Granite 4s build progress, differential setup?

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Motodeficient

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Messages
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Location
Maine
Arrma RC's
  1. Granite
  2. Kraton 6s
  3. Typhon 6s
Hey everyone!

I've got a Granite 3s that I am converting to 4s.

So far I have installed or procured:

-HW 3665SD 2400KV Sensored Motor
-HW Max10 ESC
-Kraton 4s differentials Front/Rear
-Steel input gears for Front/rear
-Arrma HD CVD's for Front/Rear
-Hot Racing diff yokes Front/Rear
-Steel Spur gear for slipper clutch

I have mocked up the Kraton 4s diff with the metal input gear and Hot Racing yokes in the front, see below picture. The diff has a little bit of side to side play in the hot racing yokes. The stock diff didn't have any side to side play in the stock composite yokes. I'm guessing this play needs to be addressed, but I'm not sure where to start. Do I need to do something inside the diff, or do I just need to get some shims to install on the outside of the diff behind the bearings? How do I know which way to shim it? How much play should there be between the differential gear and the input gear?

IMG_20240408_202855953.jpg
 
I just did the same upgrade to a Granite. The stock differential and composite housing comes with a single 0.20 shim on ring gear side. I too had a lot of play side to side in stock form after I test fit in HR yokes. Per another article stickyed in drivetrain and chassis, I got some Tekno tkr1222 shims 13x16x 0.1, some Kyosho kyo96772 13x16x 0.15, and some stock Arrma ara709052 12x15.5x 0.20 shims to set lash on mine. My HR yokes has a lot of play. Seems like I ended up with 0.40 on ring gear side and 0.20 on the non ring gear side to get the play mostly taken out. Had just a touch of play in the ring gear and pinion then. Could wiggle them back and forth and hear and feel a very small tink tink noise. Hopefully didn't set it too tight. If I did I'll soon know I reckon. But so far so good. Ran a pack or two through already with no issues.

Just my experience. Greater minds will chime in I'm sure😊
 
Thanks for your reply. So you didn't do anything internally to the differentials? Just external shims? Why did you get two different sizes of shims (I understand needing the different thicknesses)?

Do the shims go between the diff and the bearing or between the bearing and the yolk?

I did not notice any shims when I disassembled the stock setup, I may have missed it though.
 
I was a little foggy on what shimming needs to be done internally. I spun the gears and seemed sorta ok. Like the wasn't a lot of play in the shafts when moved in and out. I got new takeoffs from Jenny's and checked the oil level. Kid was breathing down my neck to get 'er running (Dad, Dad, you gonna get the differentials done today? As soon as they showed up😂😂)so that may have influenced my rush!

I got several different shims to fine tune the play. Wanted 0.10, 0.15, & 0.20 to get it as close to perfect as possible. That's why I ordered those shims I guess. The Tekno and Kyosho shims didn't fit the diff outputs as well as I would have liked but it would have worked if needed. Ultimately didn't use them.

I put the shims between the output bearing and the differential like stock form does it. Maybe your diffs didn't have them. IDK. Both my stock Granite and metal Jenny's 4s diffs had a single 0.20 shim on ring gear side between diff and output bearing
 
I’m using trb rc m12x16 shims on the out drive bearings (one pack comes with 40 shims, 10 each 0.1-0.2-0.3-0.5mm) and m10x12 (same qtys and thickness) on the pinion.

I put enough shims behind the ring side bearing (and pinion between pinion and first bearing) to get the pinion/ring mesh right then shimmed the bearing opposite the ring to take out the side-side slop left.

This left me with some in/out play in the pinion. If I shimmed it more to take that out even 0.1mm it would bind severely. I don’t see a way around that. The 8s pinion has a c-clip provision that can be shimmed against to take out slop. Unfortunately the 4s doesn’t.


The binding is mostly in 3-5 teeth of the ring gear so my suspicion is the ring isn’t precisely machined or the plastic diff case isn’t true (more likely). Same result with both front and rear. I’d love to get an all HR diff setup but it’s a boatload …. After adding the parts all up it’s close to $100 each

Everything seems tight with the plastic stock yokes because they are made a hair over size and flex when tightened then pinch everything together.
 
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