: Coming 6 speed automatic



dratts1
12-14-05, 11:00 AM
Does anybody know if the 6t70(e) I'm hearing about will work on a N*? I have a 97 with obd1 and a 98.

GreenMachine
12-14-05, 11:55 AM
it may or may not, depends on if they make a version for more powerful engines. From what I'm reading it tops out at a max torque of 280lbs-ft and 320 Horsepower. The L37/LD8 Northstars pump out 300/295 lbs-ft of torque and 275/300 horsepower. For right now no.

Katshot
12-14-05, 12:25 PM
Am I the only one asking why we need so many friggin' gears in a transmission? I REALLY think the OEMs are trying to sell us all a BS line that more is better. It's like, did you ever ask yourself why sportscars with 500HP and 500lb/ft of torque need a 6-speed manual trans? :bonkers:

GreenMachine
12-14-05, 12:36 PM
Am I the only one asking why we need so many friggin' gears in a transmission? I REALLY think the OEMs are trying to sell us all a BS line that more is better. It's like, did you ever ask yourself why sportscars with 500HP and 500lb/ft of torque need a 6-speed manual trans? :bonkers:
More gears helps with MPG at higher speeds, and in general. There are more oppertuneties for the car to go to a bigger gear thus haveing less RPMs and fuel consumption. Thats why there have always been overdrive transmissions. The theory of getting the bigger gear that might not have passing power but enough to keep speed steady. Bigger gears allow a car to do more with less. Gears these days are more than just getting you in motion.

It kinda lets the engine hold in a fuel efficient range more often. It can help with acceleration keep the car in its power range longer. Now with VVT that story changes, anyway anything over 6 is useless and 5 is pretty good unless you like driving really fast.

thu
12-14-05, 01:35 PM
In practice, the top gear ratio on these new trannies is pretty much the same on a car with a 4spd as a car with a 6spd. Take a look at the top-gear tranny ratio on the new trannies and compare that with some of the 4-speeds. Bottom line is that MPG in top gear isn't going to be affected by having all those extra gears as the top gear's ratio isn't any lower; engine doesn't spin at a lower RPM.

The advantage with having more gears is improved drivability and some MPG improvement in-town; the engine's operation can be more controlled through the use of more gears when going at non-highway speeds. The gear ratios can be spaced more closely together.

Yes, having an *overdrive* would help with MPG, but that's not these 6- and 7- speed trannies have.

The tranny gear ratios are only half the story. The final drive ratio (the differential) is the other half.

I believe the fourth gear (top gear) ratio in my 2003 STS is .65 (or so) with a final drive ratio of 3.71. Compare this to the new Mercedes 7-speed tranny: 7th gear ratio is .728 with a final drive ratio of 3.45.(http://www.supercarsite.net/ml_63_amg.htm).

Randy_W
12-14-05, 01:55 PM
The biggest advantage to more gears is tighter ratio spacing, allowing the engine to stay in a more effecient rpm range (power band), thus improving both performance and MPG.:)

Katshot
12-14-05, 01:57 PM
Okay, I get all that but;

Have you noticed that most cars haven't any HUGE difference in MPG figures as compared to the technical advancements they've received? I remember my '75 Olds Cutlass getting 20mpg highway and about 15mpg around town with a 350-4bbl and 3-speed, non-overdrive trans. My fleet cars back in the late 80's were full-size Broughams w/Olds 307's w/4bbl carbs and 4-speed overdrive trans, and got about 20mpg highway and 15mpg around town. My '95 Fleetwood gets about the same mpg as the previous examples. So what has been accomplished over the years with respect to fuel economy? Is it REALLY the reason for so many gears in our new transmissions? Does the Viper w/6-speed trans get substantially better mileage figures than and old Chevy big-block Chevelle with a 4-speed? I know these are radically different vehicles in this example but realistically, I think that as engines have gotten much more powerful, and efficient, the need for so many ratios in the trans should be LESS, not more. Especially in the case of modern performance cars. 3000 pound cars with 500lb/ft of torque should not need 6-speeds. My guess is that in the near future, you just might see OEMs starting to admit this fact and start reducing the number of gears in a trans rather than supporting the bigger is better theory (in this case, MORE is better). My guess is that a Z06 Corvette would actually be quicker through the 1/4 with fewer gears, so why not build them that way?
Sorry, rant over.

