tuning transmission

[streetrod93]

i'm going to be switching from a M6 to an A3, i was wondering if i would have to have a tune for the automatic since the 93's weren't electronically shifted. it's not a manual valve body at the moment, by it will be by christmas. if i shift the gears myself even without a tune, will i be okay?

[smoknta]

Depends on if you want a lockup convertor or not. The PCM does control convertor lockup.

[pcmforless]

Yep, what he said.!

[streetrod93]

what do you mean by lockup?

[smoknta]

A torque convertor works by slipping. This is called the stall speed. That is how you can set still and the engine idle in gear, unlike a manual that must disengage the clutch. Once a car is up to speed in a certain gear, the convertor clutch will engage and eliminate slip. You can put different stall speeds in so you can bring your car up into your peak HP and torque range quicker off the line.

[streetrod93]

i don't think i asked the question right....
what exactly do i need to be concerned about in terms of the computer when i switch to the automatic?

[smoknta]

Depends....Do you want the PCM to control the convertor lockup?

[streetrod93]

explain my options here and the affect....pcm controling the lockup vs. not controlling it
it's going to be a B&M super street fighter stalled to 3600 if that helps

[smoknta]

I think the biggest thing you will see is gas mileage. It will go down with out the lockup convertor. When it locks it is like having another gear.

[streetrod93]

so what are you suggesting my best option to do...should i look into a different converter or just have the tune changed?

[smoknta]

I run a 3600 stall and love it. I do have lockup though, but if I didn't I really wouldn't care. I do not drive it much though. If you are not concerned about lockup I would not worry about it. You will want to hook up the VSS sensor though.

I think all you should have to do is get a new tune that is for a automatic instead of the manual.

[streetrod93]

i hate to continue to ask questions that are seemingly simple, i'm not acctually this incompitent about cars, i just have NEVER dealt with automatic transmissions.
but when you refer to lockup, is this an option i should look for when buying the stall or is it exclusivley something concerning the tuning process.
and as for the tuning from m6-A3, is there any need to get back on the dyno concidering the car has already been tuned and the only thing i would be concerned about is driveablity
also, what is VSS?

[93formulaA4]

he is converting it to an A3 so i don't think he needs to worry about converter lockup. If it was a 700r4 it can be controlled internally so the answer to your question is that no you don't need the computer to control lockup. you could even put it on a rocker switch to control it manually.

[smoknta]

VSS is the Vehicle Speed Sensor. Used for the speedometer and various other PCM calculations, including but not limited to Convertor lockup.

Yes when you buy a convertor, you need to specify lockup or non-lockup. The lockup of all trannys on LT1's are controlled through the PCM, even the 700R4. I think on older cars with the TH350 and TH400, they were vacuum modulated. So may be able to control lockup with a vacuum switch. Or as stated previously, you can control it with a switch, but run the risk of damaging the tranny if its left on in lower gears or at a idle.

I would either wire it correctly or not even use it.

[93formulaA4]

there was no lockup in a 400 and very few 350's that i have seen have lockup that is what i am getting at. unless he has found a rare 350 with lockup all he needs is an electronic conversion for the speedo and he's all set. not all auto's have lockup converters

[smoknta]

I'm not to sure about the 400 but most of the 350s were lockup. The one I have is. I have a book a rebuild book at home and it gives specs for various years. I'll have to look up and see just how many actually were lockup.