Looking for advice: Gears, axles, tires, etc.

[trailpsycho]

For your set up, 4.88s and a selectable locker up front (ARB, electric, cable). If you're going to really drive/wheel it, upgrade the axles and 3rd member. My 2nd wheeling trip after the build, I blew up my stock carrier...cracked the case at the pintle bearing. A Strange or other nodular iron case is a good investment. A standard big bearing rear housing should suffice, but if you plan to beat on it, go all in and buy a package (HD housing, ARB, nodular 3rd, 31 spline alloy axles, disc brakes all at once)...you will probably save some $$ overall. It may sting at first, but you wont be able to break it down the road. As someone else mentioned, sell off your current stock 9 and recoup some of your investment.

My truck with 35s, I have to downshift on the interstate to clear longer grades in the 70-75 mph range. However, it loves 80-85 and will pull great then as the RPM range is more in the sweet-spot...but trying to carry 70 mph sucks on hills, its just not in the power band of the motor. My NV4500 is a 0.73 OD for comparison with the 4R70W. Around town, general driving and offroad the 4.88s are good...but its not quite just right for interstate driving at 70...unless its real flat.

Good luck with your choice.

 

[blubuckaroo]

Thanks for the feedback. I don’t foresee any icy/snowy road use here in Central TX. In the off chance that I did, could I unlock one of the hubs, or is that a recipe for breakage?
I was pretty happy with the performance of the original limited slip differentials, until the clutches started wearing, which is why I’m leaning towards a Truetrac in the rear. I could be convinced to put one up front, as well.
Sent from my iPhone using Tapatalk

Unless you trailer your Bronco to trails, you probably don't want a front locker of any sort.
It's one of those "bragging rights" things.%)

 

[Madgyver]

302, OD trans, 33"s tires = 4.56
if it is a 351 with same OD trans and 33"s then go 4.11

 

[blubuckaroo]

Overdrive ratios aren't all the same.
That 4R70W has a pretty high overdrive ratio, at .67 to 1.
I'd be inclined to go to a 4.56.

 

[Cooter_76]

Thanks for all the suggestions. It'll be a while before I'm ready to pull the trigger on the front axle, so I have some time to decide what to do there.

 

[blubuckaroo]

I'm doing another build on a '62 Ranchero. I just bought the T5 drivetrain kit for it from Modern Driveline.

I was asking what criteria they recommended for selecting the axle ratio. They recommended a ratio that would make the car go 19-21 MPH at 3000 RPM, and an overdrive that would make the car go 65-70 MPH at 2000 RPM.

With this recommendation in mind, I checked my Bronco with 33" tires, 4.11 gears, and a NV3550 tranny.
At 3000 RPM in first gear it went 15 MPH, and in 5th gear it was 2000 RPM 70 MPH. Geared a bit lower than their criteria for a car, but then again, I don't expect any drag races with the Bronco.

 

[Broncobowsher]

Remember that the recommendation on a Ranchero is based on a lighter and more aerodynamic vehicle. I drop to 60 MPH at 2000 RPM. For reference, that is the same as 90 MPH at 3000 RPM. Then tilt the scale to the nearest gear ratio based on if it is a big inch torque motor or a stock V8. That is if the math says 4.96 is the ratio, 5.13 with a stock engine or 4.88 with a strong 351.

Too little gear ends up hurting more than too much gear. Too little gear and you are asking for nearly all the torque the engine can make at that low RPM. Manifold vacuum goes away, fueling goes into power enrichment (carb or EFI). Doesn't pull well in overdrive and doesn't get good economy.

 

[OldBarnBronco]

I'm about to pull the trigger on some gears as my bronco has the stock 3:50. The 302 has some mods (long tube headers, cam, intake, etc), but has the C4 trans which I'm not sure I'll change very soon with 31 tires currently. I plan on going with 33” when the time comes. Based on what I'm reading 4:56 would be an ok choice? Thanks for any advise and the advice already given.

 

[Broncobowsher]

I'm about to pull the trigger on some gears as my bronco has the stock 3:50. The 302 has some mods (long tube headers, cam, intake, etc), but has the C4 trans which I'm not sure I'll change very soon with 31 tires currently. I plan on going with 33” when the time comes. Based on what I'm reading 4:56 would be an ok choice? Thanks for any advise and the advice already given.

C4, no overdrive. 4.56 is too much.
4.11 and 33" tires is a well know happy combo.
I would run 4.11 and 31s knowing that you have room in the gearing for 33s later.
4.11 isn't too much, it was a factory option.
Just saw a comment that 4.11 and 33s were the same as 3.50 and stock tires.

 

[OldBarnBronco]

Thanks! I forgot to mention I have a Comp Cams XR264rf cam in there too. I looked that up and does mention it performs better with lower gears. I'm wondering is 4:11 low enough? 1200-5400 RPM is the range for the cam.

 

[gnpenning]

You also have 4:30 as a option for those in-between needs. I did it on my 74 years ago and still very happy, works for how I use it . 32" tires, C4. I don't drive fast down the freeway and like it off road.