Diff oil and tyres

Have read the sticky and it's not the same so thought I'd post. Had two new front tyres and noticed a 'rumbling' vibration from the back at about 40-45 mph, more so when braking, striaht after fitting. At this time I had mismatched tyres on the rear (I know, not good). Changed the two rear tyres just to be safe and went on my hols to Scotland (very wet and lots of midges!).

That was 3 months ago and now I still have the 'rumbling' noise, and inspection underneath the back shows oil on the rear frame.

Did tippex tape on the VCU and it's ok. Any ideas?

You mean you havent read the threads about putting the newer tyres on the BACK axle due to how the VCU works?

Clean off the oil to see where its coming from. Check diff oil level

Am sure there will be more people along to give you advice soon

Check the oil level in the rear diff. to see if you are loosing any.
Bell engineering are disputing the tip-exx test.
New tyres being only put on the front may have caused some damage or put strain on the drivetrain. If you suspect vcu is at fault then remove it and props and see how it drives in 2wd.