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FG MT Broken tooth on laygear/diff ring gear-mod.

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Old 08-18-2007, 08:38 PM
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PBJT
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Default FG MT Broken tooth on laygear/diff ring gear-mod.

So I have a FG MT for about 4 months and over 10 tanks of fuel. I have broken about 7 or 8 lay gears/large diff gear teeth over this time. I have found I can break one just about every time I use it if I am not careful. Yes I do drive this thing like I rent it and breakage is to be expected. I know what breaks the gear and how to prevent it but I just don't like to let off the throttle over uneven surfaces. So I make changes.

I stripped my FG MT down to the bare plate cause it was dirty and looked like this.


But just before I did strip it down I did some thinking, I found that the reason why my two rear most gears are pulling or walking apart and then snapping a tooth off is Obviously because of flex. So I took a pry bar and pry'd the two gears apart....I found it was not the plastic stock engine mount flexing or the plastic stock diff housing but the weak lower plate or tounge section flexing and allowing these gears to pull apart.....esp during accell when the natural wheelly force is pulling the whole frt up.


First I tried tieing the week points together and still allowing the flex but the goal was to keep the gears from pulling apart, good results but would still break a tooth off. But alot less often. Using a column Eye bolt I secured from the top of the large engine mount to the rear diff.




Better but not good enough cause I am done with this rear flex and buying gears. SO next





Now I have a bit more weight but Zero flex and so I purchased AGAIN more gears, set the mesh and drove the truck hard. NO breaking and I know forsure I would have broken before-No doubt I would have broken one before. I have this large section bonded and bolted to the bottem and one on top 1/2 its size sharing the two middle bolts on the top of the alluminum plate.

On a side not it also will wheelie easier cause the body is now more ridgid.

Sorry bout the spling and gramer.

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Old 08-20-2007, 07:22 PM
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Default RE: FG MT Broken tooth on laygear/diff ring gear-mod.

3 tanks now and no broken gear. Never done that before.

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Old 08-21-2007, 02:45 AM
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Default RE: FG MT Broken tooth on laygear/diff ring gear-mod.

Just noticing, You still have the stock rear upper controll arms. How in the world did you manage not to breake those yet like everyone else

Also is that the stock gear carrier i see or is it just that dirty??
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Old 08-21-2007, 09:21 AM
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Default RE: FG MT Broken tooth on laygear/diff ring gear-mod.


ORIGINAL: TheFgMan01

Just noticing, You still have the stock rear upper controll arms. How in the world did you manage not to breake those yet like everyone else

Also is that the stock gear carrier i see or is it just that dirty??

After doing some searching it is odd to find that some people break completly different parts over and over then others. I would estimate 15 tanks atleast of fuel through my FG MT. And I only keep breaking the 48 tooth steel lay gears and I pulled out a frt upright. Yes I am still on both my stock rear upper control arms and have not yet broken my large plastic gear either. I have NO alluminum upgrade parts and all are still original. I have alloy engine mounts and servo saver ordered but not yet arrived. But I was convinced my problem was flex of there lower plate at the rear, and it was!

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Old 08-21-2007, 09:25 AM
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Default RE: FG MT Broken tooth on laygear/diff ring gear-mod.

If you change the rear upper arms to alloy, you will remove a lot of the flex when you jump. This will spare your spur gear and it will last a lot longer. Also change your spur gear carrier to alluminum and that will help also.
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Old 08-21-2007, 09:26 AM
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Default RE: FG MT Broken tooth on laygear/diff ring gear-mod.

check your layshaft also, that may be bent. If it is bent upgrade to the hardened version.
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Old 08-29-2007, 12:52 PM
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Default RE: FG MT Broken tooth on laygear/diff ring gear-mod.

This is the repair required if you are breaking teeth like I was. Re-inforce the rear section with a small strip of steel or other alloy, bonded and/or bolted to keep the rear section from flexing.

I have not broken another gear since and I would no doubt have broken 5 or 6 by now!!!

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Old 08-30-2007, 03:54 AM
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Default RE: FG MT Broken tooth on laygear/diff ring gear-mod.

See now, this was the problem that I was having, I never broke a steel gear, but I did wear down some small diff gears. My truck made that notorious gear "clacking" noise. I upgraded
my motor mounts to alloy but it still clacked. I had the gears pressed up against each other so hard that they were binding. And it still clacked. If you had posted this idea a couple of months ago I would have saved myself a thousand dollars in alloy upgrades. I still run my stock plastic gear carrier, it has a metal ring on the inside that the pinion fits into. And I've pulled out a front upright. I did have to upgrade my upper rear arms as one pulled out and stripped the plastic tread.


