117

This is from a post of mine on PO back in 2001 (it was so long ago that there might be a typo in it):

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">If you have read your Helms, you will see that the ATTS unit sits to the left (as you are sitting in the car) side of the transmission. It transfers torque by the operation of two clutches. These clutches engage the planetary gear assembly, or the left central gear (depending on which direction you turn). I will try to explain as best I can, how these things work, but there's no way to understand without the Helm's in front of you.

There are three central gears that engage with three planetary pinion gears. There is a left, center, and right gear for each assembly. The three planetary pinion gear assembly rotates around the center gear assembly. From what I understand, the center central gear is fixed to the center shaft, and the right cental gear is fixed to the right central joint. The left central gear is free floating, and can rotate about the center shaft until it is engaged by the clutch.

Now, the clutches engage different parts. The right clutch engages the 3-series planetary gear assembly, and the left clutch engages the left central gear.

Straight: Both left and right clutches are off, and the 3-series planetary gear assembly, left central gear, center central gear, and right central gear all rotate as an assembly, so there is no difference in the acceleration between the left and right wheels (i.e. no torque is being transferred).

Turning Right: The right clutch turns on and engages (fixes) the 3-series planetary gear assembly. This causes the center central gear to turn roughly 15% faster than the right central gear.

Turning left: The left clucth fixes the left central gear. Now the planetary pinion gear rotates around the central gears while it rotates about its own axis. Now the right central gear turns rougly 15% faster than the center central gear. Or said differently, the center central gear turns roughly 15% slower than the right central gear.

It seems to me that the center central gear is fixed to the center shaft, and the right central gear is fixed to the right central joint.

If you look at the diagrams of the ATTS unit, you will notice that the right side actually has two input shafts; the center shaft and the right central joint. The left side has just the center shaft output that couples directly with the drive shaft. The right side couples with the differential in the transmission.

Now the hard part is to figure out how the differential works. It's obviously not a run of the mill differential, as the left side of the differential must have two outputs to couple with the two shafts on the ATTS unit. I would think that one of the shafts would be fixed to the output of the engine (i.e. it's a direct connection with the final drive gear), and the other would be the output that can vary (i.e. like a regular differential).

I believe that the right central joint (the outer of the two shafts) is directly coupled to the final drive, and the center shaft is the coupled to the "regular" output of the differential. </TD></TR></TABLE>

prelittlelude

ive got to keep an eye on this thread, not that i have a sh or a 5th gen for that matter, but still cool. I wouldn't mind having a customized quazi-lsd that mounted externally..

Revi

Well moving on tonight on the ATTS unit, i took a look and the left side cover and removed it. The black hoses you see here are the oil cooler hoses that run on top of the transmission and connect to the bottom of the radiator.

Here you can see the locations of the oil orifice and the oil filter for the ATTS unit. Notice how both contained a spring, the spring in the orifice more than likely controled oil pressure throught the ATTS unit.




After separating the left cover you can see the left clutch assembly and the oil pump.


After removing a few set clips you can remove the left clutches.


Heres a look at the oil pump itself.


After removing all the internal gears, i put them all back together to show how it all comes together. I also put on the left and right clutches.



Whats interesting is the whole unit turns as one, but if you pull out the outer shafts alittle the unit unlocks and you can now rotate each side individualy. Also, the left and right shafts cometogether right inthe middle, and you can remove the planetary gear and you would have a stright shaft that runs throught the entire unit. This is where i can imagine you can create a way to install just the shafts, keeping both wheels to rotate as one. I will post a picture of the straight shaft by itself tommorow so you all can see what im talking about.


Modified by Revi at 5:22 PM 2/9/2007


Modified by Revi at 1:13 PM 8/10/2007

vinuneuro

Thanks for taking the time to make this thread, and doing a great job with pics and description. After looking at the whole thing, this is definitely a very complicated mechanism. Where do you even start in designing a part like this.

Revi

Yeah indeed its a unique piece. I give props to Hondas RD department for coming up with things such as the ATTS. To bad they couldnt make it stronger. After seeing all the parts in hand, its easy to understand how it works, but its coming up with this whole concept that is amazing.

SpyLude92

The biggest differance between this and a limited slip diff, is it offers more give in situations where a daily driver needs higher wheel speed on either the right or left. The idea of a LSD being two try and match wheel speed for best performance, less wheelspin on either the right or left under accel. The atts does this but allows for no friction in situations such as pulling of a u turn, and allows for maximum traction in say snow and ice.

