Blackfoot / Monster Beetle Thorp transmission

[squirrelnutz]

Hey guys, I recently purchased a Blackfoot off Ebay and it had a Thorp tranny in it. It's got the 48 pitch gears which makes it super quiet. I tried changing around different motors and found out that I cannot use a silver can or the black can motor because the shaft on the motor is shorter than the other stock or modified motors. I can't get the pinion gear out far enough to reach the entire spur gear. Not a big deal, I went with a Parma Cyclone II stock motor. Here's a picture of the diff.



I got 2 questions for you guys. 1.) on the axle shafts it uses two different kinds of wheel nuts. On the left side it uses the Tamiya metric nut and on the right side it has an Associated standard nut. I'm assuming there was two different versions and the guy who had this before me rebuilt or replaced one of them? Second question is: I installed this in my Monster Beetle and tested it with a Tamiya Avante 2011 motor. It works ok if I go easy on it but if I really come onto the throttle, the diff slips. I have turned the diff by hand and it feels pretty tight and smooth. I don't think it's worn out. Is it normal for it to slip like that? I have taken it apart and tried to make it slip by hand and I can't. When I put the truck on the ground and hold it from moving and give it full throttle, I can see the pinion and spur spinning while the tires are not moving.

I have since put the Cyclone stock motor in there and it doesn't slip as often (only once or twice). I also took the diff apart and re-grease it using Associated diff lube. I haven't tested it yet, I will do that tomorrow when everything is together again. Do you guys think the Avante 2011 motor was too much for it? I was hoping those Thorp diffs would be able to handle more...

[shodog]

That looks like a Robinson Racing instead of a thorp. You have to take one side of the diff apart to tighten it. While youre there you should just rebuild it with new ball diff grease. The axles may have been thorp but most of my axles use the 8/32 nut instead og a 5mm nut

[squirrelnutz]

I never knew Robinson Racing made a diff for the Blackfoot. I have taken the diff apart and re-greased everything with new Associated ball diff grease. Hopefully that fixes the slipping...

[RichieRich]

Yeah, that's a Robinson Racing unit. I would also suggest a thorough cleaning and relubing. I have the RR diff in one of my frogs and it works fantastic.

[squirrelnutz]

I have taken everything apart, cleaned and re-greased the diff. There was a 2mm washer in the thrust bearing that was completely shattered. I replaced it and put everything back together. It seems to be working good without any slipping. Thanks guys!