Why not an automatic?

[OldSkoolGP]

I guess I don't know enough about automatics, so maybe someone more knowledgeable can answer this one for me:

The whole idea of an automatic transmission is that it does the shifting so you don't have to. But they operate on the principle of hydraulic pressure through a torque converter. And it decides how much of the engine's output will be converted to usable torque for the transmission. Ones that lock up on high gear are considered to have an overdrive because they then match the engine speed to the transmission speed just like you had a manual.

My question is, why couldn't you design a tranny that did that in every gear as soon as it engaged that gear? Granted, you would still need the slip provided for starting off in first, but couldn't you make an automatic with appropriate gearing and final drive so that once a gear was engaged, the torque converter immediately locked up? To me, that would be more like driving an automatically shifting manual, not this tapshifting BS Pontiac is trying to sell.

The gear spacing in the 4T60(65)-E is pretty wide, but it's compensated for by the torque converter. I think instead of the torque converter being a compensator, it should operate more like a hydraulic clutch, but be more linear in the sense that it's either on or off.

I hate when my automatic cars shift 3 times and they only have 400-500 RPMs difference. I know there is unused energy there. At least when you lock up the torque converter you are using the full power of the engine. Am I wrong on this, or am I not seeing something correctly?

[CNCguy]

Re: Why not an automatic?

OSGP.... This has nothing to do with our transmissions, it does relate to your topic.

Back in the 70's, some guys were using automatic transmissions connected to manual clutches. All the ones that I saw were in higher horsepower street cars. A guy down the road from me had an old Anglia with a manual clutched turbo 400 behind a SBC using an aluminum flywheel. It would rev pretty quick and was cool as hell since you could take off easy or hard. I dont know what ever happened to the concept unless it was outdated by the advances in torque converters.

Some circle track cars use transmissions connected directly to the engine via a coupler and use a flex plate only for starting the motor. I think their main goal is to reduce rotating mass by eliminating the torque converter / flywheel-clutch. I knew a guy who raced a powerglide set-up, it had a toggle valve by the shifter that he flipped to apply pressure to the valve body and engage the transmission cluthes/bands. The faster that you opened the valve, the faster it engaged. The big drawback is, the transmission clutches do all of the slipping to get you moving and wouldnt last long on the street. To prolong its life, his pit crew usually gave him a little hand push before he would engage the tranny. The manual transmissions have to be pushed before engaging the tranny.

I did some quick searches but couldnt find anything on the autos with a manual clutch. I know they still sell the powerglide adapters since they are in Speedways catalogs.

Link for adapter: http://www.speedwaymotors.com/xq/asp...qx/Product.htm

Marc

[geoffinbc]

The torque conterter is there to multiply torque and allow the engine to spin at idle. If the torque conterter locked up in ever gear then every gear would be quite a rough transition. People not only want the car to do all the work for them but they also want it to be comfortable.

You are not loosing alot of energy through the torque converter. The engine is revving alot but up to 2 times the torque may be comming out of the converter.

[Hemet8]

So why is it that the same car, same weight, same evrything, but the only difference is a manual trans instead of an auto, go so much faster then the auto, stock for stock?

[z284pwr]

So why is it that the same car, same weight, same evrything, but the only difference is a manual trans instead of an auto, go so much faster then the auto, stock for stock?

A manual trans would be faster because A. You can slip the clutch and launch at whatever RPM you want, preferably max. torque. and B. A manual has less moving parts, weighs less, so you lose less power thru the drive train *you still have to get the power to the ground.

However, once you step up into faster, more high powered cars, you tend to lose the advantage because the car has torque to get off the line, and you have to slip the clutch more in a manual to prevent from spinning the tires. Eventually you step to drag cars that have high stall converters plus trans-brakes, which gives you every advantage a manual has plus freedom of no slipping the clutch, and no shifting yourself so instant shifts plus no worries of missed shifts.

[geoffinbc]

Agreed.
Plus factory cars typically come with a low stall speed converter and a shift program designed for comfort.