Also there is a focus on "Better Clutches": You can make better clutches, that will help grab a little better but the actual focus needs to be on that spring that almost killed him . The way it works That spring if im correct (not having seen the atts system, but have seen most auto trannys) to make a setup to hold more power you have to balance The Spring Tension against Fluid Pressure. The spring holds the clutches in a non load state. When fluid pressure on the opposite side of the clutches overtakes spring pressure it forces the clutches together.
So first you have to increase fluid pressure, which can sometimes be done my opening up a port that is usually bored to a certain size. This can be done with a drill bit. Then to compinsate for the increase in pressure you would have to step up spring pressure. Remember the spring has to overtake it for the clutches to stay off when needed. Once you have your Extra fluid pressure ironed out, you simply play with the clutches. If im right most transmission people refer to the clutches as "Frictions" and the plates between them as "Steels". to get better holding force with a lot of horsepower you simply change one of the steels out. steels usually come in differant thickness's honda most likey has some in stock for the atts system, so they can be set to factory specs easier. I think it would be ideal to go with thinner steels and see if you can fit one more friction and steel in more more gripping power. You probably wouldn't have to much success at this at home but a good tranny shop might make your extra ATTS a beast.

The ATTS system like an Automatic Tranny, is all about shift timing vs shift quality. Using the steps in making a auto tranny shift smooth and at the right time for the customer, you can set up your ATTS to apply more pressure at the right time, for more holding power.

This is the same reason my 92 SI automatic prelude has 230k on the transmission and still shifts awsome, shortly after i got it, one of the first things i done was adjust the fluid pressure. i have it set a little lighter than i would for full race, but it shifts as hard as my 5 speed lude with a racing clutch installed. Because the fluid pressure is a lot higher you get a solid shift under wide open throttle, a lot less lag between shifts. whats cool is sometimes when you are cruising during the summer and you do a 50%-70% take off, not wide open throttle, you can get a second gear chirp, on a auto.

Way to long story short, hehheh applying more fluid pressure means applying more clamping force to hold clutches together which equals less clutch slippage "wear" and more power to the ground quicker.

Yeah i used to work at a tranny shop and would love to get my hands on a atts not owning a SH, heh.

Revi

I was actually thinking the same theory you were about increasing the spring force, but i did not realize your theory about the fluid pressure. What about instead off making the "Steelies" thinner making the clutch discs thicker? Also, im assuming the spring i removed from the side located by the oil pump is what controls the oil pressure throught the oil orifice. Would increasing or reducing this springs tension increase oil pressure?

My hopes with this thread was to open the gate on the ATTS system since not alot of info is around about them. I do not posses the time or the hardware to modify this thing in any way. And cash right now is tight so i cant pay anyone to build or customize parts for it. But in hopes i was hoping someone would see the internals and develope ideas on improving the ATTS system. It would be nice to have an ATTS system capable of handling 300+ft/lbs of torque! The only problem i can see so far would be the ATTS ECU reading higher oil pressure readings and throwing an ATTS cel thus deactivating the unit.

SpyLude92

Thicker clutches wouldn't help, you need to increase surface area. clutch area against steel. since you can't make the clutches wider without building a whole new system, the only way is to add more clutches. Its the same theory used in the built transmissions for drag racing all over the world.

I do know if you do get more clamping force your point of failure will turn most likely to the teeth on the clutches failing. I have seen this on some auto trannys as a weak point, by far what makes automatic trannys weaker is the one way roller clutch, which i hope to never see in a honda. They are simply not reliable under load. HP=Death on a roller clutch. That is why honda automatics are so strong they are built along the same theory as a manual tranny.

As for your theory on oil pressure, id have to look closer at it, but increasing overall oil pressure will effect other things as well, so you have to be careful. That is why i mentioned opening up a specific port to increase pressure on that clutch set on its own,to keep you from having to mess with all the other adjustments in the system, and also remember, increasing overall pressure might cause it to act wierd. I think there is probably an easy way to to take out the LSD feel, but that would suck for a daily driver, not to mention prolly eat the planets.

Also FYI to all interested in this thread. Why are they called Planets/Planetary Gear sets? If you look at the planetary set he pulled out a small shaft/gear from the center of all those gears. That gear in the center is reffered to as the SUN gear, the gears that rotate around it are reffered to as planets. The Planets revolve around the sun.

thegeorge613

Looks amazing when you actually take it apart.

Now, about making it stronger . . . will cryo-treating the gears in the ATTS unit make it stronger?

