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Old 12-10-2008, 04:55 PM   #1
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Default looking for info on rebuilding diffs

Hello, I'm the new guy on the block. i'm looking for information on what type of lubricant is neccessary for the front, rear and center differentials on my ofna 1/8 scale buggy. i'm using an hpi nitro star 25 engine with a 14 tooth bell and factory spur gear. i have alot of other questions as well but i'd like to get to know some people first. i raced electric stadium trucks prior to nitro. any help would be greatly appreciated and i can try to help with all of your electric questions as well. thanks again and hope to hear from someone soon.
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Old 12-10-2008, 05:12 PM   #2
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I just rebuilt mine this past week. On the advice of the local racers I ran 5k front and center and 2k in the rear. The cars handles brilliantly. I used the Team AE silicone diff fluid, good stuff, not very expensive at all.

Here's a thread on rebuilding them. I do suggest the use of a diff specific fluid rather than a heavier grease as used in this write up.

http://www.unlimitedengineering.com/...ad.php?t=19076

Here is the diff fluid I used.. it's $3.49 a bottle. I run 5/5/2.

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Old 12-10-2008, 05:19 PM   #3
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What you are looking for is silicone diff fluid and it's available in many different thicknesses. A good starting point might be 5K up front, 7K in the middle, and 2 or 3K in the rear. Lots of different vendors to choose from too.
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Old 12-10-2008, 05:24 PM   #4
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I dont race Off-road but i do rac On-road, when you a rebuilding the diff you do it for the track u race at. if ur just bashing in the backyard or something, use what it says in the instruction manual.
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Old 12-11-2008, 06:11 AM   #5
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Default Thanks for all your help

Thanks for all your help all who responded. especially you Rearviewmirror. that link you sent was incredible. My ofna buggy has front and rear gear boxes that are open at the bottom and i'm thinking it will leak from there. how do i keep lube on the ring and pinnion in that differential. And what lube do i use.
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Old 12-11-2008, 06:48 AM   #6
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Originally Posted by shepherdluva View Post
Thanks for all your help all who responded. especially you Rearviewmirror. that link you sent was incredible. My ofna buggy has front and rear gear boxes that are open at the bottom and i'm thinking it will leak from there. how do i keep lube on the ring and pinnion in that differential. And what lube do i use.
Ok, the diff fluid goes INSIDE the sealed differential case that the ring gear is mounted on. To lube the ring and pinion, something like white lithium grease is good.

Also, which OFNA do you have?

There are a lot of variables on selecting diff fluid. Here are some rules of thumb. Note that changes to one affects how everything works, to a certain extent.

Front differential: Thinner fluid will give more "off power" steering, thicker helps to pull the car out of the turn. 5k is a good average starting point.

Rear differential: Thinner fluid allows the car to turn/"rotate" better. Thicker gives more rear traction, but can make the car lazy. 3k is a good average starting point.

Center differential: Thicker of course gives more AWD effect- that's good AND bad. Too thin makes the car not distribute power as well, slows it down. Too thick makes the car aggressive and edgy to drive. 5k is a good starting point... most of the experienced drivers with a high skill level use 7k in most cars though. (5k will make the car easier to drive if while you are getting used to it.)

To sum it up: If the rear of the car is "lazy" you can go down in diff fluid to "loosen it up." If the car doesn't turn in very well you can go down in front diff fluid. If the car is too aggressive and hard to drive overall, go lower in the center... if it is too lazy overall, go up in the center.

Hope that helps.
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Old 12-11-2008, 07:22 AM   #7
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use Mobil1 RED synthetic grease on your ring/pinions in your driveline and you will be golden.....you can get an enormous tube that will last a lifetime and a half for like $8 @ Auto Zone, then I take a small glass jar of my wifes that used to have facial foundation in and I clean it out to fill with my Mobil1 and I'm all set.......cheers!!
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Old 12-11-2008, 08:13 AM   #8
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use Mobil1 RED synthetic grease on your ring/pinions in your driveline and you will be golden.....you can get an enormous tube that will last a lifetime and a half for like $8 @ Auto Zone, then I take a small glass jar of my wifes that used to have facial foundation in and I clean it out to fill with my Mobil1 and I'm all set.......cheers!!
Yes. definitely use the auto grease from VatoZone on the ring and pinion gears outside of the sealed differential. There is some good info in this thread, if you run at a particular track ask the locals what they run. Generally the front runs a thicker fluid than the rear, but it depends on the track and the car. For bashing it doesn't really matter.
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