One of my most frequently asked question, full of misconceptions, is "should I install a shift kit?", or "how can I make my transmission shift harder?", etc.

I read an article by Gil Younger (One of the most accomplished shiftkit designers) that stated something to the effect: "A 'perfect' shift, as it pertains to transmission longevity, is a shift that you really cannot say too much about...". What he means by this, is that a good shift is not soft and drawn-out, nor is it harsh and quick; it is merely a complete change, from one gear to the next, in the most efficient manner. The most obvious thing a clutch, within an automatic transmission, needs to do is complete a shift, but it also needs to provide a cushion for a smooth transition from one gear to the next. Consider, for the moment, that your transmission has a 3:1 first gear ratio (round numbers to keep things relatively simple) and a 2:1 second gear ratio, and a 1:1 third gear ratio. Now consider that your engine needs to shift at 3000 RPM's. Obviously, using simple math, and forgetting things that may complicate matters, like torque converter slippage, etc, your driveshaft would turn at 1000 RPM's when it is time to shift from first to second gear (3000 engine RPM's, divided by the 3:1 first gear ratio). At that moment when the shift occurs, the engine must decrease in speed, to 2000RPM's, or the driveshaft (and, vehicle speed which is tied directly to driveshaft speed) must increase to double it's original speed, UNLESS the transmission provides some kind of cushion to allow the engine to slow down, and the vehicle to speed up, at a smooth rate. During this time of "cushioning", the clutches do create heat, so this time must be short enough to eliminate excessive heat generation, that could cause a set of clutches to fail.

More to the story... There is much more that happens during a typical automatic transmission shift, that must be considered, to completely figure just how long shift duration should be. In some cases, it is as simple as I suggested; a shift completion is accomplished simply by applying a clutch, and the time it takes to complete the shift is governed, completely, by the time it takes for that particular clutch pack to apply. In many cases, however, it is not as simple as that. In order to complete a shift, some transmissions must release a clutch pack, and must apply another clutch pack (I say 'clutch pack', but really mean a 'friction element' which could be a band, or a clutch), simultaneously, which becomes much more complicated. If we release one clutch, before we apply the other clutch, a "shift flare" can occur (causing the engine to momentarily rev up before completing the upshift), and, conversely, if we release the clutch after we apply the other clutch, a "shift bind up" can occur (causing the transmission to be in two gears at once, for a brief period, which is like putting on the brakes); both of these situations can lead to premature clutch failure, and eventual transmission failure. "Shift flare" causes the applying clutch to overheat, because the engine revs up causing the clutch to have to do more work. "Shift bind" causes both, the applying, and the releasing clutch pack, to overheat as they work against each other, but a shift bind may feel like a "crisp shift", often "chirping" tires or yeilding a "high performance" shift feel, while being very damaging to the transmission.

A Harsh Shift Can Actually Shorten the Life of a Transmission In addition, it must be understood that a transmission, or any other component for that matter, will last much longer if it is not "hammered on". Tires, axles, differentials, driveshafts, transmission components, etc. will all last longer if they are not hammered on, but "pushed" smoothly. Almost everyone understands the importance of high octane in their engine, to keep the engine from detonating, or 'pinging', because detonation creates extra heat, and "hammers" on the engine. Try "pushing" on a disabled car, rather than taking a run, and "slamming" into the car, to make it move; you will find that the car actually moves better if you "push" it, rather than slamming into it (and you body will feel better too). Your transmission must "push" the car, rather than "hammering", or "slamming" the automobile along.
Clutch Condition Provides Clues That Tell a Rebuilder How Well a Transmission is Shifting Back to the "cushioning effect" provided by automatic transmissions. As I said before, cushioning a shift is good, but it does not come without a price. Shift cushioning causes heat, and the longer the duration of the shift, the softer the shift, the more heat is typically generated. The "trick" is to cushion the shift, the maximum amount, without overheating the clutches. Overheated clutches are easy to recognize, when the transmission is torn down. I have found, upon disassembly, that MOST transmissions (I did not say ALL...) do NOT have a problem with overheated clutches, proving, at least, that they do not suffer from too soft of a shift. Depending upon the transmission, a harsh shift can actually cause more transmission failures than a soft shift. When I pull a transmission apart, I look for the CAUSE of the failure, and, if I find that a clutch pack suffers from excessive heat, I perform modifications that are PROVEN to cure the original CAUSE of the problem. In most cases, I find no problems resulting from shift quality concerns, EXCEPT when I have to fix a transmission that has already been "Improved" by another rebuilder. I fix many transmissions as a result of shiftkit installations, and other shift calibration adjustments, made by rebuilders who do not fully understand what they are modifying. They may modify an applying clutch pack to shift quicker, without modifying the releasing clutch pack to release more quickly too, causing a shift bind, that may feel like a "good hard shift", but actually causes the transmission to fail sooner. Upon disassembly, these rebuilders may discover two burnt clutch packs (the releasing and the applying pack), and think that these clutch packs are not applying quick enough, so they make more modifications to make the clutches apply more quickly, which causes even more bind up when they assemble the transmission again. This type of thing happens all of the time. The moral of this story is, "by not understanding the CAUSE of the problem, the technician actually made things worse, and, when it came back, they continued to make a "bad thing" even worse, again, as a result of their lack of understanding of the actual CAUSE of the problem". In addition, by making the transmission shift harder, the technician is subjecting the transmission to more "hammering" than it would normally get, which can, and does, in many cases, lead to premature transmission failure, by breaking a part, within the transmission.
[hr] Alter Shift Quality, When, and If It is Needed By Example: The 700R4, and Why I Do Not Recommend Shiftkits in 700's... Some transmissions do have shift quality problems that need to be dealt with. For example, the 700R4 transmission has a nasty habit of burning the 3/4 clutches. To "fix" this problem, many rebuilders add an "Alto" kit (or another brand of clutch pack, that are thinner, providing room for more clutches), and drill out the apply hole (which makes the clutch pack apply more quickly). In addition, to make the transmission shift harder into second gear, they change to a Corvette servo piston, which has more apply serface area. The 700R4 3/4 clutch pack usually burns up, as a direct result of a few different problems, all of which are not addressed by most technicians. Number one: the 2nd gear band must release when the 3/4 clutches apply, to produce a 2nd to 3rd shift, so, when they increase the apply area of the band,(to make the 2nd gear shift harder), they also make the band release more slowly, and,

 

wow, this is kinda retarded, nothing against you though, but my idea of a "perfect" shift is when you push the clutch in, change gears, and let off clutch.

 

i know but it also gives a good heads up to ppl that drive auto's and manuals..i found most of the info usefull

 

may i ask where you copied that from?

 

http://www.technicalevolution.com/niceshft.htm

hell no i wouldnt type all that hahaha...how did the info treat u?

 

I get sort of confused when it talks about shifting at 1,000 rpms from 1st to 2nd ?