BCaywood

Bear with me here, I'm not sure exactly how to word some of this, but I hope you get what I'm trying to say. Also, I've already done some research and tried to find a thread on here but was unsuccessful. If there is one already, please provide the link if you could.

Okay, so I've been trying to get a better understanding on transmissions and a few questions have come up. I know generally, manuals are considered better than autos, and are considered more fun. But I've also read about race specific autos outperforming manuals. Especially newer "paddle shift" automatics that are basically manuals without a clutch. I have a big question about slap shifts and manual valve body conversions.

From what I've found out so far, I know the basic function of the slap shifts, but are they simply a different shifter, or do they actually (this is the part where I'm not sure how to word it) "override" the computer so that you choose when to shift, or is it still like a stock setup, you shift and the computer still decides when the best time is to actually do it. Also, are they considered a shift kit themselves or are automatic shift kits something else entirely? If they are, what are they and what function do they perform?

Then there's the manual valve body conversion, what exactly is it? I get that it does override the computer and it wont shift by itself, or does it completely replace the computer? I read somewhere that they make the shifts firmer and quicker as well, something to do with the transmission not trying to be in two gears at once.

finally, how does an automatic with a slap shift and valve body conversion perform? Is it kind of like a manual minus the clutch? And wouldn't that be a bit faster than a true manual since the shift would be instant without a clutch? All personal preference and feel aside, which setup is faster? And how does a slap shift perform on a track, not just drag but road course.

Sorry about the long winded post with so many questions, but transmissions still confuse the crap out of me.

Thanks as always

mrvedit

First, a performance built 4L60E or 4L80E will have lightning fast shifts and, with torque management turned off, shifts will feel instantaneous. I'm confident my trans shifts in less than 1/10 of a second. Plus I can tune the shifts to the precise RPM. I'm confident that a properly built and tuned full automatic will outrun a manual valve body 99% of the time.
Of course some people don't want/have tuning software and/or simply prefer the control of a manual valve body.
While an automatic is less efficient than a manual trans, the torque multiplication of the converter at the start and after shifts often allows an automatic to have a better ET than a manual trans on the same car.

If the PCM controls the trans, it will decide it/when it will shift. I don't know this for sure, but I suspect it will help prevent over revving on accidental downshifts.
Does anyone know the details of such overrev protection?

Some aftermarket trans controllers have paddle shifters and might force shifts. Probably depends upon the specific controller.

A manual valve body conversion give full manual control and the PCM is disconnected.
A manual valve body is typically installed with a shift kit; the shift kit is what makes the shifts firmer/quicker. A performance trans will also have a shift kit.

A 4L60E/4L80E cannot be in two gears at once unless you add the hydraulic lines for a trans brake.

Regardless of a full-automatic, manual valve body or aftermarket trans controller, the performance probably depends more upon the converter than anything else. They will all perform about the same really.

On a road course things are very different as you want to want to manually control the shifts and an automatic unexpected up/down shift could cause loss of control in a turn.
Also the high stall converter preferred for drag racing will likely overheat because you are high/WOT throttle of maybe 50% of the time during a 30+ minute session. Therefore, the stock converter is often the better choice.

I do road course racing and am starting to mod my '81 Camaro with 4L65E for it. First step was to get a triple disk converter so that I can keep it locked at all speeds on the track and therefore not produce heat. Next, I am going to tune special low shift points for all throttle positions, e.g. 4th gear at 30mph even at WOT. With that the PCM and trans should respond quickly to shifter changes. Sounds OK to me in theory, but still needs to be tested. (Actually step zero was upgrading to Wilwood Corvette brakes.)

Hopefully I was mostly accurate, somewhat clear and this helps you understand transmission differences.

BCaywood

That was actually one of the most helpful and informative responses I've received since I've been on this forum. Even better considering it's on a topic I'm mostly clueless about.

So basically, if I'm going for road course or auto-x, I'm going to want to fully switch to a manual so I have full control over when it shifts and can hold the specific gear I want through a corner.

On the other hand, if I was to keep the automatic, the jist of what I'm getting is that a properly built automatic should shift faster than a manual most of the time. Also, even though it wont get as much power to the wheels due to being less efficient, it can carry more torque and shift faster, so will ultimately be faster? Especially with a well programmed pcm? What all goes into a "race built" transmission? Torque converter, shift kit, what else?

