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- 1992 XLT
A while ago, someone asked about issues relating to the fact his transmission might be a non-synchronous automatic shifting transmission. I replied that i was not aware of a difference in AT's in that regard. "Synchronous" implies two or more things operating "in synch" - whatever that might mean in a given application - and a synchronized manual transmission was a well known animal.
In manual transmissions, a synchronous transmission spins up currently unused gearsets to aid is gear meshing on shifts that DO utilize those gears, and an AT is entirely different in how it effects shifts. I thought the comment about synchronous vs. non-synchronous was out of place in reference to automatic transmissions - and said so. Well.... I ran across something tonight in trying to educate myself on the FORD 4R75W and new 6R series (always learning something) and I found the following on a website... and thought I would share it. As I do I want to note that the author was pretty inadequately informed about the differences between the 5R55S and the 4R70W, so use a grain of salt as you read this, but here is what he (or she) wrote about synchronous auto trannies:
"A “non-synchronous” shift in an automatic trans means that when the trans shifts from one gear ratio to the next, it happens by applying only one clutch or band and nothing else has to happen. The “non-synchronous” shift is seamless and has no chance of a flare happening between the gear change. The best way to explain this in a very simple way is to picture a typical 10-speed pedal bicycle that you would have to shift manually (we’ve all ridden & shifted these). You could go up and down through the gears on those while pedaling with no loss of power to the rear tire essentially. They just shifted on the fly with no chance of hitting a neutral gear between the gears while shifting.
“Synchronous” shifts means that for a gear change to happen, one device, be it a Clutch or Band has to apply and something else has to release simultaneously. This is really not a problem at moderate power levels. But, when you start to hit the trans with some very high power levels, gear changes that have to happen “synchronously” can risk an rpm flare between the gear changes. This flair can happen because one thing has to apply and another thing in the trans has to release simultaneously. When this action is happening in the trans, if it doesn’t time them and perform them accurately, an rpm flair can happen between the two actions. This can be very damaging to the trans because the flair can shock the trans very hard when the gear change is finally completed. This (flare) is what caused the most common failure in the C-4 three speed automatics commonly used in Mustangs and other Ford’s in drag racing. The C-4’s shifted “synchronously” only into 3rd gear not 2nd. And this is when they would usually break in very high horsepower applications, when shifting into 3rd gear."
For the person who may have felt "blown off" by my previous response, I eat a large dose of humble pie. My apologies.
Like I said, I an constantly learning. Hope that never changes... and even those of you who think I may "know it all"... need to know that a) I don't, and b) you may teach an old dog new things. Keep at it.
Glacier
In manual transmissions, a synchronous transmission spins up currently unused gearsets to aid is gear meshing on shifts that DO utilize those gears, and an AT is entirely different in how it effects shifts. I thought the comment about synchronous vs. non-synchronous was out of place in reference to automatic transmissions - and said so. Well.... I ran across something tonight in trying to educate myself on the FORD 4R75W and new 6R series (always learning something) and I found the following on a website... and thought I would share it. As I do I want to note that the author was pretty inadequately informed about the differences between the 5R55S and the 4R70W, so use a grain of salt as you read this, but here is what he (or she) wrote about synchronous auto trannies:
"A “non-synchronous” shift in an automatic trans means that when the trans shifts from one gear ratio to the next, it happens by applying only one clutch or band and nothing else has to happen. The “non-synchronous” shift is seamless and has no chance of a flare happening between the gear change. The best way to explain this in a very simple way is to picture a typical 10-speed pedal bicycle that you would have to shift manually (we’ve all ridden & shifted these). You could go up and down through the gears on those while pedaling with no loss of power to the rear tire essentially. They just shifted on the fly with no chance of hitting a neutral gear between the gears while shifting.
“Synchronous” shifts means that for a gear change to happen, one device, be it a Clutch or Band has to apply and something else has to release simultaneously. This is really not a problem at moderate power levels. But, when you start to hit the trans with some very high power levels, gear changes that have to happen “synchronously” can risk an rpm flare between the gear changes. This flair can happen because one thing has to apply and another thing in the trans has to release simultaneously. When this action is happening in the trans, if it doesn’t time them and perform them accurately, an rpm flair can happen between the two actions. This can be very damaging to the trans because the flair can shock the trans very hard when the gear change is finally completed. This (flare) is what caused the most common failure in the C-4 three speed automatics commonly used in Mustangs and other Ford’s in drag racing. The C-4’s shifted “synchronously” only into 3rd gear not 2nd. And this is when they would usually break in very high horsepower applications, when shifting into 3rd gear."
For the person who may have felt "blown off" by my previous response, I eat a large dose of humble pie. My apologies.
Like I said, I an constantly learning. Hope that never changes... and even those of you who think I may "know it all"... need to know that a) I don't, and b) you may teach an old dog new things. Keep at it.
Glacier
