Tamiya transmission fix with photos.

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John Glover
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Tamiya transmission fix with photos.

Post by John Glover »

This article refers to the latest Tamiya transmissions/gearbox with the black plastic covers and is not for the required for the Pershing.I was disappointed to read of all the failures of these gearboxes when looking at them they looked well engineered so i did some research. Buy E.T.O gearboxes if you are into battling but i am not and just wanted reliability out of the stock units. First Google [ Tamiya King Tiger RC 1/16 Tank Gearbox Problem] and watch video He has installed Daryl Turners gearbox brace plus Schumo axle support bearings and still failure. Final drive gear is the culprit. Then I found this old add with a great two page article with a fix for this problem .Google [Daryls tank upgrade parts-Custom RC models.]Go down column to ALL Bronze bushing rework and read both pages. Final drive gear is the culprit. Daryl no longer produces these parts so do not ask as he does not have time and has long moved on and uses E.T.O gearboxes. I looked at my brand new Tamiya gearboxes and one was not to bad but the other had more wobble in the final drive gear than it should have when moving it with my finger. Time to find a replacement bush and carry out the modification that Daryl used to do. After searching I found [ Traxxas Oilite bushing kit x10 part no 1547]Seems like these have the correct I.D and O.D but will still require some machining to fit. I have ordered some. I will produce another article with the out come of this with specs, what i had to do and photos so if any one else wants to complete this modification they may. It is a very easy process to remove the final drive gear. Remove C clip holding axle shaft assembly and remove this section. Next remove C clip holding final drive gear assembly and move shaft sideways. You will be able to remove the final drive gear with its bush. You do not have to remove the black plastic cover to do this. This is not a fix for a destroyed gearbox as you will realize after you look at the video and the article mentioned. Regards
Part two of this article: Unfortunately the Traxxas bush does not have the correct dimensions so I had a engineer make me some bronze bushes copying Daryls bush which also have a interference fit with the drilled out the centers of the drive gear. After stripping a gearbox completely i found that Tamiya used the same bush in question throughout the gearbox in the other clusters. They work with those configurations but the final drive gear should have had a full length bush as we have now have made. Tamiya. One bush suits all. Cutting corners is what I call it. I also purchased a Tamiya shim kit and shimmed each gear cluster to get rid of the very loose tolerances and so each gear face matched each other rather than being offset which some are just because of excess sideways movement in the gears. I have posted a photo of the modified gears both sides, the culprit bush and the shim kit I used. In the first photo ,you can see the Tamiya bush and how much it is missing in length to fully support the gear it inserts into.
Attachments
4 Tank.jpg
3 tank.jpg
Last edited by John Glover on Fri Apr 28, 2023 9:56 am, edited 8 times in total.
Tamiya King Tiger
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Tamiya Tiger 1
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jarndice
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Re: Tamiya transmission fix.

Post by jarndice »

Nice one John :thumbup:
Please keep them coming.
I think I am about to upset someone :haha:
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Rad_Schuhart
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Re: Tamiya transmission fix.

Post by Rad_Schuhart »

Indeed the tamiya units are bad designed from factory and they fail in the point you mention. I have them fixed with a steel bushing there.

Sorry for the tamiya hardcore fans, but all units but pershing are just bad designed and will fail.
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Son of a gun-ner
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Re: Tamiya transmission fix.

Post by Son of a gun-ner »

Wow, you've got to admire Tamiya for their authenticity, producing King Tigers with a weak unreliable final drive, one has to take a bow to them. . . . :clap:

Thank you John, this is very good of you to share your findings and remedies :thumbup:
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Son of a gun-ner
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Re: Tamiya transmission fix.

Post by Son of a gun-ner »

Mr Front, I'm only pulling Tamiya owners legs ;)

I've only ever had 12th scale Tamiya F1 kits and their 35th military kits, and was always happy with their quality and ease of building, but that was back when I was 12 to 14.

Maybe one day I'll be tempted to give a 16th tank a try :thumbup:
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Son of a gun-ner
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Re: Tamiya transmission fix.

Post by Son of a gun-ner »

LOL, it'll only be a Sherman with HVSS :D
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Rad_Schuhart
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Re: Tamiya transmission fix.

Post by Rad_Schuhart »

Eastern Front wrote:Funny thing,

I have no less than 18 Tamiya Tanks, I have never installed a single hull brace, changed anything in a gear box etc. I have never had a single failure---ever!

