Kronos XTR Used Kronos XTR - Any Diff Issues

[Jeo79]

Thinking of jumping back onto another Corally and will potentially be picking up a Kronos XTR. Trying to keep costs low so wondering does the XTR need the alloy bulk heads/gear boxes out the gate? Are there any known issues with diffs stripping on the XTR?

 

[Nelson.81]

No they pretty solid out the box my xtr probably my most reliable rig , I’ve upgraded mine just for the style points.

 

[Partydaz]

Check and make sure the diffs are shimmed and the diff bearings are good and it should be next to bullet proof

 

[Jeo79]

No they pretty solid out the box my xtr probably my most reliable rig , I’ve upgraded mine just for the style points.

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Yea this is simply a work of art mate!!! Wow looks like a proper basher truggy!!! I heat mixed thoughts on the plastic diff cases so thanks

Check and make sure the diffs are shimmed and the diff bearings are good and it should be next to bullet proof

Cheers for coming back mate.... good to know thanks

 

[Nelson.81]

Yea this is simply a work of art mate!!! Wow looks like a proper basher truggy!!! I heat mixed thoughts on the plastic diff cases so thanks


Cheers for coming back mate.... good to know thanks

Thanks, Nothings indestructible but upgrade options if need or want for it. Corally 7075, vitavon or even adu diff cases

 

[Horatio]

Nelson's builds are without compromise.

Mine chop and change a bit, depending what I'm trying to do.

Differentials are solid, but the little red O-rings are fragile. They have a tendency to look like this:

That groove shouldn't be there. When they look like that , they leak through the output. Very easy fix though....

Just make sure they aren't deformed when you fit them - and use green slime. Seals them up 100% and protects the O-rings.

Enjoy! The XTR is the best handling truck out of my holy trinity and it's far from fragile.

 

[Nelson.81]

I’m not even convinced every batch orings are the same

 

[danl]

Since they are silicone, tend to swell over time. Buna N o rings don’t swell in contact with silicone diff oil.

https://www.rocketseals.com/chemical-compatibilities/

 

[Horatio]

Since they are silicone, tend to swell over time. Buna N o rings don’t swell in contact with silicone diff oil.

https://www.rocketseals.com/chemical-compatibilities/

Interesting - another member here was stating the same.

However, most RC companies still use silicone o-rings for shocks and diffs which are filled with silicone.

Buna-N (nitrile) and silicone O-rings are both used in RC car shocks, but they have different strengths. Buna-N offers low friction and great wear resistance for smooth action, while silicone provides stable sealing across a wide temperature range and does not swell when exposed to standard silicone shock oils.

Buna-N O-Rings

• Low friction: Moves very smoothly against the shock shaft.
• Tough build: Resists tears and normal wear very well.
• Oil interaction: Can swell slightly over time when soaked in silicone shock oil, which tightens the seal.

Silicone O-Rings

• Stable size: Does not swell or change shape in silicone shock oil.
• Soft feel: Extremely plush, but can create slightly more drag on the shaft.
• Temperature steady: Works well in hot or cold weather without getting stiff.

Quick Comparison

• Best for smooth action: Buna-N (less initial drag).
• Best for zero oil swelling: Silicone (stays true to size).

I've yet to try Buna N. Zero oil swelling according to Gemini seems counterintuitive, because its the slight swelling which ensures the oil tight seal in our diffs and shocks.

Jury's out......

 

[CatEatingTroll]

Here's an uneducated question from someone who doesn't know anything. Are all 6s Corally pre-built gearboxes the same regardless of what truck they came off of? I ask this because they all seem to run the same input and ring gear combos. Since we're on the subject of diffs I thought I would ask.

 

[Horatio]

Here's an uneducated question from someone who doesn't know anything. Are all 6s Corally pre-built gearboxes the same regardless of what truck they came off of? I ask this because they all seem to run the same input and ring gear combos. Since we're on the subject of diffs I thought I would ask.

No, they are mostly interchangeable, but not identical across every platform and version.

Team Corally designed its 1/8 scale 6S lineup (Kronos, Muraco, Punisher, Python, Radix, Kagama, Asuga, etc.) around a shared drivetrain architecture, but there are key differences to keep in mind

1. Internal Cross Pins Differ by Case Type​

The internal satellite gears and outer dimensions are standard across the 6S line, but the internal cross pins are not.

• Standard composite diff cases and the stock red alloy cases use one style/length of cross pin.
• The upgraded 7075 hard-anodized tuning diff cases require shorter internal cross pins.

2. Generational Changes (V1 vs. V2 vs. V3 / Swiss 7075)​

• V1 vs. V2/V3 Outdrives: Newer revisions introduced flared outdrive cups and upgraded drive cups.
• Shim Requirements: Revisions in case tolerances mean external shimming (between the outdrive cup and bearings inside the diff bulkhead) often varies between platforms and production runs to eliminate gear lash.

3. Front/Rear vs. Center Diffs​

While front and rear diff assemblies are generally identical to each other on a given platform, the center diff uses a different outer spur gear (steel, varying tooth counts like 46T or 52T depending on whether it's a buggy or a monster truck) and different mounting spacing

4. 4S vs. 6S Platforms​

If you are cross-referencing between the 4S line (like the Syncro 4 or Kagama 4S) and the standard 6S line, check part numbers carefully. While some diff housings and internal gears carry over, components like drive cups and input shafts can differ in length and pin size.

Rule of Thumb: Internal spider gears and ring/pinion meshes swap cleanly across almost all 1/8 6S models. However, always double-check cross-pin lengths if switching casing materials (composite vs. 7075 alloy), and pay attention to external shimming when dropping a diff into a different housing.