Gear Reduction Unit

[HCCrawler]

Hello: I have an HPI GRU and the 16 tooth pinion does not seem to fit with the GRU. It fits when I use the motor mount and the 16 tooth, but not when the motor mount and pinion are attached to the GRU. I can't figure out what the problem is. The mount is in the correct holes for the 16 tooth, but does not mesh! With a 50 or 55 turn motor and the 16 tooth, without the GRU, is the GRU really needed? I plan to use 1.9 tires on the rig. Thanks

[canadianbacon]

I haven't used a GRU, but to answer the second part of your question, a 55t motor will work, but it'll still be sort of fast. I have one in mine, and it's faster than walking pace that's for sure at full throttle, but I still have decent low end control. Most people, if they don't use a GRU, go to like a 65t or higher motor. Since they're easy to change in these trucks, just try it out to see if you like it, you might be surprised.

[OSRC]

Probably not sitting flush. using the HPI GRU requires a bit of chassis trimming along the bottom to seat all the way.

[Jeepiac]

Several videos on youtube of people installing the GRU in their CC01's. I just installed one in mine last week. Some carving required, but the results are awesome. With 1.9 Trepadors, 16 tooth pinion and a 27T motor it runs at a normal walking pace and will eat every gear in the transmission without even thinking about bogging.

[Jeepiac]

https://www.youtube.com/watch?v=6EwNKWSdTKg

This may help with getting the GRU installed.

[HCCrawler]

Thanks to all!