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Mokei Kagaku

TRF503: Gear diff breakage?

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A friend of mine who owns a TRF503 recently told me that he's repeatedly has destroyed the rear gear diff internals and asked if this is a commonly known problem and if anything can be done to make it stronger.

As I don't own and have never run or built a TRF503, I don't have the faintest idea. Any advice would be highly appreciated.

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Looks like the TRF503 does not come with the double slipper setup Tamiya offers as an option on the DB01.  The idea behind the double slipper is to let the front and rear slip independently, decoupling all that inertia and reducing stress on the drivetrain.  If the double slipper fits, I'd give that a try.

The TRF503 and DB01RRR both introduced new 39T gear diff cases vs. the 37T cases used on the DB01RR and the 37T ball diffs used on the DB01R/DB01/TRF501x/TRF511x.  As such there's much less collective experience on the 503 and RRR.  All gear diff cases across the DB/TRF family used metal cross pins and gears; only the TT02B comes with plastic diff gears.

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On 9/16/2022 at 6:07 PM, speedy_w_beans said:

...All gear diff cases across the DB/TRF family used metal cross pins and gears...

Hate to be that person - but TRF211XM aslo only comes with plastic gears (metal cross shafts though)!

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Everyone already beat me to the punch. Simple answer: DB01 double slipper and TA06 metal gears. Done , bulletproof and ready to give the new car rides fits.

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17 hours ago, BuggyGuy said:

Hate to be that person - but TRF211XM aslo only comes with plastic gears (metal cross shafts though)!

That's fair.  I wasn't thinking about 2WD TRF at the time.  I pulled all the manuals for 4WD, and I did make mistakes.

  • DB01 base:  37T ball diffs
  • DB01R:  37T ball diffs
  • DB01RR:  37T gear diffs, *BA25 metal cross pins, GV1/GV2 plastic gears*
  • DB01RRR: 39T gear diffs, *MA24 metal cross pins, GV1/GV2 plastic gears*
  • TRF501x:  *36T* ball diffs
  • TRF511:  37T ball diffs
  • TRF503:  39T gear diffs, BB12 metal cross pins, BB18/BB19 metal gears

Given the spec of the TRF503, I can't see anything to improve inside the diffs unless there's room for more shims on the spider gears to reduce lash.  Outside the diffs, maybe the DB01 double slipper will help *if it fits*.

Tamiya hasn't published all the manuals for all the flavors of TRF201/XM/XMW/211, so, another subject for another time I guess.  For reference, this is where I'm looking:  https://www.tamiya.com/english/rc/manuals.htm

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6 hours ago, speedy_w_beans said:

That's fair.  I wasn't thinking about 2WD TRF at the time.  I pulled all the manuals for 4WD, and I did make mistakes.

  • DB01 base:  37T ball diffs
  • DB01R:  37T ball diffs
  • DB01RR:  37T gear diffs, *BA25 metal cross pins, GV1/GV2 plastic gears*
  • DB01RRR: 39T gear diffs, *MA24 metal cross pins, GV1/GV2 plastic gears*
  • TRF501x:  *36T* ball diffs
  • TRF511:  37T ball diffs
  • TRF503:  39T gear diffs, BB12 metal cross pins, BB18/BB19 metal gears

Given the spec of the TRF503, I can't see anything to improve inside the diffs unless there's room for more shims on the spider gears to reduce lash.  Outside the diffs, maybe the DB01 double slipper will help *if it fits*.

Tamiya hasn't published all the manuals for all the flavors of TRF201/XM/XMW/211, so, another subject for another time I guess.  For reference, this is where I'm looking:  https://www.tamiya.com/english/rc/manuals.htm

Nice details, didn’t know the 503 had metal diff gears. IM running my 511 with the dual slipper. Just needs the 501 double slipper shaft to make it fit. Odd it wasn’t standard with the kit.

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