Katshot
12-14-05, 02:00 PM
The biggest advantage to more gears is tighter ratio spacing, allowing the engine to stay in a more effecient rpm range (power band), thus improving both performance and MPG.:)

That makes total sense with an engine with a narrow powerband but today's engines with their increased output and use of technologies such as variable displacement, and variable valve timing, shouldn't need so many gears.

Lord Cadillac
12-14-05, 02:12 PM
Those are some good points, Kevin.. I was thinking the same thing as above - that the more gears you have, the more gas you'd save.. But, you're right.. We aren't saving more gas.. So I wonder what all the fuss is about...

eldorado1
12-14-05, 03:38 PM
That makes total sense with an engine with a narrow powerband but today's engines with their increased output and use of technologies such as variable displacement, and variable valve timing, shouldn't need so many gears.

I think GM is gearing up to make a move to more powerful 4 cylinders a la honda. Good gas mileage, but peaky motors.

mcowden
12-14-05, 03:50 PM
Those are some good points, Kevin.. I was thinking the same thing as above - that the more gears you have, the more gas you'd save.. But, you're right.. We aren't saving more gas.. So I wonder what all the fuss is about...

Look at a comparison of the tailpipe emissions of those cars of yesterday and today's cars. The difference will blow your mind. Gas mileage savings are secondary to emissions reductions. Most of the innovations and technology since those days of automotive engineering have been aimed at cutting tailpipe emissions. It doesn't matter what kind of mileage you get as long as you aren't dumping massive volumes of CO2, NOx, and hydrocarbons into the air, at least if you ask the EPA. We've also added lots and lots of electronic gadgets to cars since that time, and that's load on the alternator which eats gas. Those electronic gadgets help reduce the emissions and increase the mileage, and they have done wonders for safety and reliability as well as making cars easier and more fun to drive, especially on roads that aren't straight and empty. Not to mention that cars don't have nearly the torque they used to have. They have lots of horsepower, and that's what sells the car, but less torque. They have to work harder, and therefore using more gas, but they burn it in more efficient ways (injection) and ratios (computers and sensors and electronic ignition) to reduce emissions. What's the incentive to increase gas mileage? CAFE? What a joke! There are only disincentives for continuing to dump so much junk out of the tailpipe, and mileage is little more than a political tool.

eldorado1
12-14-05, 04:06 PM
What's the incentive to increase gas mileage? CAFE? What a joke! There are only disincentives for continuing to dump so much junk out of the tailpipe, and mileage is little more than a political tool.

Another form of marketing, and trying to track the shift in public want (staying ahead of the curve). Look at the Prius. When gas spiked to nearly $3, there were shortages. They were selling above sticker price. Gas is only expected to go higher.... This is exactly the same reason you see SUVs rusting away at used car lots, nobody wants them.

Katshot
12-14-05, 04:14 PM
Look at a comparison of the tailpipe emissions of those cars of yesterday and today's cars. The difference will blow your mind. Gas mileage savings are secondary to emissions reductions. Most of the innovations and technology since those days of automotive engineering have been aimed at cutting tailpipe emissions. It doesn't matter what kind of mileage you get as long as you aren't dumping massive volumes of CO2, NOx, and hydrocarbons into the air, at least if you ask the EPA. We've also added lots and lots of electronic gadgets to cars since that time, and that's load on the alternator which eats gas. Those electronic gadgets help reduce the emissions and increase the mileage, and they have done wonders for safety and reliability as well as making cars easier and more fun to drive, especially on roads that aren't straight and empty. Not to mention that cars don't have nearly the torque they used to have. They have lots of horsepower, and that's what sells the car, but less torque. They have to work harder, and therefore using more gas, but they burn it in more efficient ways (injection) and ratios (computers and sensors and electronic ignition) to reduce emissions. What's the incentive to increase gas mileage? CAFE? What a joke! There are only disincentives for continuing to dump so much junk out of the tailpipe, and mileage is little more than a political tool.

