Lunch Box gears

[Jim24 3]

Hello again,

You may have seen my last post trying to get my "new" used Lunchbox running because it had battery and receiver issues.  Well, after finally getting the radio and receiver worked out, an ESC, and having to order a new servo saver because the new servo was a different size, I finally got it out and ran her for the first time about 10 minutes ago.  Well, she ran great for about 2 minutes and then I got stuck on an obstacle in the yard (the trampoline support pole).  Freed her up and hit the throttle and all I got was a buzz.  I gave her a push and she ran and if you lift her up she goes but any amount of torque causes her gears to slip.  I have not taken the gearbox apart yet but I am guessing the old gears are either out of mesh or are stripped/stripping.  I will be taking it apart later or this weekend.

So, here is my question...  Is there a recommendation for an upgrade that isn't too expensive or do I just buy a new set of Tamiya gears off eBay for $7-10 bucks.  So far I have owned this for 2 weeks and have gotten 2 minutes of run time.

Also, the front end is SO sloppy she is bouncing all over.  I have read all about these needing better shocks, I will take recommendations on these too.

Thanks!

[berman 5317]

More than likely the little grub screw that holds the brass pinion gear on has backed out. Disconnect the motor, take the motor out, (two screws) and the two screws that hold the plastic motor plate on, then make sure the grub screw is on the flat part of the motor shaft, and tighten it up with the allen key/wrench and slot it back together.

Not much goes wrong with the gears unless the are built incorrectly, it is a pretty robust gearbox.

Yes the Tamiya CVA shock upgrade will make it handle a bit better. The U shaped mounting plates should be in the left over spares in your lunchbox kit.

[waterbok 1282]

+1 on the pinion the gears are practically indestructible.

[Jim24 3]

2 hours ago, berman said:

More than likely the little grub screw that holds the brass pinion gear on has backed out. Disconnect the motor, take the motor out, (two screws) and the two screws that hold the plastic motor plate on, then make sure the grub screw is on the flat part of the motor shaft, and tighten it up with the allen key/wrench and slot it back together.

Not much goes wrong with the gears unless the are built incorrectly, it is a pretty robust gearbox.

Yes the Tamiya CVA shock upgrade will make it handle a bit better. The U shaped mounting plates should be in the left over spares in your lunchbox kit.

Ok, great.  I was reading a bit on this after posting and that grub screw seemed to be a common issue.  As far as the shocks, I will look at those but I will have to find some of the U shaped mounting plates since I bought this used and don't have any additional parts.  Thanks guys!

[Jim24 3]

Ok guys, I had the entire gearbox apart checking everything and checked the grub screw. I couldn't see any chipped teeth or anything else wrong. Put it all back together and tried running it and it ran ok for a minute.  Then the grinding came back. If I run it at very low throttle there is no noise and the van moves normal. As soon as you "gas it" it moves slow and has the grinding sound. If I keep trying it eventually doesn't go at all except under very lite throttle.

there is no noise when you manually turn the wheels there is no grinding and the diff is working right as the wheels turn opposite as they are supposed to. 

Any chance this is a failing motor??

[StrokerBoy 772]

It's maybe not the case here, but one very common cause of 'lack of go' with Lunchboxes is the rear wheels spinning inside the tyres.  Superglue is your friend.

[Macinnis 226]

5 hours ago, StrokerBoy said:

It's maybe not the case here, but one very common cause of 'lack of go' with Lunchboxes is the rear wheels spinning inside the tyres.  Superglue is your friend.

Put rubber bands up between the rim and tire on the edges 

[Jim24 3]

6 hours ago, StrokerBoy said:

It's maybe not the case here, but one very common cause of 'lack of go' with Lunchboxes is the rear wheels spinning inside the tyres.  Superglue is your friend.

I will take a close look at that later. I'm also planning on pulling the motor off out Pumpkin and putting it in the lunchbox just to be sure. If it's neither of these then I guess it's onto buying a bag-o-gears and rebuilding it!😣

[berman 5317]

There is a little spacer that goes over the axle shaft on one side before you put it through the gearbox, have you made sure it is on there? Otherwise the diff bevel tries to move away and rubs against the counter gear causing it to slip.

 

[berman 5317]

Also make sure the diff carrier pin is there:

 

[Jim24 3]

9 hours ago, StrokerBoy said:

1 hour ago, berman said:

Also make sure the diff carrier pin is there:

 

Took it all apart and found two things. One, that diff carrier pin IS missing.  And I found one of my rear axle holders was broken at one of the screw points.. this lunchie is giving me fits!

