Hpi trophy truggy flux diff noise?

[Jse]

Had my hpi out for a spin the other day when all of a sudden it just start this grinding noise when you press the throttle and won't move. Flipped the diff the other way and it was just fine any ideas.

 

[DavidB1126]

Grinding noise can be the shimming causing the gear mesh between the diff ring/pinion being too tight or too loose, or the diff ring gear was interfering with the gear box.

But since you flipped it the other way around and it ran just fine, I think last time it was worked on the diff was put in backwards making the wheels spin in the other direction making it fight the other set of wheels. So basically, front diff is usually pulling, if flipped it would be pushing. Rear diff is usually pushing, if flipped it would be pulling. Ie, essentially running in reverse if you think about it that way.

I accidently put a rear diff in my Reflex in backwards and I was like why is it not moving, and I was like oh, I put the diff in backwards. lol. (it took me 2 hours to figure out )

 

[Jse]

I flipped both of them the same way that's the weird thing they were both spinning the right way but one way it grinds the other way it doesn't

 

[DavidB1126]

Ah ok
I would open up the gear cover/gear box, manually rotate the driveline, see if theres any physical binding in the ring/pinion
Check that all bearings are seated properly and spin/roll freely/smoothly
Take the actual diff out, spin it by the outdrives and see if anything is binding in there, if so...
I would see in the diffs and check that each of the sun/spider gears inside look good, and are properly filled with either grease or oil.

If all is good and still "grinds" I would try to add or remove shims on each side of the diff and see if the grinding stops. Basically trial and error if it does come to that part.

 

[Jse]

Yea I was in there earlier and the oil looked/smelled a little funky might just need change it's got like a grayish look to it

 

[DavidB1126]

Always good to freshen up on oils.
Also something to reference, when rebuilding if you notice any small metal chunks, if its a little, itll be fine to run. but if its alot it means the gears are wearing down. If it does look like that I would try to get new diff internals if you can

 

[Jse]

I already ordered a set I'll try them but still a bit weird it works one way and not the other wonder if they only go in one way and someone installed wrong way B4 I got it

 

[DavidB1126]

Technically speaking. Diffs can be flipped around theyll just be running in reverse but for the car to be running properly, they only go in 1 way. Possible that it was installed wrong by prev owner. doesn't hurt to rebuild stuff occasionally tho. maintenance is always good. (from someone who still needs to do a trans rebuild on my rustler that I haven't touched in like 2 years of bashing and racing lol)

 

[CertifiedMike]

The noise in only 1 direction makes me think it needs shims, a bearing is loose, housing cracked, bent or worn shaft...
In 1 direction, the gears are loading up and rotate correctly, in the other, they are finding slop. Some space to slide into or out of that allows the teeth to slip and grind instead of mesh.
Look for wear on the unlikely parts of your gears and housings. I bet thats where the issue lies.

 

[RustyUs]

I already ordered a set I'll try them but still a bit weird it works one way and not the other wonder if they only go in one way and someone installed wrong way B4 I got it

So, I'm guessing this is a used truggy. Good time to open up all the diffs and clean/inspect all the internals since you got new sun/planet gears on the way to compare. Now that you have things torn apart, may as well check the bearings, pins, etc., etc., that have gone past their expiration dates. Used RCs are a special breed. I don't care how meticulous a person says they are, or how the RC was only a well maintained race vehicle... people forget/overlook areas of their ride all the time. I don't buy a lot of used RCs. Out of the nine, ten, or eleven... there was only one that was perfect.