Truck: '04 Supercab, 5.4

I'm hoping one of you can explain this in terms even I can understand.
When going up an incline at low speed, with the shifter in "D", the truck starts in low gear, naturally. When I manually move the shifter to "L", I can feel the gearing change a bit, as if it found a slightly higher first gear. The same thing happens with the other speeds, too. The manually chosen speeds feel slightly different than the corresponding automatically chosen speeds. No, this is not a problem at all for me; I'm just curious and want an explanation of the mechanics of it all. Thanks a bunch!
Larry

 

I have no idea. I was going to say first that maybe you are just shifting out of overdrive, but if you are in first gear, you won't be in overdrive.....
I don't know how this is doing this. I suppose someone out there does. I think I may have noticed it in my 97 expy too, that I used to have, but never thought about it much.
Good luck,
MK

 

Maybe converter locks up when manually shifted??

 

Ahh! I bet that is it. I completely forgot about lock up torque converters for a minute... DOH

 

When you put the shifter in 2nd, the transmission shifts to 2nd gear, even if your sitting still. It also lowers the output of the engine since this is designed for starting off on slippery surfaces such as snow or mud. Perhaps when you move the shift lever past 2nd on the way to L, the tranny shifts to second and when you make it to L, it shifts to 1st and you feel the gear change. Just a thought.


BTW, try placing the shifter in 2nd and go up a slight incline at about 20 mph. Shift up to drive and you'll immediately feel an increase in power, even though the transmission doesn't downshift (watch the tach).

 

Thanks for the answers. I'll dig a bit into what torque converters do to satisify the old curiosity.
79 REK: Manually chosen 2nd gear, like you pointed out, is very effective. We had lots of snow on a trip last weekend. With the 4wd and second gear startup, this truck was perfect in both the hard pack and deep fresh snow.
Larry

 

I noticed the gear change and power difference as well. I was going up an incline this summer and wanted to keep the truck in 2nd, but when I shifted from D to 2nd with the transmission actually already in second, I noticed a power loss. I put the transmission back to D and there was a gain, even though this was the same gear. I also figured maybe this was due to the change in timing as this truck offers the most power possible due to the computer changing the timing to provide the most torgue at lower RPMs. Maybe this option stops when it's taken out of D? Just a theory as well as the torque converter mentioned above.
I didn't think this was a bad thing at all, but rather more of a convienence as now I'm confident that the transmission will shift as needed and provide the best power in all gears, while in D. I rarely shift into the lower gears unless I need a lower power take off for ice or snow as mentioned above (2nd gear).
I also only put into 1st if I'm stuck in traffic and just want to crawl without the transmission shifting back and forth.
Over all, I can say this is the reason I like the truck best. The power range for towing has been incredible. I've got 19k on the truck and I've towed thousands of miles with a 6,000 lb. trailer with more stability and power than I've ever had in any 1/2 ton, light duty truck. This performs more like the old 2/4 ton trucks.

Now....if I can resolve the never ending vibration, wobbling, shaking feeling when empty.

 

When you "shift" the transmission in to 2nd gear, it is not "locked" in second gear. If you are standing still, you will not start out in 2nd gear. Shifting into any gear other than D (w/overdrive) just limits how "high" in gear selection that the transmission will shift to. If were to "lock" in gear, then it would be the same as shifting a manual transmisssion into a high gear and trying to start out in that gear. You would hear the engine laboring, and you would burn up the clutch. Shifting the automatic transmission has nothing to do with the power output of the engine. The only control of the power output of the engine is the gas pedal, and this only increases revolutions per time given. I am pretty sure the lock up torque converter is what we are experiencing here.
The reason that they say to shift into 2nd gear to start on snow and ice is to prevent the transmission from upshifting to a higher gear and making the wheels spin out of control. If you are use the gas pedal gingerly on ice and snow you will be fine in any gear.
Thank you,
matt koser

 

Dude....I think you are wrong.
If you put the transmission in 2nd, it doesn't start out in first and then go to second. It is locked in 2nd. I don't know about your truck, but that is what mine does. If you read the owners manual you might find this interesting. The engine does labor and in fact ping if you start out in 2nd. The reason for starting in 2nd is so you don't have the high torque of 1st. The truck can actually start moving in 2nd, just not very well....and that is what you want if you are on snow.
I'm not sure about anyone else, but I know that I CAN NOT start pulling my trailer if I have the truck in 2nd. According to your comments, I would be able to do this as it would start in 1st and then stay in 2nd. I'm not a transmission expert, but I never hear the transmission shift if I start in 2nd.

 

Matt,
My truck also bypasses 1st gear if I manually select 2nd. Like Netguy states, that's to prevent wheelspin on slippery surfaces. It seems his truck and mine act exactly the same when manually selecting gears. (My '98 Volvo had the startup in 2nd feature, I think).
Netguy: Glad to hear it tows so well. I'll be pulling a trailer in the spring.
Larry

 

Dammit. I hate it when I am wrong... You are correct. I didn't believe you so I went and tried it. I apologize.
I just wonder, why do they put this on automobiles? I mean, other than to reduce the Torque to keep the wheels from spinning, what use does it have?
I live in the snowbelt of Northern Wi and have never gotten into a situation where I could not get out in regular "drive", using one method.
Common sense.
Doesn't this heat up the tranny/torque converter by doing this? You are taking all this torque from the motor and have to transfer it to something (energy cannot be created or destroyed, only changed) HEAT. Any thoughts?
MK

 

No problem Matt.
I have been wrong many times. Like trying to figure out this vibration problem I have. Seems I've believed the dealership all seven times they've tried to fix it. :-)
What's the defininition of insanity?
.....repeating the same thing over and over and expecting different results?
Yep, that is what they are doing to my truck!

And Larry,
You will love the performance when towing!

Take care

TheNetGuy