Ok I know what some of you will say, rebuild the diff properly. I did, 7 times, and changed Ring and pinion twice, brand new OEM gearsets. The diff is a IRS mk3 Supra 4.556 ratio , 9 pinion , 41 tooth ring gear.
To cut a long story short, I experimented with various pinion depths and pinion preloads, and found that the diff worked better with a high pinion preload, high end of the acceptable scale of TOYOTA TSRM.
My current iteration of this rebuild, had the pinion run a little shallow for the first 1000km of light break in. Pinion depth shim 1.9mm. The gear pattern looked good but it whined at 60 to 70kmh. I proceed to deepen the pinion depth back to stock shim of 1.94mm. The results are the same. The pinion preload is not low or loose. It is still tight and within spec. But on light throttle at 60 to 70kmh, the whining is at it's loudest. When I let off the throttle, it is virtually silent. I tried various GL-5 Gear oils from Toyota 85W-90, Mobil HD80W90, Mobil HD 80W90 + 25% Lucas Oil Stabilizer, and just recently Lucas Mineral 80W90.
With the lucas, there is 20% reduction in the sound. The Lucas 80W90 seem to not thin as much as the Toyota 85W90 and Mobil HD80W90.
I am looking for a 50% reduction of this whine on light throttle at 60 to 70kmh. To be clear, there is still a whine over 70kmh but the faster I go the fainter the sound gets.
I was thinking of trying a few oils.
1. Lucas Synthethic 75W-140
2.Shell Spirax 85W-140
3. Using Plain old 80W90 + Motorcraft XL-3 additive, some people have said it reduced the ring and pinion noise
I want to try to avoid using 140 weight diff oil if possible, as I think it would be like driving the car with another 70kg me in the passenger seat.
I know most of you will say diff oil wont make a difference, but a lot of people sweared by Specialty Formulations GL-5 oil which is now unavailable.
Let me know what worked for you.
Oh yes, Amsoil severe gear 75W110 did nothing on 2 previous rebuilds.
To cut a long story short, I experimented with various pinion depths and pinion preloads, and found that the diff worked better with a high pinion preload, high end of the acceptable scale of TOYOTA TSRM.
My current iteration of this rebuild, had the pinion run a little shallow for the first 1000km of light break in. Pinion depth shim 1.9mm. The gear pattern looked good but it whined at 60 to 70kmh. I proceed to deepen the pinion depth back to stock shim of 1.94mm. The results are the same. The pinion preload is not low or loose. It is still tight and within spec. But on light throttle at 60 to 70kmh, the whining is at it's loudest. When I let off the throttle, it is virtually silent. I tried various GL-5 Gear oils from Toyota 85W-90, Mobil HD80W90, Mobil HD 80W90 + 25% Lucas Oil Stabilizer, and just recently Lucas Mineral 80W90.
With the lucas, there is 20% reduction in the sound. The Lucas 80W90 seem to not thin as much as the Toyota 85W90 and Mobil HD80W90.
I am looking for a 50% reduction of this whine on light throttle at 60 to 70kmh. To be clear, there is still a whine over 70kmh but the faster I go the fainter the sound gets.
I was thinking of trying a few oils.
1. Lucas Synthethic 75W-140
2.Shell Spirax 85W-140
3. Using Plain old 80W90 + Motorcraft XL-3 additive, some people have said it reduced the ring and pinion noise
I want to try to avoid using 140 weight diff oil if possible, as I think it would be like driving the car with another 70kg me in the passenger seat.
I know most of you will say diff oil wont make a difference, but a lot of people sweared by Specialty Formulations GL-5 oil which is now unavailable.
Let me know what worked for you.
Oh yes, Amsoil severe gear 75W110 did nothing on 2 previous rebuilds.