Yes, yet another axle gear question.

[Sander]

Hi all,

I live in the Netherlands. I have a 1977 K5 with a 350TBI thm700r4 and np208. 33 inch tires and using information on this website, I went for a 12bolt rear with 4.11 (37/9) gears. Now I need to rebuilt the Dana44 front axle or find a complete one with the same gear ratio.

Now the 1st shop I went to told me there are no 4.11 Dana44's in existance. They are all 3.73. Looking online I saw there are 4.10's. (big news for the guy in question at the shop). Then he told me that if I put 4.11111111111 in the back, 4.10 in the front wil not work. He told me of a guy with a pickup that had a diference in gears at the 4th number after the point (for example using fictional gear ratios of 3.7320 and 3.7321) and in 4WD on pavement the truck would not even drive a inch. Now that is hard to believe. What is the truth? 37/9 compared to 41/10 is a diffence of less the 1%. Can that bust gears or the transfercase? To me, having less tirepressure in the rear wheels that in the front would be about the same difference or even more.

Thanks in advance.

 

[4X4HIGH]

Go tell the guy at that shop he is full of ****. yes the front gears are 4.10 and that's ok to run with 4.11's.

 

[6.2Blazer]

It's obvious the guy you are talking to doesn't have a clue with the "only 3.73" comment. There's more of a difference if the front tires are slightly worn more than the rear, or the air pressure is slightly different, than the difference between 4.10 and 4.11 gears.

 

[1BEATK5]

most 4x4 trucks came from the factory with mismatched gears by .01. sounds like you need a new mechanic

 

[K85 Octane]

huh
I always thought it was 308, 3.42, 373, 410, 456, and aftermarket. 4.11s huh. Is that a 12bolt thing?

 

[Fordum]

Way back before most of these guys were born, the Willys Overland Co. built their Jeeps with a .01 difference between the front and rear.
The idea was that the front would always be pulling the rear slightly to eliminate bucking.

A lot of companies have done so since. Toyota for one.

If you could have matched gear sets front and rear, and have the tires all be the exact same size, and drove in a straight line, then you could drive on hard surfaced roads with no binding.

None
of that will ever be true of course.

If your drivetrain is bone stock, with oversize tires and a lot of weight in the back, then you will either bind up the drivetrain to the point that the engine is unable to move the truck, or break something.

If you are like most of the guys here, and your drivetrain is overbuilt all to Hell, then most likely you will just scrub the tires.
You will be putting a lot of strain on the system, so I would not do it on a daily basis.

I am sure I will get dinged again for this, but the fact is that if your system is locked so that there is no slippage between the front and rear axles, then something has to slip when you drive because the front and rear will always be trying to turn at different speeds.

Since these guys drive on dry rocks in 4wd, they have built their drivetrains to stand it and force the tires to slip.

I drive in mud, so I don't need that much strength. When I pulled out on the highway in 4wd with about 1500 pounds of firewood in the back, my truck bogged down in about 20 feet. When I took my foot off the gas, it slammed to a stop like I had hit the brakes. (automatic tranny).

My personal opinion is that I would have broken a U-Joint if I had kept going. With that much weight I don't think I would have slipped the tires.

As far as gear ratios are concerned and what is available, listen to these guys.
Some of them probably change more gearsets in week than your guy has changed in his life.

 

[Blue85]

The "names" 4.10 and 4.11 tend to be interchanged a lot. Many people have one, but actually say that they have the other because it is the standard term for the axle they are running. So unless you have the tooth count, don't be sure it's one or the other. But like was posted before, the difference is less than 0.3% so it doesn't matter.

There are sites showing 4.11 available for Dana 44.