Got my Big Brute Running Again! But Gearbox Still Having Binding Issues.....

[Snaab9-2]

I haven't been on here in over 5 years.... but I am back! Thanks again for all of the help in the past.

Last night I figured I would give my Big Brute one last attempt at fixing it. I had purchased bearings about 5 years ago but had got so frustrated with the gear box being bound up and having given it 2 or 3 attempts to fix it (and having my 2nd kid took up a lot of time) and as I couldn't see anything wrong, I gave up and just let it sit. It was a shame as I had researched a lot and got new tires and wheels for it and was otherwise ready to run it!

Last night I gave it a final shot and got the bearings installed in the trans and it was nice pretty nice and smooth (big improvement anyway). This morning I put the motor in and everything was good until I tightened the motor where it bound up! I was so frustrated but kept fooling with it, finally figured out the problem is the 2 engine mount bolts and was able to just barely snug up the motor mount bolts (which compress the 2 sides of the gearbox clamshell) and put a little blue thread locker on the screw threads and it only had a very slight binding. I figured I would just run it even though it may have been a risk to the gear box.

Well, it ran pretty good (videos below) for not having run for almost 30 years and the 15 turn motor seems perfect! Those platinum shocks still work great and keep it buttoned down pretty good (they are bouncy as heck on the stock "shocks"). It is pretty quick but hopefully not too quick for the gear box. A few videos are posted below. The new tires don't look quite as cool as the original ones but the track and handle better for sure (and are lighter). The best part is that instead of having less than a minute of solid run time and 2 or 3 mins of slow running, it ran great for like 10 min and may have had a lot more juice in it (I didn't check to see how much charge is in it and the alarm didn't go off).

Anyone have any ideas how to keep the gearbox from binding up? I feel like it needs something in there to provide like 1 mm more space on the end with the motor. IDK if I could use some JB weld and put something really thin in the trans to space it (maybe under one of the metal cross pins or what. If I can get that buttoned down may look into tightening up the slop in the rear axles.... it is a mess with lots of play. Thanks!

https://youtu.be/3Y9j3bE1waw

https://youtu.be/7wkVeCayVEU

https://youtu.be/it_VQTkzTeg

[jwscab]

Hard to say without seeing a picture but some transmissions that have through holes for motor mounting have a boss or post inside to keep the halves from squishing. You could add some tubes through where the screws go. epoxy them in place on one half.

[juicedcoupe]

Looking at the manual, it doesn't look like it has any support across the motor mounting screws. I want to say that my Bandido (basically an Icarus) uses a similar design transmission and isn't supported there either.

Can the motor be attached to the gearbox half from inside, with short screws? Then finish assembling it?

[Snaab9-2]

Hard to say without seeing a picture but some transmissions that have through holes for motor mounting have a boss or post inside to keep the halves from squishing. You could add some tubes through where the screws go. epoxy them in place on one half.

Interesting idea. I guess I would then cut them slightly longer than the width of the gearbox to take the stress off the clam shell of the gearbox. Any idea where I would find tubes like that?

[Snaab9-2]

Looking at the manual, it doesn't look like it has any support across the motor mounting screws. I want to say that my Bandido (basically an Icarus) uses a similar design transmission and isn't supported there either.

Can the motor be attached to the gearbox half from inside, with short screws? Then finish assembling it?

IDK, I worry that it would lose the clamping of the mounting bolts.... I will have to think that one through. Thanks!

[jwscab]

Lots of hobby shops carry brass and aluminum tubing from k&s. Or a small piece of brake line, or any type of home improvement center with a hardware section might have standoffs that you can trim to fit

[coxbros1]

question from Nitro Brute thread:

The trannys are quite a bit different on my Nitro Brute vs your Big Brute. Yours just has a pinion gear/counter gear/differential gear. Mine has the input shaft coming in the back with a ring/pinion setup changing the direction of the gearing....big difference. I dont see anywhere those shims will work in yours. your best bet is to do like ole boy stated above and put those collars in place before the two halves of the case go together. 25mm long might be a good statting point. I highlighted in red where they go:

As far as that slop in the rear end, the manual calls for both rod ends like i have:

For anyone confused some questions were asked on my Nitro Brute thread

[Snaab9-2]

Thanks guys

I though I toasted the trans today... my son was driving it in the snow and it was slipping a lot.... long story short I never glued the tires and they were slipping on the tires!!! Thank goodness! I took the whole transmission off the car and was getting ready to take it apart when I thought to hook the battery back up to the motor and give it some throttle to see if I could see the pinion slipping. The gearbox was tight! It was the stupid tires that came off the beed. Oh well… I keep learning!

The trans seems to be pretty OK now with me barely tightening up the screws and using some loctite

https://youtu.be/3Emet3Xybgo

[Lowgear]

I have an old CAD file for a plate that goes between the motor and gearbox. I'm wondering if it was designed to fix this particular problem. I can't remember the details but 15+ years ago I bought some prototype parts off a guy who also included the file for me to have them manufactured. I never did, but recently found the file.

[sgirouard]

I used to have a usa-1 and had the same issue. It was really frustrating. What I ended up doing was to get metal tubes and used them as a support tubes for the motor mount screws inside the tranny case. I JB welded the tubes to one side. It took away the flex in the case I wish I could remember the dimensions but it's been a while.

[Snaab9-2]

Made a few videos of it running today..... it seems like it is running good (hopefully not excessive wear.... I don't want to open it back up as I have just barely snugged down and used thread locker to allow it to stay nice and loose).

Video:

https://youtu.be/kk87DeC9uE8

[Rider400]

That looks like a fun truck. Dig that body.