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Pics of my BROKEN Backdraft 3.5 pinion gear....

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Old 01-08-2011, 09:08 AM
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1ofmyfuns
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Default Pics of my BROKEN Backdraft 3.5 pinion gear....

Well I got the Buggy tore down and as you can see by the pics the pinion gear in the rear Diff. is toast, all else looks to be in perfect condition, it's very clear to see that the issue with these failing gears is porosity in the casting material which in itself is bad but these gears could be over tempered also which would make them very brittle, not sure about the temperbut the casting is bad thats clear.

It broke at the weakest point of the gear, it split apart at the cross pin area, that gear should have been made a few thousands thickerbeing that it's such a high stress point, this gear is not engineered very well in my opinion for the kind of material it is made of, a better NON cast steel would fix this problem.

Anyway heres the pics being that I've vented my opinion on the matter........! LOL

took these with cell phone camera so there not very good
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Old 01-08-2011, 09:09 AM
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Default RE: Pics of my BROKEN Backdraft 3.5 pinion gear....

If you look at the 3rd pic you will see a color difference in the areas where it broke, those are the bad casting areas on the gear
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Old 01-08-2011, 10:39 AM
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Default RE: Pics of my BROKEN Backdraft 3.5 pinion gear....

man i love it when im right!
arent you glad you didnt pull apart the center diff for nothing?

when you get replacement parts, add some thick grease to the ring and pinion gears.

im gonna send an email to redcat, letting them know that a couple of these pinion gears have failed. hopefully, its just a bad batch of pinions that got made.
the guys at redcat do pay attention to this stuff.
when the servo failled in my backdraft 3.5, redcat replaced it. but the replacement servo they sent wasnt the same model. so its possible that redcat knew that some of the stock servos that got shipped out were faulty. mine failed with very little/light use. the replacement never gave me any issue.
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Old 01-08-2011, 11:07 AM
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Default RE: Pics of my BROKEN Backdraft 3.5 pinion gear....

Yea after we had hashed back and forth about which diff might be the bad apple, I desided to look at it a bit closer than I had up to that point and noticed that when I tried to turn both rear wheels at the same time it was locked completely down and even after twisting just a little extra pressure on it there was 0 movement at the input shaft of the diff. at that point there was NO doubt in my mind that you had hit the nail right on the head and it was clearly the rear diff that was busted.

What had thrown my off a bit at first was the fact that the front diff wa salso locked down in the begginning and this is what initialy made me think it was the center, because I thought..... there surely wasnt anyway that both front and rear went bad at the same time and since they were both tied to the center......wala it had to be the center! but after twisting a little back and forth on the front wheels the front diff came free and is working like it should but yet as you ahd explained the issue was in the rear basd on what I had described.

I filled out the wrranty form on Redcats web site and also sent them an e-mail directly to Support@Redcatracing.com with the same pics included as I posted here in this thread, I also gave a detail explanation of what happened also just as I had done on the forum, so I figure I should be hearing something back from them in the next 2-3 days hopefuly and I'll see what they say about the warranty of my pinion gear, I hope they will send me 2 gears if they warranty it so I can have an extra on hand if the front one is bad like the rear and I wont have to go through all this again.

I already pulled my diff assembly apart and cleaned the red grease off everything and added some 7000 wt Silicone oil and reassembled it, I know some say put 2000 or 3000 in the rear and put 5000 - 7000 in front diff. but I'm not looking for and edge at a race track since we dont have any around here anyway, I just figured the 7000 would give me a little better traction by cutting down on the give in the spider gears.

Thanks nitrosportsandrunner your advice made me question myself and therefore saved me some trouble jacking with the center gear box when it wasnt needed right now.

I hope Redcat will take care of this for me, since it was clearly a faulty part.

Thanks all
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