Gex_61
Posts: 1680
Joined: 10/29/2005
From: Bakersfield,
CA, USA
Status: offline
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quote:
If I spin a rear wheel the other spins in rev. If I hold one and spin the other the fronts spin and you can hear the spur turning. Normal?
This is normal. Since the diff is allowing your other rear wheel to spin versus spinning all 3 wheels, it means your rear diff is loose.
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If I spin a front wheel all other 3 wheels turn and you can hear the spur. Abnormal?
This is also normal. Your front diff is tighter because it is transferring movement to your rear wheels instead of transferring it to the other front wheel.
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My rear diff spins very smooth when I had it out. The front one feels kinda ....kinda ...kinda "crunchy?" I loosened it until it was fairly smooth but then it felt like it was slipping all the time. I opened it up and to my naked nooby eyes it seemed fine. All balls in their places. I added some diff lube, With same results. I started all this because It started to sound like my diffs were slipping alot when I would punch it.
The tighter your diff is, the more pressure there will be on the balls. If they are not immaculately clean, it will feel like they are a little “crunchy”. Having the diffs a LITTLE “crunchy” is fine. You shouldn’t notice this while the car is driving.
I recommend leaving the front diff tight, since you want it tighter on a 4wd car. It sounds like the slipping you are hearing is coming from the rear diff. You should tighten the rear diff slightly until it doesn’t slip any more. You want the rear diff to be looser than the front diff.
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Also when you hold the diff gear and spin one of the sides how easily should it turn compared to just turning sides w/o holding onto the gear (if that makes any sense)
I can’t really show you how tight to make the diffs over the internet. This is something you get a feel for over time. Like I said, you want the front diff tighter than the rear. Make sure the front isn’t tight enough to where it is locked, and make sure the rear isn’t loose enough to where it slips. Also, you don't need to take the diff out of the car to feel how tight it is. The proper way to check is to spin either front or rear wheels opposite each other, equally. This is basically the same thing as holding the diff in your hands. The improper way, is to hold one wheel and spin the other. Since this will also spin the other wheels and the spur gear. Since the motor has resistance, there is no way you can tell how tight it is or not. Just don't do it this way.
The problem with this car is that it doesn’t have a way to get rid of excess energy. Instead of dissipating it through a slipper, it takes it out on the weakest part in the drive train, the diff gears. Hopefully the steel diff gears will fix this problem. I can live with replacing the plastic outdrives every once in a while, versus replacing diff gears every week or two. You can keep the rear diff loose, like calvino suggested, but then you would end up with flat spots on the balls, and melted diff outdrives. I think the slipper will help this car a lot, but I still think the gears are weaker than what they should be.
PS- My metal gears have arrived in the mail. Now I’m waiting on tires, and I need to paint a body. Then it’s go time in my backyard. 
< Message edited by Gex_61 -- 5/15/2008 12:52:45 AM >
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Gexunderscore61
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All Forums >> RC Cars, Buggies, Trucks, Tanks and more >> 1/16th, 1/18th, Mini & Micro RC Cars >> RE: RC18T Steel Diff and Input gears Yes/No 
RE: RC18T Steel Diff and Input gears Yes/No - 
