Felony Spektrum Dual motor 12s

[ArrmaSmokes]

Hello arrma dudes
So I’m having this problem on my dual motor felony
So I desired to swap the front diff “gp5”to the back and the back “gp6” to the front
So when I changed it used it I noticed the front would tighten up but would still roll only if pushed or with it being driven and it would hold me back
I’ve never had a problem shimming my diffs
But this is the first time I swap the front diff to back and back to front
Do I need to shim the diff cause man it’s annoying me
Ever since I did the swap of the diffs
It tightens up then let’s loose
I’m going to change the diff anyways but need to know if I need to shim them or what’s the problem it’s like if I got the drag brake on all the time I checked cups and dog bones nothing is wrong and the bearings
I can’t find the problem it’s only up front
I see a shim on the gp6 should I take it off ? Cause I’m about to throw the car away jk

 

[Moirae]

All my rigs only roll if I push them. Search matrixrc on YouTube. He has done it with zero problems. He actually around here on forums somewhere but I forgot his forum name.

 

[LicketySplit]

They use different diffs because the tires are different sizes. Swap them back.

 

[Moirae]

They use different diffs because the tires are different sizes. Swap them back.

What he did actually works but I dunno what he did wrong lol

 

[Camaroboy383]

You mentioned swapping the f/r diff location... Did you swap the input (pinion) gear as well?

 

[RedondoBeachRC]

There’s a few ways.

You can remove the shims off the tight diff and see if that fixes the issue. You can shim the opposite side to loosen it up.

But first I would try adjusting the diff cover. If you loosen the diff cover, is there still a tight spot? If the tightness goes away.. then it’s just figuring out how tight you need to attach the diff cover. On some of my cars taking the screws back a couple of turns on one side frees up the diff.

Sometimes the diff housing aren’t true to size and are warped in a very very small way.

 

[aroberson77]

While in theory swapping the diffs work, they do not mesh perfectly. It is a better idea to just get a GP5 diff with input gear and install that if you are running all 4 of the same height tire

 

[Camaroboy383]

While in theory swapping the diffs work, they do not mesh perfectly. It is a better idea to just get a GP5 diff with input gear and install that if you are running all 4 of the same height tire

This is where I was headed..... They will not be smooth if you put a gp5 against a gp6, or vise versa.. it's like putting a mod .8 pinion on a mod 1 spur, it's just not quite right on the pitch...

 

[Moirae]

I guess none of you have seen MatrixRC speed runs where he actually does it with zero issues.

 

[Camaroboy383]

I guess none of you have seen MatrixRC speed runs where he actually does it with zero issues.

Seen plenty of his videos... As mentioned above, it technically will work, the pitch is close enough.. But, tooth engagement suffers to make them operate "smooth".. he's asked why it's binding, this is why.. we have all seen it done, but it Is not the proper pinion for the ring ...

 

[Moirae]

Seen plenty of his videos... As mentioned above, it technically will work, the pitch is close enough.. But, tooth engagement suffers to make them operate "smooth".. he's asked why it's binding, this is why.. we have all seen it done, but it Is not the proper pinion for the ring ...

Then why are other people doing it with no binding?

 

[Camaroboy383]

Then why are other people doing it with no binding?

Shims.. either some, none, or side swap..

 

[aroberson77]

Shims.. either some, none, or side swap..

usually anything is possible, but whether or not it is right is another story. I wouldn't want a diff failing and would just buy the right diff, someone was selling a GP6 on the classifieds

 

[Moirae]

I read these replies and it's akin to the people in the RC discord saying "6s arrmas can't handle 8s, blah blah diff cups blah blah driveshafts". Meanwhile 8s work perfectly fine with zero problems.

All these people so quick to say it won't work but haven't even tried it while people who have actually been doing it for months and actually have EXPERIENCE with it get ignored lol. Don't blindly follow people on these forums because not everyone knows what they're talking about and there are more ways than one to skin a cat. Gather multiple opinions and use cases and make your own decisions.