Can someone explain what can be changed in AT and MT?

소녀시대

Hello again everyone! I have a question out of curiosity....

I know that people use manual cars as a race car because of the ability to be able to change the clutch. I heard that once you change a clutch to a higher quality one, you can handle much more horsepower without worrying about the clutch being "broken" (sorry i dont know the correct term). However, i heard that the automatic transmission does not have a clutch, but instead a torque converter. Is there anything you can change in an automatic transmission (something similar to a clutch) to allow for more horsepower?

Thank you!

-Francis

vipor

MT:
Clutch, Flywheel

AT:
Torque Converter

Both:
Fluid

I don't even think we have torque converters available yet. Down the line I'm sure more will be released, but those are the obvious ones.

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2009 NISMO # 0193 | QAB | Albums! | 05.04.10 (Dynojet) 291.94hp/248.28tq
Oil Cooler (DIY) | Custom Headlights | GTSPEC Braces | F.I. Long Tube Headers

NewlyIMPORTed

whats the best fluid to use?

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2011 WRX STICobb Accessport, Nameless Performance exhaust, COBB SF Intake, COBB downpipe, 20% tint, Work Emotion XD9's

nogoodname

For AT's you would need a trans oil cooler and a valvebody upgrade.

vipor

I used Red Line Synthetic. 2 parts MT-90 and 1 part MTL. Factory specs (for the MT anyways) list 75W85 as the recommended weight. MT90 is 75W90 and MTL is 75W80. If you were to purchase (2) qts of each and mix them you would have 85. Being that I live in TX and as such am prone to hotter temps, I just bought (3) qts total so my tranny fluid should be in the 87 range. I'm sure you could go all MT-90 if you'd like with no issues.

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2009 NISMO # 0193 | QAB | Albums! | 05.04.10 (Dynojet) 291.94hp/248.28tq
Oil Cooler (DIY) | Custom Headlights | GTSPEC Braces | F.I. Long Tube Headers

serturbo

After that, you can go in for a full rebuild with different internal components (clutch packs, etc) if you need it to hold more power.

소녀시대

@vipor: oooh so in an AT transmission, what breaks is the torque converter, and not the transmission gears itself?

@nogoodname: does the 370Z come equipped with a transmission oil cooler? how much would it cost to install a good aftermarket one?

@serturbo: i see that manual cars seem to be the easiest to change! i.e clutch packs. I suppose i should learn how to drive a manual car eh haha

thanks everyone

nogoodname

GTMotorsports offers an automatic transmission oil cooler and the valvebody upgrade. The 370z doesn't come with a transmission oil cooler.

terrycs

If you want to "hold" more power in an AT, you need to add clutch packs. If you want faster shifts and cooler transmission fluid, you need a valve body upgrade. Faster shifts mean less time in between gears heating up transmission fluid. A trans cooler obviously helps keeps fluid temps down.

1slow370

Ok some clarification is needed up in here. A manual transmission is just a bunch of gears with special mechanisms built into the hubs of the gears called synchros that match everything up while shifting. The weak points in a manual transmission are these synchros, the clutch, and followed by the the mechanical limits of the shafts. As far as upgraing a manual goes you can change to a synthetic fluid like redline MT-90 to helps the synchros and bearings last longer and work smoother, and upgrade the clutch to prevent slipping that causes them to burn out. Clutches are rated by the max rpm the can handle and the maximum torque they can hold without slipping.

As far as automatics go there are many more parts and much more to upgrade. unfortunately there is little on the aftermarket right now to support our cars. Automatic transmissions have a torque converter where the clutch would be on a manual car. they also have MULTIPLE clutches inside the geartrain. Torque converters buldge out with increased power levels, run hot, begin slipping, and go bad. They are basically a fluid pump(a lot more complicated than this but it will do) so changing out to a good synthetic fluid helps, as well as adding a cooler to keep the temps down and combat thermal expansion of the metal parts. The cooler also helps maintain the seals and clutches so it is one of things that must be done to an automatic transmission that is going to see more power. When available, changing out the clutch bands and plates with those of a better compound (think racing brake pads vs. stock) will greatly improve the torque holding capacity of the transmission, as well as changing out the springs to improve the shift speed and quality. Think of this step as getting a complete transgo shift kit and rebuilding the transmission all in one step. Then to further improve shifting and torque holding capacity modifications to the valvebody (think the heart of the automatic transmission, it controls where and how much hydrolic pressure is sent to change gears) are made to increase the pressure on the the clutches, and apply that pressure faster to prevent slippagge that can burn out your clutch packs, allowing the transmission to hold more torque. Finally due to complexity, an automatic transmission has more parts shoved into a smaller area than a manual transmission, so many of the parts are thin walled and have tiny shafts running through them meaning they can't hold as much power as the big solid gears in a manual. If you are making serious power you may need to upgrade some of the planetary gear sets and most notably the input shaft that the torque converter spins, to thicker stronger versions.

Cliffs notes: For a manual get a synthetic fluid, a good clutch and flywheel, and don't abuse your synchros by powershifting/not using the clutch/being an idiot.

For an automatic: Fluid, cooler, torque converter, Valvebody modification, new clutch materials, hardend input shaft, stronger planetary gearsets and drums.

1slow370

The 370z does have an automatic transmission cooler in the same place that almost all automatic cars have one, in the lower radiator tank. this isn't a good place for a cooler because it is a very small cooler and sees coolant temperatures instead of ambient air temperatures like an external cooler would.

When installing an aftermarket transmission cooler most of the time you simply disconnect the line going into the radiato and connect them to the external cooler mounted in front of the radiator. It IS usually that simple.

Edit: the factory cooler is in the drivers side end tank sorry i said bottom was think About the radiator i just replaced in my beater neon.

소녀시대

ooooh i see! so its actually possible to make an AT handle more power, but it requires more work than the MT?

kdoske

..............

소녀시대

oh crap did i read it wrong? T_T sorry

nogoodname

Anything is possible. There's a couple of TT'ed AT G37's around.