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WLToys 12428 Solid Front Axle Build Guide

Hey guys,

This is a guide for putting together the WLToys 12428 solid front axle for the WLToys 12428 crawler conversion project.  The main difference between this axle and an Axial SCX10 clone axle is that the shock mount points are on top of the axle not on a shared screw with the four link mount.  This lowers the axle about 15mm and moves the shock mount forward about the same.

A few cautions:

  • If you don't know what you're doing and feeling nervous, get help from someone more experienced in the ways of DIY.
  • Take apart your RC vehicle at your own risk.
  • Follow these instructions at your own risk.
  • Use common sense and review instructions before you follow them.
  • Knives can cut you.  Use caution.
  • Hot glue can burn you.  Use caution.
  • Brad nails can stab you.  Use caution.
  • Rubber bands can shoot you in the eye.  Use caution.  Please tell me if this happens to you, I can always use a laugh.  It's funny if you aren't the victim.  That goes for just about everything on this list but a rubber band in the eye is the funniest.
  • Screw drivers can stab you.  Use caution.
  • Drills can drill you.  Use caution.
  • Soldering irons can solder you.  Use caution.
  • Molten solder is like lava from a volcano.  Use caution.
  • Fast spinning wheels or drills or rotary tools can tear the skin right off you.  Use caution.
  • Forcing something that doesn't fit can cause damage to property or personal injury.  Use caution.
  • Connecting electronics incorrectly can release the smoke.  The smoke can't be put back in.  Use caution.  Take pictures if you don't know by heart how parts are connected.
  • Batteries can cause fires when not handled properly.  Use caution.
  • Some parts are not very durable.  Screw holes may not survive taking a screw out and putting it back in.  Disassemble your RC car at your own risk.

Notes:

  • If you are using the stock WLToys rear shocks or similar as front shocks, you may use 4 stock WLToys M2.5 screws to mount them in the crawler build BUT know that you will have to scrounge the right length screws (2x 15mm, 2x 20mm)

WLToys parts:

1x Front diff with bearings
1x Rear axle shaft cut down to use as front pinion shaft
  • or standard rear pinion shaft
  • I had a spare rear axle so I used what I had (I got the complete rear axle (no housing) with plastic gears for $5US)
  • I have not seen the pinion shaft for sale so you can make one from a 5mm steel rod (difficult) or cut down a rear axle shaft or some other shaft with 2 flat sides and a screw hole in the center
2x Front drive shaft
4x Front drive shaft bearings
4x Steering knuckle screws

Additional Parts:

4x M2x8-10mm
4x M2x6mm
Hot glue

Optional allen screws:

4x M2.5x10mm
2x M2.5x15mm
     - or M3x20mm if using SCX10 shocks
2x M2.5x20mm
     - or M3x20mm if using SCX10 shocks

Printed parts:

1x Frnt_Axle_Back_V2 - inside up orientation for quality bearing seats
1x Frnt_Axle_Frnt_V3 - inside up orientation for quality bearing seats
1x Frnt_Axle_Pinion_Carrier
1x Frnt_Axle_Link_Mnt_V3
1x Frnt_Axle_Link_Mnt_V3 mirrored
1x Frnt_Axle_CasterPH_5_Camber_0_V2
1x Frnt_Axle_CasterPH_5_Camber_0_V2 mirrored
1x Frnt_Axle_M3_Crawler_Knuckle_V2
1x Frnt_Axle_M3_Crawler_Knuckle_V2 mirrored

Assembly:

  • This is a good time to lock the WLToys diff if you want an optimal crawler experience.  I used memory foam ear plugs.  I cut disks of the material approx 5mm thick and placed a piece on each side of the planetary gears in the diff.  The rear didn't stay fully locked very long but the front has done better.  The rear remains semi-locked (it spins both wheels until the load is very unequal).  Use this method at your own risk.  I have heard of people using JB weld, silicone or epoxy in the diff.  Follow this hearsay at your own risk.
  • Clean the diff if necessary.  Do not install the diff as-is if grit has gotten on the gears.  Clean it first.
  • This is a good time to lube the bearings if you ran your WLToys a lot.
  • Check your driveshafts for signs of damage in the joint.  I have broken 2 and in both the joint failed and a piece of metal flopped around inside.
  • Cut down the rear axle shaft for use as a front pinion shaft.  The slotted end fits into the diff pinion gear and attaches with the same screw that held it in the back diff.

  • Remove the drive cup shaft from your WLToys front diff pinion gear
  • Test fit the Frnt_Axle_Link_Mnt_V3 on the axle.  Mine fit perfect on one side and not so perfect on the other.  Use a rotary tool or file to sand down the axle until the link mount fits on each side.

  1. Install the pinion bearings in the pinion carrier
  2. Install your pinion shaft into the front diff pinion gear
    1. do not apply grease yet
  3. Test fit the pinion gear with shaft to ensure the length
    1. I made mine too long by accident so I have been running a DIY spacer to keep the bearing from falling out
  4. Install the pinion carrier into the Frnt_Axle_Frnt_V3 using 4 M2x6-8mm screws.  Take care, the front bearing is not secured until the driveshaft is installed so it may fall out.
  5. Seat the diff into the front half and test the gear mesh by pressing down on the diff bearings and turning the pinion.
    1. If the pinion will not turn at all you may need to shim the pinion carrier to create gap.  Tight is OK if the gears are newer.  The WLToys axles are quite tight when new but wear in over time.
    2. If the diff will not seat fully you need to use a file of rotary tool to massage the bearing seat to make room.  Mine required no modification so you may need to review your print setting and/or print orientation.
  1. Put on the back half of the axle and test the gear mesh again.  Too tight and too loose are both bad.  If the diff fits poorly you may need to adjust your print settings and try again.  I spent quite bit of time getting these parts just right and my final versions required nothing more that cleaning off a few little zits.
  2. Once fit is good, grease the gears thoroughly and close up the axle using 4x M2.5x10-12mm screws
  3. Install the Frnt_Axle_Link_Mnt_V3 on one side and the mirrored copy on the other.  The shock mount tab must point upwards
  4. Secure the Frnt_Axle_Link_Mnt_V3s with a dab of hot glue
    1. For final assembly, the shock must be installed before the Caster block so review your build plan now to see if you are ready to continue
    2. You can remove the caster block and knuckle as an assembly later if needed
  5. Install the Frnt_Axle_CasterPH_5_Camber_0_V2 on one side and the mirrored copy on the other.
  6. Use a small dab of hot glue to secure the link mounts and caster blocks for now
  7. Install the bearings in the steering knuckles.  You may need to use a file or rotary tool to massage the bearing cups
  8. Install a drive shaft into the axle and ensure the dog bone is seated in the drive cup
  9. Insert the drive shaft output into the steering knuckle and then screw the knuckle in place.
  10. Repeat steps 12-14 for the other side

Wrench to drive or drive to wrench?

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