Kraton Arrma Metal diff case arrived yesterday

[Mike-NLD]

Justintime

Did you have any problem installing the spur gear? I got mine all put together and got to the last step of screwing on the spur gear but found out the four holes did not match up between the cup and spur gear. They are off just enough I could only get two of the four screws installed. I messed with it quite a bit using different combinations with the screws but could only get two screws in, i could never get two screws to go in opposite each other, Did you have any issues getting yours all put together? Thanks!!

What kinda truck did you put it in?
3s/4s or 6s??

 

[Justintime]

Great info. Thanx for sharing that.

Since it is an open case on both sides versus a cup design, perhaps the spur is indexed to one side only and the other side gets the steel cover opposite side. Just a thought. Try reversing the spur and opposite cover if you haven't already.
Just a thought.
Btw, did you get two gaskets with the parts?
I think that I would use Red thread locker on the screws. I feel the center diff. is by far the hottest running component. Mine at high 250's 99% of the time. That heat transfers to the motor/mount considerably.

I had no issues. Blue is all you need if you ever want to get apart. The screw holes go all the way through. Blew a rear diff before I could get this one hot enough. Just another reason to wrench lol. Two gaskets but one was cut...? Luckily I ordered some one day.

What kinda truck did you put it in?
3s/4s or 6s??

6s

 

[SHB]

Great info. Thanx for sharing that.

Since it is an open case on both sides versus a cup design, perhaps the spur is indexed to one side only and the other side gets the steel cover opposite side. Just a thought. Try reversing the spur and opposite cover if you haven't already.
Just a thought.
Btw, did you get two gaskets with the parts?
I think that I would use Red thread locker on the screws. I feel the center diff. is by far the hottest running component. Mine at high 250's 99% of the time. That heat transfers to the motor/mount considerably.

Thats a good idea to swap the two sides, should have thought about that. I did get two gaskets in my kit.

What kinda truck did you put it in?
3s/4s or 6s??

Want to put it in my 6s Outcast, center.

 

[Justintime]

Thats a good idea to swap the two sides, should have thought about that. I did get two gaskets in my kit.

Want to put it in my 6s Outcast, center.

Thats a good idea to swap the two sides, should have thought about that. I did get two gaskets in my kit.

Want to put it in my 6s Outcast, center.

I put 2 screws in across from each other, barely started them. Pull the gear or back plate up to the screw heads. Start the other 2 in and slide the gear/ plate back down to case and tighten. It was very tight but fit fine.

 

[SrC]

My parts got here early. For the stock cup I weighed just the cup. For the Arrma alum. I weighed the body, cover, 1 gasket and 4 screws, (everything that makes just the cup.)

Stock=10 grams
Arrma Alum.=24 grams

Wow. That's more than 50% additional rotating weight. Hope you are using upgraded Abec 3 (min.) sealed bearings on this diff. High temp lube on these bearings is essential. just some thoughts.

 

[PaPa Thorn]

Wow. That's more than 50% additional rotating weight. Hope you are using upgraded Abec 3 (min.) sealed bearings on this diff. High temp lube on these bearings is essential. just some thoughts.

Not sure if I'm even going to use it, but if I do I run FastEddy's because I have a bunch sitting here.

 

[SrC]

Any upgrade rubber sealed bearings to hold the grease in.

 

[Plooden]

Wow. That's more than 50% additional rotating weight. Hope you are using upgraded Abec 3 (min.) sealed bearings on this diff. High temp lube on these bearings is essential. just some thoughts.

Sorry to bring up an old post, but I just wanted to point out that it is actually a 140% increase in weight.

 

[SrC]

That's why I only use the Arrma metal diff case at the center diff. Rotating mass at the front and rear is where you don't want it. IMO.

 

[hobo]

noticed it takes out centre diff slop as well

 

[Plooden]

That's why I only use the Arrma metal diff case at the center diff. Rotating mass at the front and rear is where you don't want it. IMO.

