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Dr_GN

Frog Gearbox Grease / Rapid Wear Issue

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All,

I've recently rebuilt and started running my 1984 Frog. It still has all its original gears. When I stripped it, the gears looked in very good condition, with the exception of the motor pinion which was slightly worn in terms of tooth thinning.

Since I've rebuilt it, I've had issues with the gears randomly locking when I turn the back wheels. It's like there's debris in there, but when stripped down, there's nothing solid and large enough to cause an issue that washes out. There is a sound like gears skipping when I run it. I also noticed when dismantling, that the 18T original brass gear is now very worn, in terms of tooth thinning. There's a thin coating of brass contaminated grease spray in the vicinity as well. I've never noticed this before. I suppose the grease/brass particle mix has made an effective grinding paste.

I get the impression that the gearbox has worn rapidly since I started running the car again (only been run for about 6 times, about 20 mins per run). The wear seems totally disproportionate to that from the years I ran it back in the '80's. The only difference is that now I'm using Tamiya ceramic grease.

I've ordered a new 18T pinion (no aluminium not brass) and will try again. I'm a bit confused about the best grease to use, the ceramic seems recommended for plastic gears, and I think Lithium for metal, but the Frog gearbox has both plastic and metal gears...

Any advice? Thanks.

 

 

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What you are describing is a common issue with the Frog gearbox. When under load, the transmission side plates tend to bow out which causes the diff to skip. Sometimes, it locks up too. The only way to really solve the problem is to put in a ball diff. Otherwise, I suggest installing a new set of gears, including a steel pinion gear and lightly lubricate with ceramic grease. I believe Tamiya recommends ceramic grease on gears unless they are diff gears, then they suggest using anti-wear grease.

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51 minutes ago, RichieRich said:

What you are describing is a common issue with the Frog gearbox. When under load, the transmission side plates tend to bow out which causes the diff to skip. Sometimes, it locks up too. The only way to really solve the problem is to put in a ball diff. Otherwise, I suggest installing a new set of gears, including a steel pinion gear and lightly lubricate with ceramic grease. I believe Tamiya recommends ceramic grease on gears unless they are diff gears, then they suggest using anti-wear grease.

OK thanks. Where’s the best place to get a ball diff? And what type of grease is anti-wear?

cheers.

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I doubt you are using the original battery from 1984, either.  Back then 1200mAh was the norm for sub-c pack.  Now you have 1600mAh to 5500mAh NiMH or LiPo packs that can deliver a LOT more punch than the 1200mAh NiCds.  If you are using the original MSC, then the instantaneous power hit to the motor when you hit the throttle really does a number on the gears and diff.  If that is the case, you might consider getting an ESC to replace the MSC.

As for the ball diff, the MIP part #16210 Super Ball Diff for Tamiya Blackfoot / Monster Beetle / Subaru Brat / The Frog is what you want.  Your local hobby shop may have it or can order it, or you can search eBay for "mip 16210" or if you have a favorite online shop try searching there.  It costs US $64 which is quite expensive, but really does fix the problem.

Tamiya Ceramic grease (white) is good stuff and not the cause of the wear.  Keep using it on plastic to plastic gears, and plastic to metal gears and plastic gear diffs.  Use Tamiya Molybdenum grease (black) for metal to metal gears and metal gear diffs (looser).  Use Tamiya anti-wear grease (grey, very thick/sticky) for metal gear diffs (tighter).  Use only ball diff grease in ball diffs.

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3 hours ago, Champ85 said:

I doubt you are using the original battery from 1984, either.  Back then 1200mAh was the norm for sub-c pack.  Now you have 1600mAh to 5500mAh NiMH or LiPo packs that can deliver a LOT more punch than the 1200mAh NiCds.  If you are using the original MSC, then the instantaneous power hit to the motor when you hit the throttle really does a number on the gears and diff.  If that is the case, you might consider getting an ESC to replace the MSC.

As for the ball diff, the MIP part #16210 Super Ball Diff for Tamiya Blackfoot / Monster Beetle / Subaru Brat / The Frog is what you want.  Your local hobby shop may have it or can order it, or you can search eBay for "mip 16210" or if you have a favorite online shop try searching there.  It costs US $64 which is quite expensive, but really does fix the problem.

Tamiya Ceramic grease (white) is good stuff and not the cause of the wear.  Keep using it on plastic to plastic gears, and plastic to metal gears and plastic gear diffs.  Use Tamiya Molybdenum grease (black) for metal to metal gears and metal gear diffs (looser).  Use Tamiya anti-wear grease (grey, very thick/sticky) for metal gear diffs (tighter).  Use only ball diff grease in ball diffs.

OK great. I am using an ESC.

Do I also need to change from the hexagonal dog-bones to the newer pin driveshafts With that diff?
Thanks.

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7 hours ago, Dr_GN said:

Do I also need to change from the hexagonal dog-bones to the newer pin driveshafts With that diff?
Thanks.

The newer driveshaft system still has it's own problems, shafts dropping out etc.  - discussed on here many times . The hex shafts will work fine as long as your rear arms don't drop too far and cause binding in the cups . I only ever use hex shafts in my hex system models and limit the drop of the arms with a spacer inside the damper body under the damper piston , this also works on other hex system cars like Wild One etc

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I rebuilt my OG Frog about 5 years ago and have been tweaking it since.  I’m on my third Frog build now (my buddy’s OG Frog).  These are my recommendations:

1) rebuild your OG Frog and put it a shelf.  Never touch it. Don’t even look at it. Buy a ReRe kit and run that instead with no fear and no regrets...

2) if you must drive your OG Frog, buy NIB vintage parts and replace all the innards of your OG tranny.  You can do the same with ReRe parts for cheaper, but you lose the Vintage Factor.

3) buy a tranny side plate brace system. This is a cheap and effective way to solve the “flex” issue with the tranny.  Solving this issue takes care of many of the problems with the design of the tranny.

4) buy the Frog dog bone set.  The hex bones have been replaced with dog bones with the ReRe so the hex bones are hard to find and generally expensive.  And the dog bones don’t wear out as quickly.  See above about buying a ReRe.

5) if you have the OG rear shocks you should be fine.  But if you have replaced them, be aware that too much droop at the rear can cause problems like excessive vibration or the dog bones falling out.

6) Robinson steel pinion. Do some research so you get the right pitch, etc.

7) you may be tempted to install a more powerful motor, but I would shy away from anything more powerful than a Speed Tuned.

All this is just my opinion...  YMMV...

Terry

 

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And to answer your first question, use the grease Tamiya recommends in the manual, or try a nice thick diff lube.  Since the gears are “open”, the grease will fly out (as you have seen), so don’t use too much. Assuming you replace the gears, once the gears get a few drives to break them in, rebuild your tranny with new grease (clean out the old - toothbrush is great for this).

Terry

 

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@Frog Jumper LOL, I did the same thing you mentioned. I rebuilt the OG Frog and put it on a shelf. Then I bought another beat up OG frog for peanuts and rebuilt that with period correct hop-ups. Then put it on a shelf. :D I finally got a re-release Frog and that's what I actually drive.

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