SpyLude92

You will see failure in other areas before the gears most likely. I do know i have seen planetary failure due to wear on the pins that hold the planetary gears in. But i figure honda has probably already strenghtened these, due to the research and development they have done in thier racing history, this is afterall what makes honda such a good car, they use race proven strategy in daily drivers, making them more durable overall.

preludeguy_92

Increasing the holding force of these clutches to hold more power would be great considering the units advantages over a tourqe biasing diff. I was thinking that fabbing a belleville spring pressure plate that would fit the application would help increase force, and add to durability since they apply more pressure as they wear rather than get weaker like a coil spring. Or you might even be able to finde a way to replace the whole thing with a vicous style clutch, since they are entirely self contained and can take a **** ton of abuse. However this would take time and vast amounts of green.

Bense

this is like **** for me

smo0th

Great Thread, I have learned a lot about my car in the last 10 minutes.

prelittlelude

definately a great thread. i don't know much about 5th gen sh's so i have a couple Q's . does the atts usint only worth with a 5th gen sh tranny or will it work with any tranny you would just need to make your own mounts on the block?

how many wires run to the atts unit. does it just use inputs from the unit or does it like monitor abs sensors or something to see wheel speed?

also does the sh tranny just have a solid differential and the atts unit does everything?

i really wish i had one in my hands its hard to see exactly how everything works, i mean i get the basic idea..

Revi

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by prelittlelude &raquo;</TD></TR><TR><TD CLASS="quote">definately a great thread. i don't know much about 5th gen sh's so i have a couple Q's . does the atts usint only worth with a 5th gen sh tranny or will it work with any tranny you would just need to make your own mounts on the block?

how many wires run to the atts unit. does it just use inputs from the unit or does it like monitor abs sensors or something to see wheel speed?

also does the sh tranny just have a solid differential and the atts unit does everything?

i really wish i had one in my hands its hard to see exactly how everything works, i mean i get the basic idea.. </TD></TR></TABLE>

The ATTS unit only works on SH trannys, thought i doubt anyone has ever tried to fit an ATTS unit into a base tranny. Notice the big gray connector in the lower right side of the ATTS, that is the only connection between the motor/ecu and the ATTS. The ATTS has sensors on it directly but are mainly for ATTS function monitoring like Oil Pressure, Oil Temperature, left and right solenoid ect.


Ive also wondered about the SH differential. Wether its an open or closed differential its unknown as far as i know. Seeing how the ATTS unit controls the wheels during cornering i would assume the differential would need to be closed for the ATTS to do its job. If the differential were to be open i think it would defeat the purpose of the ATTS being able to control the wheels.

In this picture you can see the input shaft that goes into the transmission. Notice how there are 2 seperate shafts that connect to the tranny as oppose to 1 shaft comming from a base tranny intermediate shaft. Seeing how both of the shafts connect to the differential, i believe this is how the ATTS unit can separate the input form the differential and control the left and right wheels.



Modified by Revi at 1:52 PM 8/10/2007


Modified by Revi at 1:53 PM 8/10/2007

Mykizism

LOL, Im glad i dont have one of those things on my car.. looks like a lot of trouble

Tszyu1

Very interesting post. I'm happy to see information like this on H-T. I have owned my '97 SH since 1999 and just about two or three weeks ago I got to wondering if it would be possible to beef up the ATTS unit with heavy duty clutch plates. Thanks, Revi, for the great pictures and for taking the time to disassemble an ATTS unit for all of our benefit.

Time for Aqua Teens, gotta go!

aschue

Revi,

Do you still have these pics? They're not showing up in the post. I've had mine out of the car but not open. I'd like to take a peek inside with your pics.

Mine feels a little slippy sometimes especially when taking off hard with the wheels turned. Strange senstation.... It's not the clutch since I changed that and it feels the same.

Revi

I still have em at my home computer (im at work). I took them down since this thread kinda died off and it didnt get faq'ed so i took em of my server so they wouldnt take up space. When i get home i will post some of the internal pics for you so you can see what it is.

Revi

Bump for pics reposted.......if it dies out with out getting faq'ed there coming off again.

aschue

Thanks for reposting! Nice pics. saving them on my own computer anyways, will come in handy....

mafia

Bump for pics reposted, When I get bord i sit and read most post's on H-T just to see if i can learn something. And this is worth the time.

aschue

With my car off the ground, when I rotate one of the front wheels quickly back and forth it feels a little loose. Watching the axles and atts shaft that goes into the tranny it looks like the looseness is in the atts unit (backlash?) and not the tranny. Any ideas from playing with the atts assembly outside of the housings on what would cause the backlash? Worn gears I guess? I'm thinking slipping clutches would feel different....

Cruiserdude

Awesome thread, bro! I've always wanted to take a look inside, ch. 15 in the Helms has always really excited me. I hope this gets FAQ'd, its good stuff. If not, would you mind sending me all your pics, and if you have any more? Thx alot, bro, mad props go 2 u for attempting this. :D

Hawkze_2.3

Definately interesting to look at.