Why 4.1 axle?
I tow an 8000 pound trailer with a GMC 2500 with 6.0l engine, 4 speed transmission, and 4.1 axle ratio. I rarely need 3rd gear on the highway; only on steep hills. For my next truck, why not get si...
Forum Discussion
blt2ski wrote:
Let's look at this another way...
One needs with a motor producing 400 lbs of torque, an overall low ratio of ~24-1. Get their any way you want, 3-1 axle gears with 8-1 in trans, 3-1 w 4-1 in trans, 2-1 transfer case, 4-1 axle w 6-1 in trans...
Old truck, 4.1 trans 2.48 times TC of 2- less 20% for heat and slippage = 4-1so about 16-1 overall low in rwd. Not making 30% a out 16% max grade,unless we have 4 lo. We can do it.
New rig. Trans is 4.1-1 in first, with 2-1 TC, less 20% =6.6-1.
With 4.10 gears, = 27-1, w 3.63 = 24.5-1. Both should pull 20k up a 30% grade. Obviously I hope, the 4 10 setup has a bit more cushion.
Final ratio, old is ~3-1, new 4.10 in DoD 2.6-1, 3.73 = 2.4-1
Reality. Old I'd great at 60. 4.1 New at 65-70mph, 3.73 70-75 or so for same rpm.
Choose poison, I'll take new 4.10, for me, better yet 4.33....that me! :-)
Marty
You are on the right track, but are missing a issue that likely will not often happen with the light weights of RV on hard ground. But if you are at max of what load you can start with say 6-1 low in the trans, and 4-1 in the rearend. Change to a 12-1 trans, and 3-1 in the rearend. There will be much less strain at the flywheel. But if the shaft between trans and rearend will need to handle much more stress. So will the frame that holds the engine to the axle together. And if you only change ring and pinion, a lot of force is pushing the gears apart.
