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Diff Oil Leak & Signs of Overfill

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sandblaster

Well-known member
Messages
137
Reaction score
70
Location
Oregon
Tekno RC's
  1. ET48
  2. MT410
  3. SCT410
Driving Style
Basher
Looking for an education on diff's. Why does the center diff seem to leak or seep just a little oil? What is the signs of overfilling a diff? How does one keep the center diff from leaking? Thought I broke something as only had front wheel drive. Found the center diff was out of oil. All the screws where tight but it still showed signs of oil being tossed on diff area. Any pointers from those more experienced would be most appreciated. Thanks.
 
The diff shouldn’t leak. I’ve had my mt410 since they were released and my diff has never leaked. From what I’ve seen on this forum. There are extremely knowledgeable people here. I’m sure someone will reach out. My guess is gasket or orings. Good luck buddy. I’ll be watching this thread for my own knowledge.
 
Ryan Lutz's video here shows how to rebuild a perfectly built diff that aren't overfilled. They will leak if they are overfilled. As the oil expands with heat it has to go somewhere. Once it starts leaking it's most likely not going to stop as it has already created a weak point in the sealing of the diff. If it was overfilled a proper rebuild may cure your issues.


For greasing the o-rings, grooves in the out drives, diff bowl, and spur I actually use this grease now. It's the same stuff I use for building shocks. The black grease will suffice but this stuff is super thick and pastey. Make sure you're greasing all those areas.

https://www.fiercercsolutions.com/Cookies-Crap-w-syringe-applicator-LFR10087S.htm

If you're leaking at the gasket for the spur there's a couple variables. 1st are you using a plastic spur? Plastic spurs can warp and can also be manufactured not completely flat giving you a poor seal. One of the reasons I use steel spurs, especially on 1/8 builds. 2nd there's the chance the diff bowl mating surface is not completely flat. I would try a new diff bowl or if you have a table saw, glass table top, or some other surface you know should be completely flat you can set the bowl on the surface for inspection. If it's not flat you can plane it down slightly with some fine grit sand paper (600-800 grit) to get rid of the highs and lows. I haven't had to do this with Tekno diffs but with other brands I've coated the diff bowl mating surface and gasket with RTV. Using an x-acto knife apply a super thin layer just give the gasket a little help. Spread very sparingly not to contaminate the diff fluid. Assemble, then let RTV cure overnight before running.
 
That is good info. Which side do you suspect to be leaking? Spur or outdrive side? It’s the gasket if it’s on the spur and o-rings if it’s on the outdrive side.

Did you tighten the screws on the spur side in a star pattern? If not then, the spur could have warped or it isn’t flat. Are the screw heads flush or below the spur surface? If not then they aren’t tight enough.

Did you grease the grooves on the outdrives? If not it could be leaking around the o-ring.
 
Did you grease the grooves on the outdrives? If not it could be leaking around the o-ring.

This is the most common cause for leaky diffs. Don't skimp on grease around any rubber seal.. I also like to use Green Grease brand with a grease gun and rubber tip:
https://www.walmart.com/ip/Omni-Lub...66001f5-575d9282-8e89108c3ea19be6&athena=true
+
https://www.walmart.com/ip/Mini-Grease-Gun-3Oz-Refill-2-Way-Dispensing/16777573
+
https://www.walmart.com/ip/Airgas-L...-Threads-For-Hand-Operated-Guns-Only/47907255


I use this grease gun for all rubber seals in diffs and shocks, plus all metal to metal gears and CVD's. etc....
 
Thank you for you knowledge. Very helpful. Exactly what I was looking for.
 
Damn i am having this problem now. I just built my mt410 and noticed one of the diffs has oil underneath it... I haven't even driven it yet so I am hoping some fresh oil will do the trick. Did you ever have any luck finding out where the oil was coming from?

I have a feeling I didn't grease the o-rings enough. Why are some lessons so tedious..
 

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