Lockers Question

[Gabby]

Hey all! I couldn't order lockers when I bought my truck, but I understand that ARB sells an air locker, and there might be other options... What I can't figure out is what the cost would be and what exactly my options are. I have tried looking at ARB-authorized dealers in the US but I haven't come across one that seems to sell the air lockers, or if they do, I'm not seeing it.

Such thoughts? Comments? Random rantings about how Ford should allow lockers on base models w/o Sasquatch....

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[Gabby]

@Ryan at ARB do you have any thoughts or suggestions?

 

[RagnarKon]

So... the problem is the open diff and the 3.73 gearing is the ring gear is welded to the differential carrier assembly. On most ARB air lockers, you remove the ring gear from the differential carrier assembly and reinstall it on a new ARB assembly. Since it is welded on the 3.73 differential, you can't do that.

Therefore you will basically need to replace the entire differential. And since you have to replace all of the rear gears anyway, might as well re-gear to a more suitable axle ratio. And if you are re-gearing you will have to change the front axle gearing too, otherwise you'll be stuck in 2-High.

Anyhow... below are the ARB part numbers for the air lockers to get you started.

• Rear: ARB RD245
• Front: ARB RD219

 

[Gabby]

So... the problem is the open diff and the 3.73 gearing is the ring gear is welded to the differential carrier assembly. On most ARB air lockers, you remove the ring gear from the differential carrier assembly and reinstall it on a new ARB assembly. Since it is welded on the 3.73 differential, you can't do that.

Therefore you will basically need to replace the entire differential. And since you have to replace all of the rear gears anyway, might as well re-gear to a more suitable axle ratio. And if you are re-gearing you will have to change the front axle gearing too, otherwise you'll be stuck in 2-High.

Anyhow... below are the ARB part numbers for the air lockers to get you started.

• Rear: ARB RD245
• Front: ARB RD219

Ooff.... never easy, is it. So if I swap rear axels I need to regear the front to match so 4L works, yes?

 

[Neps]

https://www.bronco6g.com/forum/threads/aftermarket-locker-options.61587/

Yes- Front and rear gear ratios need to match (pretty closely), so most people that go thru the expense of installing a rear locker and gear set often go to a more appropriate gear ratio for larger tires/ more low end power. If you change the rear ratio you'll have to change the front ratio too.

It can be an expensive endeavor, so it's best to figure out your intended purpose and make the change once (if at all).

Dependant upon the type of off roading you plan, the stock gear ratio may work well for your uses.

I didn't see a reply regarding costs, so here a rough estimate for the rear end - Locker $1200, gear set and master install kit $500, compressor $350. Labor can vary greatly, but a rough guess is $1500. You might also have an additional $200 in misc gear oil, gaskets, etc.

It might be less costly, if you decide to change gear ratios to purchase an entire rear end from Ford?

https://accessories.ford.com/produc...sembly-4-46-w-electronic-locking-differential

https://www.stage3motorsports.com/2021-2022-ford-bronco-gear-packages.html

 

[RagnarKon]

Ooff.... never easy, is it. So if I swap rear axels I need to regear the front to match so 4L works, yes?

Yeah @Neps is correct and provided a lot of good info.

If you use 4 High or 4 Low (or 4 Auto, but you don’t have that), the axle ratio between the front and rear needs to match. Otherwise the wheel speeds between the front and rear will be different.

You don’t HAVE to regear, that’s your choice. But since you’ll have to buy a new ring and pinion anyway, it makes sense to regear now while you have the whole thing apart.

 

[Raptor911]

Just sell it and buy a bronco with SAS .. it will be cheaper.

Ooff.... never easy, is it. So if I swap rear axels I need to regear the front to match so 4L works, yes?

 

[Raptor911]

I have always wondered if you did all of this .. would you need to do anything to the 10-speed trans? any reprogramming as shift points may have changed after you re-geared?

So... the problem is the open diff and the 3.73 gearing is the ring gear is welded to the differential carrier assembly. On most ARB air lockers, you remove the ring gear from the differential carrier assembly and reinstall it on a new ARB assembly. Since it is welded on the 3.73 differential, you can't do that.

