why so many multi speed automatics?

[Quattro Pete]

Originally Posted By: artificialist
However, I have heard some people say they would be impossibly expensive to rebuild. I disagree.

When the 7-speed trans died on our C300, MB did not rebuild it. They just put a new one in there.

 

[artificialist]

Originally Posted By: Quattro Pete
Originally Posted By: artificialist
However, I have heard some people say they would be impossibly expensive to rebuild. I disagree.

When the 7-speed trans died on our C300, MB did not rebuild it. They just put a new one in there.

Some car makers do that while the car is in warranty. They may take the dead transmission to a laboratory to determine failure, then learn how to make a better transmission. Other times, the manufacturer of that transmission hasn't created a rebuild kit, and that is why the whole thing gets replaced.

 

[dparm]

Originally Posted By: Quattro Pete
Originally Posted By: artificialist
However, I have heard some people say they would be impossibly expensive to rebuild. I disagree.

When the 7-speed trans died on our C300, MB did not rebuild it. They just put a new one in there.



Yep, many new transmissions are considered "sealed units" and cannot be easily disassembled. If you look at the diagnostic flow charts for my DCT (Getrag), you perform tests with the special dealer diagnostic tools...and the final step is always "replace transmission assembly".

 

[Nebroch]

Originally Posted By: artificialist
Some car makers do that while the car is in warranty. They may take the dead transmission to a laboratory to determine failure, then learn how to make a better transmission. Other times, the manufacturer of that transmission hasn't created a rebuild kit, and that is why the whole thing gets replaced.


They may also rebuild it at Germany and sell it to someone else as new. Handsome profits

 

[dparm]

Originally Posted By: Nebroch
Originally Posted By: artificialist
Some car makers do that while the car is in warranty. They may take the dead transmission to a laboratory to determine failure, then learn how to make a better transmission. Other times, the manufacturer of that transmission hasn't created a rebuild kit, and that is why the whole thing gets replaced.


They may also rebuild it at Germany and sell it to someone else as new. Handsome profits

No, they'll sell it as remanufactured, often back to the car manufacturer for replacement of a failed one.

 

[Scrum67]

My 2014 Ram 1500 with 5.7 hemi has 8 speed tranny..Shifts really smooth and a pleasure to drive..After 1 year of driving mainly city is averaging 13.0 litres per 100 km.

 

[OneEyeJack]

Originally Posted By: Nebroch
Originally Posted By: OneEyeJack
Maybe it's a sign that multi-speed transmissions will be a better solution then a CVT. The most reliable one of them all would be the Prius when is not a CVT an has only one gear forward and no reverse and never shifts from one gear to the next.


Not a CVT? What is it then? Here is a hydraulic clone of it with 2 range gears:

https://www.youtube.com/watch?v=dgtIKMAjvFI


The Prius is a planetary transmission with a ring gear, a sun gear and planet gears. Nothing shifts and reverse is handled by the electric motor. It's simple and as bullet proof and things get.

 

[grampi]

Originally Posted By: edwardh1
wonder what that adds to weight cost and complexity/reliability of the trans?


Reliability is my main concern with these mega speed trannies...a lot of the automatics already had questionable reliability, adding more gears and the complexity that goes along with them only makes them more susceptible to failure...

 

[Nate1979]

Originally Posted By: grampi
Originally Posted By: edwardh1
wonder what that adds to weight cost and complexity/reliability of the trans?


Reliability is my main concern with these mega speed trannies...a lot of the automatics already had questionable reliability, adding more gears and the complexity that goes along with them only makes them more susceptible to failure...


There are 4 speeds that have issues. Lets not wear rose colored glasses thinking the old school design was long lived and reliable.

 

[supton]

Originally Posted By: Nate1979
Originally Posted By: grampi
Originally Posted By: edwardh1
wonder what that adds to weight cost and complexity/reliability of the trans?


Reliability is my main concern with these mega speed trannies...a lot of the automatics already had questionable reliability, adding more gears and the complexity that goes along with them only makes them more susceptible to failure...


There are 4 speeds that have issues. Lets not wear rose colored glasses thinking the old school design was long lived and reliable.