I get all that but it has nothing to do with the topic of the number of gears in the transmission. I agree the engines are far "greener" then they used to be, but that's due to better engine management and better fuels.
I'm telling you, I really feel the number of gears in the trans is more for marketing than anything. I mean hell, even my new '05 Jeep Wrangler now has a 6-speed! Talk about over-kill.

eldorado1
12-14-05, 04:19 PM
I mean hell, even my new '05 Jeep Wrangler now has a 6-speed! Talk about over-kill.

better than a 2 speed :nyanya:

If it's a manual, then yes that would be terrible. If it's an auto, then who's counting? :p

Speaking of the new 6 speed auto, it will be 8% more efficient, and I've heard it may be smaller than most other 4 speeds. Our land boat 4t80e's lose 25% to heat, friction, and those stupid pumps inside. That is a LOT!!! For the VIN 9 guys, that's 75HP!! That's like a honda! :crying:

So, long story short... more gears... "meh"... more power to the wheels... "yay!!"... more fuel economy... "yay!!"... more marketing power... "yay!!"... less weight (better acceleration, more fuel economy)... "yay!!"

Katshot
12-14-05, 04:36 PM
Absolutely it's a manual. And with the bottom-end torque of the 4.0 I6 in it, the LAST thing it needs is more gears IMO.

As for your take on the new 6-speed trans, it all sounds good but the REAL key to it is effecient design not the number of gears, right? So why not make it with fewer gears and in that way reduce weight, rotating mass, and complexity. Should even be able to reduce the cost and parasitic loss too.

Randy_W
12-14-05, 04:45 PM
Well the best thing for all would be CVT and it's coming to a big powerful car near you soon! The problem with CVt has been packaging, the old Subaru CVT sucked because it wasn't even strong enough for 80 h.p.. Ford has had better luck and GM is working on one for the next gen RWD cars and for trucks in about 2-3 years. That along with a proper torque convertor would keep your engine at a stable rpm through the whole acceleration process. You could in theory mash your Caddy to the floor and stay at 6500 rpm from 0-170mph!

eldorado1
12-14-05, 04:47 PM
Absolutely it's a manual. And with the bottom-end torque of the 4.0 I6 in it, the LAST thing it needs is more gears IMO.

As for your take on the new 6-speed trans, it all sounds good but the REAL key to it is effecient design not the number of gears, right? So why not make it with fewer gears and in that way reduce weight, rotating mass, and complexity. Should even be able to reduce the cost and parasitic loss too.

Well from what I understand about the new 6t70, it's really like a manual. They have direct acting clutchpacks that eliminate a lot of moving parts. If you look at it, it is hard to tell it apart from a manual. It even "looks cool". I believe that's where the new efficiency comes from (not the cool looks, the new clutches and their integrated 32 bit controller!). By going to a 4 speed, they would reduce some weight and cost, but that's about it. IMHO it's about as efficient in losses and weight as it's going to get. I have heard rumors that it weighs half as much as the 4t80e, which is like removing a dead body from the trunk of your caddy. It WILL be noticeable. The 6t70 should handle the N* torque just fine, but I haven't read the specs on the maximum gearbox torque, so I don't know if they'll be putting them in caddies anytime soon....

mcowden
12-14-05, 05:16 PM
The new M-B S500 has a 7-speed automatic. That better be a pretty smooth shifter, otherwise it would be pretty annoying driving around town. The thing would be shifting constantly! Maybe it only hits 6th and 7th if you're flying down the autobahn.

I~LUV~Caddys8792
12-14-05, 06:30 PM
I hear Mercedes Benz is making an 8 Speed Automatic!!!!!!
Is there anything the germans can't do??:bulb:

eldorado1
12-14-05, 07:09 PM
Just wait until CVTs make the mainstream market... It'll be interesting flooring the car from a stop, and just having the tach hang at 6000rpm or where ever peak hp is.

lry99eldo
12-14-05, 08:32 PM
There is a point at which more gear changes won't provide the best of all worlds and six speeds is probably just about it. Powerglides were a fantastic concept and worked well for many many cars of that day with only two forward speeds. Of course, it is the choice of so many drag cars today it's sort of ironic.
The main thing to be aware of here is a very simple rule.

