4.11s, 4R70W, and 33 inch tires

[fordguy]

I currently have the above and am finally making some progress on my build. I am thinking for the sake of time and money, running the above and figuring out gearing later. I have housings available to build. What is the consensus. this will be a driver mostly.

 

[Broncobowsher]

What engine?
I'm thinking they are a bit too tall. They will work. but not ideal. If this is simply to get it running I say go for it.

 

[Apogee]

It'll work, but if you're running a 302/5.0, then I would probably run 4.30 or 4.56 gears if I were doing gears anyway. If I thought there was any chance of going to 35's in the future, then I would be looking at 4.88's.

 

[Broncobowsher]

Correct, lower gears are ideal. Don't buy 4.11s, but you can drive with them if that is what you already have.

 

[duffymahoney]

So I basically have 33's. I think they are 32.7 or so. I have 4.11's because I originally planned on a 31.5 or 32" tire. But I talked with a few members running the same size tire and gearing and 4r70w, and they have zero issues at highway speeds. They said it downshifts to go over hills or pass or whatever. But that is exactly what it's supposed to do. I think people worry about it too much. But I shall see.

I am going to just try it. Hopefully it works fine and gets ok'ish mpg.

 

[pcf_mark]

I run 4R70W with stock 3.50:1 gearing and stock 29" tires. My converter locks and I am in 4th at 50 mph and 1,600 rpm. It is a little low I think 1,800 rpm would be better to lug the engine a little less but the converter unlocks and drops out of 4th as needed to pass or climb a hill. I love it - much quieter w/o the engine revving to the moon cruising down the highway.

 

[DirtDonk]

Agree to try it for sure. You have nothing to lose and everything to gain by using what you have now. Even if you were in the middle of a restoration and wanted to do the differential work now, I'd suggest you put it off until you've driven it to know how you like it.
It's just too important of a decision to make without a little more input.

But the good news is that you're starting from the 4.11 platform, and not the 3.50. And you're using 33's instead of 35's or 37's.
I'd ask the same question about "what engine" but at this point it's moot anyway. Just run 'em.

A decent engine and you might just find they're perfect. I'm going to run the same setup with 33's and 35's to decide. Doing that first, after the new engine and 3550s finally go it (as if!) but already decided that, even though I think a 4.56 or 4.88 would be a better choice for me with 35's, there's no way I'm not going to experiment with the existing perfectly good 4.11's first.

Good luck. And make sure to give full feedback when you get rolling. It's the kind of thing we love to hear.

Thanks

Paul

 

[fordguy]

Agree to try it for sure. You have nothing to lose and everything to gain by using what you have now. Even if you were in the middle of a restoration and wanted to do the differential work now, I'd suggest you put it off until you've driven it to know how you like it.
It's just too important of a decision to make without a little more input.

But the good news is that you're starting from the 4.11 platform, and not the 3.50. And you're using 33's instead of 35's or 37's.
I'd ask the same question about "what engine" but at this point it's moot anyway. Just run 'em.

A decent engine and you might just find they're perfect. I'm going to run the same setup with 33's and 35's to decide. Doing that first, after the new engine and 3550s finally go it (as if!) but already decided that, even though I think a 4.56 or 4.88 would be a better choice for me with 35's, there's no way I'm not going to experiment with the existing perfectly good 4.11's first.

Good luck. And make sure to give full feedback when you get rolling. It's the kind of thing we love to hear.

Thanks

Paul

this sums it up. drive what you own, it cost nothing. I already jumped the gun and built the dana with 4.11s, I already have 4.11 nine inch on the truck. I will never go to 35s.

 

[sprdv1]

this sums it up. drive what you own, it cost nothing. I already jumped the gun and built the dana with 4.11s, I already have 4.11 nine inch on the truck. I will never go to 35s.

Can always switch if it don't work just the way you want...

Just take a little more time / effort / money

 

[Broncobowsher]

The constant shifting is what kills transmissions. And those shifts are under load, which is worse. Modern stuff doesn't care, with matching engine control that kills power during a shift they can shift all the time and still last. If you can gear to hold most grades the transmission will be happy.

A good RPM to aim for in a bronco with a V8 is about 2000 RPM at 60 MPH.

 

[Viperwolf1]

The constant shifting is what kills transmissions. And those shifts are under load, which is worse. Modern stuff doesn't care, with matching engine control that kills power during a shift they can shift all the time and still last. If you can gear to hold most grades the transmission will be happy.

A good RPM to aim for in a bronco with a V8 is about 2000 RPM at 60 MPH.

This is absolutely true. My combo is 4R70W/34" tires/4.88 gears and it is perfect. RPM is around 2500 at 75mph, or 2000 at 60 mph. It will hold 4th in lockup at any speed (haven't been over 90mph much) on semi-flat ground. Cruising in town it will shift into 4th and lockup around 35mph. Up on the mountain highways it will drop out of lockup on the big hills but rarely will it drop down to 3rd. I can monitor my trans temp and see it increase when it's out of lockup. If it gets above 200 I'll manually drop it into 3rd and it will lockup and the temp will fall.

All this requires enough engine torque to push a big, square hole through the air. My 351W is making over 400 ft-lbs between 2500 and 4000 rpm. It is very happy cruising at 80 mph. A less torquey engine won't be able to hold the gear as well. Lower axle gears will also make things worse.

 

[KyleQ]

I ran 4.56 gears with that combo in my F150 and I love it - was excellent with 34" tires as well.

 

[duffymahoney]

Somewhere on this site is a chart of tire size and gear ratio, speed/ rpm for the 4R70W.

 

[KyleQ]

I've found this to be the best for looking at ratios-

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