Very true. Although those 4spd autos often were made for a decade plus and now have cheap rebuild options.

 

[grampi]

Originally Posted By: Nate1979
Originally Posted By: grampi
Originally Posted By: edwardh1
wonder what that adds to weight cost and complexity/reliability of the trans?


Reliability is my main concern with these mega speed trannies...a lot of the automatics already had questionable reliability, adding more gears and the complexity that goes along with them only makes them more susceptible to failure...


There are 4 speeds that have issues. Lets not wear rose colored glasses thinking the old school design was long lived and reliable.


Rose colored glasses? Did you not read my post? I believe I said "a lot of automatics already had questionable reliability"...my point was adding more parts to a tranny makes them more prone to failure...in other words, when it comes to auto trannies and reliability, the simpler the better...

 

[SubLGT]

Maybe it has already been mentioned in this thread, but Ford and GM have plans for a 9-speed and 10-speed trans. The Ford 10-speed may show up first in the F-150, according to rumors, in about 18 months.

http://media.gm.com/media/us/en/gm/news....ansmission.html

 

[Nick R]

Originally Posted By: grampi
Originally Posted By: Nate1979
Originally Posted By: grampi
Originally Posted By: edwardh1
wonder what that adds to weight cost and complexity/reliability of the trans?


Reliability is my main concern with these mega speed trannies...a lot of the automatics already had questionable reliability, adding more gears and the complexity that goes along with them only makes them more susceptible to failure...


There are 4 speeds that have issues. Lets not wear rose colored glasses thinking the old school design was long lived and reliable.


Rose colored glasses? Did you not read my post? I believe I said "a lot of automatics already had questionable reliability"...my point was adding more parts to a tranny makes them more prone to failure...in other words, when it comes to auto trannies and reliability, the simpler the better...


So we should take that to the logical extreme and go back to the 2 speed auto trannies of old? I think that by and large most 6 speeds are proving very reliable, with a few exceptions (some of the GM/Ford 6T75s for example)

 

[gofast182]

My car has a 9 speed auto. I don't love the trans, it's too many gears. When you're on the highway and give it moderate throttle it will kick down a couple gears no problem. If you're on the highway and you give it full throttle it takes what feels like FOREVER because it's going down 5-6 gears at once. All of the necessary mechanical action, disengagement of dog clutches and the like are what does it. I don't see the need for more than 7 gears personally.

 

[TiredTrucker]

The higher number of gears in transmissions thing is fine, if they also provide the proper differential ratio to deal with it. For instance my Silverado pickup has he 6 spd auto in it. But 6 rarely ever gets used and I live rural with very little town or urban driving. Why? Because the speed limits on rural two lane highways are 55-60, and with the rolling hill terrain thrown in, if I allow it to go to 6th, it is always having to shift on every little mole hill because the RPM's are too low for the grade. So, I just leave the trans in manual mode and only allow it to go to 5th. Less shifting, lower temps, and better mpg than all the gear hunting. So, while it was made as a 6 spd, to me it is essentially a 5 spd.

I took a look at the newer 8 spd gear ratios along with the available differential ratios in the latest Silverado offerings, and I could deduce that I would only be getting a 6 spd for the very same reason I only have a 5 spd now. It would not be feasible to use the top two gears on a regular basis due to terrain and rural highways. Obviously the target market is the 4 lane, 70 mph, highwsy commuter and grocery getter. All the while, the ads promote how much of a work truck they are.

Sure, I could move up to the 3/4 or 1 ton to get shorter rear end ratios, but that is defeating the purpose. I don't need those pickups capability and the additional weight negates any fuel savings that might come from using a shorter ratio on rural highways.

 

[grampi]

Originally Posted By: Nick R
So we should take that to the logical extreme and go back to the 2 speed auto trannies of old? I think that by and large most 6 speeds are proving very reliable, with a few exceptions (some of the GM/Ford 6T75s for example)


No, but it would be interesting to find out how much a rebuild of one of these trannies would cost...I'd bet they're much more expensive to rebuild, IF they can be rebuilt that is...

