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Old 12-10-2005, 07:02 PM   #1
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Default Help with diffs

Ok i have an ofna ultra gt, and I am more of a backyard fun kind of guy. The problem is, in really slippery stuff (mud snow ect..) i have little to no traction due to the 3 diffs. Is there any way i can lock at least the middle one? Search turned up nothing
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Old 12-10-2005, 07:18 PM   #2
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go to your local hs and look for diff oils, mugen and ofna make tsome, ranging from 1000 wt to 120000 wt, the thicker the oil, the more your diff will resist diff action, prolly 5k or 10k will suit you fine, u just have to experiment alittle
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Old 12-10-2005, 07:19 PM   #3
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Thanks man! never thought of that.
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Old 12-10-2005, 07:56 PM   #4
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You definatley want to get rid of the grease in the stock diffs and fill it with silicone oil.

I would do 3000 in the front, 7000 in the center, and 1000 for the rear. That should be a good baseline setup.
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Old 12-10-2005, 10:19 PM   #5
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like they suggested you can use diff oils to fine tune the diff action but if you dont want to bother with diff and wish to lock it completely then take out your diff from your car and there should be a set screw on the side of the diff case , you can just simply tighten it to eliminate diff action.
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Old 12-11-2005, 09:58 AM   #6
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k, thanks for the info
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Old 12-11-2005, 01:04 PM   #7
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That set screw is there to seal up the hole after you put the gear pin in & so the silicone lube does not leak out. Don't use it to lock your diff you will damage the housing and ruin the gears. You want to lock up the diff I suggest using a heavier lube like 10,000- 15,000 weight.
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Old 12-11-2005, 01:47 PM   #8
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i cannot find that setscrew reguardless. Not looking forward to dissasembling a diff
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Old 12-11-2005, 09:20 PM   #9
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if you want to lock the diff put silly puddy in it. this should lock it up but not damage the gears and is removeable.

also here is a good post i found in the grid about diffs

#7003 of 7008 by Scott Sternberg (bump) on Sun Dec 11 13:36:11 2005:Mac here are some notes I have keeped for referance. Hope this helps.

1st remember and this is all you have to remember is that a diff's job is to transfer torque to the side of the diff with the least amount of traction, ie least amount of weight transfered, ie least amount of traction (This is opposite a torsen by the way).

Center diff fluid:
Say you accelerate, weight transfers towards the rear (your buggy squats - how much depending on several factors such as rear antisquat plate, how hard you are on the gas, etc), a center diff with very light oil will "diff" more towards the front to try to balance the load and
stabilize the buggy. This is great on a slick or maybe a tight track where you want to feel the front diff pulling your car a little more and keep you from "spinning out."

Now, say you put in very thick center diff oil in your center diff. You accelerate, weight transfers towards the rear, a center diff with very thick oil will "diff" less towards the front but will give you the most torque at the rear of the buggy, ie more acceleration. This is great for high bite tracks but on a slick track you may find your rear
end swinging around more.

BUT, straight line acceleration is but one aspect of a center diffs purpose. Say you are on a track and you approach a woop section. a car with very light fluid will transfer more torque to the front of the buggy as soon as the front tires begin to loose contact with the apex of the woop, hence your rear end feels less power and consequently the
front of your buggy's nose comes down nice and fast ready for the next woop. your center diff is constantly "diffing" to keep the car balanced through the woops. Now, if you had very thick oil in the center, the nose of the buggy would come down a little slower because it will not diff towards the front so fast. This can cause your buggy
to get out of shape easily because your front tires are not in contact (think steering) as much with the ground.

Also, center diff oil can even depend on what engine you are running. if you have an OD MOD, and you go too light on the center oil, you will find your front tires ballooning to the point of almost flying off the wheels down the straight away, so you may increase the center oil weight a bit.

Ok, now for my 2 cents on front diff fluid. T
his will control torque transfer from the left to front tire and vice versa. Let's say you have very thick front center fluid and you exit a left hand 180 on the gas. Your right front tire has the most traction and hence, if you want the tightest steering, you would want most of the torque to stay on that outside tire, and hence you would use heavier
front diff fluid. However, if you want more turnin (which happens at the very beginning of the turn up until the point where your car has transfered more weight to the outside tire), you could use lighter front diff fluid.

BUT, the front diff is not just there for turning. Let's say you hit a bump with only the left front tire of your car. With light front diff fluid, more torque will transfer to the tire with the least amount of traction than with thicker oil, ie the right tire starting to come off the ground due to the chassis lifting, hence the front will stabilize itself more than a car with thicker front diff fluid.

The rear diff follows the same principle of the front diff.

I know this was long and boring and winded, but i just wanted to get my feelings out there as an alternative point of view. I am also a rc photography fan and I love watching and photographing diff action on buggies. So i am always noticing how much different buggies including
mine are diffing by watching and photographing their tires at different times.

What i said above is not the be all end all gospel but just my experience.

Oh yeah, the front diff thing is also a reason you find some buggies (at least mine) will have more front steering with a front swaybar on some of the faster corners. The bar keeps the car from transferring too much weight to the outside tire, thus reducing the front diff action.
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Old 12-11-2005, 10:40 PM   #10
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ah... another Grid member i see...
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Old 12-11-2005, 11:54 PM   #11
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Not all 1/8th scale diffs have setscrews.
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Old 12-12-2005, 12:27 AM   #12
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Quote:
Originally Posted by bigblockbuggy
i cannot find that setscrew reguardless. Not looking forward to dissasembling a diff
There is really nothing to worry about as there is not much in there that is complicated, just a couple of gears. You will do just fine.
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