Lift - tire size - gear ratios - I need to figure it out!

[dhendriksen]

So - I'm debating putting a 1.5 or 2.5 inch lift on my 1971 Bronco Sport. I think I want to run 32's or 33's, just to give it a more aggressive stance.

I have the 302 and the 3 speed manual.

I *THINK* I'm running 3.50 gears, as I *THINK* that was stock. I have the Dana 30 front end.

What gearing do I want/need? Will I need to regear if I do the small lift and tires?

 

[1969]

What’s your overall goal with the Bronco? Do you Offroad it? Rock crawl?
Are your fenders cut?

 

[DirtDonk]

First, determine exactly what you have now. Don’t guess, measure.
Broncos with V8’s came with 4.11’s as well.
Next, your tire choices will most likely fit with either lift, so just determine whether you’re going to cut the fenders or leave them uncut.
The next key component is the transmission. Will you stick with the standard transmission, or will you be going with an overdrive?
Will you be sticking with the same stock, carbureted engine, or will you be changing to a more powerful and torquey engine with fuel injection?

 

[Broncobowsher]

302 and 3-speed. OK, that is known.
The base gearing was 3.50. There was also a 4.11 option. And there is also 52 years of people changing stuff since it was built.

Back to the 302 and 3-speed. Keeping them? Maybe future upgrades? Looking at anything with an overdrive (automatic or manual) will greatly change what axle ratio will be a good choice.

You do know that with cut out fenders you can install 33" tires without a lift and it will ride and drive really good. The filled wheel wells rooks really good.

So if you have the base 3.50 gears, and you decide to put 33" tires on it. It will drive like a total dog. Slow, gutless, unresponsive. It might cruise flat highways decent.
4.11 gears are well known for a good ratio with 33" tires and a non-overdrive transmission. Gets a decent all around rig. Good in town, decent on the highway, capable of a little light off-roading.

Stepping up to an overdrive transmission and a good gear ratio could be in the 4.56 or 4.88 range.

My 1st Bronco was a '71 with a 302 and 3-speed. The base 3.50 gears were a bit off for the 31" tires. Knowing what I have learned in the 30 years since then I would say the 31" was a little too tall. The 3.50 gears would have been better with 29-30" tires.

So lets find out what gears you already have, and you total plan in the end. After that we can work it out.

 

[.94 OR]

My Bronco was cut and not lifted when I bought it in '89. It had 31" tires and likely that size for a while before I bought it and that is what I have run since. Stock 302/3-speed/3.50 gears until recently when I installed the NP435 so basically the same 3 gears as First is not a street gear. I had the clutch replaced at one point and took the flywheel in to get resurfaced and a new ring gear installed. Within a minute at the machinist, he gave the flywheel a quick look and asked me if I was running high gears. I had him show me how he knew. With that knowledge, I think 31's would likely be happier with 4.10's but I haven't ever changed mine out.

 

[Broncobowsher]

My Bronco was cut and not lifted when I bought it in '89. It had 31" tires and likely that size for a while before I bought it and that is what I have run since. Stock 302/3-speed/3.50 gears until recently when I installed the NP435 so basically the same 3 gears as First is not a street gear. I had the clutch replaced at one point and took the flywheel in to get resurfaced and a new ring gear installed. Within a minute at the machinist, he gave the flywheel a quick look and asked me if I was running high gears. I had him show me how he knew. With that knowledge, I think 31's would likely be happier with 4.10's but I haven't ever changed mine out.

That further confirms my feelings that 31s are a bit much for the 3.50 gears.

 

[dhendriksen]

The wisdom here never stops, and I appreciate it! I have 3.50's in the rear with Limited Slip, and whatever went along with that from the factory in the front.

The person I got it from bought it in 1980 and hasn't touched them, and knew the prior owner and confirmed he hasn't touched them either.

