Is GL-5 bad for our transmission
- Thread starter ghost2277
- Start date
cycleman11
Member
I was reading this topic and went to Amsoils own site where it explains the different gear set types: ie - hypoid, helical etc and found the following statement:
" Most manual transmissions have helical gears and do not require GL-5 performance ". To my knowledge the new 6 speeds have helical gear sets. Wrong or right?
I do know from previous experience if a tranny has syncros in it and you put a GL5 spec verses a GL4 spec oil, it will get very hard to shift with the GL5 gear oil and it will destroy the syncros.
Being somewhat a logical person - If our HD 6 speeds don't have any yellow metal or syncros then you can use a sync GL5 spec, most likely a 75-90 as that is the same viscosity as a 20-50 sync mc oil ( which seems to be the factory viscosity recommendation ) without incurring any real problems. That most likely explains why you can use either the GL5 gear oil or the 20-50 sync mc oil without any wear issues. ( Drain plugs of bikes using either report little or no fuzz on magnets ) The original question about the yellow metals hasn't been answered. Somebody who's torn down one of these tranny's should have the answer.
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I answered my own question when I looked in the service manual for the 6 speed in the softrails. The tranny contains both straight cut & helical. Looks like 2 straight cut gear sets & 4 helical gear sets. I couldn't find anything that looked like in would be made of yellow metal. I did see that there are some fairly small bearings that are located on the shafts that a thick oil would have trouble lubricating.
So it looks like you can use either type of oil, whatever suits your fancy.
" Most manual transmissions have helical gears and do not require GL-5 performance ". To my knowledge the new 6 speeds have helical gear sets. Wrong or right?
I do know from previous experience if a tranny has syncros in it and you put a GL5 spec verses a GL4 spec oil, it will get very hard to shift with the GL5 gear oil and it will destroy the syncros.
Being somewhat a logical person - If our HD 6 speeds don't have any yellow metal or syncros then you can use a sync GL5 spec, most likely a 75-90 as that is the same viscosity as a 20-50 sync mc oil ( which seems to be the factory viscosity recommendation ) without incurring any real problems. That most likely explains why you can use either the GL5 gear oil or the 20-50 sync mc oil without any wear issues. ( Drain plugs of bikes using either report little or no fuzz on magnets ) The original question about the yellow metals hasn't been answered. Somebody who's torn down one of these tranny's should have the answer.
===============================================
I answered my own question when I looked in the service manual for the 6 speed in the softrails. The tranny contains both straight cut & helical. Looks like 2 straight cut gear sets & 4 helical gear sets. I couldn't find anything that looked like in would be made of yellow metal. I did see that there are some fairly small bearings that are located on the shafts that a thick oil would have trouble lubricating.
So it looks like you can use either type of oil, whatever suits your fancy.
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