Shimming A Frogs Differential.

[CR-01nut]

It has been recommended that the frogs diff should be "shimmed" so it will last longer and you can run a faster motor. But what is shimming and how do i do it?

Thanks in advance for any help.

[terry.sc]

The hard part is getting some useful shims. A shim is just a very thin piece of metal sheet, for the diff you need shim washers for the 5mm shafts on the diff output, Tamiyas are part number 53587 or shims from any other manufacturer.

Firstly see how much play there is in the diff with the gearbox out of the chassis by rocking the diff outputs. If there is some free play take one side of the gearbox off, put a shim on the axle of the diff output, so the shim ends up between the large bevel gear and the bearing, and reassemble the gearbox, making sure you tighten all the bolts up. See how much play there is in the diff, if there's still movement there add another shim. Keep on repeating until you have a very small amount of play in the diff gears, but not too tight that the diff feels stiff or notchy, which means you have too many shims in there.

Be aware that the shims come in 3 thicknesses. If there's a big gap you use the 0.3mm thick ones, then use the 0.2mm and 0.1mm shims to fine tune the shimming.

[HunterZero]

I just used Tamiya 5mm shims for my Frog. Worked great. As Terry said, they come in a set with .1mm, .2mm and .3mm thickness. Shim goes between the bearing, and the diff L/R large bevel gears. Should only need one shim for each side, depending how worn your diff is and how warped the gearbox sides are.

- James

[CR-01nut]

So are they going here where the red ring is? because I do not have the car with me at the mo. (sorry for all the dumb questions)

[DudeWalker]

Other side. The side facing the bearing.

[rc-martin]

You could always use oldfrogshot's method, i've been meaning to do this to my Wild One for ages.

oldfrogshots diff strengthening method

[Saito]

No. Putting a shim between the bevel gear and the diff gear where you have circled will actually add clearance, not tighten it up. You want to place the shims "behind" or on the backside of the large bevel gears (the ones that flank the diff gear assembly). Basically like Terry said, between the bevel gear and the side output bearing.

[CR-01nut]

ok i think i have this now. so its all about putting the shims in between the bearing and the bevel gear to push the bevel gear into the spider gears on the diff. (right?)

[CR-01nut]

Ok so had a quick rummage around in my tamiya parts box and I found these. Don't know if you can see in the first pic but they are 0.5cm in the middle!

Will these be ok?

[retroman]

I have a bit of an alternative method of doing this....... My vintage Frog had a bit of play in the diff, and I couldn't find any spare shims........ So, I removed the gearbox, took the internals out, re-assembled the empty casing, and gave it a gentle squeeze in my vice, with the aid of a couple of sockets. Worked a treat!!

[CR-01nut]

I was thinking about doing something similar to that, but my idea involves a little gentle persuasion (a hammer!).

[CR-01nut]

BUMP

Because I still do not know if the shims I found above are the right ones. Anyone know?

[HunterZero]

BUMP

Because I still do not know if the shims I found above are the right ones. Anyone know?

Yes, they'll work. To check, take off the front wheel and make sure they fit nicely over the front axle. The shaft diameters are the same.

However, you might find that after adding these, depending how much play there is in your diff, the diff might be too tight and not work smoothly afterwards. If that's the case, you need to try to get some .1mm or .2mm shims.

Note that the above suggestion of squeezing the gearbox plates back into shape will work for a while (I have done this), but after a few runs the gearbox plates will tend to flex themselves out again, if you're using a powerful motor, and you'll be back to square 1.

Tapping the diff with a screw or using shims are the most effective ways to keep the diff from slipping.

- James

[CR-01nut]

Ok cheers. i guessed squeezing the side would not last too long.

Are there any upgrade gearbox sides for the frog?

[retroman]

If you search for a thread called "Ghost Frog", I think in the vintage section, this Frog has Carbon Fibre gearbox side plates. It's one well cool looking Frog

[CR-01nut]

Cool, anyone know where he got them or how he made them? or shall i pm him?

[retroman]

I guess that you can probably make them yourself, by using your Frog gearbox side plates as a template for marking out the CF. Might need some mild mods to the chassis where the gearbox attaches though, as the CF side plates will effectively make the gearbox wider.

[CR-01nut]

Ok i do not want to have to cut bits off the chassis of a brand new car. is there any way of adding more strength to the normal ones? Or should tamiya of sorted this out when they re released it?

[terry.sc]

The carbon gearbox sides will be home made, there is no upgrade part for them. As for Tamiya sorting them, they never made any changes to them even when they used them in the monster trucks. Once the gearbox sides have stretched they tend to stay the same shape for a long time.

[CR-01nut]

cheers again terry will have a crack at making them myself

i have also heard rumors about the driveshafts popping out, how do i stop this?

[terry.sc]

The old school trick to stop the driveshafts popping out was to drill holes in the rear of the trailing arms and gearbox sides and running a tie wrap across them to stop the trailing arms spreading. The modern way is to install spacers under the pistons inside the shocks to limit the down travel of the arms.

The simplest solution is just don't open the throttle when the wheels are off the ground. They don't pop out when it's on the ground.

[CR-01nut]

The old school trick to stop the driveshafts popping out was to drill holes in the rear of the trailing arms and gearbox sides and running a tie wrap across them to stop the trailing arms spreading. The modern way is to install spacers under the pistons inside the shocks to limit the down travel of the arms.

The simplest solution is just don't open the throttle when the wheels are off the ground. They don't pop out when it's on the ground.

So if i drive carefully i do not have to worry about it. i will pop a spacer under the damper piston just in case though.

PS: Terry, did you know that you are the most helpful bloke in the whole world.

[kaiser]

cheers again terry will have a crack at making them myself

i have also heard rumors about the driveshafts popping out, how do i stop this?

you got the re-re right? i belive they changed the driveshafts to the "dog bone" style. they shouldn't pop out.

original frogs/blackfoots/ect... had hex shaped driveshafts. they were awfull. the new (re-re) driveshafts are much better.

[rc-martin]

you got the re-re right? i belive they changed the driveshafts to the "dog bone" style. they shouldn't pop out.

original frogs/blackfoots/ect... had hex shaped driveshafts. they were awfull. the new (re-re) driveshafts are much better.

Nope, the re,e's pop out just as good as the hex's. Or at least mine do!!

[kaiser]

really? why the heck did they bother with the dog bone if they still fall out? lol