Arrma Metal Diff Case ARA310975

[JSmalls87]

This may be a dumb question...but I'm putting a set together right now. It only comes with (4) M3.5x16mm screws. Each diff needs 8...sooo what am I missing here? Seems like I need to order 4 more screws for each diff.

 

[Hammer Down]

This may be a dumb question...but I'm putting a set together right now. It only comes with (4) M3.5x16mm screws. Each diff needs 8...sooo what am I missing here? Seems like I need to order 4 more screws for each diff.

You reuse the 4 from the ring gear, and the 4 that come with it are for the other side plate.

 

[Adiabatic]

They designed these well, unlike the 6s version. The 6s version doesn't reuse the steel cross pin holders, and the spider gear shims and cross pins ride directly against the aluminum. Only took a few runs to wear deep grooves into the case material, which is very soft, definitely not 7000 series aluminum.

 

[JSmalls87]

You reuse the 4 from the ring gear, and the 4 that come with it are for the other side plate.

Ok it’s coming back to me now, I went with 4mm in the plastic diff case to help it not come loose. Dang wish I would’ve known they were rare screws. Oh well, Arrma sells them. AR703016 for anyone wondering.

They designed these well, unlike the 6s version. The 6s version doesn't reuse the steel cross pin holders, and the spider gear shims and cross pins ride directly against the aluminum. Only took a few runs to wear deep grooves into the case material, which is very soft, definitely not 7000 series aluminum.

Oh wow good to know. Just got a case for my 6s. Know of any better alternatives? I tend to steer clear of HR drivetrain things as nothing has ever lasted for me

 

[Adiabatic]

I don't know of anything better at the moment. I went back to stock for now. Hopefully it doesn't melt again.

 

[Moirae]

I've been waiting for this for an eternity. I had to rebuild the diffs on my RTR Kraton 5 or 6 times because of cracked cases. I dropped in the GPM cases just as a temporary fix. Since they are all aluminum, they would eventually wear out when the bearing or output cup ruins the metal they come into contact with. So when Arrma's case finally showed up, I got them for all 3 rigs. Just like the 6s cup, it's by far the best upgrade option. I threw them in my EXB first so I took a few shots of it.

View attachment 138899View attachment 138900
I can't tell whether the aluminum is 6061 or 7075 thanks to the anodizing but neither can Arrma so who cares It's still very high quality regardless but the star of the show is the harden steel cover. This is not some nasty pot metal, but a fully billet machined piece. Arrma can definitely do stuff like this if they want to.

View attachment 138905
The stock diff is somewhat coated in 100k front & rear. This is why you see so many blown tires & ridiculous diffing out to one side while turning & during airborne auto-correct attempts.

View attachment 138906
It's a good idea to remove the old fluid even if you're replacing with the same stuff. I used to be crazy anal about this when I buggy raced. I would use a car parts solvent & a toothbrush. But this is a basher, so a microfiber towel can remove most of it without getting any of it's material on the parts.

View attachment 138909
Also you want to rub some of the old diff fluid on the new seal (middle) to lube it before putting it on the cup. You can reuse the old seal (left} if it's in good shape. The right is the new seal w/o any lube.

View attachment 138911
I use 1 million cst, front & rear. It really keeps the car straight when launching & keeps the tires on the ground when turning under power. It's a bit of a pain to get out the bottle so I use a large flathead screwdriver.

View attachment 138912
The cup screws are m3.5 -3.5mm- (left) compared to a m4 (right). SO DON'T LOSE THEM. Do whatever you can to keep track of them. Magnetize bits, parts holders, bear-grip them while handling, pray , ANYTHING Trying to find a 10.9 or 12.9 m3.5x16 countersunk hex is not something I would wish on anyone.

View attachment 138914
The end result is beautiful, almost too good to be true - Now I just have to do it for the other two . . .

I broke a screw just now and I'm crying while i try to find some online

Edit: apparently they're easier to get now