I flushed my diff and transmission today. The diff is a 188mm Z3 case with a Wavetrac unit fitted into it by member Wanganstyle. It has maybe 30000 miles on it, and I originally ran Titan Sintopoid 75W-90 gear oil in it. Now it's the Motul stuff. The Titan fluid came out sort of dark and nasty looking, but I assume that there is a fair amount of wear-in that occurs on a new diff. Additionally, I flushed my Getrag 240 transmission. To be honest, I cannot remember which fluid was in it or when I last changed it since I swapped a lower-mileage spare G240 back around 2013 when I was putting my 2.1L M42 in. I believe that I last put RedLine MT90 in there, and it would likely have around 40k miles on it now. It was very nasty looking, and I had been getting a lot of noise in 2nd & 4th gears when accelerating hard. It's now also running the Motul product.
The transmission no longer makes any noise in 2nd & 4th gears when accelerating. The old fluid was supposedly a 75W-90 product, so either it was breaking down, or it just wasn't maintaining viscosity. The transmission is quieter and shifts smoother for sure. Also, I have a really noisy input shaft thanks to the 7.4lb flywheel I am running, and that rattle is definitely diminished now (make no mistake, it still sounds like a coffee can full of rocks when sitting idle with the clutch pedal up, but it's like some foam scraps got tossed in with the rocks now).
Anyway, this isn't all that important of a thread or anything, but since I've tried a variety of fluids in the diff & transmission over the years, I wanted to share the positive results that I have had with the Motul stuff in my transmission. As far as the diff, I can't tell if it is "better" or not. The car drives smooth and quiet, so it certainly did not make anything worse! This Motul product is directly recommended by the manufacturers of Wavetrac diffs.
This is the stuff, sold at various places online:
The Z3 188mm medium-case diff took ~1.7L of the stuff, and my G240 took ~1.1L of it. I added 1.8 & 1.2L, respectively, and probably 100mL ran out of the fill holes.
The transmission no longer makes any noise in 2nd & 4th gears when accelerating. The old fluid was supposedly a 75W-90 product, so either it was breaking down, or it just wasn't maintaining viscosity. The transmission is quieter and shifts smoother for sure. Also, I have a really noisy input shaft thanks to the 7.4lb flywheel I am running, and that rattle is definitely diminished now (make no mistake, it still sounds like a coffee can full of rocks when sitting idle with the clutch pedal up, but it's like some foam scraps got tossed in with the rocks now).
Anyway, this isn't all that important of a thread or anything, but since I've tried a variety of fluids in the diff & transmission over the years, I wanted to share the positive results that I have had with the Motul stuff in my transmission. As far as the diff, I can't tell if it is "better" or not. The car drives smooth and quiet, so it certainly did not make anything worse! This Motul product is directly recommended by the manufacturers of Wavetrac diffs.
This is the stuff, sold at various places online:
The Z3 188mm medium-case diff took ~1.7L of the stuff, and my G240 took ~1.1L of it. I added 1.8 & 1.2L, respectively, and probably 100mL ran out of the fill holes.