 

[iluvmud 812]

well.......... if you decide to part with it...................................................................................... ill take it

[leeroy33 17]

This may sound silly, but when I first assembled mine and test drove it after about 20 minutes I lost drive and could only hear a grinding noise. Fearing the worst I thought gearbox, turns out the nut that holds the rear wheel had loosened and was slipping at the hub. This happened a couple times.

[Jim24 3]

9 hours ago, leeroy33 said:

This may sound silly, but when I first assembled mine and test drove it after about 20 minutes I lost drive and could only hear a grinding noise. Fearing the worst I thought gearbox, turns out the nut that holds the rear wheel had loosened and was slipping at the hub. This happened a couple times.

Yessir, someone mentioned that and I tested those waters and the wheels were fine on the rims and hubs.  After taking a real close look inside, the diff pin is missing and at some point one of the rear axle carriers broke in the mount.  Looks like the screw just split it.  So now Im searching for a diff pin and a D-parts tree.  However, its going to have to wait until after payday.  This hobby has sucked my funds dry in no time!

[iluvmud 812]

On 1/30/2017 at 2:51 PM, Jim24 said:

This hobby has sucked my funds dry in no time!

Welcome to the club!!

[racer1 117]

It's extremely unusual for one of these gear boxes to fail if built correctly.  As other have stated. Ensure the spacer is in place on the Left (when viewing from the rear) side of the gearbox.  From there I would look at the screws that hold the gearbox together. It's very easy to over tighten these and once stripped there is little you can do other than going to a longer screw an nut combo.  Beyond that I would make sure that the screws that hold the adapter plate to the motor are tight and then ensure that the motor is tight in the gearbox.  Lastly you need to check that the rear wheels are installed correctly and key into the hubs and that the Wheel nuts are on tight. 

 

[Jim24 3]

Update...Well, after waiting for a new rear axle mount to come from one person and the diff pin from another and then finding time to put it all together (just now)...fail...

Still works under light load but as soon as you gas it, it grinds and moves only slightly faster.  SOOOOOO, I took it all apart again and examined everything even closer, even taking the axles completely out this time.  Noticed something I had not seen before on the axle gear on one side...cracks in the plastic on the ring around the axle nut.  I had not seen these before but I think under pressure of full throttle the cracks expand and cause that side to not mesh properly with the diff.  I cant see ANYTHING else as the teeth all look fine.  So, a bag of gears with new axles has been ordered, should be here Saturday...hopefully this is the end and I will actually get a run out of her...

[Jim24 3]

Update: She runs.  I put in all new gears since I bought the whole bag.  She runs like a champ now, no grinding.  I guess that cracked axle gear was the problem all along.  Now its onto upgrades.  Appears shocks and chassis braces are the first necessities for both this and my wife's midnight pumpkin!

[berman 5317]

I would look into Ampros body mounts for the MP, and some alloy ones for the LB, and maybe Ampros gearbox pivot if you are that way inclined.

[VagabondStarJXF 350]

I've got some chassis braces for both Lunchbox and Pumpkin ready to print via Shapeways if you're looking!  (I hate self promoting my stuff but I gotta pay for my next Tamiya fix somehow!  )

[Terz1 745]

They look great vagabond. 

[VagabondStarJXF 350]

52 minutes ago, Terz1 said:

They look great vagabond. 

Thanks.  

[Jim24 3]

On ‎2‎/‎18‎/‎2017 at 5:50 AM, VagabondStarJXF said:

I've got some chassis braces for both Lunchbox and Pumpkin ready to print via Shapeways if you're looking!  (I hate self promoting my stuff but I gotta pay for my next Tamiya fix somehow!  )

I have actually looked at the 3rd shock replacement brace you have and I am planning on getting it for both units.  But I have to save up for front shocks for the Lunchie first, this thing bounces around like its on a trampoline and wont even turn if you are on the throttle at all!  This used Lunchie I bought is bone stock and now older and really in need of upgrading.  The MP handles much better and most of that is because the front shocks are actually still working, the Lunchie is just a pogo stick!  But I will be looking at braces too!

[VagabondStarJXF 350]

While the chassis braces are mine the trans brace is not by me but by AMPro who is Pintopower on here. (I wish I could take credit for it ). I've got one of them on my Pumpkin. It fits really well. I haven't finished the build so I haven't had a chance to test it yet.