Montana Owners Club - Keystone Montana 5th Wheel Forum - View Single Post - Rear End ratios - GVWR

trukdoc · 07-23-2006, 04:22 AM

I will try to help. Gear ratio is simular to leverage. 4:10 gears have more leverage that 3:79.
Old school was 4:10 or higher, keep in mind even up into the eighties trucks had nowhere near the pulling power of todays engines, particularly diesels. Onboards electronics have made incredible changes.
The higher gear ratio was needed to simply pull the load, anyone having an old Ford 6.9 or GM 6.2 can tell you what I mean.
But today with HP much higher and advances in transmissions the lower ratios pull very well. Not to mention better fuel economy.
As far as safety goes the ratio has little to do with it, with the exception of mountain driving. The lower ratio will help with engine braking. My Ford has engine braking through the transmission as part of the tow package. Now when I say mountain driving I am not talking about going down the interstate and going over a pass. It is up the middle of the rockies. But with some common sense Is still is not an issue...slow down.
As fas as CGWR and GVWR if you stay within specs the braking and mechanical needs are met. I will ruffle some feathers here but any vehicle will safely tow more than they are rated at due to the built in safety margin. Rule of thumb is 20%. With that said the closer you come to the limit the closer you come to problems. Again common sense.
GVWR is total weight of the truck, CGWR is combined load of truck and trailer. One more thing to factor in is the load rating of the tires.

07-23-2006, 04:22 AM	#6
trukdoc Montana Master Join Date: Oct 2004 Location: Sulphur Springs Posts: 748 M.O.C. #2220	I will try to help. Gear ratio is simular to leverage. 4:10 gears have more leverage that 3:79. Old school was 4:10 or higher, keep in mind even up into the eighties trucks had nowhere near the pulling power of todays engines, particularly diesels. Onboards electronics have made incredible changes. The higher gear ratio was needed to simply pull the load, anyone having an old Ford 6.9 or GM 6.2 can tell you what I mean. But today with HP much higher and advances in transmissions the lower ratios pull very well. Not to mention better fuel economy. As far as safety goes the ratio has little to do with it, with the exception of mountain driving. The lower ratio will help with engine braking. My Ford has engine braking through the transmission as part of the tow package. Now when I say mountain driving I am not talking about going down the interstate and going over a pass. It is up the middle of the rockies. But with some common sense Is still is not an issue...slow down. As fas as CGWR and GVWR if you stay within specs the braking and mechanical needs are met. I will ruffle some feathers here but any vehicle will safely tow more than they are rated at due to the built in safety margin. Rule of thumb is 20%. With that said the closer you come to the limit the closer you come to problems. Again common sense. GVWR is total weight of the truck, CGWR is combined load of truck and trailer. One more thing to factor in is the load rating of the tires.