How To Avoid Leaky Oil Differentials?

[chris.alex 1068]

What do I have to pay attention to when assembling oil-filled differentials to ensure that they are really leak-proof? I have the feeling that about every third differential I build is leaking. What could I do better? Less oil? Thicker oil?

I would be very grateful for some tips. 🙂 What are your experiences and recommendations?

[alvinlwh 7022]

Green slime all the sealing surfaces like o rings, gaskets, etc... changing to a different oil just to prevent leaks defects the purpose of an oil different since you are meant to be able to use a variety of oil thickness suited to your needs. 

[Howards 593]

Don't go too wild on the screws - doing so warps the cover and lets oil out. Finger tight, go from there. 
 

[dannymulder 937]

Better o rings, do not use the black tamiya ones, buy the red ones, or use an other brand.

[Pylon80 3409]

Not much to add to the Green Slime and light screw torque good advice above. Perhaps just a reminder that you have to tighten the screws in a star pattern with multiple passes, increasing the screw torque ever so slightly with each pass. Not doing so will warp the cover and cause a leak. Also, on some diffs I have had to sand the face of the case on 400 grit sandpaper after having inserted and removed the screws once. This removes the small burr around the edges of the screw holes that can cause a leak as well.

@chris.alex which chassis and diffs are you using?

[chris.alex 1068]

Thank you guys for sharing your thoughts. It's very helpful. As luck would have it, I recently bought a small can of Green Slime. When the center diff on my XM01 started leaking last week, I used Green Slime when reassembling it. It's better than before, but still leaks a little oil. Maybe the spur gear doesn't fit in the diff case as well as the ring gears (GB2/GC2) that are used in the front and rear diffs. The latter seem to be leak-proof. (#22049) 

The other diff which is leaking a bit, is the rear one in my TT02SR (#54875). Maybe I should try the newer XV02 diff (#22049) which is compatible too? 

And finally the XV01 kit oil diffs (similar to #54471) have been leaking until I locked them. 

All in all, I tend to think: 

Even though I am always particularly careful when screwing into plastic, it is possible that I have tightened the diff screws too much.

 

[Pylon80 3409]

6 minutes ago, chris.alex said:

the rear one in my TT02SR (#54875). Maybe I should try the newer XV02 diff (#22049)

I have both. The 54875 leaked the first time I built it but I admit I had overtightened the screws and the ring gear/cover was clearly warped. I have since then rebuilt it with Green Slime (I replaced the fiber gasket just to be sure) and it has been completely leak free since then. If you add the TG10 gears and cross shaft to have all 4 gears inside it makes for a bullet proof, if heavy, differential! I have it setup that way at the front of my rally car and it's very nice. The 22049 was built from the get go with Green Slime, I was very careful to tighten it "just so" and it never leaked; it's at the back of an on-road car at the moment.

Edit: another 'detail' for you @chris.alex which you probably know already: you have to fill them only to the level of the cross shaft. This allow leaving a pocket of air inside the diff. If you do not do that, the oil has no way to expand when temperature changes and the diff is bound to leak at some point.

[Grumpy pants 5221]

This is great, I’ve got an XV01 to reassemble sometime soon, I already have some green Slime in my spares and Red ‘O’ rings 😎

[guggles 269]

I just use grease  /problem solved

in all seriousness though I think everybody has got this down pat. One thing I may add is like shocks all differentials can leak if sat around for long enough. I think just moving the fluid around from time to time can keep things from drying out and leaking.