chargedvx6

I have just had my 4L60E built with all the good stuff and am considering going to a full manual valve body. The Aussie L67 PCM has issues keeping up with engine speed when it comes to automatic shifting once a few mods are on board.

Most people here are going FMVB but I am concrned about extra wear on the trans during upshifting without PCM commands. I have absoloutely no intention of downshifting the trans but will need to upshift manually.

The reason I'm asking is I have the option of getting a loom interface to temporarily manualise (track days) or physically mod the valve body so it is always manual shifted.

Pros and cons are what I need

Circle-D

iTrader: (21)

Here are a few other options besides the FMVB. You can get a modulator installed that will keep line pressure more consistent than the EPC can, which will hopefully make the shifting better. You can also get a stand alone computer from TCI - I think - that will control the transmission. They have a faster processor and hopefully eliminate the problem. We have never used the TCI, but have done quite a few modulated systems. They work very nice.

The biggest con on a FMVB is shifting error. If you want to win races you need consistency. It is hard to shift the exact same every time and most wins in bracket racing can be decided by 0.01 or less.

Chris

Gilbert@Ace Racing

Chris has some good ideas. Indeed the vast majority of the units we build will leave with a Vacuum Modulator. The reason is simple. I do not want the PCM to have any range of authority over the Line pressure in my performance units. There is too much room for error in Tuning.

A stand alone controller is a very good option here... TCI makes a nice unit, but I prefer the Compu-Shift controller myself. It is very user friendly. If you go that route feel free to contact me for some detailed Tuning guidelines that are not spelled out in the accompanying Manual.

As far as wear and tear on the unit, we have had tremendous success with our Full Manual 4L60E's. I do not believe that it produces any more wear and tear than an automatic unit does.

And Chris is spot on when he says a manually shifter unit is not consistant. It's a fact.

Good Luck!

g

chargedvx6

Wow, good replies there fellas. I have heard about the Vacuum modulation but understand nothing about it other than it acts upon the pressure valve like a hydraulically shifted unit?

Where does the mod unit get its' pressure reference from, (assuming that's how it works)? If it's vacuum controlled would I need to calibrate the vacuum feed depending on my manifold vacuum (the car has head and cam so vac is different) or does the modulator itself have adjustment?

As for the TCI controller, no one is using them in Australia that I know of and am unsure how it interfaces with the PCM. Would the tuner disable the stock PCM control of the trans and default it to the TCI unit?

chargedvx6

bump, need to know

chargedvx6

Might be a dumb question but everyone says it harmful to downshift an auto so if you go to a FMVB what changes to make it safe?

performabuilt

iTrader: (25)

I don't really think its any more or less safe IMO , Though honestly I have manually down shifted forever in all my cars even my escort and really have not run into issue. Thats why wen our customers ask I say do what you want to do .

jakeshoe

iTrader: (14)

Downshifting is OK, just don't do it under heavy deceleration. If you are cruising in 3rd at say 40 mph and need to shift down to accelerate, it's fine. The problem is the way a sprag is loaded on a decel downshift, it is driven by the rear tires and planetary function is acting backwards on the sprag in many cases, plsu you lose the cushion of the converter.

Someone said it well here the other day, do your shifting to mimic the way the car shifts from the factory.
The car doesn't decel downshift until very low speeds.