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MontyMole

Greasing diffs for a Terra Scorcher

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Hi everyone,

I've just now taken apart my Terra Scorcher for some maintenance: in particular, I wanted to take a look to the differentials. Right now, they are just packed with MoS2 grease, which I guess it's doing it's job for protecting the gears, but I find them to be pretty much free; there is not much resistance to the action. My aim is to have a firmer differential in the front and one more flowing in the back, which I reckon is the norm. I now do have some AW grease, how should I put it to achieve my goal? Just a film of it on the gears and moving parts, with some more if I want the diff to be stiffer?

In general, what are your setups for this model (the Thundershot family, of course)?

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I bought a tube of CeraGrease for my upcoming Dragon build. I also have some really goopy Mugen silicone diff lube...  I’m curious to see what others say...

Terry

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[1] If you want to almost-lock it, you could use putties.  Tamiya sells one, there are other brands too.  Too hard for my purposes, I only use this in my Konghead.  Dynahead includes this in the kit.    

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[2]  If you are in US, "Bad Horsie Diff lock grease" has been my favorite.  It's somewhere between putty and grease.  It doesn't lock, but it slows things down quite a bit.  Very very sticky stuff that doesn't wash off from your fingers for days. 

I've put this in Wild Willy 2 in 2001.  20 years later, it still maintains the same stickiness (one on the left is 20 year old one).  When WW2 catches a tree root and stands on one wheel and the wheelie bar, this gets it out.  If putty was available 20 years ago, I'd have used it because WW2 is quite heavy.  Most of my buggies get this.  It's like chewy toffee or caramel (not that I've eaten it -- don't eat it kids!).  

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[3] Very similar to above, but "grease" would be "3 Racing Ultra High Viscosity Gear Diff Oil."  (AW grease is there for size comparison)  You can find it easily on ebay.  Stickier than AW grease. 

This should be good for most buggies.  After a year in the container, it separated a bit. I found some watery stuff around the edge of the container, as if it's leaking a few drops of water.  If you use the solid part, it should be fine.  

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[4] For on-road cars and lighter vehicles, like Dancing Ricer, etc, I use AW grease.  It's the go-to limited-slip-differential grease for most people. But it's the weakest stuff I use.  

TjZjjbD.jpg

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Bit left field, and feel free to ignore me...

I built my Terra Scorcher using all of the supplied grease for the diffs and like you the diffs spin freely. The grease is very light though, which is fine for the propshafts and other ancillaries.

Next time I rebuild it though I'm going to pop in some Silkolene Pro RG2 grease. It's the stuff I use on the suspension pivots and wheel bearings for my motorbikes. It's significantly thicker than the Tamiya supplied stuff, it's very resistant to viscosity changes due to heat, and it's also highly water resistant which hopefully shouldn't be an issue here. Also, it's about £9 for a half kilo pot, and you can use it in your car/around the house/garage doors, pretty much anywhere where you need lubrication to stay put. I know it's not RC specific, and doesn't come in a tiny little tube from a model shop, but I think it's worth a go...

silkolene-pro-rg2-synthetic-racing-greas 

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Juggular hit on most of the options I see people suggest. I'm a total noob at diffs but have asked similar questions on the forums in the past. General consensus was 'tighter up front, looser in back'. I'm putting the tamiya diff putty (or) 3 racing grease up front, then the AW grease in the rear. I will say the diff putty is a bit weird to work with - it clings to the metal bits and 'crawls' along the exposed surfaces, even crawling out of the diff itself along the drive shafts. People suggest it takes a few battery packs to really set up. I found it useful to build the diff and run it with a drill on low speed for a couple minutes. Diff putty dissolves in the presence of other greases so clean the diff well before applying. In the event you need to remove it a bit of paint thinner will wash it clean away.

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When you are using grease, I would make sure to check if it's plastic safe.  Automotive stuff could contain petroleum and that could crack plastic.  

 

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@Juggular that's quite an interesting post, thanks. Regarding using high viscosity oils, do they work in non-sealed differentials, or will they eventually leak? Because looking around it seems to be easier to find those, evidently the market is all around sealed oil and ball bearing diffs, no such thing as a dedicated diff grease for gear diffs.

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On 6/3/2021 at 4:09 PM, MontyMole said:

do they work in non-sealed differentials, or will they eventually leak?

My M07 can take liquid diff oil.  The other 3 dozen or won't take liquid.  I use Bad Horsie stuff (sparingly) even on completely open diffs from 1980's, like the Grasshopper, Hotshot, etc.  (please ignore the gray thing, that's plumber's grease -- for water resist treatment of the gearbox)  This much bad horsie stuff won't fling out.  

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Below is Lunchbox gearbox.  It's hard to see because the gears are all white.  

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Putties would work only within proper diff housings.  3Racing Ultra High Viscosity thing would benefit from a diff housing too.  At the same time, it might even be okay to use on open diffs. 

Below is what it looks like today, after a year of lying around on its side.  I would have thought it would have leaked, or clumped to one side.  But didn't.  I had a piece of paper wrapped around it to catch any watery substance, but there was none.  So I got that wrong.  You don't want to pack your diff housing with this stuff anyway, it would be totally locked.  If you use it sparingly, it should be okay with most diffs.   

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