Adam, TD, Can You Help Me?!

[HyperFX]

I purchased a used DEX410. I was told by the previous owner, the diff oils were 20K/10K. I drove the car for a few weekends, making only minor adjustments, because the setup was very good "as is".

OK, time for fresh fluids. I open the diffs to find...very little, and very dirty oil, or grease, in both diffs. No leakage at all, just under filled diffs, or small amount of grease. BUT, the car handled very well this way, although there was a little understeer in medium to tight turns.

I wanted to get rid of a little rear traction to increase my corner speed, so, based on the 20K/10K info I received, I went to 15K/ 7K. This produced very little rear traction. Now, I'm thinking increasing the rear diff to 10K or reducing the front diff oil to 10K, to regain rear stability. Is this correct, or is my logic "we todd did"? LOL! (Say it out loud several times!)
(edit: Now, I'm thinking thinner oil will increase traction/stability?)

I believe, now, that the 20K/10K info is wrong, and the car was handling well with low filled/grease only diffs.
SO...
How do I duplicate the good handling when the diffs were low? Thinner oil? Grease only? Help from the TD pro's?!

I don't have previous experience with oil diffs, (yes, it shows. duh!) and I'm in need of experienced racers help with this, please. I really need to know the basics of how diff oil viscosity affects the handling of the 410, both front and rear.

The track surface is medium to loose traction. Clay mix, partially packed, with loose, moist, soil on the surface. Moist during all heats and mains.

Adam, TD, or anyone, do you have a minute to educate an "oil diff noob" before I race in the morning?!

Much Thanks, in advance!

[samd]

Hi I think the general rule is less grip lower weight oil, high grip higher weiht oil. I wouldn't worry too much about your diffs looking underfilled, mine do when i change the oil and if they had 20wt/10wt this will look a bit like light grease when you come to change the oil.
It's a personal think but I have my base set up 12.5wt/7wt going to 15wt/10wt high grip or 5wt/10wt low grip.
Hope this help, I'm sure others will chip in with some better info.
Sam

[mark christopher]

Originally Posted by samd

Hi I think the general rule is less grip lower weight oil, high grip higher weiht oil. I wouldn't worry too much about your diffs looking underfilled, mine do when i change the oil and if they had 20wt/10wt this will look a bit like light grease when you come to change the oil.
It's a personal think but I have my base set up 12.5wt/7wt going to 15wt/10wt high grip or 5wt/10wt low grip.
Hope this help, I'm sure others will chip in with some better info.
Sam

i hope your not running those oils or you mean 12.5K?

the diffs do not want to be "full" or they will leak oil out

[samd]

My mistake typo, 12.5k wt/7k wt etc.

I make sure my diffs are 'full' just not pressured - i fill them to the top of the axels which makes the diff full when the top is put on, i didnt think having any air in was a good idea, maybe im wrong?? This is how ive always built them.

[annonymous]

hello

i want to try to achieve something like a spool affect, so what front oil? 20k, 30k? what? what oil do i need in the rear to still allow the rear to rotate and not push?

I run at the same track HyperFX does, so you have some basis on how the car reacts to the track

thanks

[mark christopher]

put 100,000 or500,000 oil in the front and 5000 or 7000 in the rear