Finding a diff for the Axial SCX10 transmission

[Chewbacca]

Since the 3d10 thread has been hijacked / side-railed a bit by this topic, I thought I'd start a separate topic on the options for finding a differential for the SCX10 / Injora transmission.

These 2 threads had their take at finding a solution:

3s10 build -> suggests using the Tamiya TA06 differential

3d10 Thread

Graphite Runner Build -> suggested using the RC10 B4 diff (last post from 2013)

Graphite Runner Build

here the relevant pictures are no longer online since they were on Photobucket -> come on guys make screenshots of your pictures and upload them directly here, that way they remain on this server!!!

[Chewbacca]

Here is what was posted in the 3d10 thread:

Pictures of the aluminum version of the transmission:





those cases seem to have enough material in the bearing seating to deepen the depth of the bearing hole by 1mm or maybe a bit more on each side.

Picture and text by XLR8:



Quote:
Yes, the BBX diff assembly is too wide to fit the plastic Austar/Injora cases.
Austar/Injora assembly width outside-outside bearings approximately 21.2. Bearings are 5mm wide
BBX assembly width without shims (I removed them after taking the photo) approximately 24.3. Bearings are 4mm wide.

O.A. width of Austar plastic cases is about 25.2mm so there isn't much material available for modification. Maybe it's possible to increase bearing bore depth.
end quote

[Chewbacca]

Last post for now.
Instead of drilling the tranny case, perheps some material could be milled off of the diff housing on a lathe to move the bearings closer together.

Now is this the Tamiya diff we're talkig about? :

Or the ball diff?:

Of course with the FAN RC stuff - when available - on the market this whole endeavor becomes kind of obsolete.

[XLR8]

Thanks for creating this thread. This is perfect.

Maybe not entirely obsolete. As you’ve mentioned, if you own a Stealth and need new parts, then Fan RC is the way to go. However, if you have the Austar transmission and would like to install a diff, then this thread might be useful.

To summarize our most recent discussion a bit further, the Austar/Injora transmission is similar to early Axial and uses a 52t gear and its cases are counterbored for 16mm bearings so it includes 8x16x5mm bearings (21.2mm assembled bearing width). Tamiya TA06 diffs (p/n 54306 ball, 54471 gear) are also 52t but they are wider (24.3mm) and ride on 10mm bearings. Bearings fitted to the ball diff in the photo above are 10x15x4mm.

Bearings inboard -- modifying the diff:
A TA06 (or BBX) ball diff could offer the simplest swap IF the outdrives can be modified to move the bearings inboard (approximately 1.5mm/side if using 4mm wide bearings) – as you’ve mentioned in your last post. It’s worth trying but the outdrives are almost certainly hardened steel and I haven’t had much luck lathe cutting or drilling hardened steel but my equipment isn’t the best.
The TA06 gear diff is plastic (nylon?) and potentially easier to mod but the assembly is sealed so it features internal counterbores to hold o-rings and this could make it difficult or impossible to reduce its width.

Bearings outboard -- modifying the cases:
This requires increased bearing bore depths. As mentioned in a post above, the cases are 25.2mm wide so only about 0.45mm would remain after the mod – tricky to do unless you have good equipment.

Anyway, my plan is to order a gear diff and if it’s not possible to move the bearings inboard then I will try to modify the Austar’s plastic cases to move the bearings outboard and fit 10x16x4mm bearings.

I will update when parts arrive.

[XLR8]

I was about to order the Tamiya gear diff assembly (54471) and it suddenly occurred to me that the diff gear and side plate assembly is almost certainly too wide to fit the Austar/Injora case. That case is very narrow and closely hugs the gears.

Maybe the Tamiya ball diff (54306), with outdrive bearing seats modified to allow the bearing to ride farther inboard (reducing OA bearing to bearing width), would be a better candidate for this swap. Of course, the ball diff is designed to work with dog bones but I'm using Traxxas universal shafts for my Porsche project car. I need a diff with 5mm dia. drive axles not drive cups.

Not sure what I will do at this point.

