Arrma 3/4S metal diff bound 1/4th turn. Losing my mind

[bukshypro]

Are the bearings fully pressed onto each side? They should be flush up against the diff. I use a socket and the plastic handle of a screw drive to tap it tight. If all is good there…

Hold the input gear shaft and move the ring gear back and forth. A tiny bit of play is fine so if you hear a slight clicking sound you’re good. If there’s a lot of play, remove 1 of the shims and try again. Make sure you tighten the yoke screws well when testing it.

Yes, the bearings are fully pushed in. The red metal yoke is perfect fit, it goes in well and it stays there, but I can take it out without much struggle if I want.
I will try the above, but the clue from my pictures was that the bottom outdrive seems to not be straight for some reason. if you look for perfect 90 , it is not.

 

[Velodromed]

Yes, the bearings are fully pushed in. The red metal yoke is perfect fit, it goes in well and it stays there, but I can take it out without much struggle if I want.
I will try the above, but the clue from my pictures was that the bottom outdrive seems to not be straight for some reason. if you look for perfect 90 , it is not.

Can’t really tell from the pics unfortunately…

 

[1999fd]

hey people.
I don't understand the physics of this whatsoever, but I took it apart again and just put all 3 shims on the opposite side and everything is perfect.

Lmao, by putting the shims on the top, I actually loosened the whole thing. Now Im unsure how to decide whether the mesh is tight enough or not.

Anyway, I got some pics, who can spot it?

View attachment 266664

View attachment 266665

View attachment 266666

Maybe you ordered a wrong part? Or they gave you the wrong one? It seems that it's fully screwed in. So it can't be the input gear bearings. I'm really confused about your problem.

 

[bukshypro]

Can’t really tell from the pics unfortunately…

Maybe you ordered a wrong part? Or they gave you the wrong one? It seems that it's fully screwed in. So it can't be the input gear bearings. I'm really confused about your problem.

hey both,
something actually happened but Im unsure what exactly. for me it seems the outdrive gear is not exactly straight. However, when I took it apart tonight, I put it back together with 2 shims on crown gear side and 1 shim on opposite side. Now I would say it's 99.5% perfect. I still feel a very very tiny bit of bind, but that is without grease. with grease, I'd say it's perfect.
I will leave it like that, so I don't have to deal with all the crap of sending it back. if I ever take it apart again, i'll be looking for the outdrive gear and and what's going on there.
thanks for help everyone.

Ps. I popped the driveshaft back until I get smth new. it will drive but it will be weak, which is ok

 

[Velodromed]

hey both,
something actually happened but Im unsure what exactly. for me it seems the outdrive gear is not exactly straight. However, when I took it apart tonight, I put it back together with 2 shims on crown gear side and 1 shim on opposite side. Now I would say it's 99.5% perfect. I still feel a very very tiny bit of bind, but that is without grease. with grease, I'd say it's perfect.
I will leave it like that, so I don't have to deal with all the crap of sending it back. if I ever take it apart again, i'll be looking for the outdrive gear and and what's going on there.
thanks for help everyone.

Ps. I popped the driveshaft back until I get smth new. it will drive but it will be weak, which is ok

If it works run with it. I’ve actually done that before, had to put a shim on both sides. Every differential is different so you have to take that in the consideration and work with them as they are.

 

[1999fd]

hey both,
something actually happened but Im unsure what exactly. for me it seems the outdrive gear is not exactly straight. However, when I took it apart tonight, I put it back together with 2 shims on crown gear side and 1 shim on opposite side. Now I would say it's 99.5% perfect. I still feel a very very tiny bit of bind, but that is without grease. with grease, I'd say it's perfect.
I will leave it like that, so I don't have to deal with all the crap of sending it back. if I ever take it apart again, i'll be looking for the outdrive gear and and what's going on there.
thanks for help everyone.

Ps. I popped the driveshaft back until I get smth new. it will drive but it will be weak, which is ok

If it works it works.

 

[Velodromed]

Ps. I popped the driveshaft back until I get smth new. it will drive but it will be weak, which is ok

I’ve boiled the connector and popped the drive shaft back in while still warm, then pressed the tabs together firmly and held tight for awhile. It worked well and they have lasted many packs...

