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Old 12-15-2009, 01:13 PM   #1
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Default Do I have a worn diff?

How can I check for a worn diff, and ring pinion gear. If i turn each drive cup side to side on the rear diff (with fresh fluid), it has a "geary" feel, unlike a totally fluid feel of my other two. Is it a sign of being worn out?

also, when free spinning the diff in the gear box, i get a deep "gear whine" noise that I do not get out of the front. the gears look pretty decent. Are these worn?

Thanks 871
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Old 12-15-2009, 01:36 PM   #2
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if i were you i would just get new gears. It would bug th crap out of me during a main thinking if it will go or not.
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Old 12-15-2009, 01:49 PM   #3
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Please don't just get new gears that is not necessarily needed . More than likely when you rebuilt your diff you put the internal gears back together in a different order than when they came out. Therefore the wear surfaces are not meshing the same as before and feel a bit notchy. One tank of fuel will fix that.

Regarding your ring and pinion. Is there a lot of slop between these gears? Have you attempted to shim them tighter, clean them, check for dirt particles? With a high wine sound, you most likely have a diff shim out of place, check their tightness. I hold the rear outdrives with my fingers and then rotate/wiggle the rear driveshaft coupler back and forth. There should be a tiny amount of play. If that binds they are too tight, place a shim on the diff cup side. If it is a huge click, you need to put a shim on the ring gear side of the diff. (vice versa if this is a losi 8ight b/t rear diff)

The gears in your drivetrain should last a long time. It just takes a little tweaking from you to make sure they are good to go.
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Old 12-17-2009, 03:13 AM   #4
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Default Try this,.....

Put new gaskets on the diff. Sometimes they get squished over time and it compacts the gears a little, but otherwise the different order thing that was mentioned sounds convincing. Ring gear clearance is tricky. Sometimes putting shims in weird places will help, but only if you do it, take the time to experiment with a shim in the pinion side too.
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Old 12-17-2009, 07:32 AM   #5
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Hey thanks for all the good advice, especially on shimmin. I hope I set every thing right.....basically one shim less than a fully tight mesh, giving it a tiny bit of back and forth.

I went ahead and orderd a brand new diff/rear end assy with everything for 40 bucks on ebay, so I have a spare diff to try different weights. it even came with a new center drive shaft, which are 20 bucks anyways and I needed one so I figure I paid 20 bucks for a new diff, cups, case, gears, and bearings!

Late! 871
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