Diff Building Help: Notchy Gears

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obessedwithrc

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When re-building the BLX diffs, how "notchy" should the diff feel after a re-build?

Notchy, but turning?
Completely butter smooth?

I'm curious if there is a break-in period that takes out "some" notchiness or if the diff should be completely smooth before installation.
 
Having just rebuilt 2 diffs this past weekend - they should be buttery smooth.

If you have a brand new set of gears in your diff then *maybe* you might get it feeling a little notchy, but I haven't noticed this myself.
 
Yeah. That's what I thought. I am using a brand-new set of gears. I'm also using Vitavon & Hot Racing 31mm aluminum diff cases and TekJo gaskets. I'm also using Mugen shims, 2.25mm pins from hardened steel that I bought from McMaster, and M2C racing drive cups.

Maybe it's the combination of parts from different brands that are throwing off the ability to get everything to line up correctly.
 
You could be right about the mix of parts there. Look closely at the Sun gear pin. Its length and diameter. (I cut my own out of HS Drill blanks) As a result the Sun gear clearance is usually what makes the diff feel notchy. The Sun gears can rock back and forth. A slight bit of notchyness can be broken-in and may relieve it. But too much is no good. Sometimes you have to decide when "Good Enough" is good enough. These diffs are not perfect. Despite all the upgrade parts you throw at them. Once in a while I will get a notchy diff with a new rebuild. Just happens sometimes. Look into the sun gears and the shims first.
I assume you are referring to the standard Open Diffs here.
I use Mugen Seiki E0206 gear shims on theses diffs.. Did you replace the stocker gear shims at all? Stock ones are soft and easily bend and the gears get misaligned to each other. Can cause notchyness also. In a perfect world, diffs should be very smooth.
The TekJo gaskets can even be off a bit. Too thick or thin compared to the stock gaskets.
Some ideas.
 
Last edited:
Hey SrC. Yes, I'm referring to the standard 31mm open diffs and I'm also using Mugen Seiki E0206 shims. I did also think about the TekJo gaskets being too thick as well. I'd imagine if there's just a hair of notchiness, that's not too big of a deal. I'm just worried about creating extra heat. But I get your point—what's "good enough?" Ha! That's very hard to do for a perfectionist.
 
Try loosening these screws a tad. You want them tight enough to make a seal but too tight can cause issues.


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I was thinking about maybe adding Loctite to the screws (I'm using aluminum diff cases) before I build the diff, and then letting them dry overnight—that way the diff fluid and Loctite don't mix. Thoughts on that?
 
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