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mongoose1983

Orig. Brat gearbox. Need advice from TCers with experience on it.

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Need advice from TCers with experience on the original Subaru Brat gearbox.

Spent last night rebuilding an original 1983 Brat chassis and could not solve this problem. I'm using the B5 parts (the white plastic cups that use no bearings) but for some reason there seems to be something missing in the build as they don't stand out of the gearbox completely. I've checked the building steps thrice before giving up. I am using all of the original parts and this time I feel frustrated. Was wondering if there are some TCers that would explain what's wrong with this.

I understand not many of you like the original non-differential gearbox (not that the one that comes with diff is a marvel, anyway) but I'm turning on to this just for the sake of originality, you know.

Here's some photos of the gearbox (notice the white plastic cups) and the manual that I followed step by step.

You all have a great Sunday! :)

DSCN3537_zps3a690347.jpg?t=1379190111

Bratgearboxprob_zpsf0453c35.jpg?t=137919

58038_006.jpg

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Erich, are you saying that if you install the f3 parts, there is a gap between f3 and B5 which allows it to shift from side to side?

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I will check my parts box - I may have enough parts to build up a standard Brat gearbox. If so, I can build one up and let you know if there is anything peculiar!

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Erich, are you saying that if you install the f3 parts, there is a gap between f3 and B5 which allows it to shift from side to side?

Hi mate! the problem is the white plastic cups not standing out completely, as it happens in the Frog's and nowadays ORV gearboxes. I mean, they have that tab to help them stay in place, but they seem to be needing some extra part that I can not seem to find out what it is, not even when following the manual online. They just get inside and the gearbox doesn't work properly. :(

Hi Grastens. Thanks, that would be awesome!

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There are only a few possible causes for the problem you describe.

The minimum distance between the B5 parts is determined by the width of the diff gear and e4 and the B5 parts themselves. That's it. If that width is less than the distance between the gearbox metal plate shaft holes, then the B5 parts will "push in" and lose their position.

So, the answer has to be one or more of the following:

1. The diff gear has been cut or worn down to be thinner than stock.

2. The e4 part that plugs into the diff gear has been cut shorter or worn down to be shorter than stock.

3. The B5 part(s) were cut or worn down in the inside part that touch the diff(right side) or e4 (left side).

4. The B5 part(s) were cut or worn down on the outside lip that touches the gearbox plates.

5. The gearbox plate(s) are bent or bowed outward from stock, allowing more space between them and thus the B5 parts don't stick out as far as they should and can lose position.

58038_006-cropped.jpg

Try this:

1. Take the gearbox apart.

2. Build the diff per the above picture. Measure the distance between the outer lips of the B5 parts (the part of B5 that touches the gearbox metal plates).

3. Put the gearbox plates back on, but don't install the diff gear from step 2. Measure the inside distance between the metal plates through the diff shaft holes.

If #3 is a few mm larger than #2, then that explains why B5 don't stick out like they should. Something's been worn or cut or bent.

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I'd say you have built it correctly. I've just compared to my New Build original, and that is the exact same. I think if you have a look inside the white parts you should see that the plastic inbuilt bearing is actually not as wide as the part if you put a bearing in.

uo9t.jpg

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I can confirm that Champ85 and Tipsy are correct, having today found enough components to build up a stock O.R.V. gearbox. I was unable to find the original B5 pieces, but came up with near-identical solutions using the B2 parts and offset plastic bearings to give the same dimensions as opposed to the ball bearings that are recommended for the B2 components.

The result is the same, with the pieces not fully extending to the gearbox halves. So long as they do remain stationary, though, they should be fine for regular use. As such, your gearbox should be in good shape!

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Thanks, Champ85 and Tipsy!

It's too late tonight and I've to spend the Sunday with the girlfriend tomorrow. I will dismantle the gearbox Monday night and then I'll come up with more photos and comments.

By the way, yes Tipsy, that's exactly what happens with the gearbox I have here. I don't know, but it should not be like that. I wonder if the Lancia has the same problem (?).

Thanks again for your help. Very appreciated. You guys have a great Sunday! :)

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Always happy to help if I can :)

The Lancia does have the same problem, since the two cars in stock form use the exact same components. My O.R.V. gearbox was in fact from Lancia parts, since I do not own a vintage Subaru Brat.

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Erich, can you add some washers or shims to help "push out" the B5 parts or does that cause undesirable binding?

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Erich, can you add some washers or shims to help "push out" the B5 parts or does that cause undesirable binding?

Can't deny it crossed my mind to try that. Just not sure how that would affect the functionality of the gearbox. I hope I have a minute to try that tonight. ;)

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I'd say you have built it correctly. I've just compared to my New Build original, and that is the exact same. I think if you have a look inside the white parts you should see that the plastic inbuilt bearing is actually not as wide as the part if you put a bearing in.

uo9t.jpg

I wanted to let you guys know that just today I solved this. There is no specific mention in the original manual about this issue, but if you use the white plastic cups that can carry bearings or nylon bushes the gearbox fits, looks, and works fine. So I have another reason to thank my good friend, blackfoot_dave. :)

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Nice that you figured this out. The gearbox has enough problems on its own without parts shifting side to side. So could this be considered a manual screw-up? I would guess thousands of Brats were built back in the day per the manual...'course there was no internet for people to complain about gearbox build problems back then.. just the LHS and the guy behind the counter.

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I think all these small imperfections are making our beloved collictibles complete at last. Isn't it? :)

I do have an original early Brat (with the narrow front bumper) and though it is new built out of the box, the gear and axles have extreme slope in all directions. However, that does not bother (me) because it is a Display model and I will not run her anyway.

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Ive never built a brat gearbox with the solid differential, but every monster beetle or blackfoot I have built has never had the problem.

Maybe the blackfoot differential spaces the bearing carriers out further.

They do wear badly due to the poor tolerance between them and the gearbox side plates. I only use my modifed MB as a runner and that has the yellow plastic CRP bearing carriers installed. They are a much tighter fit and take out all the slop in that area of the transmission :)

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The space is there to accommodate the use of the B2 part instead of B5 as stated in step #9 in the Brat manual. To be honest I've never used the B5 part, all ORV chassis cars with this gearbox came with both parts. Only the Brat & Lancia rally manuals show that you can use both, after that all ORV manuals says to use B2 & the B5 part is shaded out as not used but is still included.

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Well, when I built the gearbox I was shocked to find out there was something wrong, like this.

Anyway, last night I was replacing the rear axles and found out the Brat's cups doesn't have a hole in the middle to fit the small shaft that's in every other ORV based vehicle that came after 1983! :o

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Not sure what your problem was here. Tamiya gave you two options as per the manual above.

if you use the the spacers with no bearings they are quite a nice fit. However by the fact that no bearings are used wear does take place at a greater rate as such if using used parts you can have a lot of slop. I remember mine in the day and over time the gearbox became noisy due to this wear.

Even if you use the bearing carriers with ball racers they still induce wear between the ally plates and the b5 part.

from the first picture it looks like they might be a bit worn in comparison to tipsys pic.

By the way nowt wrong with the solid diff especially on sand !!!!!

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huh! i never realized that the original brat trans was so different from the frog, blackfoot, etc. don't think i've ever even seen the two-piece main (non-diff) gear before!

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