I am not saying it doesn't happen, I think the difference may be that I never drive my tanks full throttle (straight driving or turning) its an unrealistic speed for one and I know it puts extreme stress on the units.

I have done alot of battles and watched guys do the sweeping shots, you know shoot and rotate your tank---real fast, hate it, its unrealistic to the tanks and this too stresses the transmissions. I guess if all you want to do is win the battle, I never do it.

So the point, if you run it to scale and stay true to the tanks performance you should never have an issue..

my 2.2 cents

Cheers!
Hi, I never drive at unrealistic speeds, and I dont do jackrabbits back and forth and all those things you mention, but I do drive a lot. Very long distances, tank patrols with my sons and so on, and I have experienced that wear.

You can see the detailed fail here:
http://www.customrcmodels.com/files/RCP ... PGRADE.pdf

And it happened to me. The rest of the gearbox was fine except that wheel and the one next to it, just because the bad design. In the rest of my tamiya tanks I installed a steel bushing and they are running perfect for years.

It is indeed a massive design flaw that they corrected in the pershing unit...
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Davjacva
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Re: Tamiya transmission fix.

Post by Davjacva »

Here's my two cents, sort of. I was one of the builders of the DANVILLE battlefield back in 2003. I am friends with Daryl Turner, Willy Loewer, and know and have most of the high-end fixers that have come there. A long time ago after an event and drinking ny the pool at the Comfort Inn after an event, Daryl and I talked about how the Danville field is really a hyper-proving ground. For example, the first event there had about 15 tanks and at the end of the weekend 11 of them had broken transmissions. The reason then was that the fill dirt contained a plethora of tiny rock and coupled with the intense driving g during combatting really late transmissions. Willy had the initial fixes and teardowns and these were since copied and Daryl came out with some others like the brace and they both came up with two similar designs for track tension (Willy uses steel tracks). The Danville field is no longer a tough place to battle as it's really been cleaned up and most of the field is like driving on concrete almost. The next problem, but much less is battling, especially at events where you have to battle from 2ft away and the back and forth nonsense. This will wear out gearboxes. If you just like to drive your tank, and battle from an adequate distance, and your gears are lightly oiled, not bare or heavy[attracts dirt], your gears will last a long long time. I just put Tamiya type 1 gearboxes with a long can motor into my heavy ass VK4501(P) and I put in an outside bearing for the long shaft, and there is no deflection of the shaft while running, and it moves es the weight adequately. Now my upcoming Wecohe Panthe has a 3mm hull plate under the hull to prevent twisting. The KT really has this problem and needs this addition. Hope this helps. Jake
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Son of a gun-ner
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Re: Tamiya transmission fix.

Post by Son of a gun-ner »

I agree with Mr Front, Dialectric Grease, could be better than thin greases or oil, sticks like sh*t to a blanket. Although Brass as a material is classed as a self lubricating metal, it still needs a little help to keep it quiet when it wears.
Also it won't harm rubber, or allow shorts if it gets in the wrong places, and it's very good as a corrosion inhibitor.

Next time you replace a standard type of bulb in your cars, especially older classic cars, spread a LITTLE bit of this grease in the metal bulb holder, the part that retains the bulb, not the contacts, it'll hold moisture back and make it easier to replace bulbs in the future. Also good for spark plug caps, stop the rubber sticking to the ceramic, and for sealing electrical connections to hold back moisture ingress. Vaseline is also good for this :thumbup:
Mick - The grit in the underpants of life!
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TOTM needs YOU :thumbup: support YOUR TOTM competition, I'm doing my part, are YOU?
John Glover
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Re: Tamiya transmission fix.

Post by John Glover »

One thing i know from my past profession is a oil based grease will weaken plastic and nylon through soak from the oils.You cant see this happening by the human eye but it is so that is why Tamiya recommend their ceramic grease for their gearboxes.It is not oil based.There are plenty of greases out there that are not oil based.When you kook at Tamiya;s early style of gearboxes they were heavily dependent on plastic/nylon gears so ceramic grease.The latest series of gearboxes still has some nylon gears and the turret and elevation motors also, so what do they recommend.You guessed right.All i know is if you apply oil based grease to plastic/nylon drive gears you may not realize it but you are helping towards premature wear and failure.Regards John.
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