rjoseph244510 14 Posted December 7, 2019 Hi guys I am very much a newbie to rc cars and have treated myself to a Tamiya Egress kit for Christmas as a nice way in to the hobby. I also purchased a very old and battered Dark Impact from eBay with the idea that I would restore it after I had built some confidence through the Egress. Anyway, the Dark Impact finally arrived (fully built) and so I connected everything up to see if it worked. After some messing around I finally got the thing, sort of, working which I am chuffed with. However, it by no means runs smoothly so I know there's a lot of work to be done on it. One thing that really stands out is the fact that when I lift the car up and manually spin one of the rear wheels the other three wheels hardly turn at all. The same can be said for one of the front wheels where if I turn it then the other three wheels hardly turn at all. What is strange is that if I turn the other front wheel there is better movement (though be no means perfect) in the other three. A further clue is that I can spin the rear wheels and hold the drive shaft still but I can't easily do this with the front wheels. Like I say, I haven't a clue when it comes to the various components in rc cars and what they all do. This is why I have the Egress project in the pipeline so I can slowly learn as I go along. However, the issue with the Dark Impact is bugging me. Without stripping the whole thing down, what would you say are the most likely cause of this? Any help would be fully appreciated. Best regards Rod Share this post Link to post Share on other sites
Superluminal 3750 Posted December 7, 2019 Ball diffs could need tightening or they are knackered and need replacing. Share this post Link to post Share on other sites
Quailane 33 Posted December 7, 2019 The Dark Impact uses ball differentials in the front and rear. They are more maintenance intensive than gear differentials. Take the ball differentials apart and rebuild them as per the instructions. Also check to see if there is anything amiss with them. Share this post Link to post Share on other sites
Wooders28 4723 Posted December 8, 2019 As above, balls diffs require a bit more maintenance than gear diffs, so need a rebuild every so often. The balls can become , not ball shape any more, and also wear a groove in the plates. An upgrade is to use 3mm tungsten carbide diff balls, as they stay ball shape for longer than steel balls, but depends on what kind of power you're planning (you can find them on ebay faily cheap, but you'll need 20 to do both diffs). Tamiya do do a gear parts bag though, which has replacement plates and steel balls. Share this post Link to post Share on other sites
WillyChang 1814 Posted December 8, 2019 If balldiffs aren't built correctly & slip too much, the heat will warp plastic parts... it's best to fully rebuild with fresh plastics/balls/plates. With any used RC, if you've no idea who & how it's been originally built - it's best to totally strip it down, clean and rebuild according to manual. Inspect every moving part for wear, every shaft for bends and every other part for impact damage & stripped screw holes. 1 Share this post Link to post Share on other sites
rjoseph244510 14 Posted December 8, 2019 Thanks guys, much appreciated. I'm not going to pretend that I 100% know about the terminology but you've all definitely given me a great starting point. Hopefully, my experience building the Egress will stand me in good stead when I look to restore the DP! Thanks again and best regards Rod Share this post Link to post Share on other sites
Superluminal 3750 Posted December 8, 2019 I would be inclined to give the dark impact a go first as it will be a good learning excersize and parts are readily available (although aftermarket hop ups are harder to find) If you get used to fixing and running this it will put you in good stead for the egress and give you an understanding of each of the components and how they function. Start off with some JIS screwdrivers. Share this post Link to post Share on other sites
rjoseph244510 14 Posted December 9, 2019 Thanks Superluminal The only problem I have with this approach is that I don't yet have the manual for the DP. Therefore, if I strip the thing down I may struggle putting it back together. However, you do make a good point so I may source the manual asap. Thanks again Rod Share this post Link to post Share on other sites
Superluminal 3750 Posted December 9, 2019 https://www.tamiya.com/english/rc/rcmanual/58370impact.pdf There you go - next step, screwdrivers!!! Get spannering - no excuses. Share this post Link to post Share on other sites
rjoseph244510 14 Posted December 9, 2019 Thanks Superluminal - Much appreciated! Rod Share this post Link to post Share on other sites
