Not sure what has changed in recent years, but more and more I am seeing and hearing about transmissions being notchy when cold, but shifting perfectly when warmed up. Speaking about manual trannies. It happens in my car all the time but we are even seeing it in companies that have been traditionally known to produce the best transmissions - such as BMW and Honda. My tranny is very notchy when cold, but as soon as you get some heat in it , it shifts really well. The owner's manual even goes out to state that this is normal. Is this a function of the transmission fluid, or just the construction tolerances of modern manual trannies ?. It seems to take my car about 15-20 minutes of constant city driving before it seems to heat up enough to work smoothly, it isn't super rough when cold but just a bit notchy. But once you get some heat in it the thing shifts perfectly. Just curious about this phenomena because I'm not so sure that it is all fluid related, I used to thing it was fluid related but I am hearing this complaint from many owners lately in all makes and models.
Warm Trannies Shifting Better, Any Reason ?
- Thread starter Idrinkmotoroil
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The synchros might be using a harder or treated, case hardened material for longevity. The heat may cause expansion for just the right slip into gear. Just a thought
JHZR2
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Id have to guess that in time, transmissions have been targeted to some extent as a source of some energy loss that could be translated into higher fuel efficiency, higher RWHP, etc.
With the changes in designs, as gradual as they may or may not have been in time, perhaps some of the qualities have been effected at one point or another, as workarounds slowly get develloped.
But this is just a guess. Id have to think that over time, transmissions have been improved and changed/tweaked, and whenever such things occur, new issues arise. Maybe
JMH
With the changes in designs, as gradual as they may or may not have been in time, perhaps some of the qualities have been effected at one point or another, as workarounds slowly get develloped.
But this is just a guess. Id have to think that over time, transmissions have been improved and changed/tweaked, and whenever such things occur, new issues arise. Maybe
JMH
Shannow is "spot on". I speak from personal experience of driving manual trannies for 35 years. Each tranny is different and the trick is to match the fluid to the tranny and your climate and what type of shifting quality is more important to you. I live in NJ so we get fairly hot summers and fairly cold winters. A viscous fluid will work great in the summer but s*cks in the winter. ATF, which my tranny is spec'd for works decently in the winter but horribly in the warm to hot weather. I compromised and went with MolaKule's SF SynchroGide. It's about 2-2.5 cST's more viscous than ATF and 2-2.5 less viscous than SF's MTL-P. So far in 18*F temps the SynchroGlide was just as easy to shift into gear as the ATF. And in 75*F temps the SynchroGlide is soooo much better. No more crunching when shifting because the ATF thinned out to even less than 7-7.5 cST. I could probably use the MTL-P all year round but my winter shifting would probably be more difficult than I would want. And I don't to change tranny fluids for different seasonsquote:
Originally posted by Shannow:
it always has been fluid related.
viscosity, viscosity index and additives.
edit...just got to find the right combination for YOUR trans.
Whimsey
Whimsey and Shannow are right.
There is a secondary possibility, of the metals expanding to tighter clearances, changing alignments, and engagement distances.
There is a secondary possibility, of the metals expanding to tighter clearances, changing alignments, and engagement distances.
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