XRAY - Model racing cars

Hi

What grease or oil should I use in my diff ! I rebuilt the diff a few weeks ago when I got the car using hudy super diff grease and have only used the car a few times since then indoors on carpet. I raced it on a indoor tarmac track on sunday and the car was too rear end happy steering/coming in and out of corners. A top driver at the meeting looked at my car and said the diff felt grunchy and dry that was why my car was rear end happy. Does any one have any ideas as to what grease or oil I should be using in my diff ? Are there any special diff building tips ? Any other ideas as to how I can stop the rear end from being too happy would be great.

Cheers

1st thing i do is strip it , clean every thing , check the diff plates are flat and then sand the diff plates with 800 sand paper , this gives the balls some thing to grip too .

Then using Marc Rienhard , or Assosiated black diff grease i put a small ammount of grease on the plates and then pick the balls up with a small spot of grease on a 1.5mm allen driver drop them into the pully that is half built with one of the diff halfs and a plate , then i put the other half on and add some black anti wear greas to the thrust bearing ,

screw it all together loosly turn the out drives for about 5 mins tightening the screw a little at a time till it is tight enough , then add it to the car , hold 1 wheel and give ¼ throttle for 10 to 20 seconds then do the same with the other rear wheel , tighten so you cannot turn the pully when you hold the rear whels and you should have a perfect diff

good luck Phil

I am sure we all have our different methods/foibles. My approach is not entirely the same as Sidecarphil.

The first thing I do is to leave a new XRAY diff alone! IMHO in having run them for 4 years now, they work fine out of the packet and last for ages.

I either run the diff in on the bench, as Sidecarphil describes, or on the track (couple of laps slowly, tighten up the diff 1/8th-1/4 wheel turn, repeat). The only point I disagree on is “so you cannot turn the pully when you hold the rear wheels” For me that is too tight; track and conditions will influence this but I basically run my 10.5 with a looseish diff on my track. So for me, holding the pulley and one wheel, it is difficult but possible to turn the pulley using the other wheel – and I might loosen it off a 1/8th turn from that position – diff tightness is always difficult to articulate in print!

If I am rebuilding the diff then ditto Sidecarphil’s comments except
I use XRAY diff grease
I don’t put any grease on the plates
I put a blob of grease in the palm of my hand and then the 12 balls and roll them around to get them all nicely covered
I use a circlip remover to pick the individual balls up and drop them into the pulley holes.

HTH Pete

How to build a perfect diff:

Clean all parts thorougly with brake cleaner

Use HUDY black grease in the thrust bearing 106210

Sand the diff rings with 600 grit wet sand paper

Use HUDY super diff grease 106212 on the rings (a fairly big quantity)

And then add all diff balls

Tighten lightly, and put in car

Run-in the diff when in car and holding one wheel and let the other spin, but slowly

Tighten until it won't slip by the force of your hand

If it still slips, try to replace the thrust bearing and also the snap ring which has caused some problems for some people lately. If the other diff parts are very old these need to be replaced as well.