Since you brought up the 4l65e, I've read that its not worth it to swap into a car that already has a 4l60e? If I've got this correct, the main difference between the 4l60/65/70e is strength, so if you built them, what would the difference be between them, or would any difference disappear once you start tearing them apart and rebuilding them? And what about the 4l80e? I know its a heavier duty transmission, but isn't it also heavier overall? And wouldn't a built 4l60/65/70e be as good as a 4l80e but weigh less? To clarify, I'm looking at hopefully 600hp at the wheels (lofty, i know, but have my reasons), which I know the 80e can handle and the others need built in order to handle.

One last thing, all of these transmissions are 4 speeds, but aside from drag cars (which mine wont be) aren't more gears better, for economy and high end speed?

I hope I didn't take any info from that the wrong way, and understand it correctly.

Thanks as always.

mrvedit

Your interpretation is very accurate. You are getting the idea.
While an automatic is generally faster on the drag strip than a manual due to torque multiplication in the converter, torque multiplication only occurs when the output RPM of the converter is below its stall speed, e.g. 2000 stock and 3600 performance. Above that you have 1-1 coupling with about 5% power loss. Since you would keep the engine above 3600 RPM on a road course, an automatic will be slower there. And that 5% loss all goes into unwanted heat. A converter becomes 100% efficient when it locks up, but only expensive triple-disk converters can handle lockup at full power.

The main change to a "performance" trans is the shift kit, which mostly consists of a few parts to increase hydraulic line pressure and drilling the separator plate to flow more volume to each clutch. Higher pressure + more volume gives you faster shifts, and (if kept within reason) less wear and less heat. The 4L65E added a few stronger parts, but any 4L60E/4L65E/4L70E can be built up with stronger stock or aftermarket parts.

At 600rwhp I would recommend a 4L80E unless you have a Vette or other very tight-fitting car. With an aftermarket converter it only weighs 50lbs more and "eats" only 5HP. However its tighter gear ratios tend to make any high-powered car faster. A modestly built 4L80E will easily handle 600rwhp and cost perhaps $2500. A 4L65E will cost $4000+ to handle that power and still not last as long as the 4L80E.

More gears is overrated. In my 6 speed automatic BMW I drive the road course in 3rd and 4th, manually shifting it. If you want economy don't drive a 600HP car.
3rd gear (1 to 1) with 3.73 rear will go close to 140mph at 7000rpm. Unless you are going to Bonneville, that should be plenty.
Close ratios are useful for squeezing the last bit of performance and the 4L80E is better at that. (My 4L65E is close-ratio, but that adds another $800+.)

Mongoose350

iTrader: (1)

I'm currently planning a build that I intend to be a 240/280z with a turbo LS1/TH350. I like the idea of a manual shifted auto so that I can still have some driver experiance, and to eliminate wireing it up to the pcm.

Here's where I'm unsure though. While looking at some builders websites, I see several differant options that I don't understand. Full manual forward with engine braking, without engine braking, full manual reverse.... What exactly does this mean? Also, this won't be a DD, but it will be street driven. It's purpose is mostly going to be that of a fun street rocket that can drive itself to the track, and back home. I'm not going to autoX it, and overall cornering is not a concern, within reason of course, I'm not going to throw a spool in it.

Now in my 4th gen with the 60e, when I brake the trans falls out of gear or neutralizes. Is that somthing I would have to control manually as well? Say I'm in 3rd at 60 and I take an exit so I brake to 35. Will I have to put it in neutral until I get to the desired speed then put it in 2nd, in that manner? Off throttle, neutral, brake, put in gear, throttle? That's somthing I'd like to understand better before making the decision.

Also OP, a manual valve body has a shaft that is connected to the shifter. As you go through the gears, it moves and blocks/opens various pathways in the valve body, thus forcing the trans to shift into that gear. So basically, if you shift from 1-2, it should be basically instant or there's not enough pressure in the hydraulics.

One final question. Do the TH350/400's have lock up or can be built to have it? It being a streetable car, I'd rather not have it unlocked while cruising down the highway. Waste of fuel and adding heat and stress to the trans.