shaun89
1/2 ton status
i know typical auto trannys loos 20-25% of there power through the drivetrain,but thats on a 2wd car, is there much of a difference with a 4wd truck?
CK5
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drivetrain power loss?
- Thread starter shaun89
- Start date
I would think a transfer case would draw an additional 10% depending on the size and type of case. Severe driveline angles could absorb a little, the big thing would be rotational losses from a large/heavy wheel and tire combination. I wouldn't be surprised if you lost 20 or more hp on a chassis dyno with a large 37" plus tire over a stock size tire.
Thunder
3/4 ton status
bigblock72 said:
Yup power loss thru 4x4 with larger than stock tires is shocking.
My G tech tells me I have 168 HP to the ground with a 89 TBI with basic perfomance mods. I guess that aint too bad concidering the pre 87 carb truck 350 only put out 165 SAE net.
shaun89
1/2 ton status
hmm...that does make sense,i guess when i put my engine in it wont have anywhere near 400 hp at the wheels.....o well....thanks for the input
though,good to know little random stuff like this.
though,good to know little random stuff like this.
It all depends. Manual transmissions (and t-cases too) are pretty efficient. With only roller bearings and helical cut gears I would bet their efficiency is over 95%.
Auto transmission vary, and most of their draw is more of a straight hp thing and not a %. IIRC a TH400 takes ~40 hp and a TH350 or 700R4 is closer to 25 or 30.
Differentials are not very efficient because they have to change the direction of the torque. Again, they vary but most are around 90% efficient.
An AWD or fulltime 4WD vehicle will have at least 10% less power to the ground than an identical RWD vehicle.
Auto transmission vary, and most of their draw is more of a straight hp thing and not a %. IIRC a TH400 takes ~40 hp and a TH350 or 700R4 is closer to 25 or 30.
Differentials are not very efficient because they have to change the direction of the torque. Again, they vary but most are around 90% efficient.
An AWD or fulltime 4WD vehicle will have at least 10% less power to the ground than an identical RWD vehicle.
Easy to find where the power is going, find the hot spots. Anything in the powertrain that gets warm is converting power into heat. The hottest parts are converting the most power. Would be easy to point at an auto trans' cooler & say "ditch those trans', they're obviously power wasters" and you'd be only partly right. Recall that you usually slip the clutch a little when getting started. Clutches live a brutal life. They also convert power into heat while being slipped, yet they aren't given any way to loose that heat.
BTW it isn't solely the auto trans in a 2wd that saps power, it's everything in the powertrain + all of the accessories. Anything the engine drives (alternator, A/C, PS Pump, etc.) subtracts from the power that makes it to the rear wheels. SAE HP numbers include some of this (vs. the way it was done in the '60's), but I'm not familiar with if the accessories are set to max demand or what.
And the number for the total (not just the trans) is more like 30%-35%
BTW it isn't solely the auto trans in a 2wd that saps power, it's everything in the powertrain + all of the accessories. Anything the engine drives (alternator, A/C, PS Pump, etc.) subtracts from the power that makes it to the rear wheels. SAE HP numbers include some of this (vs. the way it was done in the '60's), but I'm not familiar with if the accessories are set to max demand or what.
And the number for the total (not just the trans) is more like 30%-35%
