XRAY - Model racing cars

I want to know what the effect of having a too heavy or thin oil is in the front differential.

Does too heavy generate understeer and too thin generate oversteer?

I race on high grip carpet, on foam tyres.

I don't think the hudy setup guide covers the effects of this setting.

It feels like the car is pushing on exit because I am using too heavy front oil, does this sound correct?

I use 50k front, 3k rear.

2.9 front spring, 2.3 rear.

front kit roll bar, none on rear.

ride height about 4.5mm all round.

Thank you

Generally speaking, whatever the situation, If I need more steering, do I use a lighter front diff oil?

50k sounds very thin to me, even for foams.

Have you tried 500k or 1million?

I've tried Hudy 1mil, didn't like it (far far far too twitchy) and when I feel my diff against others it still feels a little stiff. So I'm on 50k now.

Does anyone have a tip for removing old oil (the 1mil was very sticky and I couldn't quite get it all out). I used a toothpick for what feels like an eternity on all of the teeth of the gears!

It was suggested I try 50k, but am thinking of reducing it to 40k.

I am wondering if the cross contamination has made an odd handling trait

I was thinking of using a stiff toothbrush and cleaning the inside of the diff out and the gears with this, but what can I use to get the old diff grease off easier as its really thick?

I don't want to use a chemical that weakens the gears and casing if that makes sense, what do the team guys do in this scenario?

Many thanks

I recall others talking about warming the thicker oil to make it easier to get in, maybe the same will work for removal?

If it's going to be a nightmare I would consider selling the diff to someone who can use it and buying a new one, or cleaning it as best you can and buying new internal gears.

Thanks for the reply.

I would rather not as they are about £40 a pop (if I replace the whole diff) but yes I do see where you are coming from.

Replacing only the gears, maybe

For removing such a thick silicone oil, just drop some vely light silicone oil trying to desolve it (eg 500 or 1000).

I may try your suggestion Tak, but I do not think it will work.

The 1,000,000 is very thick, sadly I do not think the two will mix and come out

Here is my solution for anyone who is changing from very thick oil to much thinner.

I took the diff apart as usual.

I removed the clear o ring as they are not needed anyway.

I then took every piece out from the differential, put a tiny bit of 30wt shock oil in the differential casing, mixed it up a little, waited a for an hour, then tipped it upside down onto a thick layer of kitchen towel, then used several cotton buds in the diff casing to remove the remains of the thick oil mixed with shock oil. (1 mil I think it was).

I then used tooth picks on the gear casing and every gear tooth to remove the rest.

It was rather time consuming, (about 2 hours in all!) but saved buying a new differential @ £40

Thank you for the suggestion Tak, I did not think it would, but it made the process easier.
I then refilled with my chosen oil (40,000cst) and replaced both the paper gasket and the large thin black gasket.