want me to send both diff gears in along with pinons so they can see whats going on with them.? anyone had this problem? and for spending 510 bucks for a kit you would think that they could help ya out a bit and shim them from the factory a bit better.
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Old 04-18-2011, 10:45 AM   #2
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never heard of anyone having that problem. they probably want you to send them in because there could be some kind of casting flaw or something like that.
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Old 04-18-2011, 10:49 AM   #3
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Originally Posted by stuntryda View Post
ok bought my second mbx6t mspec and after break in on the motor ( tank idled through and 2 tanks on track ) 2 heats and 1 main, both front and rear ring gears and pinions are totally roached! i noticed them clicking so i reshimmed both and toned down my break front and rear and still destroyed them. called mugen they want me to send both diff gears in along with pinons so they can see whats going on with them.? anyone had this problem? and for spending 510 bucks for a kit you would think that they could help ya out a bit and shim them from the factory a bit better.
I started running a 6T mspec in December 2010 at a freq of 2 race days per month a 5 day race at the nitro pit and a 3 day Nat Warm up. I had the front diff give on me this past weekend. I didnt know they ate gears like that either but it was clicking and I have been told to shim it tighter when it does that. Theres a member on here that is doing ceramic coated gears taht he says last a good while. I am dropping them in. But I agree they should last longer.
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Old 04-18-2011, 11:06 AM   #4
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I have a couple of friends who race for Mugen, and they have said that with new ring and pinion gears you have to shim, run them a couple of heats, check and re-shim, and check again after a couple more.

Supposedly once you have done it once or twice, they will be good to go. But the first initial runs are almost like you have to break it in. I raced an O'donnell Z01B-SG last year, it was the same way.
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Old 04-18-2011, 11:08 AM   #5
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ok bought my second mbx6t mspec and after break in on the motor ( tank idled through and 2 tanks on track ) 2 heats and 1 main, both front and rear ring gears and pinions are totally roached! i noticed them clicking so i reshimmed both and toned down my break front and rear and still destroyed them. called mugen they want me to send both diff gears in along with pinons so they can see whats going on with them.? anyone had this problem? and for spending 510 bucks for a kit you would think that they could help ya out a bit and shim them from the factory a bit better.
I raced mine all last year never had one completely go but did have the gears get a little messed up I caught it before it totaly went. Ialso check my diffs every three to four races for gear mesh, fluid and bearings and rebuild if necessary. Every diff case may also require a different amount of shimming for example I just replaced both of my cases and I had both .2mm shims on the gear side on the new case and it was too tight but so I have one on each side on the rear I have 2 .2MM and 1 .15mm shims on the gear side without the.15mm there was to much backlash in the gears and there was a little bit of play inside the case. And since these are new cases I will probably check them after my first race.
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Old 04-18-2011, 11:37 AM   #6
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You need to check the gearmesh every 2-3 races. The sooner the better. I check it almost every race, especially when breaking the diffs in.
Also lube the ringgear. If the ringgear isn't lubed, the gears will heat up more and faster and the plastic bulkhead will expand of the heat. This causes the backslash in the gears and in the worst case, stripped gears.

I'm running my mbx6 for almost a year on astroturf (very high grip) without problems.
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Old 04-18-2011, 11:53 AM   #7
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I have been racing mugen for over 2 years. The gears last forever, I still have the original set. And you want a very small click of play. I listened to someone on here who said shim slightly tight, grease and break in. Well it starting doing what you described. Lucky for me I break my stuff down often and caught it. Shim you ring and pinion like you would your spur/bell. Also, take the top of the diff case and lightly sand it flat on a table to make sure it is even and flat.

Then check the evenness by setting your diff on the center diff mount and spin it. It will expose any unevenness no matter how small. Mugen gears are bullet proof if treated and maintained right.

ETA, not quite as loose as the spur/bell, just a hair tighter. I shoot for smallest amount of play, but there is still a "click". If your ring gear is even all around and your mesh is right, it is almost impossible to strip them

Hope this helps
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Last edited by dreaux; 04-18-2011 at 12:24 PM.
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Old 04-18-2011, 11:56 AM   #8
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I have been racing mugen for over 2 years. The gears last forever, I still have the original set. And you want a very small click of play. I listened to someone on here who said shim slightly tight, grease and break in. Well it starting doing what you described. Lucky for me I break my stuff down often and caught it. Shim you ring and pinion like you would your spur/bell except a hair tighter. Also, take the top of the diff case and lightly sand it flat on a table to make sure it is even and flat.

