Rukik

Good day everyone,
I have had to replace 2 diff ring and pinion gears in my front diff in 2 weeks. I haven't had this problem before so I am assuming I am doing something wrong. The pinion gear keeps breaking teeth and chipping the ring gear. The bearings are new, and the shaft is straight. What should I look for that could cause this?

RustyUs

Did you do anything to the shock travel, or ride height?

First, check for any binding from the universal drive shafts as you go through the full range of the front suspension travel.

Secondly, make sure to have no lateral side-to-side movement of the ring gear (Redcat calls it a crown gear) when putting it in the gearbox. Shimming as necessary. After that, the gearbox pinion gear (drive gear) should feel smooth as you work the diff by hand. Wouldn't hurt to minimize play, by shimming, on the drive gear as well. You'll know if you went too far on the shimming, or if something isn't right when the front and rear diffs feel notchy.

Maybe you got a bad batch of gears? That's been known to happen. Look into getting replacement gear from a different source.

Igottabeme

I had a similar problem with my Redcat Volcano replaced the pinion and ring only to strip both of them again. I changed the gearbox housing and have not had a problem since, Don't know if that's your problem just might be something to try.

Good luck!

Rukik

I ordered a new set of gears. Should have them by Friday. I'm thinking I may have gotten a bad set of gears. I have aluminum diff housings and base plate so I know there is no movement. The front and rear end are solid. I'll try shimming the diff. Which should I use to shim the lateral movement of the crown gear it's pretty tight in there allready with the way the bearings sit in the case. I can shim the pinion gear much easier so I think I will start with that.

RustyUs

Finding shims to work and fit properly will sometimes take a bit of digging if not provided by Redcat platform. If you have aluminum gearboxes, then you should be good to go unless the tolerances are off. Plastic gearboxes are more susceptible to temp change. Combine that with bad bearing maintenance, hot/cold/hot/cold, and the diff gears wearing down, you then have slop beginning to form. Slop then results into gears not being able to fully engage each other...you left with gears stripping . In your case of diff's pinion gear teeth "breaking", to me, that sounds more like a bad batch of metal.

RustyUs

Diff pinion gear shim = 3Racing (#3RAC-SW08) Stainless Steel 10mm Shim Spacer 0.1,0.2,0.3mm Thickness
Differential shim = Team Associated #92079 15mm Differential Shims

Rukik

perfect thank you for the part numbers!

the bearings are brand new, changed them 2 weeks ago when I replaced the first set of gears. The pinion gear comes with a new shaft when you order it, I only ran 2 batteries through before the second set went.

RustyUs

You are welcome. It took me a bit of thinking and digging through different models to get the right sizes.

Picture is from another platform. Same principle can be applied to the diff drive gear (pinion gear) on the Tornado.

Rukik

Closer inspection, I found lateral play on the crown gear, off to my local hobbie shop to see if they have shims in Stock.

Rukik

I got the shims, I shimmerd the lateral play out of the diff, the mesh seems right, but when I put it together the gears sound louder. I added and removed until I had the smoothest motion. The mesh has a slight gap like when doing a pinion spur mesh, just a slight play. does this seem acceptable or am I going to chew through the teeth because it is to tight?

RustyUs

Ultimately you want some play. Should'nt have to cram/force any shim to fit. You just don't want slop. Your fingers be you best gauge.

Rukik

Ok, 1 less shim I have slop, 1 more I have to cram it in. So I guess run it and see what happens hahahaha

Rukik

Some feed back on what I have found. We finally have our snow course up and running and the shims worked wonderfully. I figured out what was causing the front diff to tear teeth apart. The off shimming was most likely a factor, but I found the major culprit. Anyone who is running a redcat tornado, volcano, or any other 4x4 with the same platform, as well as the hsp, and exceed counterparts, the front c-cup on the center drive axle it held on by a m3 grub screw. After enough torment the grub screw will loosen, even with thread lock, and allow for a foward and back play, the center dogbone will not allow the c-cup to fall off and since the diff imput shaft is slotted to mate with the c-cup it will not vibrate either. The c-cup acts like a retainer for the diff pinion gear and when it comes loose you can have almost 1/4 inch play. Bye bye gear mesh in the diff, and hello broken teeth. To fix this I took a 3/32 or 2.4mm drill bit, used a marking punch to mark the input shaft and drilled a 2.4mm hole (recommend a drill press, or a skilled hand) to install a m3 screw pin. Then shim the shaft if necessary and no more problems. You do not have to do this for the rear diff and the shaft has e-clips and a pun for the spur gear, as well as the motor mount to keep it solid. Hope this helps.

​http://www.rcuniverse.com/forum/off-topic-forum-cars-trucks-buggies-more-392/11659346-my-tornado.html#post12494392​​​​​​

posted a few picts of my rig.