This winter i built a new axle with strengthening in the lower center part of the axle wich created a bigger oil capacity of 2,1 liter. The bigger capacity gives more durability and cooler oil.
I use Eurol 75W140
After some trobble with the previous mk20 axle and Castrol B373 oil i choose to go for a modern oil (75W140) and now for a bigger capacity diff. Did 3 years with the previous diff on the 75W140 oil (1.2 liter diff) Last year the old mk27 diff had a leak and blew the diff due to lack of oil.
The new axle also gives the rearaxle 1 degr. camber for the radials.
Interesting, my car developed a mega vibration at Snetterton late on in race 1 which I suspected was either tyres (the balance weights came off the fronts), the prop shaft (which was ok) or something else transmission related. Temperatures were very high during race 1 and shot up alarmingly on returning to the paddock, water temp gauge needle went beyond maximum up to the stop pin. For the later races Mark rigged up a means of holding the rear deck open to assist air flowthrough (this kept racing temperatures to the high end of reasonable) and the wheels were balanced which reduced vibration from ridiculous to just teeth rattling. Inspection yesterday revealed a tooth was largely missing from the differential’s pinion and that a locking bolt was missing from the axle cage, the latter was likely to have been shaken out by the subsequent vibration.
I put the likely root cause of the above down to insufficient airflow through the car resulting in unacceptable running temperature for the diff compounded by the unusually hot conditions. If you are in doubt as to your car’s underbody and diff temperature under racing conditions, the air temp is in the 30's and there is no cloud cover to reduce the direct radiation from the sun I’d recommend introducing something to improve flowthrough. Any effect on driveability can ultimately be resolved.
