How to shim your Arrma diff

WoodiE

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This is something we get asked a lot on the forums and nearly every single time the answer to those threads are to watch this video. So as suggested, I created a sticky thread for this very question.

We can also use this thread to have a "one place to go" for this information.

Also check out the thread: Shims that work for Arrma diffs


Enjoy!
 

deadair

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I know I posted this in another thread but after reading different threads/youtube vids, I think this would be a good place for everyone to see this question and answer.

Do you treat all 3 diffs the same?
 

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Links to shims -
For the internal shims -
Mugen Seiki Differential Washer Set X6/X6T/M-Spec
https://www.towerhobbies.com/cgi-bin/wti0001p?&I=LXJAM6
that Mugen set is often sold out.

For the external shims -
Tekno RC Differential Shim 13x16x.1 EB48 (10)
https://www.towerhobbies.com/cgi-bin/wti0001p?&W=003058064&I=LXDWDG&P=K

Some Protec 3.5x12 x 0.2mm shims -
https://www.amainhobbies.com/protek-rc-3.6x12x0.2mm-differential-gear-washer-10-ptk-h-5914/p188802

and the Arrma shim set -
https://www.amainhobbies.com/arrma-washer-5x18x0.3mm-6-ara709024/p409556

Note, that if you buy a diff internal gear set, it comes with the small 3.5x12 shims -
https://www.amainhobbies.com/arrma-differential-gear-set-ara310436/p409428
 
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Jerry-rigged

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Motorider

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Hello everyone. First post here. Took an Arma Kraton v2 in trade for a stock rtr bomber. Tore down the diffs for inspection and found a nightmare. The ring and pinion gears are all toast. The gear mesh on the motor was wicked tight. Zero play. The diffs were all missing factory shims and filled with plain old marine lithium grease. I can't imagine this thing worked well for him.

Anyhow in my search for parts I have become very dissappointed. Either these things fail a lot and parts are in high demand, or there are supply chain problems. Either way it sucks. What I ended up doing was buying 2 complete diff sets off of flea bay for $68 shipped. Hell the ring gears are $20 alone. I was; however, very pleased with the ease of access. Thanks Arma.

The big question is what version of diffs did I buy and will they come with the 5x18x.2mm shims installed. I really want to get this car going this week.


Your shims listed don't all work out. The arma part number ara709024 is for the 3.5x12x.15mm shims.

I'm in dire need of the 5x18x.2mm shims. Any arma part numbers?

Also, what oils are working well for everyone in the diffs?

Thanks for any and all guidance.
 

Jerry-rigged

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Anyhow in my search for parts I have become very dissappointed. Either these things fail a lot and parts are in high demand, or there are supply chain problems. Either way it sucks.

yeah, you can say that... Hobbico only supplies probably 1/2 to 3/4 of all the hobby shops, and owns Arrma. Supply chain problems are an understament...

The diffs do not have the 18x5 shims from the factory, only the smaller 12x3.5 shims... And yeah, those 18x5 are hard to find. Seems I have heard of some people using either the Tekno 15x5 shims (for the EB410) or the 18x6 (for the SCT410). Also the Mugen shims for the "high traction diffs" and the AE B8.3 diff shims supposedly work, although I don't know the exact size of those shims.
 

Motorider

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The diffs do not have the 18x5 shims from the factory, only the smaller 12x3.5 shims... And yeah, those 18x5 are hard to find. Seems I have heard of some people using either the Tekno 15x5 shims (for the EB410) or the 18x6 (for the SCT410). Also the Mugen shims for the "high traction diffs" and the AE B8.3 diff shims supposedly work, although I don't know the exact size of those shims.

I thought the 5x18mm shim went behind the sun gears inside the diff. The guy in the video for the bulletproof diff on armas website installed it. Called for part number td310475. That is a 5x18x.2mm shim. I could care less what stock came with. I want this thing to last. If it goes like my yeti xl did, I'll sell this thing and get the tekno mt410 I really wanted.

Anyhow, so what's the preferred diff fluids?
 

Jerry-rigged

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exactly, you need to put that 18x5 shim behind the sun gear. The Planetary gears come with shims from the factory, I believe - the smaller 12x3.5. You want all 6 shims (2x sun shims, 4s planetary shims) - then check for binding / slop, and adjust with more / fewer shims from there. Also, don't forget the 16x13 shim for the external bearing - this one will protect the ring and pinion.
 

Motorider

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exactly, you need to put that 18x5 shim behind the sun gear. The Planetary gears come with shims from the factory, I believe - the smaller 12x3.5. You want all 6 shims (2x sun shims, 4s planetary shims) - then check for binding / slop, and adjust with more / fewer shims from there. Also, don't forget the 16x13 shim for the external bearing - this one will protect the ring and pinion.


Thanks. Good explanation. I noticed a good amount of slop on both outdrives. I assume that the sun gear shims will take that up. Can't wait to get this thing online.
 

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exactly, you need to put that 18x5 shim behind the sun gear. The Planetary gears come with shims from the factory, I believe - the smaller 12x3.5. You want all 6 shims (2x sun shims, 4s planetary shims) - then check for binding / slop, and adjust with more / fewer shims from there. Also, don't forget the 16x13 shim for the external bearing - this one will protect the ring and pinion.[/QUOTE

So the extra shims are in addition to the original shims that are already in it?
 

Jerry-rigged

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So the extra shims are in addition to the original shims that are already in it?

No, you want to start with one shim behind all 6 gears. Use the stock shims or the extra shims, but not both. 6 gears, 6 shims, then reassemble, and check for binding / slop, and add or remove shims as needed.
 

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As advised here of the forum, I'm now shimming my diffs & started with my front diff on my V3 Kraton. I've built diffs before, but not Arrma diffs. I have the diff all clean and also fully understand how to shim them, so no problems there. However, I cannot remove the internal sun gear on the diff cup side. The other side (which has the large external crown gear) was easy to remove the sun gear. However, the sun gear is quite deep down in the diff cup side, and hard to get at, so very difficult to pull it off the pin/outdrive compared to the other side. I've even tried using needle nose vise grips (which should work), so not sure why I cannot remove the sun gear on the diff case side? I want to add a new bearing on this side, plus remove the o ring to lube with some green slime & most importantly, I need to add a 5x18 shim on the diff cup side. Also, what is the small set screw for on the side of the diff cup, as not one video addresses this? Very frustrating to already have problem on my 1st diff...

PLEASE HELP ???
 
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