Sound in rear differential after replacing input gear?

[Sejintsume]

I posted this on Reddit earlier without much traction. I recently stripped out the input gear on my rear differential for my senton. I bought the arrma heavy duty one and I threw that into my truck and since doing that it has been making a noise when moving. I've tried swapping out the differential for a new one. Tried greasing it up with Mobil 1 synthetic. Anyone got any other ideas? I did notice my spur gear looked "fuzzy" but it seemed to spin fine.

I do have a set of input gears from a senton being shipped from JennysRC to try in the car too, but I'm at a loss as I'm unsure what could be causing this noise. I replaced the input gear, replaced the entire differential. Below is a video of the sound.

https://imgur.com/a/Hakap33

 

[Kla912000]

Not getting any sound with the video.
That spur gear looks good.

 

[jondilly1974]

I posted this on Reddit earlier without much traction. I recently stripped out the input gear on my rear differential for my senton. I bought the arrma heavy duty one and I threw that into my truck and since doing that it has been making a noise when moving. I've tried swapping out the differential for a new one. Tried greasing it up with Mobil 1 synthetic. Anyone got any other ideas? I did notice my spur gear looked "fuzzy" but it seemed to spin fine.

I do have a set of input gears from a senton being shipped from JennysRC to try in the car too, but I'm at a loss as I'm unsure what could be causing this noise. I replaced the input gear, replaced the entire differential. Below is a video of the sound.

https://imgur.com/a/Hakap33

View attachment 153735

She is squealing a little. Something not right. Did you assemble the rear diff with the shim on the correct side? Did it spin freely in hand? Did you also replace the Ring gear?

 

[Sejintsume]

She is squealing a little. Something not right. Did you assemble the rear diff with the shim on the correct side? Did it spin freely in hand? Did you also replace the Ring gear?

So this may be a stupid question. But what diff shim? I ordered a set of shims, as I heard they do need shimming eventually. But I haven't shimmed anything with the differential. Is there a side this should have been added to? It does spin pretty freely in my hand, but it does hit a point where it binds up a little bit although it seems to only be in one spot of an entire rotation.

For the ring gear, do you mean the big gear on the differential case? I replaced that entire differential with a new one from Jenny's rc.

 

[morrjr71]

It could be a shim issue, but I rather doubt it since this happened with the new differential as well as the old one. You just may have gotten a bad input gear: a new input gear from Jenny's should help you determine if the input gear is indeed the problem, or if the problem lies elsewhere.

Also check the input gear bearings: if worn they could be allowing the gear mesh between the input gear and the ring gear to change during rotation. I would suggest you change them just to be sure they aren't the problem or aren't adding to an existing problem.

Good luck!

 

[Sejintsume]

It could be a shim issue, but I rather doubt it since this happened with the new differential as well as the old one. You just may have gotten a bad input gear: a new input gear from Jenny's should help you determine if the input gear is indeed the problem, or if the problem lies elsewhere.

Also check the input gear bearings: if worn they could be allowing the gear mesh between the input gear and the ring gear to change during rotation. I would suggest you change them just to be sure they aren't the problem or aren't adding to an existing problem.

Good luck!

Thank you for the input. I just threw in an extra input and bearing set that I had purchased and it still seems to bind up in there. I'm going to see about shimming this.
Shimming it didn't seem to make a difference. When you're spinning this do you spin it by the drive shaft or the wheel axles? I've noticed if I do it by the wheel axles it almost binds always. If I do it by the drive shaft it spins pretty freely.

It always feels "notchy" when spinning by the main drive shaft though.

 

[jondilly1974]

So this may be a stupid question. But what diff shim? I ordered a set of shims, as I heard they do need shimming eventually. But I haven't shimmed anything with the differential. Is there a side this should have been added to? It does spin pretty freely in my hand, but it does hit a point where it binds up a little bit although it seems to only be in one spot of an entire rotation.

For the ring gear, do you mean the big gear on the differential case? I replaced that entire differential with a new one from Jenny's rc.

A shim is a really thin washer. It helps adjust your gear mesh, which is how tight or loose they feel. If too tight, it will bind. If too loose, they strip out. Another factor is the diff yokes. They do warp over time or possibly melt if they get hot enough. It’s easy to over tighten the yoke screws. Try backing them out a small rotation and see if that frees up your diff.

