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Old 12-06-2010, 02:25 AM   #6496
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Originally Posted by xray racer View Post
Just for a point of mention Sosidge,

You CAN fit the photon diff and spool in the scythe , you just have to modify the shock towers to clear, and run the 37t belt set-up.

Wasn't sure if you had tried this or not.

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I hadn't, because I had taken some measurements outside of the car and assumed they wouldn't fit.

Aside from that, I don't have the belts etc. from the big pulley setup.

Maybe a job for someone else that wants to build a hybrid!

I'm quite happy with the steel Scythe spool but the moulded Yokomo diff outdrives are a weak point.
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Old 12-06-2010, 02:37 AM   #6497
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I just never liked the yokomo diffs in the car when i ran it, with the 37t belt you can use a tamiya diff with 3mm balls which was much better, but the photon diff does fit, just a slight file of the bearing carriers does the trick, and you have to notch the shock towers.

Anyway, enough of the scythe lol, it was/is a great car though



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Old 12-06-2010, 11:29 AM   #6498
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Originally Posted by sosidge View Post
I have the Tamiya o-rings (from #53574) and have no leaks. This is using the original shaft guides too.

I will try that today... thanks!!!

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Make sure that your shock shafts are not scratched up. They may be cutting into the o-rings and causing the leak.
nope no scratches... but good point thanks!!

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If tamiya ones dont work, then I'll try those...thanks!!!
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Old 12-06-2010, 04:40 PM   #6499
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I will try that today... thanks!!!



nope no scratches... but good point thanks!!



If tamiya ones dont work, then I'll try those...thanks!!!
Alternatively, you could add a maybe 4mm x 0.2mm shim between the o-ring and the plastic shock guide to give the o-rings some added "squash" so it will seal better.
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Old 12-06-2010, 04:48 PM   #6500
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Alternatively, you could add a maybe 4mm x 0.2mm shim between the o-ring and the plastic shock guide to give the o-rings some added "squash" so it will seal better.
Wouldnt that pinch the shock shaft though? If the shim is metal, it will scratch the shaft too.

----------------------------------------------------------------------------------------------

I had zero shock seal issues with my kit. Im glad... i hate leaky shocks. IMO shock prep is everything. Even new shock shafts get polished before use. I found a teflon lube i have used for years that works well for shock assembly. You have to use something to ensure seal integrity.
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Old 12-06-2010, 05:02 PM   #6501
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Wouldnt that pinch the shock shaft though? If the shim is metal, it will scratch the shaft too.

----------------------------------------------------------------------------------------------

I had zero shock seal issues with my kit. Im glad... i hate leaky shocks. IMO shock prep is everything. Even new shock shafts get polished before use. I found a teflon lube i have used for years that works well for shock assembly. You have to use something to ensure seal integrity.
The 4mm shims will have enough room around the shaft and will not contact. The trick is to use the correct shim thickness so that it will pinch the o-ring just a tad without accessive pinching to the shaft.

I have done it many times on my Tamiya shocks with TRF blue o-rings with success.
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Old 12-06-2010, 05:04 PM   #6502
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I am using the u-pro spool and wondering if replacement spool cups are available. Would anyone know if other spool cup will work?
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Old 12-06-2010, 05:17 PM   #6503
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Originally Posted by old-man View Post
The 4mm shims will have enough room around the shaft and will not contact. The trick is to use the correct shim thickness so that it will pinch the o-ring just a tad without accessive pinching to the shaft.

I have done it many times on my Tamiya shocks with TRF blue o-rings with success.
Hm. I have used a combination of the thin teflon shims available with the older AE shock rebuild kit in other cars in the past (4 thin teflon shims and 3 o-rings). I wonder if they might fit, and allow one thin teflon shim and two o-rings with no compression, and still provide shaft guide/protection...
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Old 12-06-2010, 05:50 PM   #6504
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so speaking of shocks -- i learned an important lesson this weekend -- shocks are the most important part on this car (and i guess every car -- so don't be cheap & lazy)!