Therefore you will basically need to replace the entire differential. And since you have to replace all of the rear gears anyway, might as well re-gear to a more suitable axle ratio. And if you are re-gearing you will have to change the front axle gearing too, otherwise you'll be stuck in 2-High.

Anyhow... below are the ARB part numbers for the air lockers to get you started.

• Rear: ARB RD245
• Front: ARB RD219

 

[RagnarKon]

I have always wondered if you did all of this .. would you need to do anything to the 10-speed trans? any reprogramming as shift points may have changed after you re-geared?

Yup your hunch was correct. You have to change the module configurations to help out the engine/transmission/ABS function correctly. I personally do this on FDRS, but it can also be done with a ProCal4 from Ford Performance if you guy one of the Bronco tunes. (I’m sure I can be done with Forscan too.)

I don’t actually know where the speed sensor on the Bronco is, but on most vehicles it’s on the output of the transfer case or transmission. That is “upstream” of the differentials, so if you regear your speedometer will also be incorrect. When moving from 3.73 to 4.70… if your speedometer says you are going 80 you are actually going mid-60s.

 

[Gabby]

So... the problem is the open diff and the 3.73 gearing is the ring gear is welded to the differential carrier assembly. On most ARB air lockers, you remove the ring gear from the differential carrier assembly and reinstall it on a new ARB assembly. Since it is welded on the 3.73 differential, you can't do that.

Therefore you will basically need to replace the entire differential. And since you have to replace all of the rear gears anyway, might as well re-gear to a more suitable axle ratio. And if you are re-gearing you will have to change the front axle gearing too, otherwise you'll be stuck in 2-High.

Anyhow... below are the ARB part numbers for the air lockers to get you started.

• Rear: ARB RD245
• Front: ARB RD219

Alright, I thought I had the 4.10 but I have an open 4.46. Do you know if the ring gear is welded on that one as well? Is that a problem with all open diffs?

 

[RagnarKon]

Alright, I thought I had the 4.10 but I have an open 4.46. Do you know if the ring gear is welded on that one as well? Is that a problem with all open diffs?

Ohhh... you have a manual transmission. Yeah, unfortunately it is still welded. If you look at the part diagram it looks like separate components, but they are welded. Below is the part diagram for your differential:

Compared to a locking differential. Notice how the ring and carrier assembly has holes for bolting the two together.

 

[Gabby]

Ohhh... you have a manual transmission. Yeah, unfortunately it is still welded. If you look at the part diagram it looks like separate components, but they are welded. Below is the part diagram for your differential:

Compared to a locking differential. Notice how the ring and carrier assembly has holes for bolting the two together.

Where did you get the assembly drawings?

 

[RagnarKon]

Where did you get the assembly drawings?

Parts catalog.

 

[HoosierDaddy]

What size tires do you plan to run?

My opinion is the 4.46 is fine for up to 33" tires.
I bought 35's (34.5") and feel the 4.46 gear is a bit too tall, thus explaining the factory 4.70 for the 35's.

In factory trim, 4.46 and 30" tires, I felt it was very overgeared. Some folks love that. I did not, that is what the C gear is for.

Several others that have done 35's agree with the 33" statement, but there are a few that think the gearing should still be lower .. 4.7 or more.

 

[Gabby]

What size tires do you plan to run?

My opinion is the 4.46 is fine for up to 33" tires.
I bought 35's (34.5") and feel the 4.46 gear is a bit too tall, thus explaining the factory 4.70 for the 35's.

In factory trim, 4.46 and 30" tires, I felt it was very overgeared. Some folks love that. I did not, that is what the C gear is for.

Several others that have done 35's agree with the 33" statement, but there are a few that think the gearing should still be lower .. 4.7 or more.

I hadn't thought of going past 30s for tyres. I only wanted a rear locker for times when I'm out and get hung up in sand or mud, but I'm not into rock crawling or anything terribly serious. That's one of the reasons I got the base w/o the sas upgrade.

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