lowcel

iTrader: (80)

I'm still pretty new to this hobby so I'm not real sure about maintenance on certain parts of the car. About how often does a diff need to be rebuilt? I'm sure there is a way to tell by feel but I don't know how to do it yet.

trerc

iTrader: (89)

It will feel 'gritty' thats the best way to describe it.

yokemad

xray diffs won't feal gritty at all LOL even after 3-4 months...
we asked that to elliot harper he thinks once every 10 runs ! For the best results...

lowcel

iTrader: (80)

Thanks for the replies. If once every ten runs I guess that would mean about once a week. I do two heats and a main on Friday and three heats and a main on Saturdays plus some practice runs.

What grit sandpaper should I get to sand the diff rings?

trerc

iTrader: (89)

600 works well

lowcel

iTrader: (80)

Thank you, I'll make a quick run to NAPA then start tearing some cars apart.

CarbonJoe

If you're running 17.5, the diffs should last quite a while between re-builds, hotter motors abuse the diffs more, so they get built more often. Be aware that if you are merely turning the wheels by hand to feel for "grittiness" you might be feeling bad hub bearings (especially if you hit the boards frequently). The outer hub bearings take a toll from repeated impacts. Do yourself a favor and order some replacement hub bearings and diff thrust bearings from Avidrc.com. I probably replace the hub bearings twice as often as the diff gets rebuilt. Also, the front diff gets rebuilt more often than the rear (for foam cars).

Check out Jilles Groskamp's diff re-build video (about 10:38 long):
http://www.youtube.com/watch?v=YOMu6Fu3orI

lowcel

iTrader: (80)

Thanks everyone for all of the help. I went ahead and rebuilt both diff's in my T2 (VTA) today and the diff in my Speed-T. They were all feeling pretty rough. I decided to skip on the T3 today, it still felt pretty good to me. I'll probably do it before next weeks races.

The bearings on my T2 are feeling pretty bad. I guess I'm going to have to place an order for a few sets. I thought about getting ceramic but to be completely honest I'm not nearly good enough to justify the expense. I figure I'll just go with cheapies and replace them when necessary.

trerc

iTrader: (89)

For bearings you can't beat Avids. The revolutions (one side rubber seal one side metal shield) are really nice and for a buck I don't even bother to clean them, when they feel gritty I just pitch em.

Here's a link http://www.avidrc.com/

If you already use the Avid bearings then I'm not telling you anything you don't already know

CarbonJoe

The ceramics aren't worth it, especially for hub bearings. They're 5x the cost, and don't last any longer. If you really feel the need for ceramic bearings, use them in the layshaft and diff holder bearings. For club racing, they're a waste of money.

lowcel

iTrader: (80)

Actually this is the first time that I have bought new bearings since I used to race twenty years ago. A buck a bearing sounds pretty good to me though.

I don't feel the need to spend anymore money than necessary so I'll skip the ceramics all together for the time being. If I find some money burning a hole in my pocket later on I might try some but until then it will be $1 bearings for me.

lowcel

iTrader: (80)

Probably a dumb question but where can I find the sizes for the XRay's without having to take them out and take the calipers to them?

Nevermind, think I've found them.

Diff holder bearings - 10x15x4
Other bearings - 5x10x4

Are there any other sizes I'm missing?

CarbonJoe

Hub bearings (with stock plastic hubs) are 5x10x4. If you have the alu hubs and use the inserts, those are 5x9x3, which I feel are too fragile for TC hubs. I skip the composite holders so that I can use 5x11x4 in the hubs.

lowcel

iTrader: (80)

Avid is out of the revolution 5x10x4's.

CarbonJoe

The standard 5x10x4 rubber shielded bearings are fine as well. The stock Xray bearings are rubber shielded. Avid appears to have the rubber shielded ones in stock.