i had rebuilt two sets of V2 shocks -- one which I 'tested' the 40 degree o-rings, and they felt OK so I kept them installed and just refilled with oil -- the other which felt a bit rough so I replaced the o-rings. well, after a little failure in Q1 by breaking a steering block after not checking them after a crash in practice i asked Larry to look at my car before going out for Q2. what he did was a simple test of the car by pressing down on the front of the race ready car, and then the rear of the car. he immediately shakes his head, hands the car back, and hands over his car. i repeat the test for myself - and i can feel the difference (but i have no clue if there is a way to measure this other than just looking for the feel of it). the cars have the same (or nearly) the same setup on them, and mine felt as if I had 100 weight in it. without time to pop on the other set of shocks i go out for Q2 and put a run in to get back to the A-main sort.

back in the pits i take off the shocks with the re-used 40 degree o-rings, and install the other shock set with the new o-rings. i perform the "press down" test on the front and rear -- it is much softer now, and feels like Larry's car. so what did that mean on the track? well about 0.3s/lap. heck the car was running so well that i missed my marks for the first 2 minutes and were tapping out badly so i spent the rest of the run trying to hot lap around the track playing follow the leader.

i know it sucks to have to do this much maintenance, but it clearly yields results. i guess i've just been foolish before, but at least i'm starting to see the light. it really sucks to fail before you even hit the track. i won't let that happen again (or at least the shock failure happen again...)
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Old 12-06-2010, 05:52 PM   #6505
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Guys i hate putting down a product but these u pro diffs are junk. I have 2 they leak like crazy notchy as hell and I blew one set of gears first time out in 17.5 boosted class. I also tried removing shims etc and they only got worse. Am I missing the secret to these things. I do hear alot of people using them.
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Old 12-06-2010, 06:00 PM   #6506
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Guys i hate putting down a product but these u pro diffs are junk. I have 2 they leak like crazy notchy as hell and I blew one set of gears first time out in 17.5 boosted class. I also tried removing shims etc and they only got worse. Am I missing the secret to these things. I do hear alot of people using them.
I am running one with 125,000wt in the front, and it works fine. I have run it with 17.5 spec and boosted.
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Old 12-06-2010, 06:07 PM   #6507
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Guys i hate putting down a product but these u pro diffs are junk. I have 2 they leak like crazy notchy as hell and I blew one set of gears first time out in 17.5 boosted class. I also tried removing shims etc and they only got worse. Am I missing the secret to these things. I do hear alot of people using them.
IMO, all gear diffs have a long way to go before they'll be as reliable as a well built ball diff. My u-pro's will stay in my pit box too, just can't keep up with the maintenance.
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Old 12-06-2010, 07:17 PM   #6508
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IMO, all gear diffs have a long way to go before they'll be as reliable as a well built ball diff. My u-pro's will stay in my pit box too, just can't keep up with the maintenance.
Ironic, since one of the selling points for the gear diffs across all of the modern TC platforms was reduced maintenance.
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Old 12-06-2010, 09:18 PM   #6509
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I think more consistent during a race, or over a full meet is more the gear diff selling point, I gather guys were finding ball diffs fading during a race, and/or needing to have a few on hand during a meet to keep the feel consistent.

It's possible gears are just easier to build and tune as well, no one ever really said hey this here gear diff is bullet proof and will late forever, just they may provide better tuning/feel in some situations.

Really if you look at the rebuild kits for the upro diff it's cheap enough to rebuild, life of them seems directly related to oil weight, given that I'd say if your going lite expect to rebuild fairly often, though perhaps just not as often as a ball diff.
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Old 12-07-2010, 12:30 PM   #6510
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Maintenance? what maintenance?

I remember just few years ago we(racers) had to do TON of stuff, if we wanted to stay in a "A"main...

Build motors...brushes,spings,cutting the comm, align the brush hoods, break it in

batts... discharge,cycle,zapp and ofcourse depending on the company IB vs IP vs GP some were more finicky over the other

tires (foam) dont even get me started..

And top it all off we still had to do what we do now, set up , tweak , etc etc

Now days all I do between heats... shoot the breeze with the boys!!!
I kind of miss doing all that on a RACE day...kinda....HA!
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