Mad Rat diff help!!

[dapanz]

I badly need your help!! I'm racing with the Mad Rat since this spring and the car has always been terrific. I've never had any kind of problem but with the diff. The original one was not that bad, but the "stop push ball bearing" was gone just after three runs. I changed the broken part and use the car for the Italian champs (5 qualifyng legs and 5 finals): the set up was really difficult, I've spent the whole saturday on it but at the end the diff was responding well, even if it was really rough and not smooth as B4 ones. So I decided to mount a full BFast set. I tested this sunday on carpet and at the beginning it was perfect, but after 3 runs of around then minutes it started to be really noisy (it started to scrape whenever it was working), but I'm not able to figure out why it's doing so. Since I'm getting mad trying to fix it, I'd like to start from zero and rebuild the whole diff using all new parts (I've another BFast set ready) and in order to do so I need a step by step help from you, because it's clear that I'm not able to do it by myself...and it would be helpful also because I've just bought a XPro that I'd like to race this winter indoor!!! Thanks

[ben44]

With your B-fast diff did you the grease?
Look if your ball beraring are all Ok.

[ben44]

Oops send 2 time

[dapanz]

Yes, I've used grease on the diff, the BFast one and it seems as all the ball bearings are ok, but this evening I'll check it better, even if I've used a new set...

[ben44]

You use one for the diff and one with graphite for the thrust ball

[dapanz]

yes I've used both. What I don't understand is why at the beginning the diff was perfectly working and after a while it started making noise. This evening I'll re-check everything ant let's see if I'll find out something...

[ben44]

Did you putt the scru of the diff near the motor plae or the other side.

I don't know why your diff do this noze because with my i do mabby 50 pack and i haven't any problem. I re built them every 10 pack or a race.

[dapanz]

Did anyone knows if the SC10 (the satellite one, same as B4.1) diff would fit?

[ben44]

It's will be difficult with the ball bearing US than EU.
Look your diff, look if the setup of it haven't change befor

[dapanz]

Just finished working on the diff. I dismantled it and found nothing wrong. Could it be that it was too tight? could it be that run after run the excessive tightness and the great traction of the carpet were too much for the grease and the diff started to become rough and noisy? How can I find out how much I've to tighten the diff? and the clutch? Thanks again.

[Cameo]

Slipper clutch - I'd be more inclined to suggest this is the cause of your noise. If the pads are worn/glazed up then your clutch is not working correctly. Replace the pads of clean them up then set as per the manual about 3 full turns in from flush (Only guessing).

The BFast diff kit you refer to is it the SX10 one? The reason I ask is the brass shims are very important for the diff to work correctly.

Next diff tightness. You should tighten it to full (spring bottoms out) in your hand then back it off 1/8 to 1/4 of a turn. NOTE - You must break the diff in as per the bfast instructions first.

Good luck hope some of this info helps you sort it out.

[dapanz]

thanks a lot for the advice. I've just find out that I completely forgot to break the diff in... thanks again