Best Diff Ratio for set up?

[rhsautoshop]

So my students are progressing nicely on our 67 bronco project. We are currently building the engine (302) with Throttle Body injection.

The owner wants a fun driver that will occasionally be used around the ranch and for hunting season.

Behind the 302 we are putting the NV3550 and using the factory Tcase.

The bronco is getting a 3.5" lift and at least 33" tires possibly 35".

What gear ratio in the Diff will give this a great road ride while keeping decent manners off road? I was thinking in my past research that many were going to a 4.10 or a 4.56 but I can not seem to find my old thread.

 

[gick70]

4.56 sounds good!

 

[Apogee]

Great calculator to determine speed versus RPM and practical shift points.

http://www.grimmjeeper.com/gears.html

 

[rhsautoshop]

Great calculator to determine speed versus RPM and practical shift points.

http://www.grimmjeeper.com/gears.html

Is there a carrier split on these diffs? On jeeps for example you can have a 3.83 and higher on one carrier but to go 4.10 and lower you need a different carrier.

Thanks

 

[Apogee]

Is there a carrier split on these diffs? On jeeps for example you can have a 3.83 and higher on one carrier but to go 4.10 and lower you need a different carrier.

Thanks

The Ford 9" doesn't have a carrier split, however the front D44 will split at 3.92.

 

[Socal Tom]

With that tranny, I'd go with 4.10s for 33 inch tires.
Tom

 

[Blue Bastard]

My vote is 4.56 to make room for 35” tire and to make the first gear nice and low while being able to make the 5th gear usefull


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[ChrisC74]

I have a nv3550, 33" tires and 4.30 gears. Very happy with my choice.

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[Nothing Special]

Depends on what you want. I have a stock-ish 302, NV3550 and 33" tires. I really like my 4.10 gears. Engine revs are pretty low so not so much droning, starts in 2nd gear work pretty well if I'm not on a hill, or towing, or in a hurry and when I need it more power is only a gear shift away. That said, I drive like an old man and (as implied) I don't mind shifting. Most people seem to prefer spinning the engine faster than I do, and want it to jump when they step on it rather than needing a downshift to make a pass. So most people prefer deeper gears, 4.56 for 33s and maybe ever lower for 35s.

 

[Broncobowsher]

4.56 would be a good pick.

 

[blubuckaroo]

The NV3550 has way different gearing than some of the other overdrives. It has a very low 1st & 2nd, and a moderate overdrive. If your axle gearing is too low, you'll loose the advantage of both of those qualities.

 

[sprdv1]

4.56 would be a good pick.

X4..... I'd go that option

 

[sprdv1]

You should post up pics on the project....

 

[Broncobowsher]

The NV3550 has way different gearing than some of the other overdrives. It has a very low 1st & 2nd, and a moderate overdrive. If your axle gearing is too low, you'll loose the advantage of both of those qualities.

Which is why I didn't recommend the 4.88 or 5.13 choices.

 

[SavageBurro]

drove my buddies w nv3550 35s and 4.88s and it was perfect.

 

[kens bronco]

I'm running 4:56 gears with a zf5. Never ran 33's but it does great with 35's and currently 37's. It wheels great, with overdrive no problem running on the Interstate.
Kenny

 

[661buster1963]

4.88 and 35 inch tires is only turning the motor at around 2500 at 70 mph, if you have a nice tight steering and suspension to want to drive it 70.

4.56 will spin 2338 at 70
4.11 will spin 2107 at 70
5.13 will spin 2630 at 70

what engine speed you feel good about on a long trip, or even planning long trips? That NV3550 sure covers a wide array of gear choices from 0.76 to 4.0

I have over built my engine (about 400 ftlbs) to fear the NV3550 wont be a good choice so I am looking at 4.88, 35" tires with a wide ratio ZF small block tranny

 

[blubuckaroo]

Which is why I didn't recommend the 4.88 or 5.13 choices.

You'll see I made no recommendation, but yes, I think 4.56s would be perfect for this application.
I have 4.11s but never plan on going over 33" tires. It's Perfect!