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48.4 center diff binding

Nicochau

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Dear RC friends,

I'm rebuilding a used EB48.4 that I bought some time ago and had noticed it had a really bad turning radius. It just would not pivot properly.

After checking everything (including replacing the servo) I came to the conclusion that it was the center diff that was likely faulty. I removed it and noticed it is binding. Did a quick rebuild and is still binding... Anyone has an idea of what could make it bind and how to fix this?

center-diff.JPG
 

Billl DeLong

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Just a guess, but as filthy as the diff looks, I would rebuild it again, but make sure there are no metal shavings/grime that are lodged in the teeth inside. Perhaps flushing it with brake cleaner (after removing the rubber seals), soak the gears and let every dry completely before re-assembly. Verify the shims are not missing too!

It's possible that the diff case may have been "cooked" and the plastic melted due to any empty diff that wasn't properly maintained. If so, then replace the diff case and be sure to never let the diff run dry and do rebuilds every 20-25 battery packs ;)
 

Nicochau

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Just a guess, but as filthy as the diff looks, I would rebuild it again, but make sure there are no metal shavings/grime that are lodged in the teeth inside. Perhaps flushing it with brake cleaner (after removing the rubber seals), soak the gears and let every dry completely before re-assembly. Verify the shims are not missing too!

It's possible that the diff case may have been "cooked" and the plastic melted due to any empty diff that wasn't properly maintained. If so, then replace the diff case and be sure to never let the diff run dry and do rebuilds every 20-25 battery packs ;)
hi Bill,

i did a quick check, it was not empty but the fluid in there was dark like I have never seen. Checked all teeth, rubber seals, shims and nothing was missing or compromised.

i believe it is a good idea to get a new case before throwing all fresh seals in there.

Also did tekno sell spurs this color? I have only seen them black.
 

Billl DeLong

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Yes, the original .1 kits came with the yellow-ish spur gears



If you have not completely flushed the fluid/grime out of the diff, then I would be willing to bet you have a chunk of something causing the binding :(
 

Nicochau

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Yes, the original .1 kits came with the yellow-ish spur gears



If you have not completely flushed the fluid/grime out of the diff, then I would be willing to bet you have a chunk of something causing the binding :(
full cleaning on the way.

here is another of the diffs for your pleasure 😂

4D86D1EF-EF45-43C1-812E-EC42C2146CE4.jpeg


Oh boy... that’s no shelf queen for sure...
 

Kronuxx

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Don't wanna hijack the thread here, but didn't want to make a new post for a simple question but I am wondering: What is the usual color of diff fluid that is properly meshed vs one that isn't once you open it to look? My diff fluid after like 2 uses was a dark gray color. Not black, but definitely a dark gray.
 

Billl DeLong

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A milky gray is acceptable, but any darkish brown should be replaced, every 20-25 packs is a good estimate, I know some guys will rebuild every 6-10 packs! The fluid isn't the only thing that needs to be replaced either, you should also remove the rubber shields from the bearings and soak/blow out the dirt with compressed air, then re-pack fresh grease in the bearings, also packing fresh grease on all rubber seals in the diffs and shocks.
 

Kronuxx

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A milky gray is acceptable, but any darkish brown should be replaced, every 20-25 packs is a good estimate, I know some guys will rebuild every 6-10 packs! The fluid isn't the only thing that needs to be replaced either, you should also remove the rubber shields from the bearings and soak/blow out the dirt with compressed air, then re-pack fresh grease in the bearings, also packing fresh grease on all rubber seals in the diffs and shocks.
Thanks for the info Bill.
 

Nicochau

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Following the diff horror story mentioned above, I thought you guys deserved some diff and bearings love. :)

Clean bearings with fresh high end aviation grease:
IMG_2210.JPG


The grease I use is Mobil 28 aviation grease with following specs:

FeaturesAdvantages and Potential Benefits
High viscosity index (VI) synthetic base stock with no wax contentAllows wide operating temperature range - outstanding high and low temperature performance
Provides thicker fluid films protecting against wear of equipment parts operating at high temperature
Causes low resistance during start-up at very low temperatures
Excellent protection against wear and corrosionSuperb bearing protection and helps extend bearing life and reduce bearing replacement costs
Extreme-pressure protection characteristicsAvoids excessive wear, even under shock load
High thermal/oxidative stabilityLong relubrication intervals
High resistance to water washoutMaintains excellent grease performance in adverse weather and other water-exposure conditions
 

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