NZJohn 78 Posted July 23, 2021 I’ve just done my first hop up of a Frog. But I’m getting a horrible grinding noise at low speed. The upgrade was 53908 FROG Assembly Universal Shafts. And whilst I’m pretty sure I follow the instructions I’ve clearly missed something. The only part I did add was to put a plastic o ring into each of the two parts that go into the gear box. There’s nothing obviously wrong I can see Share this post Link to post Share on other sites
toyolien 4680 Posted July 23, 2021 Not much we can suggest without a few pics or a video? Share this post Link to post Share on other sites
Frog Jumper 3661 Posted July 23, 2021 Try a complete tear-down and re-build... Terry Share this post Link to post Share on other sites
RichieRich 685 Posted July 24, 2021 Make sure the cross pins haven't worked loose. Was it making the sound before you installed the new universal shafts? Share this post Link to post Share on other sites
NZJohn 78 Posted July 24, 2021 Cheers. It was running smoothly before with the kit standard shafts. I’m going to strip it back to the gearbox. And start the hop up assembly again. I kind of got caught up today with painting a decals 😜 Share this post Link to post Share on other sites
NZJohn 78 Posted July 31, 2021 Ok, I’ve taken the universals and wheels off. With just the two shafts left sticking out of the gearbox the motor and gearbox is running smoothly and no issues. But as soon as I put the universal shafts and wheels back on I’m getting the same awful grinding sound at low revs… see attached video. I need help! FullSizeRender.mov Share this post Link to post Share on other sites
Frog Jumper 3661 Posted July 31, 2021 Maybe I’m old and deaf but that sounds like it’s supposed to. It is a little clicky but I think as the parts break in, the sound will diminish… Share this post Link to post Share on other sites
Fuijo 880 Posted July 31, 2021 If you remove the rear shocks and prop up the rear suspension arms so that the drive shafts are horizontal does it still make the noise? If not, how far can you lower the arms before the noise starts again? 2 Share this post Link to post Share on other sites
NZJohn 78 Posted August 1, 2021 19 hours ago, Fuijo said: If you remove the rear shocks and prop up the rear suspension arms so that the drive shafts are horizontal does it still make the noise? If not, how far can you lower the arms before the noise starts again? Yes. This does make a huge difference. If I push the wheel up so they are closer to horizontal you don’t get the grinding noise at all. So is this normal. And when slack the rear wheels are just at too much of an angle? So the weight of the car pushes the universal joints more horizontal and reduces / eliminates the noise? Share this post Link to post Share on other sites
Fuijo 880 Posted August 1, 2021 32 minutes ago, NZJohn said: So is this normal. I don't know tbh. I'm sure I've read somewhere that the universals don't work as well as the dogbones at extreme angles. Which is odd; you would think the hop-up designed for it would work with it, wouldn't you? If it were me, I'd either go back to the dogbones, or keep the universals and put an internal spacer, like an o-ring or two, under the damper piston to stop the shocks extending so far. 1 Share this post Link to post Share on other sites
NZJohn 78 Posted August 1, 2021 1 hour ago, Fuijo said: I don't know tbh. I'm sure I've read somewhere that the universals don't work as well as the dogbones at extreme angles. Which is odd; you would think the hop-up designed for it would work with it, wouldn't you? If it were me, I'd either go back to the dogbones, or keep the universals and put an internal spacer, like an o-ring or two, under the damper piston to stop the shocks extending so far. Ok cheers. That’s a bit of a let down. The hop up isn’t cheap either. I’ll revert to the kit dog bone joints and test again Share this post Link to post Share on other sites
NZJohn 78 Posted August 2, 2021 UPDATE; I’ve found a solution. And thanks to those that commented here. TLDR: the hop up universal joints cause a grinding sound at high angles. When moving the wheels closer to horizontal they operate smoothly and without the rough noise. So I opened the shocks and put a 5mm piece of tubing over end of the piston. This reduces the distance the shocks travel and makes the car lower to the ground. And problem solved! 2 1 Share this post Link to post Share on other sites
RichieRich 685 Posted August 3, 2021 This makes sense as the frog has really short half shafts for a rather large amount of suspension movement. Newer cars have longer suspension arms and longer shafts so the angels aren't as extreme. I believe this is why the original frog hex shafts would round off. 1 Share this post Link to post Share on other sites
Juggular 4964 Posted August 9, 2021 On 7/24/2021 at 7:11 AM, NZJohn said: That's a good looking Frog! When I restore my Frog, I want to go with the original color scheme. Maybe I'll leave the roof clear too! 2 Share this post Link to post Share on other sites