3rd gear questions - 6 speed Automatic

[Aldakoopa]

I've been using the manual mode to short-shift and save gas. I usually start out in 2nd, and shift into 3rd as soon as possible, but it seems to act a little funny when doing this. When the car is cold, I can only start off in 1st or 2nd, but when it warms up after driving it for a bit, I can start from a dead stop in 3rd. Is that normal? That's the first question, now for question #2: when I'm accelerating from a dead stop and shift from 2nd to 3rd (at 2000 RPM), it seems to have higher RPMs than when it was in 2nd, usually up around 2500-3000 RPM for a second or two, and it's definitely in a gear because it's still accelerating, then it shifts automatically again, still displaying M3 on the gauges, and drops down to about 1500 RPM. At first, I was assuming the "automatic" shift in 3rd was the overdrive kicking in (maybe?), but the higher RPMs for the first couple of seconds makes me think that it's actually shifting down into 1st and then realises it needs to be in 3rd. It only does this when accelerating from a dead stop, no matter if it's warmed up or not. If it is warmed up and I start off in 3rd gear, it has that same "automatic" shift around 2500-3000 RPM. If it's cold I usually start in 2nd and it still acts funny in 3rd. If I'm decelerating, there is no mysterious second shift in 3rd gear, and if I don't come to a complete stop and don't drop below 3rd gear, it will not "automatically" shift. Just wondering if anybody else has the same issue, or if there is a perfectly logical explaination for this and it's nothing to worry about...

 

[Eric Smit]

Over active torque converter?


-Eric Smit

 

[Aldakoopa]

Would that really only cause a problem in one gear?

 

[Eric Smit]

Maybe if it isn't gear specific, but throttle and load specific.


-Eric Smit

 

[2FR35H]

Same issue with my 2LS 1.8L unfortunately can't say no more than that as I clearly have no idea as to what it might be.... Performs fine in the rain though strangely enough.. not quite sure what relevance would be with that said but yeah you aren't the only one.

 

[esymr2]

How much fuel do you save by starting in third? What's your average MPG?

 

[LS1notFOUND]

I would think you would actually use more fuel as your foots probably to the floor to get it to move in third from a stop.

Also the more your in to high of a gear the more your torque converter is going to slip to try and keep the car from stalling out and fight for the powerband. Its the clutch of the automatic put basically.

From what I understand, starting in 2nd is more of a getting the car going in poor traction situations thing.

 

[rdss]

I agree with LS1notFound, you can't start off in 3rd when it's cold because, well, the fluid is cold and the PCM/TCM probably hasn't moved out of its cold start mode. And the fluctuation of RPM's is the Torque Converter doing its job.

Have you gotten many tanks through the car doing this? If so, how does it compare to just letting the economy tune 6 speed automatic do its job?

 

[Aldakoopa]

Ok, that's starting to make sense now. I actually haven't driven it at all in regular drive, I've only been using the manual mode. I also haven't calculated my actual MPGs either because I personally haven't had to fill it up yet, and I want to hit the trip gauge when I do to calculate it. The dealer has filled it up twice for me, and my parent's borrowed it once and had to fill it up too. The gauge cluster says I'm getting 32 MPG around town and 39 on the highway, but I know it's known to be overly optimistic.

 

[Aldakoopa]

I would think you would actually use more fuel as your foots probably to the floor to get it to move in third from a stop.

Actually, my foot isn't to the floor, I'm still only pressing lightly because I'm trying to save gas. But, could it be that if I'm shifting too soon into third that it actually does downshift into a lower gear to accelerate up to a speed it can actually handle in third?

 

[rdss]

With that said. I think you should fill it up where ever you're at tank wise and drive it in drive for 5-10 tanks in auto or your manual style and then do the opposite strategy with another 5-10 tanks. If you have other people drive the car that's fine, just have them give you the gallons filled and mileage at fill up and continue your logging. I will bet you will find that there isn't much difference and that the way that GM/Chevy produced their full economy vehicle does quite well with a 6 spd auto.

 

[Aldakoopa]

Yeah, I'll try that. I haven't had the car too long, and I was actually in Ohio without it for half the time I've owned it. Still though, I've put about 800 miles (give/take 50 miles) on it since I've had it, and It's only been filled up twice, currently at 1/4 tank... so that's not too bad I don't think.

 

[AxelRipper]

Maybe you should try leaving it in auto mode and driving it? If it is anything like any other modern auto's I've driven (granted, thats not a lot of them) then when you're in M3, you've just made it so the highest gear it will go into is 3rd. When it comes to a complete stop, it should still drop into 1 or 2.

 

[rdss]

He is starting in 3rd and manually shifting through 4th, 5th and into 6th. I agree with the leaving it in Drive and let it be for a while and see where he falls out.

 

[Aldakoopa]

Just a little update on this, I have found out after driving in just regular drive for about a week now, that if I'm light enough of the gas it will automatically shift at 2000 RPM anyway, so I was just wasting my time shifting manually apparently.

It doesn't do any weird shifting in regular drive, and it seems like I get just as much gas mileage like you guys said. I still haven't really measured it, I just started doing that last week as well. I will have some actual results soon though.

 

[TIEfighter]

I have the 1.8L 6 Speed and I drive everywhere in 'D'. Unless I feel like being a ricer then I shift it into 'M'