[XLR8]

I've stumbled upon something interesting tonight. The gear diff assembly for the Kyosho Dirt Master will drop right into the Axial/Austar/Injora transmission cases. The Kyosho diff is the same width, tooth pitch and tooth count as the stock diff-less gear. All that is required are a couple 10x16x4mm bearings and it fits perfectly.
This is the Ultima SC gear diff (UMW604) that is used in a number of modern Ultima-like vehicles and Kyosho has them in stock at the moment. There's also ball diff for the Ultima SC (UMW602B) and it's a good bet that diff will fit this transmission as well.

[GoMachV]

I ordered one and it arrived today, printed a pair of bearing adapters cause who has 10x16 bearings on hand lol. Fits and works well! Now, I will say it's a little wider than stealth but that's not a bad thing especially if AE continues to make their CVA shafts too short lol. This will also work well for another project I have going that needs a wider diff. Thanks for the tip!

[XLR8]

I ordered one and it arrived today, printed a pair of bearing adapters cause who has 10x16 bearings on hand lol. Fits and works well! Now, I will say it's a little wider than stealth but that's not a bad thing especially if AE continues to make their CVA shafts too short lol. This will also work well for another project I have going that needs a wider diff. Thanks for the tip!

You're very welcome. I'm just happy to have found it.
Mine is scheduled to arrive on Monday. It's going straight into the tranny for the 934. With only 2wd, that car is wicked to drive even with soft tires and a mild brushed motor. Hoping with a functioning diff, I can step up power and speed a bit. We shall see.

[Chewbacca]

I've stumbled upon something interesting tonight. The gear diff assembly for the Kyosho Dirt Master will drop right into the Axial/Austar/Injora transmission cases. The Kyosho diff is the same width, tooth pitch and tooth count as the SX10….

UMW604.jpg

This thread might also be the solution to another project of mine. I need a confirmation that the Tamiya and Kyosho Diffs also use the 48dp pitch. Or are they MOD 0.5, close but still too different?

Thanks,

Tony

[XLR8]

I've stumbled upon something interesting tonight. The gear diff assembly for the Kyosho Dirt Master will drop right into the Axial/Austar/Injora transmission cases. The Kyosho diff is the same width, tooth pitch and tooth count as the SX10….

UMW604.jpg

This thread might also be the solution to another project of mine. I need a confirmation that the Tamiya and Kyosho Diffs also use the 48dp pitch. Or are they MOD 0.5, close but still too different?

Thanks,

Tony

While I can't confirm that the Dirt Master diff gear is 48dp, I can confirm that it runs quiet in the Austar transmission.
... and, the 934 drives much better now and can handle more power.

Mr. Google says:
"A "48 diametral pitch" is equivalent to a "0.5 module" - meaning they represent the same tooth size, but use different units of measurement; diametral pitch is based on inches, while module is based on millimeters, with the conversion factor being 25.4mm per inch; therefore, a larger diametral pitch number corresponds to a smaller module value, and in this case, 48 DP is equal to 0.5 module."

Actually, they are very slightly different but could be impossible to measure -- like 32dp vs. 0.8 mod.

[Chewbacca]

Thank you XLR8,

unfortunately that is not quite correct what Mr. Google had to say. See the table below. 32DP is close enough to work with MOD 0.8, but the mismatch between 48Dp and MOD 0.5 is too big. Especially the smaller the gears get. I have a 20T input shaft from Team Durango that I wanted to use with the RC10 stealth gearbox. Once that is installed, the gear mesh becomes "crunchy" I don't have a better word to describe it.

Here's the table:

[Chewbacca]

I just remembered that I have parts to answer this question myself -DUH!

So, I have already successfully installed the Axial AX30394 20T drive gear with the STRC top shaft for a Traxxas Bandit into an AE stealth transmission. How I adapted the metric shaft into the imperial case is a different topic. Anyway, the gear mesh is PERFECT, so the Axial gears are 48dp. Now you guys say the Kyosho Diff also is a perfect match, that is enough for me.

THANK YOU all!!