So I've got the 3.50's. Sounds like I need to re-gear. Currently it has P235/75R15's (which I believe are ~29's?) and acceleration already isn't great.

I do plan to keep the 3 speed manual, and I don't plan on doing really any offroading. I have a new Bronco, Badlands with Sasquatch and we take that wheeling a lot. This Bronco is for fun and cruising around town when the weather is good (please, don't hate me).

 

[Okie69]

For fun around town I’d regear for 33s with stop light to stop light fun in mind and leave it stock height. If it’s already cut that is…

 

[dhendriksen]

For fun around town I’d regear for 33s with stop light to stop light fun in mind and leave it stock height. If it’s already cut that is…

It is stock height. Has had almost no modifications ever.

 

[DirtDonk]

No hate here. At least you still go off road in something!
But in reality you’re with the vast majority of modern Early Bronco owners. They’re basically being used for cruising around town, or the beach if you’re lucky enough.
Didn’t used to be that way, of course, but it is what it is now. No harm, no foul as they say…

You might measure your tire to get an exact diameter. They can vary slightly from manufacture to manufacture, and it doesn’t hurt to know exactly what you’re dealing with.
There have been plenty of uncut rear fenders that fit 31s, but it’s not just as simple as mounting them and going.
Sometimes they interfere with the leading edge of the rear wheel well And so one of the solutions traditionally has been to move the axle back an inch or so.
Not a difficult, or expensive task in most cases.

Wheel width and offset matters greatly at this point.
And depending upon where you live, the tire shop you deal with might not mount a wider tire on a narrower rim, in case you’re thinking of going with stock wheels.
Sounds like the stock wheels might still be on there? There’s another discussion in the forum started yesterday I think about using stock wheels freshly powder coated with some different size tires.
The tighter they are tucked inside the wheel well the slightly better the clearance is with the leading edge.
The suspension lift does not matter as much for interference in this location, but it can still help to a certain degree.
Especially with the tires tucked in tight.
But then, of course, you run into Clarence issues with the front radius, arms when turning tight.
It’s always something!

 

[Broncobowsher]

Going from 29" tires to 33" tires (ignoring the error that tires are often not really what they say they are) is about a 14% increase in tire size. To get back to the same effective gearing you have now would take almost a 4:1 gear ratio. A 4.11 would be just a breath more gear.

Now the question is if the overall driving with the 29" tires is what you want to maintain once you go to 33s? Maybe a touch more gear?

When you do the gears, start with only the rear axle. Go drive it around. 4WD won't work as the ratios will be too mismatched. But you can feel if you like the choice in gear. If you feel it is wrong, you are only changing the rear. Once you like the ratio in the back then spend the money on a matching set of gears for the front.

 

[chuck1022]

So - I'm debating putting a 1.5 or 2.5 inch lift on my 1971 Bronco Sport. I think I want to run 32's or 33's, just to give it a more aggressive stance.

I have the 302 and the 3 speed manual.

I *THINK* I'm running 3.50 gears, as I *THINK* that was stock. I have the Dana 30 front end.

What gearing do I want/need? Will I need to regear if I do the small lift and tires?

4lo.com will let you put in all the info and you will get rpm....speeds.......all that.

 

[blade]

There have been plenty of uncut rear fenders that fit 31s, but it’s not just as simple as mounting them and going.
Sometimes they interfere with the leading edge of the rear wheel well And so one of the solutions traditionally has been to move the axle back an inch or so.
Not a difficult, or expensive task in most cases.

Wheel width and offset matters greatly at this point.

I have 31" tires on my 74 with uncut fenders and no lift. I used the 80s f150 bronco spoke wheels. I had a tiny bit of rub on the leading edge of the rear quarter. a light bump with a mallet fixed that.

 

[DirtDonk]

It is stock height. Has had almost no modifications ever.

If the rear fenders remain uncut, I would not even consider 33s. Yes, it’s doable (and you can check out member 1sicBronconut’s bronco) but it’s a lot of work and not for the faint of heart or non-committed!
Stick with 31s or smaller would be my recommendation.

