Can't seal a diff to save my life

[Hector_Fisher]

So what am I doing wrong?

This is the same situation with both my SCT and my MT, they both keep leaking out all diff fluid (center and F/R). I've assembled everything to a T, as shown in the manual. Leave a little room at the top, tighten down the spur bolts in a cross fashion until they stop moving. But they still leak.

Took apart my MT410 today since I saw the center diff looking like this:

All screws were tight, not one was loose.

Gasket is intact. I seriously don't know what I'm doing wrong. Of all my RCs, my teknos have been my worst leakers.

My next step is to fill with 500k (highest i have) and try that. I'm hoping that would stop the leaking, but that's not much higher than 100k stock.

Everything looks like it was assembled correctly on the inside.

 

[MAVERICK]

I have had similar issues

Manual states keep 1 mm at top empty I think I I have had better luck around 2mm empty

 

[Hector_Fisher]

I have had similar issues

Manual states keep 1 mm at top empty I think I I have had better luck around 2mm empty

Since I'm currently in the process....
More or less than this?

 

[MAVERICK]

In my opinion I would pull some out

I am not saying it’s right but it has worked for me

Make shur you spin the gears and get all the bubbles out

 

[Ferrebee88]

Have you tried emailing Tekno customer support? They are actually pretty good at responding. I have build the SCT 410.3, 2 MT410s, EB410, EB48, and the list goes on and have never had that issue. Maybe luck of the draw, but if you have some messed up parts they will help you out.

 

[nub]

I've done them all like this and never had issues. The one time I did have a leak was when I reused the gasket even though it looked fine. The gaskets are cheap so I just replace them.

 

[Nicochau]

I heard you can stack two gaskets. One other thing I noticed is that once it starts to leak, it will not stop. You should try to fill it less.

 

[Hector_Fisher]

In my opinion I would pull some out

I am not saying it’s right but it has worked for me

Make shur you spin the gears and get all the bubbles out

Ended up taking a little more out. I don't remember how much I filled it last time (would have tried to mimick the picture in the manual), but at least this time i'll have this picture as the reference point.

I heard you can stack two gaskets. One other thing I noticed is that once it starts to leak, it will not stop. You should try to fill it less.

I've noticed that. Doesn't seem to make sense, but it's happened on my SCT and MT. Almost like there's a siphon effect or something.

So which would be worse, overfilling or underfilling? If I had to guess, overfilling would cause it all to leak out (still not sure how), and underfilling would cause... a weaker filling diff? Lots of air bubbles in your diff fluid?

 

[KnowAir]

If it were just one or two diffs, maybe a warped cup or ring/spur or gasket..but acrossed multiple rigs and diffs, not likely. Might just be over filled as others have stated. My experience is that while having the perfect amount of fluid will surely be best, having less is better than too much..
These things will run with barely any fluid in them for quite some time. Not bragging of course, but I've done it. Not intentionally but, I'll admit my maintenance regimen is not what most do.. I've opened diffs to find them basically just wet..otherwise almost empty, still working "fine" though.

 

[KnowAir]

Ended up taking a little more out. I don't remember how much I filled it last time (would have tried to mimick the picture in the manual), but at least this time i'll have this picture as the reference point.

I've noticed that. Doesn't seem to make sense, but it's happened on my SCT and MT. Almost like there's a siphon effect or something.

So which would be worse, overfilling or underfilling? If I had to guess, overfilling would cause it all to leak out (still not sure how), and underfilling would cause... a weaker filling diff? Lots of air bubbles in your diff fluid?

I agree, over filled is "worses".. I think it creates excess heat. Once heated, it's got to go somewhere, in this case, it's forcing it's way past the gasket and output shaft o rings.. it would eventually balnce out, after making a fine mess, but, can't be good for it.

 

[Hector_Fisher]

I agree, over filled is "worses".. I think it creates excess heat. Once heated, it's got to go somewhere, in this case, it's forcing it's way past the gasket and output shaft o rings.. it would eventually balnce out, after making a fine mess, but, can't be good for it.

Well if you want to talk about "barely wet" diffs. Those were the Kaiju replacement diffs i ordered. I looked inside and i don't think i could see enough oil to fully even cover the gears...

