[samurai]

Forums were full of spyshots of the refresh and news that the 10AT will most like come to the lower models since it was already in the ZL1 and the Mustang refresh. So if you were surprised by the 10AT in the refresh, you should have just googled what's upcoming for the car.

[Norm Peterson]

Originally Posted by crosive

I would only be upset if the A10 was the same as the ones in the zl1's, those things are monsters in more ways than 1.

since the A10 is supposedly a weaker version of an A8 with 2 more gears, I'll pass.

There are more differences than just a couple of gears and another friction element, and strength can be 'adjusted' by things like gear and shaft material selection. Perhaps one of those 'other' differences is at least potentially involved in the A8 shudder issue - something that gets very brief mention in a certain A8 technical article that doesn't show up in in a similar A10 article written by the same author.


Norm

[bturner2]

When my A8 isn't shuddering or "soft, bang shifting" between first and second I love it. Unfortunately I'm on my second flush and live in the cold north where those "only when cold" issues happen every time you get in the car when it hasn't been running for more than an hour.

Honestly I could live with the cold only issues if they fix the shudder problem. Other than the shudder I really am happy with my car.

[crosive]

Originally Posted by Norm Peterson

There are more differences than just a couple of gears and another friction element, and strength can be 'adjusted' by things like gear and shaft material selection. Perhaps one of those 'other' differences is at least potentially involved in the A8 shudder issue - something that gets very brief mention in a certain A8 technical article that doesn't show up in in a similar A10 article written by the same author.


Norm

I didn't mean to dumb it down, I know there are more differences than just numbers, but going by the strength rating, the A10 for the zl1, aside from numerous other differences, is higher than the A10 for the SS's. The strength rating for the A8 and the zl1 A10 are supposedly the same, on paper. I've not done a whole lot of research on the zl1 a10 workings, but what I've learned, it functions very differently from the 8l90 and the 10l80/10r80 in how it queues up clutch packs and whatnot. That is what I'd love to have in my car, even if it still just an A8

There is possibly something in our A8 that causes the tc friction material to wear down faster, but given how everything works, unless GM has employed something exotically different in this transmission vs others, it really limits it to only a few things in the transmission itself that could cause the problem in the tc. *if* it is, then it most likely will be the pump itself. That isn't good, but it is still a replaceable part that should restore full functionality. but given what we collectively know and have been told, it's either not that, or not *just* that.

I don't pretend to know exactly the cause of our shudder issue, but going by my own knowledge, what others have contributed, what I've gathered from professionals in the sector, and techs from gm itself, I'd say I atleast have a decent idea of what's causing it. I'm really anxious to see what "fix" gm has in store, even though I've had a "fix" done already, and the problem is thus far, fixed in my car.

[Norm Peterson]

You might want to look further into the pump . . . some sort of efficiency-enhancing feature analogous to the L99 could be involved.


Norm

[crosive]

Originally Posted by Norm Peterson

You might want to look further into the pump . . . some sort of efficiency-enhancing feature analogous to the L99 could be involved.


Norm

the reason I, personally, don't think it's the pump, is because one of the fixes you can do is 0 out the slip tables on the tcm. this causes that pump to effectively stay on all the time. as far as I know, there haven't been any ill effects of this. Atleast none that anyone has made known.

[Mountain]

Honestly, the A8 is not really far behind the A10 as far as the "oohh, aahh" factor. Being behind both, really, the thing I like the most about the A10 is the tuning in manual mode. The way the A8 is tuned in automatic mode is really, really good. It just falls short in manual mode. But this is something that can be fine-tuned with a tune very easily.

Initially, after driving an A8, than testing some A10's, I was head-over-heals in love with the A10. But, after driving in an A8 again, and than an A6 (Silverado), I actually prefer the A8 due to the gear ratio spread (main gears and OD gears).

[Norm Peterson]

Originally Posted by crosive

the reason I, personally, don't think it's the pump, is because one of the fixes you can do is 0 out the slip tables on the tcm. this causes that pump to effectively stay on all the time. as far as I know, there haven't been any ill effects of this. Atleast none that anyone has made known.

My question there is whether it's a matter strictly confined to the slip tables, or if it's what the slip tables are commanding the pump to do (or not do).


Norm

[HDRDTD]

Originally Posted by ScatPack

It would sure piss me off that I just bought a brand new camaro, and boom the next year they put in the A10 in place of the A8. Anyone else feel like that?? The A8 is a great trans, but A10 is two more. And more is better...lol

No more than when I ordered my 2011 2SS/RS M6 convertible fully loaded
and before it could be delivered, GM announces the ZL1.

[crosive]

Originally Posted by Norm Peterson

My question there is whether it's a matter strictly confined to the slip tables, or if it's what the slip tables are commanding the pump to do (or not do).


Norm

The slip tables, as they are, allow a degree of slip (5-10 I believe). once it sees it, the car switches from the low pressure to the high pressure pump. The slip disappears, high pump off, low pump on. This is the shudder you (and I) feel, as it happens many times per minute.

Zeroing out the slip tables basically makes the high pressure pump stay on all the time.