 

[TiredTrucker]

Maybe, maybe not. Everything is about volume. Some would argue the same way regarding the 18 speed in my commercial truck vs a 13 speed that many others have. Yet, I can get a factory rebuilt 18 speed for almost the same price as a factory rebuilt 13 speed. How? Volume, Watson. The 13's are in more demand than the 18's. So the mark up is more on the 13's. This is one of the reasons my truck has an 18 instead of the 13. More flexibility in operation, and no added cost. Not sure if this same idea will be what folks see regarding 6 speed and 8 speed auto transmissions. We'll have to wait and see.

 

[A_Harman]

Originally Posted By: TiredTrucker
The higher number of gears in transmissions thing is fine, if they also provide the proper differential ratio to deal with it. For instance my Silverado pickup has he 6 spd auto in it. But 6 rarely ever gets used and I live rural with very little town or urban driving. Why? Because the speed limits on rural two lane highways are 55-60, and with the rolling hill terrain thrown in, if I allow it to go to 6th, it is always having to shift on every little mole hill because the RPM's are too low for the grade. So, I just leave the trans in manual mode and only allow it to go to 5th. Less shifting, lower temps, and better mpg than all the gear hunting. So, while it was made as a 6 spd, to me it is essentially a 5 spd.

I took a look at the newer 8 spd gear ratios along with the available differential ratios in the latest Silverado offerings, and I could deduce that I would only be getting a 6 spd for the very same reason I only have a 5 spd now. It would not be feasible to use the top two gears on a regular basis due to terrain and rural highways. Obviously the target market is the 4 lane, 70 mph, highwsy commuter and grocery getter. All the while, the ads promote how much of a work truck they are.

Sure, I could move up to the 3/4 or 1 ton to get shorter rear end ratios, but that is defeating the purpose. I don't need those pickups capability and the additional weight negates any fuel savings that might come from using a shorter ratio on rural highways.


I hear you about being able to use the top gears in a daily driving situation away from the expressways. I can't get my Camaro into 6th until 67 mph, so on my daily 35 mile commute, I can only use 6th for about 4 miles of it. The rest of the time, I'm in 5th doing 45-60 mph.

I did some road load horsepower calculations a few months ago comparing the GM 6- and 8-speed automatics and found that the 8-speed would have a speed advantage in climbing grades at max GCW. This is because it has more closely-spaced ratios and can better allow the engine to operate in the heart of the torque curve at 45-55-65 mph. Of course you can forget towing in 8th gear unless you're going 75 mph downhill. It has no gradeability in 8th.

 

[MCompact]

I read an article that interviewed a BMW powertrain engineer, and at this point Munich is holding at 8 speeds; the ZF 8HP is an outstanding bit of design, and the engineer stated that adding a ninth gear might increase fuel economy by 1%- and that gain could well be offset by the increased weight that adding another gear would cause. The 6HP and 8HP boxes are the first automatics that I like just about as well as a DCT/DSG- and the first ones I found to be as responsive as the 1975 3HP22 in my '02.
That said, I still prefer three pedals in all but big sedans and SUVs.

 

[supton]

Never had a problem with my manual transmissions holding gear on hills...

I wonder, these new 8+ speed transmissions, I wonder how tolerant they will be to something breaking. I mean, lose a gear, keep on going, still have 7 to pick from, right? One could hope!

*

Originally Posted By: TiredTrucker
Maybe, maybe not. Everything is about volume. Some would argue the same way regarding the 18 speed in my commercial truck vs a 13 speed that many others have. Yet, I can get a factory rebuilt 18 speed for almost the same price as a factory rebuilt 13 speed. How? Volume, Watson. The 13's are in more demand than the 18's. So the mark up is more on the 13's. This is one of the reasons my truck has an 18 instead of the 13. More flexibility in operation, and no added cost. Not sure if this same idea will be what folks see regarding 6 speed and 8 speed auto transmissions. We'll have to wait and see.


On a tangent: how long do you expect that transmision to last? I've always thought those transmissions were good for like ever. Abuse aside that is. I've heard of doing in-frame engine rebuilds and whatnot; but never thought about the rest of the drivetrain wearing out. Different world from passenger cars!