42310 Tamiya 37t Aluminium differential pulley Review

When Tamiya introduced the gear diff for the TRF419 the improved smooth operation improved lap times and consistency over a 5 minute race, it also was reliable and strong. However it was more prone to leaking than the earlier unit. So it was with great interest when I noticed that alongside the low friction aluminium front pulley Tamiya had also released a new aluminium differential pulley. I was intrigued to see what it could offer over the standard plastic pulley, so I promptly got one to test out.

Inside the packet you get the differential pulley and a spare gasket.

As you can see the quality of the machining is very good and the part is very well made. The pulley is coated with low friction fluorine coating which aims to increase the rotating efficiency.  

The outer ring is anodised for extra strength.

I popped the pulley on the scales and it weighs only 6g so it is about 3 grams heavier than the original plastic half.

I rebuilt one of the differentials to test this pulley. I always use the red o-rings, I find these are smooth and they also seem to hold off any oil from leaking from the out-drives. 

I assembled the differential with 2k oil. I run on a very tight circuit and whilst this does compromise the initial turn compared to the 5-6k that I like to run on slightly more open tracks it keeps the rear end nice and planted on some of the very tight sections.

I also apply a liberal amount of green slime on the gasket, O-Rings and also on the inner edge of the other diff half.

The new differential pulley fits on more tightly than the plastic part. It is still a smooth fit, but it is more snug. Once the screws are attached I then use a toothbrush to get rid of the excess grease and wipe the differential down.

You can see that the diameter of the outer ring on the new aluminium differential is smaller than the kit plastic part so it is a little lob-sided. It doesn't affect the performance as the belt is still kept nice and straight. 

As you would expect the aluminium differential pulley is the same width as the previous plastic part so installation is just as normal with no shims needed.

I have been using this pulley for several weeks and I can honestly say that I do not really notice any difference in how the car behaves or feels. The negligible extra weight doesn't make any difference in the rotating mass, so there is no effect in the way that the TRF419X pulls out of the corners. Although I am currently running 13.5 blinky so it may be more pronounced with 17,5 or 21.5.

The diff itself has stayed leak free from the main pulley. although again I never really had issue with that before. From a maintenance point of view, the pulley fitting is really snug, so it is quite stiff to actually separate when you are changing oil.

I have been on a local club winning streak since the diff pulley was fitted, although I think it is just because of other factors such as warming up my diff before a race. So overall I would not say that it is an essential hop-up unlike the Tamiya 42309 37T front one way pulley which made a tangible difference in they way the car felt in the corners.