I serviced my car on Saturday at work. and changed my gear oil when i drained it, it was black been in there 60,000 miles never been changed and my 3rd gear whined on knock down from 4th,
refilled my box thru the reverse light sensor, which is just above the filler hole, left the overfill plug out till it started coming out and then tighten that up. then put an extra half a litre thru the reverse sensor hole.
tested it and at first didn't seem to make any difference but the more ive drove the car it dont make the noise as much any more. i can cog down at 50 mph into 3rd and no whine now.
just an idea if any 1 else wants to try and cheaper fix to see if it helps