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  1. #1
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    Question Diff Oil - front vs. rear

    Why run heavier diff oil in front and lighter in rear? Although there are many opinions of what weight of diff oil to run, every combination I have found includes heavier oil in front and lighter in rear. For example...10k-7k, 50k-30k, 30k-5k.

    I understand that the lighter the fluid, the better the truck will turn(more slipage). The heavier the fluid, the more straight line traction but less ability to turn(pushing straight). SO, the front of the truck does the turning....why put heavier oil up there?

  2. #2
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    well heavier oil in the rear pushes the front tires forward more without letting them turn as much

  3. #3
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    yup, thicker fluid in the rear will make your truck push in corners and loop out

  4. #4
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    You want the front tires to pull the truck thought the corners not to be pushed. If the truck is pushing the front wheels it makes it harder to steer. I would go with 7000 in the rear 50.000 center and 10,000 in the front and see how it goes.
    4x4 Slash 5.5 Big Block

  5. #5
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    Thanks all. I guess this applies whether it is a racer or basher, right?

  6. #6
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    Bashing it doesnt matter as much but it will still help

  7. #7
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    If bashing I would install 100.000 oil in the center diff.
    4x4 Slash 5.5 Big Block

  8. #8
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    If I switch to bigger tires (2.8"), should I put heavier weight oil front and rear? Instead of 10-50-7, switch to 20-50-15?

  9. #9
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    Quote Originally Posted by Team Notyap View Post
    If I switch to bigger tires (2.8"), should I put heavier weight oil front and rear? Instead of 10-50-7, switch to 20-50-15?
    If you install 2.8 tires and add heaver oil to the diffs. It will really heat up the motor. I would not recommend this.
    4x4 Slash 5.5 Big Block

  10. #10
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    When you corner hard under throttle, the inside front tire has the least amount of weight, and is the most prone to spin, sometimes spinning in the air, losing power and torque to the outside front tire> The outside front tire needs enough torque to pull the truck around the corner, and sweep away dust, it also adds a little understeer. In the rear, if the fluid is too thick, both wheels spin, and it can oversteer suddenly, lighter oil in the rear keeps both from spinning until you add a lot more throttle, so if only the inside wheel is spinning, the outside wheel has more lateral traction, and is slower to oversteer. The rear also tends to have the suspension compressed more than the front, and any rough patches can make it unstable if the diff is too tight, thinner fluid makes it track straighter and react less to rough tracks. The slash is so quick to oversteer it takes a lot of adjustments that would make a truggy or monster truck understeer like a pig if they had the same numbers.

  11. #11
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    i run 30,000 front, 10,000 rear and slipper and it does pretty good for bashing but im about to move up to 50,000/30,000. i haven't run it yet but i just put 2.8 trenchers on 3.2 maximizers yesterday and it added 1 1/2 lbs. i hope things wont get too hot w/ the mmp 2400 in a 7.504 lbs. vehicle

  12. #12
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    Quote Originally Posted by alucard0822 View Post
    When you corner hard under throttle, the inside front tire has the least amount of weight, and is the most prone to spin, sometimes spinning in the air, losing power and torque to the outside front tire> The outside front tire needs enough torque to pull the truck around the corner, and sweep away dust, it also adds a little understeer. In the rear, if the fluid is too thick, both wheels spin, and it can oversteer suddenly, lighter oil in the rear keeps both from spinning until you add a lot more throttle, so if only the inside wheel is spinning, the outside wheel has more lateral traction, and is slower to oversteer. The rear also tends to have the suspension compressed more than the front, and any rough patches can make it unstable if the diff is too tight, thinner fluid makes it track straighter and react less to rough tracks. The slash is so quick to oversteer it takes a lot of adjustments that would make a truggy or monster truck understeer like a pig if they had the same numbers.
    So what oil do you recommend for the diffs Front, center, and rear ????????
    4x4 Slash 5.5 Big Block

  13. #13
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    I bash and race at 2 different tracks. For bashing and running on a big 1/8 scale track that is hard packed clean dirt with a little dust deep in corners I run 30k-100k-10k. It's stable enough over some bumpy fast sections, slides and pulls around the couple hairpins well, grips for good acceleration on long straightaways and short sections leading to big jumps, and throttle steers nice to handle big sweeping corners. On the small 1/10 SC packed dirt and dusty track I run occasionally I run 10k-50k-5k, it's a lot tighter, a little more bumpy. The lighter oil helps it handle flatter, and keeps more stable over rough patches, also keeps from breaking loose and spinning out on a couple dusty corners, throttle steer is smoother.

  14. #14
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    Quote Originally Posted by alucard0822 View Post
    When you corner hard under throttle, the inside front tire has the least amount of weight, and is the most prone to spin, sometimes spinning in the air, losing power and torque to the outside front tire> The outside front tire needs enough torque to pull the truck around the corner, and sweep away dust, it also adds a little understeer. In the rear, if the fluid is too thick, both wheels spin, and it can oversteer suddenly, lighter oil in the rear keeps both from spinning until you add a lot more throttle, so if only the inside wheel is spinning, the outside wheel has more lateral traction, and is slower to oversteer. The rear also tends to have the suspension compressed more than the front, and any rough patches can make it unstable if the diff is too tight, thinner fluid makes it track straighter and react less to rough tracks. The slash is so quick to oversteer it takes a lot of adjustments that would make a truggy or monster truck understeer like a pig if they had the same numbers.
    Great explanation. Thanks. I just reinstalled everything with 10 - 50 - 7. I'll see how I like it this weekend.

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