And yes the ring gear is the one built into the diff cup on a 3S car. If you bought the whole diff from JRC, then you’re probably good. It should have came with a single shim on the ring gear side. It will be on the inside of the output bearing.

 

[Sejintsume]

A shim is a really thin washer. It helps adjust your gear mesh, which is how tight or loose they feel. If too tight, it will bind. If too loose, they strip out. Another factor is the diff yokes. They do warp over time or possibly melt if they get hot enough. It’s easy to over tighten the yoke screws. Try backing them out a small rotation and see if that frees up your diff.

And yes the ring gear is the one built into the diff cup on a 3S car. If you bought the whole diff from JRC, then you’re probably good. It should have came with a single shim on the ring gear side. It will be on the inside of the output bearing.

Thank you! There is definitely a shim in there and adding a second one didn't seem to help. I stopped by my LHS and they suggested that the sound/bind would work itself out as the gears spend time running together.

Can't really argue with that logic. But, I guess given I've bought a spare of every piece of the differential at this point I can just run it.

 

[jondilly1974]

Thank you! There is definitely a shim in there and adding a second one didn't seem to help. I stopped by my LHS and they suggested that the sound/bind would work itself out as the gears spend time running together.

Can't really argue with that logic. But, I guess given I've bought a spare of every piece of the differential at this point I can just run it.

Yeah plastic gears aren’t always molded perfect and will wear in. Put a pack thru it and see what happens. Worst case you buy another diff.

 

[Ruzty1311]

So same thing happened to me and yes, the small binding is sometimes normal and no matter how much you back the screws out on the yoke it'll still sometimes do it. I went through this with MULTIPLE and I'm talking about 5 different brand new input gears and 5 brand new diffs from Jenny's RC (spares) and I got binding no matter what I did shim wise or backing out screws. The culprit ended up being the plastic diff yoke. Bought a new set and the binding was 80% gone. There was still just the slightest bind but I was able to tighten the screws down to the fullest and it was free play again.

Even after going with metal yokes, metal input gear, metal diff ring i STILL got the SLIGHTEST binding but it was so much better than all the plastic that used to be in there. Interestingly enough, I got less binding with the GPM yoke than the HR yoke so I might be buying GPM yokes for the fronts of my two 3s rigs instead of HR which I thought was the better fit. (I only did the rears of my Typhon and Granite since that's where I was busting input and ring gears the most).

 

[Sejintsume]

So same thing happened to me and yes, the small binding is sometimes normal and no matter how much you back the screws out on the yoke it'll still sometimes do it. I went through this with MULTIPLE and I'm talking about 5 different brand new input gears and 5 brand new diffs from Jenny's RC (spares) and I got binding no matter what I did shim wise or backing out screws. The culprit ended up being the plastic diff yoke. Bought a new set and the binding was 80% gone. There was still just the slightest bind but I was able to tighten the screws down to the fullest and it was free play again.

Even after going with metal yokes, metal input gear, metal diff ring i STILL got the SLIGHTEST binding but it was so much better than all the plastic that used to be in there. Interestingly enough, I got less binding with the GPM yoke than the HR yoke so I might be buying GPM yokes for the fronts of my two 3s rigs instead of HR which I thought was the better fit. (I only did the rears of my Typhon and Granite since that's where I was busting input and ring gears the most).

Thank you!!! I had a feeling I should try replacing that next. After all, what's left at this point? Thank you again!

 

[Ruzty1311]

Thank you!!! I had a feeling I should try replacing that next. After all, what's left at this point? Thank you again!

No problem

 

[Sejintsume]

No problem

This was 100% the problem. I got a new yoke and it spins freely.

 

[Ruzty1311]

This was 100% the problem. I got a new yoke and it spins freely.

Awesome man! I went through so much to try to figure this issue out haha Glad it worked for ya

Also it does sound a little bit of a louder than normal pitch/squeal. Maybe just double check your mesh isn't too tight and also check the slipper clutch to make sure it isn't too tight either. Sometimes video can pick up the sound better than in person as well so you might be ok

 

[morrjr71]

The new Hot Racing aluminum yokes for my Typhon 3s arrived this afternoon. I hope to get them installed this weekend.

 

[Jsky87]

Everytime I come here looking for answers I find them. I just bought new diffs from Jenny's and have the same problem. Now I can skip all the Bs. Thanks guys