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I personally just use mobile 1 synthetic grease in my diffs.
It's cheap for the amount you get and can be found at most auto parts stores.
It's cheap for the amount you get and can be found at most auto parts stores.
Diff oils and shock oil are all something that have to be tuned to your preference but heres some info I found on another site that may prove useful. I have no personal experience with it. These two guys were talking specifically about the HR diff for the 2wd slash and racing it.
The Hot Racing diff for the 2wd uses the stock planetary gears internally, and they are not like the gears in a bevel gear equipped differential. You will need oil of 30,000wt or greater, depending on your driving surface. If you put in the typical oil from a 4x4 diff (5k, 7k, 10k, etc) you would notice no difference at all. The tiny gears will just whip it into a foam and render it useless. I run 100,000wt and 120,000wt most often in loose/dusty conditions. A buddy of mine has fun 300,000wt in his. In general, the higher traction the surface, the lower the oil weight.
Dr Isotope (The guy that posted the above statement) is correct. The Traxxas gear design requires a heavier fluid to be effective than other design diffs. I am running 100k on mine for a very tricky low grip outdoor track. I just started running a high bite tight indoor course and believe the diff is too thick for that course. I will be dropping to 50k or so at my next rebuild. Anything much less than 10-15k in the slash rear end is about like the grease that was in it stock!
Heavier diff fluids will hurt the truck turn in on corner entry and overall make it push some. But they improve forward traction on a low grip surface. Under power on corner exit, heavier fluid tends to make the rear want to step out slightly as traction brakes, but it is more of a controllable drift. Lighter diff fluid will improve turn in on corner entry and allow the truck to rotate better. It does not apply power as evenly under acceleration and can allow power to go to the unloaded tire and reduce acceleration. This can result in slightly less overall forward bite. It can also allow the truck to "diff out" when turning under power. When the truck "diffs out" the weight transfers to the outside tires and unloads the inside tire. This causes the outside tire to lose power and the inside tire to spin up. This can make the truck spin out or roll over very aggressively at times. The truck rolls because the front tires gain traction as the truck loses forward bite and the outside takes more side bite as they slow down. Watch a full sized SC truck run....they cannot lift in the corner, if they do...well...same thing.
So, lots of words to say diff fluid is a preference to driving style, truck type, and track type. I like to sling my truck in and drift a bit, so heavier fluids for me. As I gain experience and improve throttle control, I am finding a need to reduce diff fluid weight so I can roll the corner more.
The Hot Racing diff for the 2wd uses the stock planetary gears internally, and they are not like the gears in a bevel gear equipped differential. You will need oil of 30,000wt or greater, depending on your driving surface. If you put in the typical oil from a 4x4 diff (5k, 7k, 10k, etc) you would notice no difference at all. The tiny gears will just whip it into a foam and render it useless. I run 100,000wt and 120,000wt most often in loose/dusty conditions. A buddy of mine has fun 300,000wt in his. In general, the higher traction the surface, the lower the oil weight.
Dr Isotope (The guy that posted the above statement) is correct. The Traxxas gear design requires a heavier fluid to be effective than other design diffs. I am running 100k on mine for a very tricky low grip outdoor track. I just started running a high bite tight indoor course and believe the diff is too thick for that course. I will be dropping to 50k or so at my next rebuild. Anything much less than 10-15k in the slash rear end is about like the grease that was in it stock!
Heavier diff fluids will hurt the truck turn in on corner entry and overall make it push some. But they improve forward traction on a low grip surface. Under power on corner exit, heavier fluid tends to make the rear want to step out slightly as traction brakes, but it is more of a controllable drift. Lighter diff fluid will improve turn in on corner entry and allow the truck to rotate better. It does not apply power as evenly under acceleration and can allow power to go to the unloaded tire and reduce acceleration. This can result in slightly less overall forward bite. It can also allow the truck to "diff out" when turning under power. When the truck "diffs out" the weight transfers to the outside tires and unloads the inside tire. This causes the outside tire to lose power and the inside tire to spin up. This can make the truck spin out or roll over very aggressively at times. The truck rolls because the front tires gain traction as the truck loses forward bite and the outside takes more side bite as they slow down. Watch a full sized SC truck run....they cannot lift in the corner, if they do...well...same thing.
So, lots of words to say diff fluid is a preference to driving style, truck type, and track type. I like to sling my truck in and drift a bit, so heavier fluids for me. As I gain experience and improve throttle control, I am finding a need to reduce diff fluid weight so I can roll the corner more.
WickedFog
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Is that safe for plastics? Regular lithium grease isn't, and when looking that up it is lithium based.
I've been using it for well over a decade in my RCs and I've never had any issue with it. Hell, Amain sells the stuff.
https://www.amainhobbies.com/gmk-supply-mobil-1-grease-gmk0115/p-qqqetzqqlzxxactz
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WickedFog
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Cool. Thanks.
I had no idea it had lithium products in it though.
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If it isn't damaging your plastics maybe it being synthetic helps? I don't know enough about chemistry to give any thoughts on it. I just found out about lithium grease the other day. I watched a video by Matt from Scale Builder's Guild and he uses Lucas Oil lithium grease on all his gears, so I grabbed some to try it. But after reading up on it, it isn't recommended for plastics.
I mean I havent tore any of my diffs/transmissions with grease in them down in probably 5 years but I never noticed any issues with it before I took a hiatus. I will definitely report back if I find out anything different.
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in my slash 2wd HR diff i started with 7k. no difference
then went 10k.. better
i now have 15k and will be racing this weekend. i’ll let us know how that works.
taking small steps..
the diff really affects the handling. wd slash seems tough to dial in.
any setup sheets out there? i refer to them for all (4) or my tekno cars
then went 10k.. better
i now have 15k and will be racing this weekend. i’ll let us know how that works.
taking small steps..
the diff really affects the handling. wd slash seems tough to dial in.
any setup sheets out there? i refer to them for all (4) or my tekno cars
Not sure about set up sheets but yeah. diff and suspension set up can really play a big role in performance 
JCsRCcar
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I used 100k silicone differential lube in my 2WD Rustler with HR diff case and it is perfect. It acts like a psi differential now but isn't so stiff that it oversteers or breaks traction. Even in the dirt its very balanced after some chassis tuning.
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