Hot Racing Steel Helical Spiral Gear Set w/Aluminum Cover Plate for Traxxas 1/16

This is a great gear set for the 1/16 erevo vxl. I have not broken this one like the stock diff and it also gives me a little more speed and torque. I highly recommend this product regardless of the price it is worth every penny.

There's a lot to say about these diffs. I'll break it down between good and bad, but first, here's the problem with the stock diffs: Problem: The stock Traxxas diff housing/ring gear is made out of crappy sintered metal that is very weak. Also, whatever mold/die Traxxas uses for their gears creates a slight seam along the edge and across the teeth that is so small and slight that it cannot be seen, only felt. This seam causes a deformation in the shape of the gear teeth that results in a VERY noticeable "tight" spot in the gear mesh. To eliminate this tight spot, one must shim the differential gear mesh far looser than is ideal for the other 95% of the gear teeth. Obviously, this is not great. Here's where the Hot Racing diffs step in.... The good: 1) These are undeniably stronger and more precisely manufactured than the stock Traxxas diffs. Actually CNC machined and hardened steel gears are going to blow sintered gears out of the water all day. 2) Because they are CNC machined, shimming is a breeze and you can get a very close, consistent mesh every time with these diffs. 3) Once assembled, they install well and run very smooth. The helical teeth are quiet and should last a very long time with proper shimming. The bad: 1) These diffs do not provide any way to incorporate o-rings into the case. You can use the output shaft o-rings, but fluid will still leak at the seams where the case pieces meet. I solved this by using a q-tip to "paint" a thin layer of RTV silicone on the mating surfaces of the round carrier barrel before assembling. This should seal it up well, but HR could have EASILY slightly changed the design to incorporate an o-ring just like the Traxxas version does. 2) The output shaft o-ring bore on the non-ring gear side fits the o-ring well and should seal up great. The o-ring bore on the ring gear is machined way too big and fluid will likely leak from this side. There's nothing you can do about this. Oh well. 3) The three screws that you use to bolt the whole assembly together are immersed in the diff fluid. The design of the middle barrel could have easily been slightly changed the make the screw holes separated to isolate the screws from the diff fluid. This is a problem because you need to use threadlocker on the screws to ensure that they stay tight over time. Well as soon as you put the screw in, it will get covered in diff oil and the threadlocker will not work. Threads have to be clean and dry. 4) Because of the reasons mentioned above, the proper assembly of these diff units is by far the most meticulous, time-demanding diff I have EVER assembled. I hope they last a long time, because I don't want to rebuild them ever again. I had to do all sorts of weird steps to get the case sealed, then to fill it, and then to get screws installed in clean, dry holes with threadlocker on them. Very annoying and completely avoidable with some minor design changes. 5) Once built, one diff feels AMAZING. The other diff feels like the internal gears are packed too tight. Since you have to use the internal gears from the Traxxas diffs, I pulled the used set from mine to build these. Maybe the not-so-smooth diff is because my internal gears are getting really worn out, or maybe the machining tolerances on the HR parts have pushed the gears in too closely on one of the diffs. Only time will tell for sure. I'm hoping whatever tightness is there will wear out over time without destroying the gears. And after the huge PITA that is was to get them assembled properly, I'm inclined to run the truck and see what happens. Takeaway: Like a lot of Hot Racing products, these could have been very easily much better, but they just kinda fell short of the mark. Overall, I think they will serve me well after I went the extra mile to get the most out of them. If I experience any catastrophic failures over time, I will try to remember to update this review. I do give Hot Racing some credit though. Their customer service recently (October 2025) has improved dramatically. As always, Amain is great

Amazing differentials for the 1/16 E-Revo VXL. The stock diffs would strip out after about 2 days of 3s LiHV racing. These diffs have not stripped or clicked at all. They are extremely quiet and fit perfectly into the Traxxas case. They are on the expensive side, but you get what you pay for. They are built differently than the stock differentials, but I figured it out and they work as expected. Update: This differential somehow survived smashing into a curb at 50+mph. My transmitter spring broke, and my throttle didn’t return to zero, and my souped up mini E-Revo smashed into a curb at 52mph. All it broke was my plastic center driveshaft…..no clicking though. Buy this, you won’t regret it!