Slap in a higher stall converter and raise the shift points and firmness and shorten the shift time. You will spank any stick driver. The speed of an auto will far outweigh the small difference in power loss.

Back in the day the difference in power loss was quite alot. Today it is quite minimal.

[HisCar]

Interesting quip.. In the early eighties JATCo. (Japanees Automatic Transmission Company) made autos that were smart enough to jump from any gear strait to any other gear if it saw fit. 4-1 if the conditions were right. It's torque converter could also decide to "Lock-Up" in any gear if the car stayed at a constant speed.
Oh, manual tranny has more gears(usually)and there-fore the car has better 'leverage' toward the pavement. IE-it can push the car forward faster because more gears = shorter ratios. The greatest thing about manual tranny's is that most people dont know how to drive them or when to shift. That red-line THEN shift thing is way overrated and usually incorrect. So if your racing someone with a stick stock to stock and they think their fucking richard petty then you have an advantage because the auto will shift at decidedly better rpm's than some retarded neck in 'git-r-done' mode....unless your racing a Z28 or something. A car like that can only go so slow

[SHOoff]

Funny. Take a Saturn SC2. The Manual will beat the Auto out to 60 ft. After that the Aut will take it for the rest of the 1/4 (providing you put it in 'Performance shift' mode. Thats the advantage of an automatic on a car that's got a lot of power. After the car is so fast, you having a manual will slow down your times. Since a properly built auto can shift faster than even the best of drivers could hope to.

My 440t4 in my Toronado woudlnt shift right. Once it didnt go into 4th gear, it would just lock the converter while it was in 3rd. I know with my GTP being electronic controlled you can have skip shifts programmed into the PCM.

I thought that the TCC was just electronically controlled? So couldnt you hook up a switch to engage it in any gear that you want? I think i've heard of this before. What practical use it has on the street, I have no idea.. but i'm sure you can do it. Just make sure you unlock it for a stop light.

[gpse3400]

The 440-T4 aka 4T60 was a little odd in some ways. The TCC was electronically actuated. Yeah you can wire up a switch and manually activate it but it really serves no purpose. GM sets it to come on at the right time. If it comes on in 2nd gear you'll notice a hug drop in engine speed and the engine might not respond the way you'd like it too. Oh and the hydraulic circuit doesn't allow for the TCC to enable in 1st gear in this tranmsission family. So even if it's stuck on it'll never affect stop and go other than a huge drop in rpm when going into 2nd. What I found odd about the 440 was that if you wanted a top speed out of your car, you couldn't floor it because it would never up shift to 4th, unless you messed with the TV cable. The 700 R4 was like that. Standard Tranmissions are fine for what they are but living in a populated area such that New York is, its really a hassle. Plus some standards shift like crap, but I think GM did good on the W cars though....I like the auto because I know personally that you can do lots of interesting things to it, you can buy performance parts for it, and GM still supports is which is the best part. If you make the tranmission the way you like it, I find it to be just as fun. Personally I think my transmission is a riot! The way it bangs up and down thorough the gears. And that Drive Chain just downright makes it sound cool.

[SHOoff]

Heh.... my 440t4 was pretty messed up though. At one point I ended up unhooking the TV cable AND the vacume modulator. The valve body was messed up and it wouldnt shift. Once I unhooked both those parts it wanted to stay in whatever position the shifter was in. Which, since it was a beater car.... was just fine with me. Eventually I started to lose 1st gear though.

I like the 4t65e in my GTP though. I'd almost kinda like to have one in my cav. I dunno how the 4t60e is (i'd imagine pretty close to the same) but it seems like mine is fiarly responsive when you want it to do something. More than i normally expect out of a stock auto tranny.

[TurboGt]

I use to have a Typhoon and there were quite a few people that hook up a switch to the tcc, in the 1/4 they would drop a .1 but that was abot the max they got. Some of the people on the forums said it wasnt worth it.