If you are beginning to take driving your TT01 seriously, this is an essential upgrade for any owner.
I personally have my TT01 setup for drifting, and the first hopup (upgrade) any drifter should buy IS THIS SOLID AXLE to replace the rear differential. It really makes a big difference to how your car drifts - the back end comes out much easier and mid drift control is really improved. The back end of your car doesn't suddenly get traction when you don't want it and you have lots more throttle control mid-drift with this fitted.
Don't bother messing up your existing diff by glueing it or gunging it up to 'lock' it - that doesn't make sense, ruins a perfectly good part and it not reliable! GET THIS PART INSTEAD and have a component you can rely on!
Also, for racers it would be advised that you replace the FRONT differential with one of these - MUCH better performance for cornering!
The part is well packaged (as always with 3Racing parts) and is very well made. What I like about this part is that you can easily and cheaply replace the main gear - RCMart sell then and they are VERY cheap! It makes me happy that I can get replacement parts for this so easily without having to replace the whole part - much cheaper in the future.
I had no problem fitting it - it was quick and easy and everything fitted perfectly. I just opened up the gearbox and replaced the differential with this.
PLEASE DO MAKE SURE you get the 3Racing (#TT01-01) Swing Shaft For Tamiya TT-01 part (as shown in the description) to go with this, the normal Tamiya dog bones don't fit so you have to use the swing shafts - which are also highly recommended!