Originally Posted by zeng
Originally Posted by Avery4
Originally Posted by zeng
Both, IMO.
At a particular clutch system (of First Gear, or Second Gear and so on within a transmission system), individual line pressures (psi) AND clutch friction material areas(square inches) are selected to meet a typical design criteria of 3 times peak torque (lbs-in) value .
Acknowledging this torque transfer capacity would deteriorate with use, in particular in relation to oil aging(?) phenomenon, the increased line pressue allows a larger margin of deterioration of torque transfer capacity , hence increased 'abuse' of oil aging one could tolerate .
Now, would this increased line pressure leads to oil seal leaks ?
I would speculate
no as typical auto transmission line pressure is typically 25 - 35 psi say, whereas as a typical oil seal system could withstand thousands , if not hundreds of psi .(Note: What is your increased pressure value?)
A locked converter shift would result in marginally higher 'shock' during torque transfer phenomenon, in relation to unlocked converter shift .
However, this increased 'shock' (from locked converter) would be milder in relation to a typical manual transmission torque transfer shock with dry clutch system .
Hence, its longevity cannot be worse off than a typical manual transmission as found in similar Honda Civic .
Just my
That makes sense, thanks for all the great information! So is the person who told me that I am causing excessive clutch wear by causing gear overlap wrong?
There cannot be a phenomenon of gear overlap, if by overlap means gearing sets for two different output speeds are engaged and function simultaneously within a transmission system .
Instead in up-shifting, there is a time delay in prior release of lower speed gear engagement to be followed by subsequent engagement of higher speed gear , never overlap in simultaneous gear engagement of two differing speeds .
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The way he explained it, the PCM normally momentarily reduces pressure during shifts to create an "in between gears" moment so one clutch disengages before the next engages so there aren't two clutches engaged at the same time, but now that the PCM can't reduce pressure, one set of clutches is engaging before the previous set is completely released, basically causing the transmission to be in 2 gears at the same time fighting itself internally for a split second every time it shifts.
In up-shifting, once the lower speed gear/clutch disengages (as determined and instructed by PCM with time as a function) the fluid pressure (of say 30 psi) is released to transmission oil sump at near zero 'atmospheric' pressure in a normally function system . During pressure drop phenomenon ,it's pressure cannot be maintained at reduced value of say, 25 or 20 psi (for so many seconds or miliseconds) AND continue to 'perform' a function within the said gear/clutch system .
Time delay (in miliseconds or seconds) is the primary parameter in the initial release of lower speed gear/clutch system to be followed by subsequent engagement of higher speed gear/clutch system .
An engaged gear/clutch system comprises piston pressure of say, 30 psi (as per design and construction) .
A disengaged gear/clutch system has a piston pressure of 0, in a normally functioned system
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I would think that I would be reducing overlap if anything since the shifts are now quicker. Thanks
Putting it in another way, I would say a quicker shift comes with a reduced or lower time delay in between engagement/disengagement .
Great explanation, thank you so much! I was wondering if I was possibly increasing the engine's load by maintaining a higher line pressure, so I tested that. To put it simply, what I did is I plugged the solenoids back in, lifted the front end of the car, started the engine, shifted to drive, and noted the speed that the speedo read idling in 4th gear, about 35 MPH. Then while it was running I unplugged the solenoids to raise the pressure to maximum. I noticed no change in the engine's sound and the speedo didn't drop.
From this quick test, I came to the conclusion that I am not increasing the load on the engine by maintaining a higher line pressure. This test is sensitive enough that I can drop the speedo reading by several MPH simply by turning the headlights on, so if there is any additional load on the engine, it is way less than the load of the headlights. Thought you or someone else may find that interesting since I sure did
Also, I'm wondering what you think of having the old fluid analyzed to see what the wear metals are. Would this provide any useful information? I am thinking since that wouldn't tall me anything about metal fatigue it would be a waste of my money, but what are your thoughts on this?