Another diff question - input gear

[Mopsik_Klopsik]

Hi, I like finding problems that doesn't exist... and I found one.

Which one is the proper way to mount the diff pinion gear?

Option 1 : squeezing both pinion gear and input cup against the bearings with your fingers.
Option 2 : pushing only the pinion gear

With option 1 I can feel a lot more resistance when spinning the diff, there is no slop on the pinion gear. Option 2 is the oposite - diff spins more freerly but there is a bit of movement on the pinion gear as the parts aren't as hardly pushed against bearings ( I think ).

What is your way of assembling it? Does it even matter how I do it?

 

[Garcbomber]

1, you want zero-minimal axial movement in that input gear. Otherwise you are changing ring gear surface area engagement. Flicking throttle/brake/reverse will be loading and unloading that mesh. If you let the input float too far, it’ll contact the diff carrier.

Proper shimming of the input is more critical than the ring gear, you want them as tight as possible to the point they bind. Then remove the thinnest shim to free up, especially when running alloy bulkheads/carriers.

 

[Hector_Fisher]

How tightly are you squeezing when doing option 1? What truck? Are bearings fully seated? Is the input cup rubbing against the bulkhead?

I'll give a option inspecific response: The input gear will be shoved against the bearing as soon as the truck starts to drive under it's own power. The diff pinion and diff spur gear will want to separate themselves based on the geometry and applied torque. This is the reason to shim the pinion, so it's at the proper geometrical location with the spur gear. I have several RCs that don't have a input cup installed in the way you're describing (they are held in because the center drive shaft keeps them there), and they don't have issues. So i would think that as long as you have the input cup installed to where it won't come off, then you should be good.

Be sure to shim your input gear if needed!

 

[Mopsik_Klopsik]

How tightly are you squeezing when doing option 1? What truck? Are bearings fully seated? Is the input cup rubbing against the bulkhead?

I'll give a option inspecific response: The input gear will be shoved against the bearing as soon as the truck starts to drive under it's own power. The diff pinion and diff spur gear will want to separate themselves based on the geometry and applied torque. This is the reason to shim the pinion, so it's at the proper geometrical location with the spur gear. I have several RCs that don't have a input cup installed in the way you're describing (they are held in because the center drive shaft keeps them there), and they don't have issues. So i would think that as long as you have the input cup installed to where it won't come off, then you should be good.

Be sure to shim your input gear if needed!

I think why with option 1 there seems to be more resistance when I spin the diff is because the input gear now spins with the bearings rather than inside them without them ( bearings ) also spinning. With applied power from the motor and all of those forces affecting gears, the input gear mounted like in option 2 will probably also start to rotate along with the bearings. The difference is noticable only while spinning by hand.

I much more preffer first opiton as there is no unnecessary play in the gear assembly. Question is whether is it good or bad for the bearings, to have these two parts pressing against them like this ( I must admit I used quite a bit of force to push the input cup )

I'm using 0.1 shim instead of 0.2 as the diff was binding.

 

[Mopsik_Klopsik]

But since you say your differentials ar fine... then I probably shouldn't care so much about the way I assemble it.

 

[JLspeeddragon]

I am getting ready to put these on the F/R of my Talion Rebuild..
Here is the possible problems I'm wanting to solve.
With the input gear not pushed inward to the diff case spinning freely, I can hear the gears clicking as I turn the input.
If I put forward force to the input (pushing the ring gear further in) forcing it flush with the casing, while turning it, I no longer hear the gears clicking and getting a much better mesh..
So Question is, how should I go about shimming the ring gear (13T) to get a much tighter mesh?
Do I put shims between the bearing and the casing? or..
put a shim between the ring gear and the bearing?
Of either case what's the inside Diameter / Outside diameter shims should use?

BTW I have already put shims on the drive cup (Diff gear side) to push the diff gear inward previous to the above mentioned information. I can still hear the clicking noise If I spin the input center drive cup freely. I do not hear clicking if i push input towards the diff casing (closing the gap) and spinning it.

 

[Garcbomber]

There's too much landing surface for the set screw on the Arrma input gears, if you've already repositioned the rear center diff input cup you can shim it away from the input bearing into the bulkhead. I punch my own shim stock, but a thin washer the proper diameter will suffice to prevent the input from floating too far axial towards the differential ring/crown gear. Again, composite housing have big tolerance and flex so you have more "grey-area" tolerance designed for a high production RTR. Keeps assemblers from reworking on the line, allowing resources to continue throwing components together when building.

 

[Mopsik_Klopsik]

Do I put shims between the bearing and the casing? or..
put a shim between the ring gear and the bearing?
Of either case what's the inside Diameter / Outside diameter shims should use?

I used 8x12x0.1 shims between the ring gear and the 8x19x6 bearing. I setup my diff gears mesh same as motor pinion and spur gears.