Wondering if anyone has seen a chart that shows torque numbers to rear wheels after power goes through the transmission gears.
It must be something like:
1st 500ft lbs
2nd 400ft lbs
3rd 300ft lbs
4th 200ft lbs
5th 150ft lbs

The engine produces 570ft lbs but what is making it to the ground after going through the tranny??????
Towing a heavy trailer and just curious as to power lost in higher gears.

 

There is probably a 15% loss of power through the gear train, except in 4th gear which is 1:1 through the tranny and might only be 10% gear train loss. The lower gears multiply the torque, only the overdrive 5th gear reduces it. The final drive ratio of 3.73 (or whatever you have) again multiplies it.

The over all gear ratios (according to Wiki anyway) are therefore
first 11.6:1
second 8.28:1
third 5.78:1
fourth 3.73:1
fifth 2.65:1

Rear axle torque would be 570 times the gear ratio less 15%, or close to that so...

First RAT - 5,620 ft lbs
Second RAT - 4,011 ft lbs
Third RAT - 2,800 ft lbs
Fourth RAT - 1,807 ft lbs
Fifth RAT - 1,284 ft lbs.

Now, the engine produces it's maximum torque at 2,000 rpm, under full throttle and a matching load - in other words with a load that exactly balances the engine power so the engine cannot gain RPM. My truck won't let that combination of things ever happen - it will always shift gears to a gear that lets the engine run at closer to maximum HP, since HP is what does work. So you will basically never actually see maximum torque except on an engine dyno.

Edit: In terms of power lost, aside from the 15% or so lost in friction inside the transmission and the differential, there is no power lost. It all gets transfered to the wheels at very close to the same power level (the loss inside the transmission will vary a bit depending on what gear you are in). At peak torque, 570 at 2000 rpm, the engine is making around 217 hp. Take away 15% and you get around 185 hp. At 2000 rpm, the rear wheels will see that regardless of what gear you are in or your road speed - if you can get it at full throttle at 2000 rpm (which if you had a manual trans I guess you could. Do these come with a manual trans option?).

Brian again

Brian

 

That makes a lot of sense & answers my question perfectly!!!
I'll be pulling my trany into 3rd and taking advantage of that 30% boast to the rear wheels.
Give it's choice it gears down to 4th -- pulling a big trailer up an extended steep hill in the heat 3rd is so much easier on the trani.

 

Good info MC5C. Explains why my truck likes 3rd/tow haul in the mountains. Lock in the cruise at 55 to 60, app. 3,000 rpms and let her climb. That's with a 31' 5er in tow. Reps.

 

Here is my theory: It's horespower that counts - torque is mostly a way to measure horsepower. Let's say a given hill and load combination needs 175 hp to climb. In fifth gear, at 2000 rpm, the maximum rear wheel hp will be about 185 hp, so you will be running the engine at near 100% of capacity - it will do the job, but at max effort. In fourth gear, at 2500 rpm you get closer to 227 rear wheel hp (presuming crank torque of 560 ft lbs), so you are using only around 75% of the available power - the engine is working hard, but with lots of headroom so it will run cooler and easier. In third gear, you'll be at 3000 rpm, guess at 550 ft lbs of torque, rear wheel hp will be around 270 hp and the engine is running at less than 65% of available power, coolant and oil is circulating faster and getting cooled better. In theory, at least, fuel used per hp/hour is less near the power peak, so the engine is actually more efficient. I think it's all good. (I guessed at the actual numbers, but they illustrate the point...)

Brian

 

I wish my mind worked like that- just spin it easier in a higher gear!!!

The easiest way to really get my mind around this is the gears on a old 5 speed bike. Your legs are the engine; here comes a big hill--what is easier, spinning up or grinding it out????
I used to ride a lot & used annoy novices because I couldn't keep my mouth shut when I came across them grinding it out. Told them to watch cycling on TV. Spin, Spin, Spin!!!

For some reason my truck seems content to stay in 4th gear & I figured becuase it's got so much power & 50 computers just let it do what it wants!
That works 90% of the time BUT with a 12,000 trailer on those extra steep, long, hot hills I will now override it & manually pull it into 3rd.
OR is my truck SPECIAL???
I see lots of other guys on here pulling even more weight up steeper longer hills & they just let the truck do it's thing.

Awesome info- I suspected s much but the numbers shown & your logic are way more informative than I had imagined!!!

 

I just let the truck decide what gear to be in, it's smarter than I am. I do tend to take it out of cruise in the hills and drive with my foot, and gradually slow down on the way up the hill to delay a down-shift. That saves fuel, for sure, in my mind at least.

Brian

 

Your foot (if used sensibly) will always be more cost effective than CC . Even on a relatively level road. The CC will never really "take it's foot off the pedal" like your foot does.

Unless it keeps you from getting speeding tickets!

 

The reason the cc works so good on my truck where I go is that it's a steady 6 to 8% grade for app. 13 miles. In 3rd, tow/haul she just stays steady and the 3rd gear gives her the leverage and rpm's to stay cool.