The biggest annoyance with underfilled center diff is basically turning the truck into FWD, cause the fronts are always spinning. But yeah, no real big concern as long as the gears are coated and you're not diff'ing out all the time.

I could understand if too much oil cause a needed pressure release when it heats up. But how would it all drain out??? You'd think once enough leaks out, pressure would equalize???

I think going higher thickness will help.

 

[KnowAir]

Well if you want to talk about "barely wet" diffs. Those were the Kaiju replacement diffs i ordered. I looked inside and i don't think i could see enough oil to fully even cover the gears...

The biggest annoyance with underfilled center diff is basically turning the truck into FWD, cause the fronts are always spinning. But yeah, no real big concern as long as the gears are coated and you're not diff'ing out all the time.

I could understand if too much oil cause a needed pressure release when it heats up. But how would it all drain out??? You'd think once enough leaks out, pressure would equalize???

I think going higher thickness will help.

True..so your Tekno diffs were basically empty after opening? Hmm..that is puzzling. I guess I've been lucky with mine, IDK. Strange. Perhaps start with new o rings and gaskets.

 

[KnowAir]

I do know what you mean about the kaiju diffs too, that seems a common theme with rtr diffs in my experience. The Arrma and TC diffs never seem "full" either.. honestly I just run em that way. Perhaps I just have low expectations, LOL.

 

[a2lowvw]

Since I'm currently in the process....
More or less than this?
View attachment 9076

That looks too full. Drop the other sun gear in and see how full it is before reassembly. I had one leak and found out it was overfilled.

 

[Hector_Fisher]

That looks too full. Drop the other sun gear in and see how full it is before reassembly. I had one leak and found out it was overfilled.

I think my only complaint is that I would be following the tekno instruction manual directly. So if what you're seeing here is too full, then tekno is telling you to fill your diffs too much.

The tekno manual contradicts itself. Manual says to fill to 1mm below top (just over the top of the gears), but the top of the gears are NOT 1mm below the top of the case. In my picture, the oil level is about 2mm below. And i even took some out after i took this picture.

Which, fair enough, maybe i was filling too full the first time. But but how then is ALL the fluid leaking out?

 

[KnowAir]

I think my only complaint is that I would be following the tekno instruction manual directly. So if what you're seeing here is too full, then tekno is telling you to fill your diffs too much.

The tekno manual contradicts itself. Manual says to fill to 1mm below top (just over the top of the gears), but the top of the gears are NOT 1mm below the top of the case. In my picture, the oil level is about 2mm below. And i even took some out after i took this picture.
View attachment 9078
Which, fair enough, maybe i was filling too full the first time. But but how then is ALL the fluid leaking out?

Got me.. I don't know why this is happening. Maybe my diffs aren't as safe as I'd thought? I really haven't paid them much attention. With the mt410, I built it per manual suggestions. I didn't care fore the steering with 100k in the front, or even the 50k in the rear. I thinned both down quite a bit after a few months of use. I'm something like 30k front and 7 or 10k rear. I run a track mostly though. It works quite well, but honestly I plan on running whatever the ET48 calls for next service.. whenever that might be.
The sct410 hasn't seen a whole lot of use yet, say 15-20 packs, no visual signs of leakage so far.
I know many change fluids routinely, not me. I don't see the benefit..but then again, I'm just a basher (and a meathead) soo..

 

[Bill Becher]

Be careful that the for screws that hold the diff together are lined up with the holes in the bottom.

 

[a2lowvw]

I put the other sun gear in once it’s nearly full and fill to 1mm below the top.

 

[elbrujo58]

with my poor eyes find it hard to be consistent filling my diffs. I have just purchased a tiny kitchen scale and will use it to weigh my diffs when filling with oil. hate to be a name caller but that is how Xray recommends filling them. I have yet to rebuild the diffs using this method on my eb410 so I cannot tell you what to fill them to

 

[VRC]

I’ve had this problem with my tekno diffs. How I think I’ve remedied the problem was less fluid, even tightened and not over tightening. I have an arrma 6s that that was a problem on and didn’t have anymore diff gaskets and wanted to run. So, I used some silicon gasket maker and haven’t had the problem yet. Now I don’t use gaskets on my arrma. When I run out of gaskets for the teknos I will do the same. BTW, I mostly bash so I’m not getting into my diffs multiple times a week. Or however Many times racers take apart their diffs.