http://en.wikipedia.org/wiki/Semi-au...c_transmission

i searched this wondering if there was something like it out there and i was amazed to find that their was. i mean...clutchless manual transmission? its the benefit of having a manual transmission without the hassle of having to clutch right?

please correct me if im wrong.

this seems so useful, idk why anyone would want a manual transmission unless they really just enjoyed using the clutch, or they couldnt afford a Semi-automatic transmission (not really sure what the price is for a decent one)

i just wanted to know why i wouldnt want one of these!

what does the manual transmission have over this?

is there something im not understanding?

i would love to know what everyone else has to say about it and if i really am not understanding this.

 

Cost aside, now you're adding weight, and things to go wrong. Things you can't get at NAPA or AutoZone. Things most mechanics have never seen, don't have instructions for, and don't have the special tools as needed. Our floor pans weren't designed for them, they don't bolt to the LSx, let alone a 350, and they have no provisions for the torque arm. If you can't clutch, there are full-manual valve bodies for the 700R-4, or you can get a paddle-shift 6-speed 4L80E. Give me a T56. I can clutch, very well and very happily. Porsche or Bugatti may brag about shifting in 60 milliseconds, but any shift-kitted auto can shift quicker. The proof is barking the tires, which those new exotics can't do. Besides, nailing the launch then ripping 3 perfect powershifts is so rewarding that it's well worth learning to clutch unless you're disabled.

 

yeah, i see what you mean. i kinda rushed into asking the question instead of actually doing the homework myself first. after i really started reading about it, i saw why it isnt used in most modern day cars. thanks for the insight.

 

I suppose I was trying to lessen your enthusiasm, but this reads like you're going along to get along. I like when people disagree with me, and I like to see new ideas tried. Now you have some idea what you're up against, and that may be what you wanted.

 

VW Beetles had this back in the 60's and 70's. It was called an Autostick transmission. I believe they used engine vacuum to work the clutch, instead of a normal pedal.

 

thats neat, always knew VW was pretty advanced but didnt know they had stuff like that back in the 60's and 70's. just on the beetles though?

im not really going along to get along, but after i spend about 2 hours that night reading about it and seeing why it was so expensive and not regularly used, i decided to drop the idea lol. but who knows, maybe some aftermarket company will come out with something one day that will be compatible with modern vehicles, instead of having to spend insane $$$ on like a new GT-R or somethin

 

 

As far as I know, it was just the beetles. Could have been on the buses too though.

 

A manually shifted automatic transmission isn't really a semi-auto because it still uses hydraulic pressure to actuate the gears. My powerglide has no automatic feature and I need to manually shift through each gear but all I'm doing is moving the spool valve in the valve body to tell the transmission what gear I want to be in without it needing modulator valves etc to do it automatically.

The closest thing I know of a semi-auto is a Lenco transmission or any other variation like that. Each gear is a separate box that bolts to the next. Each box uses a planetary gear system just like in an automatic transmission which doesn't need a clutch to shift gears. Manually shifting in and out of the gear gives you a gear reduction or 1:1 ratio. This is the type of transmission you see in a Prostock with the multiple leavers for each gear. Every time you pull back the next leaver, you're moving another planetary from reduction to direct drive.

Lets say you have a 5 speed. When in first gear, all 5 boxes through a combination of gear reductions, give you your first gear ratio. As you shift up through the gears, each box is shifted from a gear reduction to direct drive until all 5 gears are in direct drive.

In simplest terms, the minimum you can have is a 2 speed with one box. The gear is in reduction or in direct drive. Lets say 1.76 in, 1:1 out. Now you want to make a 3 speed. To get a lower first gear, lets say 2.52, you can't just add a 2.52 ratio at the end because it also needs to go through the 1.76 gear. Your new first gear box would be 1.43 ratio. With both boxes in reduction, 1.43 x 1.76 = 2.516 (2.52) first gear. When you pull the first gear box out of reduction to direct drive, the second box reduction is 1.76. When you pull that one out of reduction, they're now in 1:1 or high gear.

Because they use a planetary system like an automatic transmission, a clutch is only used to start and stop the vehicle and isn't needed to shift through the gears.

A typical Lenco transmission is around $1000 per gear plus you need a neutral and reverse box. Each gear is in or out of a ratio so a separate box is needed for neutral or else you could never have the engine running without sepping down on the clutch to keep it from moving. Adding a reverser gives you a reverse but technically, you'll have just as many gears in reverse as you would going forward but one speed is more than enough.

Eaton Roadranger in heavy trucks has what could be considered a semi-auto transmission called an Autoshift transmission. Some have a clutch pedal to start and stop the vehicle, some use a centrifugal clutch without needing a clutch pedal. The transmission is a basic 10 speed manual transmission but the XY box on top which replaces the normal shifter is controlled by a computer to select the gears. Even though it's a manual transmission, the computer shifts the gears just like an automatic.

 

ive seen one of these offered in a late 70z transam maybe even 80 or 81 but i think it was a 79, i was confused as to how it worked but the stick had a "j" shape instead of a straight line like and auto..

 

How about a manual valve body and a set of lightning rods?

 

the auto clutch goes back much further than anyone here has mentioned . I took my drivers test in 1955 . (I know i'm older than dirt) I took it in a 49 Packard that was so equipped . 3 on the tree , had a dash switch , you could elect to use "regular" clutch or "auto" clutch . I faked use of the clutch pedal for the test . back then in florida if you took the test in an auto. your license restricted you to auto. only . "what's OLD is NEW again" , to those that doubt , check out the "wiki" reference in 1st. post . damn i'm old , time for a nap or a beer . think i'll have a beer . what's "OLD" really is "NEW AGAIN" . good luck to all .

 

I'm holding out hope for a T56 with a lockup torque converter in place of the clutch. Lock only in sixth, and only during high-vacuum conditions, with a brake switch to unlock.

 

Barking the tires means squat. I've seen crap B&M shift kits that bark the tires everywhere, reduce transmission life, and don't do squat for actually decreasing shift times.

700r4's are notorious for the 1-2 bangshift with stock valvebodies.