Then check the evenness by setting your diff on the center diff mount and spin it. It will expose any unevenness no matter how small. Mugen gears are bullet proof if treated and maintained right.

Hope this helps
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Old 04-18-2011, 05:09 PM   #9
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All diff bulkheads may have different play when shimmed. I immediately shim between the diff cup and the bearing and one on the outside of the ring gear. It is about the right tightness and once you start running, of course it will generate heat which causes the housing to expand/break-in. The Japaneses shim the new diffs/bulkhead tight and allow the heat to mesh it. It sounds crazy but that what was recommended by the mechanic/RC advisor. I have done it and never had issues. Basically no play when the housing is bolted but no binding. Thatís why I shim inboard of the bearings. But do not make it so tight that you cant even spin the diffs when bolted up.
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Old 04-18-2011, 05:31 PM   #10
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when I ran the 6t and the 6 I never had any problems with the gears, but seen people have some issues. Like said above I never shimmed them to were they didnt have any play. Reason being if the chassis flexes during a crash and the mesh is to tight then you will have problems. I always left just a tick of play in them. And I alway use mobil 1 red grease on all of my ring and pinions and after quite of bit of fuel mine still look new
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Old 04-18-2011, 05:58 PM   #11
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Default One aditional note....

I noticed when I shimmed my m spec buggy that the bulkhead lets the diff bearings move too much so the simple fix is to drop one drop of superglue on the inside of the bulkhead cover where the bearing rides and let it even out and dry, then when you screw the cover down it will hold the bearings tighter and keep ur mesh where you set it longer....

The easiest way to check mesh is to hold the center axle and rock the outdrives back and forth when the car is assembled. If there is more than a tiny ammount of play take the diff out and shim it a bit closer, and take ur time doing it. I've ofund if you use a shim on the inside of the outer bearing and the bulkhead you will get the pinion locked in without front to back play...basically put a med thin diff shim in the bulkhead then the outer bearing where the center cvd rides...

Also if you put a small shim on the diff gear side, and the diff case side before you put the bearing on it your adjustment will stay put longer than using alot of shims that slide over the outdrive bearings.....those should be for fine tuning....
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Old 04-18-2011, 07:05 PM   #12
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shimming only helps if the bearings are good, replace often.
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Old 04-19-2011, 07:53 AM   #13
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well thanks for all the advice guys, im sending both front and rear diffs in to mugen, and ordered 2 ring gears and pinions should be here this week sometime. hopefully they give me an answer, anyhow on to the next question, has anyone ever underdriven the rear of their truggy??

have read alot about guys doing this in the mbx6 buggy but not to much in the truggy? whats your thoughts on this i do happen to have a 44 RING AND 13 PINION at the shop? hmmm
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Old 04-19-2011, 08:06 AM   #14
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well thanks for all the advice guys, im sending both front and rear diffs in to mugen, and ordered 2 ring gears and pinions should be here this week sometime. hopefully they give me an answer, anyhow on to the next question, has anyone ever underdriven the rear of their truggy??

have read alot about guys doing this in the mbx6 buggy but not to much in the truggy? whats your thoughts on this i do happen to have a 44 RING AND 13 PINION at the shop? hmmm
Next time you might want to bid for diffs and pinions on ebay. Then you'll have a good selection of spare diff parts.
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Old 04-19-2011, 03:20 PM   #15
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Quote:
I noticed when I shimmed my m spec buggy that the bulkhead lets the diff bearings move too much so the simple fix is to drop one drop of superglue on the inside of the bulkhead cover where the bearing rides and let it even out and dry
Yes, the outer diff case has far too much room for the bearing to move. I believe it's a necessity to eliminate this.

I use two strips of aluminum tape cut precisely to fit the bearing bed of the outer case. Snugs them up nicely. Two strips should tell you....there's too much room here.
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