Monster Beetle gearbox oddities

[Davecul]

Hi All

Got an MB this week via eBay, really pleased with the overall condition and will be going in the showroom later.

That said...

It was supplied "RTR" with a battery, controller etc. So feeling confident I charged the battery and tried to have a "drive" indoors as it was a bit wet out.

It goes and stops and steers, all quite nice.

However, if you give it full acceleration it just makes a funny noise and doesn't really accelerate.

I know the MB has gearbox issues but I couldn't find anything that exactly matched my symptoms. I took the gearbox to bits last night, it all looks virtually brand new, no missing teeth on either the main or counter gears and the metal differential and bevel gears look perfect. The plastic gears are marked as "Blackfoot" but I think I've read that they use the same gearbox so this shouldn't be a problem? I put it all back together and done all the screws up as tight as was reasonable, but it's no better than it was.

The drive shaft Hex's look fine and not worn down, which I know is another problem they can have.

Anyway, any advice on how to fix it or what's wrong?

Thanks,

Dave

[tonysmini]

Have you checked that the pinion is meshing correctly with the spur gear? I got a TB01 that used to drive around fine until you gave it full beans then the pinion would jump across the spur gear, even though it was on the right sized hole in the motor mount.

[Panther]

The problems I've had with my Blackfoot gearbox are as follows:

-Worn pinion gear starting to slip which was replaced

-Worn bushes in the gearbox which are now replaced with bearings causing the gears to move around and slip

-The diff was causing the side plates of the gearbox to flex and allow the diff gears to slip so there's now a screw holding that together

-Worn wheel axle bushes allowing the axles to slop around and the drive shafts to slip; now changed to bearings

Try those things first. The next problem I think may be too much play in the rear swing arm joints which will then cause the drive shafts to start slipping again. I think I may mount the rear swingarm on bearings once that happens.

Also as Tony says, check your pinion gear is meshing properly.

[roadog1aj]

I agree with the above posts, and definitely recommend rebuilding the gearbox, and installing bearings. Plus the extra screw installed as Panther suggests will take care of the known issue with plates flexing enough to allow the gears to slip. You can still get everything you need to build a new gearbox for decent prices. I just did a resto of a Monster Beetle and was able to do a complete gearbox, and swing arms. I just wish the adjustable motor mount could still be had.

[spac51]

Take a close look at the shape of the teeth on the metal side gears for the diff,they have a tendancy to wear quickly and cause slipping,normally this shows up as good drive in reverse,but noise going fwd.