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Old 10-02-2012, 01:39 PM   #1
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Default Help - Sprint 2 oneway front Diff Install

Hello all,

I am sorry if this is not the place for it but I have tried searching here and googling and cannot find the answer I am looking for.

I recently started getting into the Electric RC drift cars and purchased a Sprint 2 RTR. I have already upgraded a few things like Castle Sidewinder 5700kv Brushless & ESC, locked the rear diff, Lipo, Steering Servo, and a few other things.

Now I have this HPI oneway front differential that I am in the process of installing but ran into a problem where when taking out the stock diff i noticed the bearings are kind of stuck on there and cannot just put the oneway in its place since there is a gap where the bearings would be

I am not sure if I need to use those bearings and put it onto the oneway. Iv read that all you need is to use the old bearing (not coming off stock one easy), or purchase an "O" ring, or just have the Universal dogbones.

Can anyone help me with this, its most likley a simple solution but for some reason I am lagging on finding out what to do.

If it is the option of using the stock bearing from stock diff, any tips on getting it off without damaging?

Thanks, any help is appreciated ,

-Jay
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Old 10-02-2012, 06:32 PM   #2
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I think you may be confusing a few pieces from the instruction manual with each other. You do need the bearings off the original gear diff to install the one-way front diff. If these won't come off, take the original diff to the LHS and they should be able to fix you up with some bearings of the same size for a pretty reasonable amount (typically 2-7 dollars depending on brand).

You can likely get the old ones off with some fiddling, but they can get "stuck" if they aren't pulled off squarely. Try pushing hard on the bearing as if you were installing it on to the stock diff. If it has become wedged, this should square up the bearing and hopefully make removing them easier. Conversely, I've also used a thin screwdriver as a prybar and basically worked the bearing off moving the screwdriver around the bearing in quarters, i.e. pry up, move the screwdriver 90 degrees pry again, move the screwdriver 90 degrees, and so on.

The O-Ring I believe came with the one way (or the stock diff, can't remember) and goes into the cup to hold the dog bone AND the cup in place. I can't remember how many HPI recommends in each cup, but essentially there should be only a slight gap between the dogbone and the cup through the suspension motion.

The universals are nice and I have them on my car, though you'd still need the o-rings or the cup could literally fall out of the one-way.

I hope this helps and good luck with it. It'd probably help if I had a few photos, but unfortunately I have a locked front diff on my car at the moment as I broke my one-way cups the last time I took it to the track. Maybe someone else will have some pics.
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Old 10-02-2012, 08:42 PM   #3
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+1 AMorgan


Help - Sprint 2 oneway front Diff Install-sprint-2-sport-manual-10613044-copy.jpg

If the cups (gear differential shafts) (parts circled in BLUE in picture = HPI86015) are buggered from the dog bones slamming them = hard acceleration / stopping - you're pretty much boned.

Unless you can file off the damage and slide the bearings off.

Tape off the bearings completely before filing to keep them clean.


The bearings are HPIB030 - $16.00 list price for two.

If there is no damage to the drive cups from hard use and the bearings are just stuck - you can try this - put the diff in the freezer for several hours and then try to slide them off.

Last edited by Marv; 10-02-2012 at 10:02 PM.
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Old 10-04-2012, 11:10 AM   #4
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Thanks for the info guys!

I got the bearings off and all is well. I was thinking they were suppose to look like skateboard / rollerblade bearings. When I took them off I thought I damaged it but it was fine, and everything went back together nicely.

After seeing Marv's post on how to fix a bunch of things I need to get an extra 2 O rings for the shaft in the diff (already 1 in each side.

The rear belt tensioner is a must, its so loose right now...the belt is actually grinding away above it on the bottom of the rack and shredding itself.

The only other major problem I am seeing right now is since I shaved down the C arm buckle, the dogbone seems to pop out? when the wheel is at a certain rotation/turning angle. I have not run the car yet besides on its stand, and it did not get stuck during that, but when manually messing with the wheels / turning it does get caught. Im affraid that will happen when im actually running it and will cause more damage. Maybe once i put the extra O ring in the front it will help prevent that.

Thanks again for all the help!
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Old 10-04-2012, 11:38 AM   #5
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Glad to hear you got the bearings off.

The rear belt tensioner is beautiful thing to have.

You might consider those kevlar reinforced belts from Tough Racing.

Shaving back the C block hub stop gives more turning but also increases the angle that the dog bones will run when full turn... I have two 'o' rings stuffed into my front diff drive cups... I had my C blocks shaved back about 50% - which may be too much (in retrospect).

My shocks are in the OEM position, so I use the front tire to bottom shock eye as my guide to set my radio end points.

I'm getting a little hop/bind(?) on full tight turns, but it might be because one of the 'o' rings is now "crush fit" and needs to be replaced, or...?


I have parts coming in (possibly today) for another version of a front belt tensioner mod.

Once done & tested I'll post it.

Also, I 've done a front C block upgrade to get rid of the C block/hub and C block/control arm slop - still have to track test it before I post it.

Quote:
Originally Posted by RC-Jay View Post
Thanks for the info guys!

I got the bearings off and all is well. I was thinking they were suppose to look like skateboard / rollerblade bearings. When I took them off I thought I damaged it but it was fine, and everything went back together nicely.

After seeing Marv's post on how to fix a bunch of things I need to get an extra 2 O rings for the shaft in the diff (already 1 in each side.

The rear belt tensioner is a must, its so loose right now...the belt is actually grinding away above it on the bottom of the rack and shredding itself.

The only other major problem I am seeing right now is since I shaved down the C arm buckle, the dogbone seems to pop out? when the wheel is at a certain rotation/turning angle. I have not run the car yet besides on its stand, and it did not get stuck during that, but when manually messing with the wheels / turning it does get caught. Im affraid that will happen when im actually running it and will cause more damage. Maybe once i put the extra O ring in the front it will help prevent that.

Thanks again for all the help!
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Old 10-05-2012, 02:45 AM   #6
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Quote:
Originally Posted by Marv View Post
I have parts coming in (possibly today) for another version of a front belt tensioner mod.
Front belt tensioner mod is up, post #116 - http://www.rctech.net/forum/electric...ows-ear-8.html
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