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Old 04-03-2008, 09:53 PM   #1
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Default Help please with XXX gearbox mounts

Hi all,

I have a couple of Losi XXXs, and while they are awesome cars, I seem to keep breaking the rear lower mounts of the gearbox ( where the screws come through the chassis plate into the gearbox)

SO, I'm wondering if there is a hop up, or 3rd party fix for this?
someone must make an alloy mount or something.

Any help greatly appreciated

Stu
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Old 04-04-2008, 12:43 AM   #2
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Don't worry about it. As long as the gear box sits flush w/ the rear chasis plate the car will drive great. If you get a new trans case then pre thread it b4 you stick those screws into it next time.
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Old 04-04-2008, 08:07 AM   #3
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Originally Posted by party_wagon View Post
Don't worry about it. As long as the gear box sits flush w/ the rear chasis plate the car will drive great. If you get a new trans case then pre thread it b4 you stick those screws into it next time.
I have to worry about it, half of the plastic piece where the screws go into the gearbox is no longer there !
I did pre thread, but am now on I think my 5th gearbox casing !
SO, currently the gearbox is JB welded into place as otherwise it would just slide up.
Would a picture help?
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Old 04-04-2008, 10:48 AM   #4
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I worry that this is the biggest problem of XXX. But XXX and XXXCR Gearbox Casing is way better than on XXXBK2 - I had to change it almost every race. I have changed gearbox casing on XXXCR after one season.
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Old 04-04-2008, 12:14 PM   #5
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Oh I feel your pain. I donít know how many tranny cases I have broken at that location. It comes from tail end landings and the crazy big jumps we have at our track. The only thing I found that helped was to put in a little longer screw. My kit came with 3/8-inch flat head screws in that location. I found Ĺ-inch FH to be too long. 7/16-inch Flat Head screws seem to be just right. The little extra length has given my tranny more durability when I tail-end land it. Actually I have not broken a tranny since putting the longer screws in. The downside is itís difficult to find 4-40 - 7/16 Flat Head screws. The only ones I know of are from Associated. You can get them from Tower Hobbies(Tower Part No. LXSZAO, AE Part No. 9765).
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Old 04-04-2008, 12:17 PM   #6
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I'd get a new case, tap the holes slightly, and slowly screw the 4-40's in.

1) Make sure you are using 4-40 x 3/8" FlatHead screws (Part # LOSA6210), not anything longer or bigger like a 5-40 or 3mm screw or anything.
2) Don't over tighten them, just get them in snug and make sure they don't back out. Don't use a power drill, or over-crank those.

I've never had that part of the case actually break off, but i have cracked the case on the side of where those screws go in, after a lotof use, but it takes a while to get to that point.

The other things to make sure are: the area on the shock tower and tranny case where the long 4-40 x 1-1/2" screw goes horizontally, is not worn out, either on the Tower or case. This could cause the tranny to move slightly, putting more stress on those rear-lower screws. Might want to check that the tower isn't worn out there as well. Also make sure your rear pivot plate (LOSA2108) is not cracked or worn wayy out, might not hurt to replace that as well.
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Old 04-04-2008, 01:43 PM   #7
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Also, when you install the tranny make sure the long 1-1/2" screw doesn't turn the case by overtightening. If it tweaks the case a direction it can add stress to the area you are having problems with. Basically don't over-crank any of those screws, just make sure everything ends up flush.
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Old 04-04-2008, 02:56 PM   #8
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I've had better luck with slightly longer screws too. Regarding odd length screws: I have a set of electrical pliers, you know the kind that strip insulation off of various wire sizes, that also includes a threaded cutter section. I use these to make custom length screws, not just for this spot either. Very handy multi purpose tool.
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Old 04-04-2008, 05:01 PM   #9
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Great, I'm not alone in this....
we should start a support group !

I suspect a lot of my issue is the rough nature AND large jumps on my local track.
I was pretty sure though that I saw an alloy piece in one car at an event I was at, maybe not but something was different, is there a Trinity piece, or something else that could fix this?
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Old 04-04-2008, 05:51 PM   #10
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The only fix I can think of would be an alloy tranny. It breaks when the motor guard impacts the ground first then shoves the tranny up and out. The tranny breaks away at the exact depth of the 3/8 FH screws. By using 7/16 FH screws more material would have to fracture. That is why the 7/16 FH screws add some durability. The holes in the Tranny is deep enough to take a 7/16 FH screw but no more. I try harder to land level or nose down but for a long while my local track had two jumps that would send the car 6 feet in the air. The occasional tail landing was harsh on the XXX. The longer screws seem to be working plus more effort toward smoother landings. Like mentioned above, not over tightening the screws is important.
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Old 04-04-2008, 06:51 PM   #11
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Could stiffen the springs and or shock oil, sounds like chassis slapping too hard on the landing. Tap the brakes to nose down on the landing. Sounds like you might be landing rear end down first. Just a thought....
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Old 04-04-2008, 07:03 PM   #12
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Could stiffen the springs and or shock oil, sounds like chassis slapping too hard on the landing. Tap the brakes to nose down on the landing. Sounds like you might be landing rear end down first. Just a thought....
Maybe, trouble is though all the B4 drivers don't have to change their driving style to save from breaking their cars !
I don't really think it's that though as I also broke one running indoors with only a small jump where the car was landing flat.
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Old 04-05-2008, 11:29 AM   #13
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i wish i had a digi camera and show how i can lauch my old xxxt off the peak of my roof and land in back yard if on wheels drive away never broke tranny case but now i said it it will happen yes i break arms and casters and chassis and pivot blocks but mostly break ballends wow i think u should follow the advice of tapping the holes and after running the first time with the new case check the screws again mebey your gettin tranny cases from a bad plastic lot i don't know just the first i'm hearin of this prob.
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Old 04-07-2008, 12:00 AM   #14
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Quote:
Originally Posted by losi god View Post
i wish i had a digi camera and show how i can lauch my old xxxt off the peak of my roof and land in back yard if on wheels drive away never broke tranny case but now i said it it will happen yes i break arms and casters and chassis and pivot blocks but mostly break ballends wow i think u should follow the advice of tapping the holes and after running the first time with the new case check the screws again mebey your gettin tranny cases from a bad plastic lot i don't know just the first i'm hearin of this prob.

Don't know what to tell you. Maybe the temp outside where we run is cooler? Maybe your truck is easier on the mount due to the larger tires?

Either way, I really want to run my buggies this Summer, and I have a couple of new gearboxes on order, but I'd like them to last all SUmmer if at all possible.

thanks for all the replies
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Old 04-07-2008, 06:26 PM   #15
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you could put some weight under the front pivot block to help balance the car in the air.
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