I think you are on to something here. I hope that new FG owners see this thread if they have problems.
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Old 08-30-2007, 06:35 PM
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Default RE: FG MT Broken tooth on laygear/diff ring gear-mod.

look like you will need some new parts you should try www.badboyhobbies.com they got everything you will need
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Old 10-02-2007, 02:40 PM
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Default RE: FG MT Broken tooth on laygear/diff ring gear-mod.

Anyone following this thread, re fg laygear breaking off a tooth. Since re inforcing the bottem plate of my FG MT I have not broken a tooth, also I have stepped up my driving habits that would have been a definate break before. Well over 10 tanks now since the repair and no broken tooth. Where as I was breaking one off just about every time out.

I am also STILL running on all original plastic mounts on engine and diff with 25+ tanks of fuel. Definate repair to my problem and likely yours too.

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Old 10-03-2007, 04:16 AM
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Default RE: FG MT Broken tooth on laygear/diff ring gear-mod.

You're still running the plastic motor mounts, and you do not have that notorious gear clacking noise. You, my friend, have pinpointed the true cause of this problem. I only wish you had done it sooner. I'm glad for you that you've not wasted a bunch of money fixing this issue.
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Old 11-20-2007, 09:06 AM
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Default RE: FG MT Broken tooth on laygear/diff ring gear-mod.

Well I have completely worn out my rear diff pinion gear and did not break a single tooth on the rear diff since I added this brace. FG needs to add this bracing right from the get go.

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Old 11-20-2007, 01:18 PM
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Default RE: FG MT Broken tooth on laygear/diff ring gear-mod.

sounds good , how thick is your peice of steel?
i might get some thing laser cut at work
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Old 11-20-2007, 03:57 PM
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Default RE: FG MT Broken tooth on laygear/diff ring gear-mod.

I believe it is 1/8 inch thick. I also have a matching strip on the top but not as long because it would not fit between diff drum and belly pan.

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Old 11-21-2007, 12:12 AM
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Default RE: FG MT Broken tooth on laygear/diff ring gear-mod.


ORIGINAL: PBJT

I believe it is 1/8 inch thick. I also have a matching strip on the top but not as long because it would not fit between diff drum and belly pan.

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is it stainless steel ?
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Old 11-21-2007, 06:45 AM
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Default RE: FG MT Broken tooth on laygear/diff ring gear-mod.

My piece is not stainless steel and it is just a simple stip of unpainted metal. But now that I know the idea works and actually did fix the FG problem IF I were to redue this bracing I could get a bit more fancy with it. I am just happy I am no longer breaking a $40.00 gear. I use to break this gear every tank of fuel or so and have not broken it now in countless tanks of bashing and Baja racing.

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Old 11-22-2007, 06:05 AM
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Default RE: FG MT Broken tooth on laygear/diff ring gear-mod.

[sm=thumbs_up.gif]Kind of makes you want to buy another truck, so you can do it again. Huh?
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Old 11-25-2007, 06:36 PM
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Default RE: FG MT Broken tooth on laygear/diff ring gear-mod.

I need 2 fn' parts and noone has them listed as available... argh !

ARGH !!!!!
[:@]

Layshaft gear, and a wheel hub drive with 2grubscrew knockouts for my FGMT.

argh !!!!
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Old 06-05-2008, 06:31 PM
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Default RE: FG MT Broken tooth on laygear/diff ring gear-mod.

Countless tanks of fuel through this FG MT and since I put this bracing under the truck and a matching one 1/2 its length on the top I have not broken or chipped a rear diff or pinion tooth. Now my brother has a FG MT Jeep with out a brace and has not experience the same problem I did. Maybe I have a poris or poor quality belly pan. Before the brace I could not get a tank of fuel out of the large gear on the rear diff no matter how tight I ran the mesh. Now Zero problems even with poor overlap of the gears. I now have Cat5 gears off the bell so no more melted plastic


The gears get driven hard.


You can see the bracing under the truck.


Hope this info helps.

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Old 06-05-2008, 10:31 PM
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Default RE: FG MT Broken tooth on laygear/diff ring gear-mod.

Do you still have the plastic motor mounts? I had a ton of problems with my FGMT also. I fell down an expensive Elcon slippery slope. While you fix yours for a couple of bucks.
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Old 06-06-2008, 07:36 AM
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Default RE: FG MT Broken tooth on laygear/diff ring gear-mod.

I still had 100% plastic before when I was breaking teeth and the same 100% plastic for a very long time afterwards. I now have only Alloy large mount since I stripped out my screw mounting holes on the bottem, but my tooth snapping problem was long fixed with this re-inforcing prior to replace the engine mount.

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