Tips for dealing with stubborn diff gear

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Stormwind

Stormwind

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Corally RC's
  1. Kronos
I have just spent 2 very frustrating hours attempting to rebuild my rear differential after replacing the main gear.

The issue I am having is that the new gear appears to have a slightly smaller inner diameter than the old one where the planetary gear case fits into it.
The old one is very easy to fit and take apart whereas the new one is very, very tight.
So tight in fact that the only real way I found of screwing the case on is to kind of sit it resting gently on top and then go around each screw giving each half a turn until they pull the case into the slot on the gear.
This has the drawback of the gear getting pulled on at an angle that does eventually straighten up once all 4 screws are tight but something in this process is causing the planetary gears not to mesh correctly and I either end up with the gears slipping (too loose), locking up completely or locking one way.

I have eventually given up and had to resort to leaving an oily mess all over my kitchen table which I suspect is not going to go down too well in the morning.

Has this happened to anyone else? I feel like my only option is to take my rotary tool to the inside of gear to try and widen the diameter a little. My only worry there is that I have no metal working experience and possibly don't even have the right tools for the job (I have no clue what all the tips for my tool are supposed to be used for 😛). I'd also be worried that I'd make it even or something and end up with a leaking diff.
 
Hmm, that sounds so strange. Are you able to post pictures to show a side-by-side comparison of the two main gears?
 
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That's not right.

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The diffs are a fairly standard design, similar to many others.

Things to watch - cross pins C-00180-184 - make sure they are flat to flat.

Make sure the pins C-00180-205 are located correctly and that the gears are sitting on them properly.

The case C-00180-098 should fit perfectly into the steel crown gear, with a paper gasket to ensure leak free operation.

I personally recommend that you do a dry assembly first - then once satisfied that everything fits - then fill with oil.

If you can't press the assembly together with your fingers, something is wrong. Don't attack anything with the Dremel. It might be that the steel crown you have been supplied is the wrong part.
 
It might be that the steel crown you have been supplied is the wrong part.
Click to expand...

I've had something like this happen before. I ordered the correct part # for my Arrma slipper assembly, but it didn't fit. It turns out the part was the wrong one. Someone in the warehouse must've packed the wrong part into the baggy. This sort of mistake isn't common, but it can definitely happen.
 
ridgehead44 said:
I've had something like this happen before. I ordered the correct part # for my Arrma slipper assembly, but it didn't fit. It turns out the part was the wrong one. Someone in the warehouse must've packed the wrong part into the baggy. This sort of mistake isn't common, but it can definitely happen.
Click to expand...
Mystery solved - hopefully! 🤞
 
The old and new gears definitely looked identical. They were certainly the same size in terms of outer diameter when I compared them as I was thinking along the same lines.

When I came down in the morning to give this another go I found the reason for the locking up was due to a broken planetary axle. Luckily I had a replacement and I managed to fit the main gear on again and everything is fine now. Possibly the machining of the gear wasn't quite up to scratch 🤷‍♂️
 
Stormwind said:
The old and new gears definitely looked identical. They were certainly the same size in terms of outer diameter when I compared them as I was thinking along the same lines.

When I came down in the morning to give this another go I found the reason for the locking up was due to a broken planetary axle. Luckily I had a replacement and I managed to fit the main gear on again and everything is fine now. Possibly the machining of the gear wasn't quite up to scratch 🤷‍♂️
Click to expand...
Glad you've got it sussed. 👍💪
 
This is like every time you go to break, you hear the gears grinding every time you hit the throttle your gears grinding. If so, I'm experience the same BS
 
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