front and rear gear ratios

[61K10]

I have a eaton ho33/32 that i put 3.38's in the rear as that's all that is avl. the front is a dana 44-5f. this is all in my 1961 k10. what i have found on the web is they have to be within 1% +or- a little. closest for the 44 is 3.31's which is 1.02%. a problem on payment all locked up? probably? only dirt or snow? how about a little smaller tire up ft? tk is all stock except eng and a few other things. sorry to be long winded here.

[jeffahart]

You can put a little less air in the front tires, that with extra weight on the front will get you an effective smaller diameter. I think a smaller tire would throw it way off and would look like $hit. How ofter are you in 4x4. You notice it when your locked. I'd run it and not worry if you don't notice it.

[Stocker]

As far as I am concerned, no matter how perfectly matched your gear ratios / tire diameters are, NEVER lock in 4WD on any hard surface. Only engage 4WD on surfaces that are slick enough to allow tire slippage and therefore avoid driveline binding up. Of course this applies to our old-fashioned 4WD systems that truly lock the front and rear driveshafts, not to full-time systems or AWD which utilize a center differential.

That said, if 1% + or - difference in final gearing is acceptable as you say, then 1.02% will be just fine.

[argonaut]

Stocker took the words out of my mouth. Since our transfer cases have no differential between front and rear output they should never be in 4wd on dry pavement.

Kimble I think what you really need to decide first is, what is your desired optimal gear ratio? If that iant the 3.38 then second question, is your desire for the ideal ratio stronger than your desire for the ho33? If so then go get a 12 bolt. If not them just the 3.31 up front.

[andrewmp6]

Most mud drag racing trucks run two different ratios front and rear,Like said as long as your not on dry pavement it shouldn't have any problems.The other option is lose the eaton rear end for a later rear end like a 12 bolt or bigger depending your needs.

[61K10]

Thanks guys for the reply's-----I want to keep the ho as it fits the truck as the front dana is the stock closed knuckle. the org info decal says never use 4wd on pavement. as the ho is all new and axles/bearings are in good shape i will put 3.31's in the front.

Jason---the 3.38's are to make it highway friendly to some extent. just need some pro info about this. Just rebuilt the sm420. need to put it back in.

[kwmech]

Years ago I worked for a company that converted trucks to 4wd. The closest we could match ratios was a 3.54 front to a 3.64 rear (3%). Never had any issues off road. As stated before, exact ratio match even on the pavement will bind up the drivetrain

[61K10]

kwmech-- thanks for the reply, you seam to know your stuff. I guess for now it will be a 2wd tk till i add the 3.31's. I have already did the axle u-joints and hub bearings.

[1976gmc20]

If the front/rear ratios are not exactly the same then it seems like it would be better for the front to be running just a wee bit faster (lower numerical ratio) because the front always has farther to travel on corners.

Years ago I remember a John Deere road grader ad which said the front axle drive was set to be 10% faster than the rear drive wheels. This was back when front axle drive was a new thing in graders.

A slightly faster front axle ratio might even be an improvement over identical axle ratios ???

[argonaut]

Originally Posted by 1976gmc20

If the front/rear ratios are not exactly the same then it seems like it would be better for the front to be running just a wee bit faster (lower numerical ratio) because the front always has farther to travel on corners.

Years ago I remember a John Deere road grader ad which said the front axle drive was set to be 10% faster than the rear drive wheels. This was back when front axle drive was a new thing in graders.

A slightly faster front axle ratio might even be an improvement over identical axle ratios ???

Better for tight turns. Worse for straight line. Maybe tractors turn a lot more and a lot sharper? I don't know I'm not a farmer.

[1976gmc20]

Originally Posted by argonaut

Better for tight turns. Worse for straight line. Maybe tractors turn a lot more and a lot sharper? I don't know I'm not a farmer.

Road graders are pretty darn long and don't turn very sharp normally.

I think the idea was that front wheels were pulling a little faster to get better steering control in snow, or other soft conditions.

Seems like a 4wd truck off road would be making a lot of tight turns, unless mud bogging in which case the road grader front wheel over-speed concept might also actually work to an advantage.

I don't know but I've just always wondered about this.

[ryanroo]

I imagine the over speed in the grader is just to combat the length and the dual rear swing axle thingy. With the weight of the engine over the rear and that long length it would have a tendency to push through the corners. Pull the front faster and you help the situation significantly. The same thing would apply to a 4x4 in a lesser degree. As stated these trucks have no give in the driveline for variable speed front to rear. It is recommended not to engage the front axle on high traction surfaces. I've done it for years, especially in the winter if these lady needs a truck to get to work. Better to just stuff it in 4x4 and send her down the road. Never have had any issue, and none of my trucks have ever been awd.

Your set up will work fine. I wouldn't road drive it in 4x, but otherwise i would doubt you even notice

[1976gmc20]

Originally Posted by ryanroo

I imagine the over speed in the grader is just to combat the length and the dual rear swing axle thingy. With the weight of the engine over the rear and that long length it would have a tendency to push through the corners. Pull the front faster and you help the situation significantly. The same thing would apply to a 4x4 in a lesser degree. As stated these trucks have no give in the driveline for variable speed front to rear. It is recommended not to engage the front axle on high traction surfaces. I've done it for years, especially in the winter if these lady needs a truck to get to work. Better to just stuff it in 4x4 and send her down the road. Never have had any issue, and none of my trucks have ever been awd.

Your set up will work fine. I wouldn't road drive it in 4x, but otherwise i would doubt you even notice

I taught my lady to shift 2hi <---> 4hi a long time ago. Now we have a Jeep with a full time option and I must admit that it works pretty slick. Otherwise my general rule is just leave it in 2hi until you really need 4wd

One thing that always bothered me was using 4 low off road in rough but dry conditions

[RedRoad]

I guess no slick rock (moab) for that 3% difference!

Jeffahart I sent you a PM