3Racing Tamiya TT02 Gear Differential Review

The TT-02 is a popular first time racer for many, one of the things that it is missing for those who are tuning the chassis at the race ...

The TT-02 is a popular first time racer for many, one of the things that it is missing for those who are tuning the chassis at the race track is a sealed gear differential. Recently I noticed that 3Racing had released a gear differential for the TT-02. I have some plans for racing the TT02 type S this year in some classes, so I thought I would take a closer look.

What version of Differential do I need?

Before ordering one for your Tamiya. 3Racing make two different versions of the gear differential. 
  • Part no TT02-10 is made for Standard TT02 with the fat plastic drive shafts (Std TT02's)
  • Part no TT02-09 is for anyone that runs the metal drive shafts or univesals (Including TT02R and TT02 Type S) *Note you will need drive shaft cushions for the dogbones. 
For this article I am building the differential for my TT-02 TypeS so I ordered part no TT02-09.

Building the Differential.

Looking in the packet all of the parts seem to be very well made. 

The plastic is chunky and the differential joints seem to be made from spring steel.

The first differential joint is mounted though the 39t main TT02 gear. I doused the 5mm o-ring with some shock oil to ensure it doesn't snag. 

Once through you can add the large shim and the retaining pin.

Now its time to do the other side, same procedure as before, it helps to have a pair of tweezers to insert the pin

Now fit the 18t bevel gear. They are a chunky 0.8 pitch but make sure you trim any excess off the sprue, otherwise they can damage the gears and the diff will not run smoothly. At this stage you want to add some of the oil to ensure that there are no bubbles trapped.

Now its time for the main 10t bevel gears. They are mounted on a plastic cross joint, I know some would rather this be steel or alloy but I think it should be fine with the stock motor that I will be racing with. (13.5 blinky). With the bevels mounted you fit the shims behind them and lower the completed section into the differential.

Now add more of the differential oil (I used 3k oil). You want to do this until the oil covers the centre cross joint, not any more as that will be too much and you will get the differential weeping as it will over filled. 

The next stage involves fitting the gasket. The actual gasket is quite large and I needed to spend a bit of time to prepare it to actually fit well. I took my time to remove the screw holes so I didn't tear it. The gasket is also a little larger than the actual recess that is on the gear, so to make it more seated I inserted the screws to hold it in place and tucked it in with a pair of tweezers. 

Now you just need to fit the two halves of the differential together. The kit screws have 2.6mm width screws with 1.5mm hex heads, this normally wouldn't be much of an issue but the plastic is very hard so you will find it a pain to assemble, a dab of grease helped but it was a pain. Again make sure the two halves are straight and attach the screws in a cross pattern to ensure that they go together nice and straight. 

The final diff was assembled and it actually felt pretty good, a little stiffer than what I would expect for 3K but I am sure that it will be fine after a gentle run in. I must also mention that the differential comes with a spare gear for the prop shaft. I decided to use this as even though it is the same as the Tamiya one, 3Racing may have a slightly different tooth profile on their bevels so it made more sense to use that. 

The final differential with oil weighs just 23.1g that is only around 2g more than a stock TT02 differential, and 17g lighter than the fat old TT02 differential.

Track test

I've given the TT02 type S a few runs now and the gear differential has been spot on.  The handling of the chassis is much more consistent than the stock differential with AW grease. Head to head with the ball differential it is also better as there is more bite from the gear differential. 

Post racing I have also noticed that there is no leakages from the unit. I swapped out to 5k as I wanted more on power steering and the effect was immediate. 


For those who are trying to get a little more serious with racing their TT02 chassis this is a great hop up. After around 12 runs the differential still feels smooth and I haven't had any failures. It is much easier to tune than any of the other alternatives out there.

Note it should also fit in a TT01 chassis as the TT02 and TT01 differentials are interchangeable. 
TT02 6104072446131980986

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