People constantly use heavier wheel and tyre combos. This would put significantly more strain on the driveline than heavier diff cups. I can't see the increased diff weight causing much, if any additional wear and tear, especially if you weigh up the tighter tolerances and less friction they result in.

More than happy for someone to prove me otherwise, as I have no tangible proof yet.

 

[3d-rc.myshopify.com]

It's all bad. Yes extra rotating mass is never a good thing. You will feel the extra weight... not that it even weighs that much..... more directly off the motor aka center diff then through the gearbox which has a gear reduction in it.
That's why lightened flywheels and balancers are a big thing in the 1:1 car world

 

[Plooden]

It's all bad. Yes extra rotating mass is never a good thing. You will feel the extra weight... not that it even weighs that much..... more directly off the motor aka center diff then through the gearbox which has a gear reduction in it.
That's why lightened flywheels and balancers are a big thing in the 1:1 car world

What if you're running say a HW 4985SL, surely it would have no Ill effect, and the extra durability of metal diffs would outweigh the extra weight?

 

[3d-rc.myshopify.com]

What if you're running say a HW 4985SL, surely it would have no Ill effect, and the extra durability of metal diffs would outweigh the extra weight?

There are pros and cons to every scenario. Doesn't matter which motor ,all has the same effects. Just a matter of preference. For a basher. Its run what ya brought. For the racing world. It all makes the difference.
Lighter driveline = longer battery life, quicker revving, quicker deceleration when let off the throttle , slightly cooler temps, less amp draw

Heavy driveline= shortened battery life, slower revving, longer to slow down on deceleration, slightly warmer temps, more amp draw

When I raced I prefer a heavy driveline, it would take some of the hit out of the punch out of turns so I could roll onto the throttle a bit earlier. And through switch backs I could let off and the car could carry it self through the turns while losing minimal speed. Where as a lighter driveline took a lot more finesse I just didn't have. Hell still don't have. So end of the day. Run what feels comfortable to you. There is no right or wrong. Just here to have fun.

 

[MrTitanium]

Too bad they didn't machine it to still use the X pin steel inserts.

X-Pin steel inserts? Are you referring to the little tombstones?

 

[SrC]

I like my drivetrain lean as possible. Composite cross pins in diffs are used by many higher end rigs for a reason. Lessrotating mass in the drivetrain allows for very fast spool up speed. More efficient.

 

[Plooden]

There are pros and cons to every scenario. Doesn't matter which motor ,all has the same effects. Just a matter of preference. For a basher. Its run what ya brought. For the racing world. It all makes the difference.
Lighter driveline = longer battery life, quicker revving, quicker deceleration when let off the throttle , slightly cooler temps, less amp draw

Heavy driveline= shortened battery life, slower revving, longer to slow down on deceleration, slightly warmer temps, more amp draw

When I raced I prefer a heavy driveline, it would take some of the hit out of the punch out of turns so I could roll onto the throttle a bit earlier. And through switch backs I could let off and the car could carry it self through the turns while losing minimal speed. Where as a lighter driveline took a lot more finesse I just didn't have. Hell still don't have. So end of the day. Run what feels comfortable to you. There is no right or wrong. Just here to have fun.

Excellent insight, thanks for that. I think I'll run full metal diffs for the sake of durability, it is a basher at the end of the day and I have made it heavier elsewhere anyway. I'd rather the durability over reaching top speed half a second quicker anyway.

I like my drivetrain lean as possible. Composite cross pins in diffs are used by many higher end rigs for a reason. Lessrotating mass in the drivetrain allows for very fast spool up speed. More efficient.

Those would be race rigs.

 

[BashingBrian]

Composite cross pins in diffs are used by many higher end rigs for a reason.

Where do you get those from..?? ?

 

[Batman]

Any update? Anyone else used them?

 

[olds97_lss]

Any update? Anyone else used them?

After fighting with them last year in my outcast, I've had 4 full sets of packs through it. So far, no diff issues. Guessing time will tell.

My issue thread:
https://www.arrmaforum.com/threads/issue-with-the-arrma-alloy-diff-cup-seems-too-long.14517/