3.31 gears at 40,000 lbs gross.
Just to give a bit of a feel for how different gear ratios would behave while towing I locked out 10 then 10th and 9th then added them back again while travelling on a straight stretch of road w...
Forum Discussion
ShinerBock wrote:RoyJ wrote:
The counterpoint being raised is given an enthusiast driver who cares about his truck (not a fleet driver), towing heavy with a 3.31 puts very little additional stress on components other than the driveshaft / u-joints.
This is where we disagree. I know that the added stress put on the driveshaft/u-joints is also placed upon the output shaft of the trans which in turn is being held to the input side of the trans via clutches. I don't see how anyone can say that there is added stress on the driveline, but not added stress on a clutch and output shaft that is connected to that same driveline.
I'll start by saying we're talking RV use, NOT commercial under-speed cases. In the latter case you would have higher average torque in the transmission input side, because you're purposely lowering the cruising speed. So with a fix cruising hp requirement: we drop the rpm by 25%, up goes engine torque by 25%.
In the RV case, we're locking out 9th / 10th. So if cruising rpm is identical, engine output HAS to be identical. Engine does not know what rear end there is, only the total gear reduction ratio.
If you look at my chart earlier, both 3.31 and 4.30 truck engines are putting out ~420 hp and ~800 lb-ft of torque. The only difference is the 3.31 truck in 4th, and 4.30 truck in 6th. The flywheel / TC clutch would not know the difference.