That slipping is what kills the tc friction material, so once it starts, it won't stop, it can just be hidden by either zeroing out the tables, or forcing the car into v8 mode. V4 mode, and the transition to and from is where the tcm allows the most slip, so that the pulsing from that mode aren't felt so prominently.

The flushes are to remove that friction material from the transmission as they will cause premature wear on the clutch packs.

bottom line, if you have the shudder, your tc is toast. you can bandaid the situation at best and perhaps make the shuddering not felt so often or so much. The only way we know of to actually fix the problem is a decent tc that doesn't have a shit-ass paper friction material that is flat, and not warped because of the way it was manufactured. Then you need a proper friction fluid. Then you need to remove the slip tables so that the high pressure pump won't allow any slip (thus degrade the tc friction plates). That, should in theory, solve the problem once and for all.

[ChickenPoop]

I am getting an estimate from David at Vengeance as we speak for a tune and a new converter . This ain't gonna be a problem much longer.

[Mountain]

Originally Posted by crosive

The slip tables, as they are, allow a degree of slip (5-10 I believe). once it sees it, the car switches from the low pressure to the high pressure pump. The slip disappears, high pump off, low pump on. This is the shudder you (and I) feel, as it happens many times per minute.

Zeroing out the slip tables basically makes the high pressure pump stay on all the time.

That slipping is what kills the tc friction material, so once it starts, it won't stop, it can just be hidden by either zeroing out the tables, or forcing the car into v8 mode. V4 mode, and the transition to and from is where the tcm allows the most slip, so that the pulsing from that mode aren't felt so prominently.

The flushes are to remove that friction material from the transmission as they will cause premature wear on the clutch packs.

bottom line, if you have the shudder, your tc is toast. you can bandaid the situation at best and perhaps make the shuddering not felt so often or so much. The only way we know of to actually fix the problem is a decent tc that doesn't have a shit-ass paper friction material that is flat, and not warped because of the way it was manufactured. Then you need a proper friction fluid. Then you need to remove the slip tables so that the high pressure pump won't allow any slip (thus degrade the tc friction plates). That, should in theory, solve the problem once and for all.

This is about the most theoretically-right statements made about this issue. The only thing I am not sure about is the "low" and "high" pressure pumps. I was under the impression the A8 had a typical gerotor setup, driven off the torque converter and used the pressure solenoids and valving to control pressure.

Edit: A8 pump is a vane-type run off the torque converter , but not directly; it is run via a chain connected to the inputshaft. Only this one pump; pressure control is via pressure solenoids and valves. The basic theory, above, is still right.

[crosive]

Originally Posted by Mountain

This is about the most theoretically-right statements made about this issue. The only thing I am not sure about is the "low" and "high" pressure pumps. I was under the impression the A8 had a typical gerotor setup, driven off the torque converter and used the pressure solenoids and valving to control pressure.

Edit: A8 pump is a vane-type run off the torque converter , but not directly; it is run via a chain connected to the inputshaft. Only this one pump; pressure control is via pressure solenoids and valves. The basic theory, above, is still right.

A unique pump drive design allows for off-axis packaging very low in the
transmission. The pump is a binary vane type which effectively allows for
two pumps in the packaging size of one. The design and packaging strategy
enables low parasitic losses and optimum priming capability and provides
for ideal oil routing to the controls system, with the pump located in the
valve body itself.

At low speeds, both ports supply pressurized fluid to the transmission to meet
demand.

Higher speeds require a lower displacement, and only one discharge port
supplies pressurized fluid.
The fluid from the other discharge port recirculates to the suction side,
reducing the losses in the system and improving overall efficiency of the
transmission.

A binary pump also responds quicker to a reduction in engine speed.
The pump adjusts to changes in demand sooner than the slide on a variable
displacement pump.

so in effect, you are right, there is technically only one piece, but it acts as 2 pumps, a high and a low, and a degree of variability in between

[Mountain]

Originally Posted by crosive

A unique pump drive design allows for off-axis packaging very low in the
transmission. The pump is a binary vane type which effectively allows for
two pumps in the packaging size of one. The design and packaging strategy
enables low parasitic losses and optimum priming capability and provides
for ideal oil routing to the controls system, with the pump located in the
valve body itself.

At low speeds, both ports supply pressurized fluid to the transmission to meet
demand.

Higher speeds require a lower displacement, and only one discharge port
supplies pressurized fluid.
The fluid from the other discharge port recirculates to the suction side,
reducing the losses in the system and improving overall efficiency of the
transmission.

A binary pump also responds quicker to a reduction in engine speed.
The pump adjusts to changes in demand sooner than the slide on a variable
displacement pump.

so in effect, you are right, there is technically only one piece, but it acts as 2 pumps, a high and a low, and a degree of variability in between

Interesting.

The TCC circuit in the A8 is also more complex than I thought. It has the TCC solenoid and valving to control one side (apply) of the hydraulic circuit, but it also has solenoid control on the other (exhaust). Most automatics have only have had the TCC solenoid and valve control on the one side (apply), leaving the other side (exhaust) basically open.

What I am saying is the TCC control is more controlled and complex than what most might expect.