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Old 02-09-2004, 08:35 AM   #1
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Default TC3 transmission help

ok, i really need some input on the TC3 transmission proper shimming...

So far, my bulkheads are fine and the bearings spin freely, however, i feel like it s still not as free as it should..

What can I do precisely to improve this.. i seem to have a lot of front/rear play in the rear transmission with the spur gear assembly... it spins nicely but once all assembled, it s nowhere near as good.
And in the front, it seems not very good.. acceptable, but not so good ? it seems a little notchy..not ultra smooth.

Overally, how can i make it spin ? what does it take ? what is that so well kept secret ??

Is it just a matter of break in ??

thanks in advance all TC3 gurus..!
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Old 02-09-2004, 08:58 AM   #2
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i drimmeled out the whole input shaft section and replaced it with solid ball bearings it seemed to help and make the diff spin freely


rob
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Old 02-09-2004, 09:00 AM   #3
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did you do this front AND rear ??

thx for the idea though
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Old 02-09-2004, 09:05 AM   #4
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yea i removed all that little notch that is there on the frount that spaces the two bearings out and put a 3rd in there and the same on the rear

Rob
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Old 02-10-2004, 04:22 AM   #5
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I see you are running the BMI chassis. When I put the transmission into this chassis I found most of the binding was coming from the alloy centre shaft mount (in front of the spur gear). I had to cut away a fair bit of the graphite half U clamp and re-shim in order to get everything really free.....
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Old 02-10-2004, 04:24 AM   #6
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yes thanks..that seems also to be an issue, it s never the same twice. I ve got an extra clamp so i ll try to work on the existing one..
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Old 02-10-2004, 04:30 AM   #7
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I ended up putting thread lock onto the screws and not tightening down fully...otherwise there would be a lot of binding in the centre bearing......
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Old 02-10-2004, 01:31 PM   #8
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Hi

on the B.M.I. chassis you might need to run a small spacer between the bearing/motor mount and the stock bearing cap.

as for the diff cases I usally lightly rework the cases so all the bearings fall out of each case half. as for shiming I noramlly don't use any shims on the plactic diffs and will shim as needed when running aftermarket diffs.

WVracer:

Hi, you might want to make a small apacer to fit inbetween the input bearings instead of another bearing. (lighter weight, and less binding). I have done this on some cases I have modded.

Thanks
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Old 02-10-2004, 01:39 PM   #9
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Blueprinting your diff. cases will help free the drivetrain also.
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Old 02-10-2004, 10:22 PM   #10
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I have a Sears Craftsman rotary tool (a cheap Dremel) and it came with two bits that are the perfect size to match the larger transmission bearings, and the input bearings. I first used the smaller bit just to make the input bearings seat without any tightness, then I had to use the bigger one and bring back one of the diff bearing seats further out (toward the wheel) about 1mm. After doing this, the outdrive will rub on the case, so I rested the shaft of the bit on the outdrive hole, and slid it in a semicircle to take off some material from the side of the transmission case.

After doing this, I was able to shim my diff (w/ IRS Lite-Drives) away from the pinion gear and finally had some play between the gears. Before doing this I had absolutely no play between the diff and pinion gears. Previously I had taken about 1mm off from the pinion and the case directly behind it, to shim the pinion back, but it wasn't enough.

It's the imperfections in the molding process that cause small intolerances in all the parts to build up and you have no play between the gears. As the composite cools, it shrinks, and it is impossible to precisely calculate the rate it will shrink.

Last edited by Speedo; 02-11-2004 at 10:01 AM.
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Old 02-11-2004, 07:12 AM   #11
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Quote:
Originally posted by TimXLB

WVracer:

Hi, you might want to make a small apacer to fit inbetween the input bearings instead of another bearing. (lighter weight, and less binding). I have done this on some cases I have modded.

Thanks
tim

thanks i'll give that a try

Rob
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Old 02-11-2004, 11:26 PM   #12
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i really dont think drive train matters that much chad miller at socal has one of the worst drive trains and yet he is one of the fastest guys there he's the youngest and very close to boing the fastest guy at socal and he's only in the 7th grade i think well i think its all about the drivingsomething i need to work on
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Old 02-11-2004, 11:49 PM   #13
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Perhaps, but a free drivetrain usually leads to a quieter car, which is nice to have. I don't know about other people, but when I finally freed up the transmission in my TC3 I noticed the car felt much smoother.
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Old 02-12-2004, 04:18 AM   #14
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People spend 100s of dollars to get that extra 0.01v on their batteries......this is for free (excuse the pun!)...so why not??

But you're right....nothing beats driving skills......
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Old 02-12-2004, 06:42 AM   #15
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A completely free drive train isn't all that it's cracked up to be. Granted it needs to be free of major binding and blown bearings, but people obsessing about free spin on the bench isn't necessary.

At last year's Reedy TC Race, Travis Amezcua was having what he thought were motor problems. He was significantly slower than everyone else from mid to end of the straight. His drive train was extremely free, so free in fact that when it got to high RPMs the shaft and input shafts vibrated so violently that it actually cost him speed. He rebuilt the drive train pretty much stock and saw a significant improvement in overall speed.

Bottom line, make sure the drive train is smooth and will free spin for 5-8 seconds with rubber tires. If you do this, you'll be fine.
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