It takes a certain amount of energy to do a certain amount of work, period.

Unless automotive engineers come up with something better that petrol as we know it, there won't be much improvement with 4 wheels on the ground holding up 1000 lbs. each to carry our sorry asses to the corner store, period.
Weight and friction are our biggest enemy and that is emperical. So there is no near future gas saving transmissions out there.

Weight and friction reduction, as well as a new fuel source is the only real answer besides less population needing that transportation. And I'm willing to bet that possibilty is a lot closer than our grandkids want to know about.
lry99eldo

eldorado1
12-14-05, 09:20 PM
Or getting rid of that evil power robbing torque converter... :suspense:

ewill3rd
12-14-05, 09:41 PM
It's my understanding that the increased number of gears is for 2 reasons.
1. It improves the drivability of the car, more shift points but better computer control makes the transitions between gears practically seamless. Much better than the far apart ratios of yesteryear.
2. Money... in today's car world more is better and just the term "6-speed" I think draws people in. Yes it's true most of the 1st and final gear ratios are the same. Actually I think that emissions come into play in all this too. (so maybe that's really 3?)

The 4T80 is a MONSTER. If you have ever had to try to lift one you'd know what I mean. They are huge too. The 80 is the load capacity and I can imagine going down to a 70 that will handle a N* will save them some weight and some money!

I find it odd that I haven't heard of this transmission, where did you guys find this info? You'd think someone would tell me!
LOL

chevelle
12-14-05, 10:55 PM
The advantage of automatic transmissions with more gears is that the torque converter can be designed to be much "tighter" with less slippage. Since the trans has more gears to better keep the engine in the proper operating range of RPM via gearing instead of torque converter slippage the overall efficiency of the vehicle is improved. Some of the transmissions have lower first gears to help launch the car better with taller final drives. Also, the overdrive gears are split into two overdrives so that the powertrain can stay in an overdrive gear more often. With a trans like the 4T80E there is only one overdrive that is fairly tall so the vehicle can not operate in "overdrive" as often as desireable nor will it stay in overdrive in hilly terrain.

Yea, right, 75 Cutlasses getting 20 MPG on the highway and nothing has changed regarding efficiency. LOL Wake up. An equivalent car of today gets 30 or 35 on the highway with lockup torque converters and more gears in the transmission. Oh, and, by the way, they also emit about 1% as much pollutants as that 75 cutlass and are much faster to boot. Who says nothing has changed...???

One advantage to having 6 speeds (or more) in a manual gearbox is the advantage of having enough gears to always having the engine in the correct ratio for ANY situation. You might never use 1 gear for normal driving but it is helpful crawling over rocks in rough terrain. Don't normally need it? Don't use it. I frequently drive manual transmissions and skip gears all the time. A manual transmission Corvette drives perfectly fine in town using only 1 and 4. People drive manual transmission cars and, for some unknown reason, feel that they have to use all the gears and then bitch about having to shift too much. Skip shift to the gear you need and forget about the rest. 1 and 4 are all that are needed in many cars but 2 and 3 come in handy at the drag strip or on a road race course. To totally understand and appreciate the "need" for all the gears provided you have to use the vehicle across all the operating conditions it was designed for. If you don't you will probably wonder why all those gears are there.

