Pardon the fact that I'm a dumb-a**, but can someone explain how the valve body works and what upgrading does for performance in the G35?

 

Oh come on. With all the motorheads and rocket scientists we have on this board, no answers? I'm going to be really disappointed if I don't get an answer.

I bet the guys over at FiatDriver.com could tell me!

 

I was hoping someone else would teach us all about AT valve bodies. Oh well!
(I'm no rocket scientist for sure. I'll leave that up to Hydrazine.)

Here's a very basic overview based on my current understanding of our AT. The valve body is an electro-mechanical hydraulic device that receives it's orders from the TCM (Transmission Control Module) and to some degree from the ECM (Engine Control Module) through the CAN network. Unlike many cars the G35/350Z AT controlled by a separate computer, the TCM.

The TCM controls the transmission's operation by "telling" the valve body solenoid valves when to allow AT fluid to flow through the various valve body passages to a specific component. At various times ATF is routed to clutch packs including the input clutch, forward one way clutch, 1st one way clutch, 3rd one way clutch, high and low reverse clutch, direct clutch... I'm sure you get the idea.

The TCM also regulates the AT's line (hydraulic operating) pressure. The TCM thinks it's job is to provide smooth, seamless shifts. Part of how it does this is to control line pressure at the factory setpoint.

So how do you improve the quickness and firmness of AT shifts? Basically three ways:

1) The easiest way is to just reprogram the G35/350Z TCM. Have the software do the work. Unfortunately, no aftermarket company has "gone where no one's been before".

2) Increase the line pressure mechanically so the TCM can't reduce the operating pressure over time..

3) Modify valve body passages, solenoid valves, etc.

Note: There are numerous variations in TCMs, TCM software programs and valve bodies depending on the year, model, VIN and cycle of the moon.

Attached are a couple of pictures of my valve body.

DaveO

 

GurgenPB has posted on this before. You might want to cross reference that in a search.

I have never actually read of a transmission failing though so I am beginning to wonder if these upgrades are really necessary (as long as the shifting is occurring as usual).