 

[Madgyver]

keep it stock height. 30x9.50 no regear needed. my opinion.

any suspension lift and you need to deal with steering geometry.
any bodylift and you need to deal with clutch and throttle linkages

determine your final plans on this rig. it will snowball if not managed correctly.

 

[bmbm]

So - I'm debating putting a 1.5 or 2.5 inch lift on my 1971 Bronco Sport. I think I want to run 32's or 33's, just to give it a more aggressive stance.

I have the 302 and the 3 speed manual.

I *THINK* I'm running 3.50 gears, as I *THINK* that was stock. I have the Dana 30 front end.

What gearing do I want/need? Will I need to regear if I do the small lift and tires?

Looks like your rear fenders are cut.
Your body bushings and springs may never have been replaced. If your body bushings are original they are probably very flattened out so if you just replaced with new body bushings it will be raised a bit but you probably won't be able to notice really. A good option is get new rubber body bushings and a 1" body lift kit from one of the vendors, I did that and could see a bit more stance. For my Bronco the 1" lift did not require changing anything else but I heard the 2" or higher body lift requires additional work. If your springs are still original, you can tell by measuring, then they have sagged quite a bit. A stock height set of new springs from one of the vendors will probably increase the height enough to notice especially on the back, possibly a 1" lift from springs and 1" from body lift so you are at 2" lift with no extra work like suspension mods etc. Cheap and relatively easy/fast.
Separately if you go with 33" tires you may want to look into moving the rear axle back. There is a way you can move it about an inch, maybe a bit more don't remember exactly but easier to do if changing out the leaf springs and not a huge job. I intend to move my axle back when changing out the springs even though mine will have 31" tires. I think it looks better.
Also as stated your wheel width and backspacing will become a factor in the equation with larger tires and would probably warrant measuring that for your base info.
If your acceleration is poor now with 235 tires you may need a rebuild or a 351 or something but that three speed is not a positive contributing factor it is best suited to a tractor. I have never missed mine.

 

[dhendriksen]

keep it stock height. 30x9.50 no regear needed. my opinion.

any suspension lift and you need to deal with steering geometry.
any bodylift and you need to deal with clutch and throttle linkages

determine your final plans on this rig. it will snowball if not managed correctly.

You’re absolutely right about it snowballing. I mentioned it has had very modifications but one of those is the rear fenders were cut. Another is the 3 speed was moved to the floor.

 

[BGBronco]

Assuming we're talking about the Bronco in your avatar. Very Nice.

I have a 1.5" lift on my Bronco. Stock height body mounts, 33s and cut fenders. 3.5 Gear Ratio. Very happy with this setup and it does not feel underpowered to me.

I can't tell what size tires you have now but a new set of 32/33 BFGs would raelly change the look of your current set up. Not sure about tire sizes with your uncut front fenders but personally, I would cut them to match the rears. If you lift don't cut / lift, this will definitely be a consideration.

 

[gnpenning]

A option that hasn't been mentioned is you can go to 4:30 gear if you want a little more off the line fun but don't need a high speed highway gear.

 

[dhendriksen]

Assuming we're talking about the Bronco in your avatar. Very Nice.

I have a 1.5" lift on my Bronco. Stock height body mounts, 33s and cut fenders. 3.5 Gear Ratio. Very happy with this setup and it does not feel underpowered to me.

I can't tell what size tires you have now but a new set of 32/33 BFGs would raelly change the look of your current set up. Not sure about tire sizes with your uncut front fenders but personally, I would cut them to match the rears. If you lift don't cut / lift, this will definitely be a consideration.

Yes, it is the Bronco in the avatar. THANK YOU! I think the stance on your Bronco is awesome! Would your setup have worked with the front fenders uncut? I'm not too keen to cut the front fenders.