 

[ajdragon]

Hi

I would almost bet that the plastic around one of the screw holes in the diff case is slightly crowned causing one side to be .0001" or .0002" higher then the other side. I could see the ring gear wobble when you where free spinning the diff on one bearing. What you could do is rotate the diff until it starts to bind and then stop turning the diff, then on the opposite side of the diff draw a line "with a permanent marker" over the ring gear and diff case, that spot is where your problem will be at. To find out if the problem is the diff case or the ring gear, you will need to rotate the ring gear 180 degrees, if the binding moves to the opposite side then the ring gear is your problem, but if the binding remains in the same spot then its your diff case.. If it's the diff case you can use some 2000 grit sand paper to take some material off the marked side of the case, if its the ring gear you can replace it or get some break in compound and up it on the side that is binding and then rotate the diff back and forth about 1 or 2 dozen times, and then clean every speck of the compound out of the gears.

 

[Velodromed]

Hi

I would almost bet that the plastic around one of the screw holes in the diff case is slightly crowned causing one side to be .0001" or .0002" higher then the other side. I could see the ring gear wobble when you where free spinning the diff on one bearing. What you could do is rotate the diff until it starts to bind and then stop turning the diff, then on the opposite side of the diff draw a line "with a permanent marker" over the ring gear and diff case, that spot is where your problem will be at. To find out if the problem is the diff case or the ring gear, you will need to rotate the ring gear 180 degrees, if the binding moves to the opposite side then the ring gear is your problem, but if the binding remains in the same spot then its your diff case.. If it's the diff case you can use some 2000 grit sand paper to take some material off the marked side of the case, if its the ring gear you can replace it or get some break in compound and up it on the side that is binding and then rotate the diff back and forth about 1 or 2 dozen times, and then clean every speck of the compound out of the gears.

When I first got into the hobby, I wanted everything to be free spinning and perfect. So I would spend an hour sanding gears down because I noticed that the composite gears are not always fully symmetrical and would catch in areas. Then I stopped doing that because they would break in anyway after a few packs. So what was said above is a good idea. If it’s not the yoke, you may have to sand the gears down a little bit in the ‘high’ spots. Or just run them and let them break in.
Edit: I forgot you are dealing with a metal differential. Sanding won’t work so well with that

 

[bukshypro]

Hi

I would almost bet that the plastic around one of the screw holes in the diff case is slightly crowned causing one side to be .0001" or .0002" higher then the other side. I could see the ring gear wobble when you where free spinning the diff on one bearing. What you could do is rotate the diff until it starts to bind and then stop turning the diff, then on the opposite side of the diff draw a line "with a permanent marker" over the ring gear and diff case, that spot is where your problem will be at. To find out if the problem is the diff case or the ring gear, you will need to rotate the ring gear 180 degrees, if the binding moves to the opposite side then the ring gear is your problem, but if the binding remains in the same spot then its your diff case.. If it's the diff case you can use some 2000 grit sand paper to take some material off the marked side of the case, if its the ring gear you can replace it or get some break in compound and up it on the side that is binding and then rotate the diff back and forth about 1 or 2 dozen times, and then clean every speck of the compound out of the gears.

thanks for your response! I've been marking the side that was up and it was exactly 25%, I tried tightening, loosening screws, but then just gave up cuz didn't understood where it was coming from. I made a few pictures, of the whole diff that I posted above because I felt that the one of the diff outdrives is not exactly straight 90degrees as it comes out. I could also confirm that with the marks I put on the plastic housing, where I found the 25% spot that was a bit up.

I actually got it good enough with fiddling around with the shims at the end. At this point I spent more on parts than my Arrma itself, which on its own is not a problem since I am having tons of fun and I feel I became an expert(on my own scale) of this hobby and I keep learning every day.
However, I have 3 (almost 4 now) children and a loving wife and I simply can't put as much time into making things 1000% fit my OCD, so I gotta compromise.
For the full precision I will be building some Schumacher kits and don't push the Arrma for that. Even the person in the hobby shop told me that their version of limitless that worths £1000+ has wobbly tyres, so I kinda lost my belief there ;/