dratts1
12-14-05, 11:26 PM
I just found a GM news release on Pennocks fiero forum. (My 97 is in a fiero with a 3 speed automatic) The release states the weight at 273 lbs wet. First gear is 4.48 which should be great for the hole shot. fifth gear is 1:1. Sixth gear is .74:1. So main shift advantages appear to be faster start, closer ratios, overdrive for economy. claimed 8 percent improvement in performance and 4 per cent economy. So we wouldn't save the weight of that dead body in the trunk, My weight figures are 296 for the 4t80, so there would be a weight saving of 23 lbs. It is pretty compact, and from one of the pictures I've seen it looks like it might have the starter mounted on the trans. I don't see how that would work unless the torque converter was locked out during start. Anyway, My 3 speed is going to go for at least a 4 speed. 4t60, 4t60e, 4t65e or 6t70e

eldorado1
12-14-05, 11:37 PM
I don't see how that would work unless the torque converter was locked out during start. Anyway, My 3 speed is going to go for at least a 4 speed. 4t60, 4t60e, 4t65e or 6t70e

No, I think it's just put in "opposite" the northstar. It still engages the flexplate teeth, it just sits on (in) the transmission. Hopefully they will keep it accessable. Having to drop the tranny to change the starter would suck.

chevelle
12-15-05, 12:08 AM
Or getting rid of that evil power robbing torque converter... :suspense:

Torque converters multiply the torque for improved off the line performance. They do slip some but do not rob any power per se. With modern lockup torque converters the torque converter does not slip at all at higher vehicle speeds where the torque converter clutch can apply so the torque converter itself becomes transparent to the trans and engine as it is no longer slipping and driving the input shaft of the trans at engine speed.

GreenMachine
12-15-05, 06:34 AM
The first application of this new tranny is the Saturn Aura. This tranny is rated at a max 280lbs-ft of torque. That one wont end up in a Cadillac. There will be a version for the Cadillac probibly in the future. Maybe a 5 Speed tranny that is another Ford/GM co-creation. Then again the FWD Cadillac is on its way out and we might see a DTS or similar RWD in the next few years for which the northstar already has been coupled with a 6/5 speed autos. FWD is pretty good for snow though, not as much tail-wip as RWD which is known for whipping the tail around. Supposingly FWD is more fuel efficient but I don't know about that one. I guess it really just preferance and FWD has been around on Cadillac for a long time, and its just now that they are making performance minded RWD.

Anyway an automatic transmission isn't like a manual in that there are "differant" gears. Theres really one gear that sends out differant ratios based on what parts spin and such. Look here for more info on that: http://auto.howstuffworks.com/automatic-transmission.htm

ewill3rd
12-15-05, 07:41 AM
I am also confused as to why so many people think that torque converters are so "evil". In fact from what I know torque converters are incredibly efficient under acceleration but under cruise conditions they start to lose their luster. That's why the TCC was invented to eliminate the one remaining flaw in the design of the torque converter. (man that sucks to type!)

I am curious to know how this hatred for TCs developed or what information is out there to identify the TC as such an evil and inefficient device.

Katshot
12-15-05, 09:23 AM
Maybe due to ignorance of the actual inner workings of the converter?
As for saying that multiple gears allow a "tighter" converter, unless you have some SERIOUSLY LOW first gear (which few vehicles do to my knowledge), the converter can't be too "tight", that's why the TCC was brought into the automotive mainstream as ewill3rd pointed out.

This is getting a bit off track from what I intended. My original post was intended to point out that multiple gears were originally used as a means of keeping engines with narrow powerbands from falling "off the cam" as it was known. As engines have become better at providing broad powerbands, the need for so many gears in the transmissions is questionable at best IMO. I beleive it's more for marketing than anything. The proof is certainly in the pudding these days as you can find many vehicles that have far more gears than they really need. My example was a sports car with 500lb/ft of torque that has a 6-speed manual trans. I'm not the only one who's making this point these days, if you read road tests you've probably noticed similar comments from aknowledged industry experts. Just wait, you'll see. Soon you'll start seeing cars with fewer gears. My guess is, it will be in a Corvette of similar car.

ewill3rd
12-15-05, 11:31 AM
I think the reduction in gears will coincide with the expiration of the warranty on vehicles that have 6 speed automatics with lots of failures ;)

I agree it's approaching rediculous. I didn't see a need for the 5L50 in many of the Cads these days. 6 gears seems even more troublesome.
I haven't heard a lot of talk of failures though... only time will tell.