Diff problems

[KryptoRoxx]

Ok been experimenting with some different gear oil for my diffs and all of a sudden right after I find a great mix for my driving style I shear the gears out of my rear diff. I know I put it back together right but just to make sure I take everything out, clean it, and put it back together. So test #2 comes around and I'm still having problems with my driveshaft coming loose now in the rear. Again the front is still fine. The only thing I can think of is that I replaced the brake rotors at the same time with the diff fluids and these things really lock down. I'm gonna check the brake pads and everything but I really don't think that my brakes would cause a rear diff to shear. Oh yeah btw it's a Kyosho 777 buggy. (Mainly because I've busted 90% of the 7.5 parts and I replaced them with 777 parts but oh well). Any ideas or suggestions would be great.

 

[Scrogg]

Need more info. What driveshaft is coming loose? What gears broke. Kyosho are a pain to set the rear diff up correctly. I can make a Savage X diff break dogbones all day long, the Kyosho still kicked my ass for a while.
If it is your center rear driveshaft, you need to leave a tick 1-2mm of back and forth play to keep the rear pinion bearings from overheating. Sounds like a chassis brace may be the culprit if it is being ejected. I took a dremel and keyed the smooth end of the pinion gear so the set screw had something to bite into. Mine would always slip and slide.. Take a pic, give me a bit more info. I know these rigs pretty well.

 

[KryptoRoxx]

I'll have some photos for you tomorrow. It's late here in Japan but that sounds like it makes sense. I did shear the pinon gear instead of the actual differential. Just out of curiosity why would a chassis brace be the culprit? I will definitely get the info you need though. Afriad that I'll have to reconstruct the scene rather than show you the real thing but if it helps set my front and rear up so there isn't any more shearing I'll be happy.

 

[Scrogg]

You sheared the pinion? Sounds like you meshed it too tight. You probably need to order new diff housings. The Kyosho diff housings are soft, some are bad right out of the package. They can't take any abuse. I highly recommend a new diff housing/bulkhead. Set the mesh a little loose at first, it tends to tighten up as you tighten all the screws down. I have caught hell with these diffs, A Kyosho Factory Driver told me what I am telling you..He was dead on right. I replaced the bulkhead and ditched all the wood screws, no more problems.

 

[KryptoRoxx]

hmmmm....I have seen some aluminum diff housings for the inferno on fleabay. You think those might do the trick as well since the kyo housings are soft? I already ditched the self tapping screws. Those made no sense whatsoever.
I found a link for ya to look at them. They're almost 100 bucks but if they take away my diff worries then it would be well worth it. http://cgi.ebay.com/Alu-F-R-Differe...pt=Radio_Control_Vehicles&hash=item2eac8be057

 

[Scrogg]

Kinda pricey but it would solve all the flexxing gear box issues. when I put al. diff bulkheads on my savage i never had an issue again. find some cheaper for us! lol
The included hardware is garbage though. Black oxide hex screws, the only way to go. One other thing. The split case design would be a lot more time consuming for maintenance. I change bearings and fluid every 2 hours. It gets old but to be race worthy it has to be done. Bashing, every 4-6 hours would be fine.

 

[KryptoRoxx]

One curious question on changing the diff fluid. I run a heavy oil all though my diffs because it helps with the really loose stuff that's on the track where I practice (everyone in Japan loves the drift scene sadly). I usually check my diffs but I only change about once a month. I run my car about 3-4 times a month tops for a couple of hours.

I will keep my eyes peeled!! Trust me I didn't like the price either lol. I was going to do the pics but my wife threw out the pinon gear (currently I work on the dining room table so if I accidentally leave something out and it's obviously busted....it disappears lol). I am searching. I believe that GPM racing makes those parts. I'm doing some good looking though. If I find something it will definitely be posted

 

[Scrogg]

What you are racing on is totally different than what I do. I have found a setup that works for me on everything form hard pack dusty blue groove to soft loamy conditions. Pretty much only use two different tires and thats it, small ride height adjustment here and there... If you want the details of my setup LMK. Everyone that has driven my rig loves how smooth, predictable and consistent it is. I just suck driving consistently, I keep pushing myself to be faster without mistakes....Get mad at myself when I do make a mistake and drive even worse... LOL, Not enough time to practice like the big boys.

 

[KryptoRoxx]

I wouldn't mind hearing about the details of your setup at all! My buddy runs an Xray and a Losi 8 buggy but I'm the only one with a 777 that is even trying to tune the handling.
Here's what I have so far figured out. I'm still waiting for my shock oil so that is whatever was in it stock. For my diffs I run 300k in the middle to lock it up and then #50000 Mugen in the front and #100000 Mugen in the rear. In my shocks I run a mid angle on the rear shocks and medium springs and a really soft angle in the front with stiff springs. I have about half a degree toe and 1 degree negative camber up front and then 1 degree toe in the rear with 1 degree neg camber in the rear. It's pretty stable in turns and really hard to make the ass slide around even when you want it to. It rides a lot higher in the front than in the rear. I'm having a little bit of trouble with stability in little bumps though in a straight on the track. Hopefully that made sense to you and you can give me a hand. I'm working on upgrading to the big bore shocks and I just ordered a lighter chassis from Dragon Racing (heard they were pretty decent).

 

[Scrogg]

The Dragon chassis is great. I love mine.
I have the Big bore shocks with stock pistons. 700wt. Mugen oil at all 4 corners. Kyosho Red springs rear, Blue in front.
Diffs, 7K front, 10K center 3k or 5k in the rear depending on if I want the rear tighter.
I run VP Pro Cutoffs LPR whells and tires. They are a medium compound with a tread pattern similar to bow ties. They hook up beautifully for accelerating and have just enough side bite to be predictable. You can pitch it sideways and feather the throttle and never roll over with these tires. Love em'! I tried a set of soft AKA Citiblocks this weekend. WAY too much traction. Made the rig very sketchy.
Rear toe is 2.5 block with the 3 degree anti squat plate. -2 degrees camber in rear.
Front has 1 degree of toe out, -2 degrees camber.
Ride height is arms level in front, slightly higher in rear. Brake bias is roughly 40% in front, 60% in rear. You do not want the front tires to lock up. You want the back tires to be right at the point of locking up. This keeps the truck rolling where the front tires are pointed on hard braking into corners.
Your diff oils are too thick. It will always fight you trying to drive with that thick diff fluid.
This is what I started with and made the changes that suit me. Hope it helps.
http://www.kyoshoamerica.com/downlo...ed_Tebo__-_Silver_State_2009_-_2009-06-09.pdf