New Rear Differential and Brakes

[EricLar80]

Thinking about buying a new rear 9" differential as part of my resto. If you were starting over, what would you build?

I do know that I want rear disc brakes that have a working parking brake. Debating 35 spline axles, semi-float and a truetac. I am willing to spend on upgrades so long as they have function; I don't need flashy upgrades. I definitely don't want to deal with leaks.

Considerations:
- Full floater 31 spline or semi-float with 35?
- 1350 u-joint or 1310?
- Which brakes?
- Truetrac or ARB? (I have arb in the front)
- Anything else I am not considering?

 

[Yeller]

full float 35. Ruff stuff used to have a slick set up for that with trophy truck parts that as 5x5.5 compatible, don't know if it will work with an explorer disc set up. IMO semi float will leak, its just a matter of time.
explorer style brakes
ARB in the rear
1350 ujoints.

 

[markw]

Yep, what Yeller said. Good start for a NORRA racer. Just can’t be in Pioneer with FF. Do you have a AA extreme output shaft with 1350 flange to go with the 1350 yoke?


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[EricLar80]

Do you have a AA extreme output shaft with 1350 flange to go with the 1350 yoke?

No, I don't. Have considered both the extreme output and an atlas. Atlas starts to get pretty spendy but maybe that's worth it to get 3.00 low gearing.

 

[jamesroney]

Your signature line says you have a Dana 60. Why in the world would you downgrade to a 9 inch?

If you are going to run a true-trac, then you really want that 60. If you are going ARB, you also want the 60. If you are running anything other than a Detroit or a Spool...you want the 60.

The 9 inch carrier is too small to hold a decent locker.

A junkyard 60 with Torino Big Bearing Ends and 35 spline semi float axles works great on 35's. I'm moving back to drums on the rear next ttime.

 

[Yeller]

By the time you rebuild your 20 and put 35 spline outputs you can justify an atlas. Having broke gears and cases on 20’s in the long run it’s a savings.

Not to start a massive debate but the ring and pinion in a 9” is stronger than a 60. However start pushing hard enough to break the weak links in a 9”, the differential or the pinion shaft, the gears start failing in the 60 so pick your poison.

 

[Broncobowsher]

So many different housing options as well. If considering a full float, might as well go with a fabricated housing. Just about everyone has there own version. At least a new HD housing. The stock Bronco housing is the second weakest link in the stock rear end. No point in putting hood parts into a flexy housing.

Daytona pinion support. Check the gearing options, there is a bigger pinion spline option as well. That gets overlooked until someone twists off the pinion. I think it is 35 over 28.

How much tire? How much engine? How will it be driven?

The option list is nearly limitless. You can even get 10" gears if you get all the other parts right.

And don't forget the Hi9 options as well, if driveshaft angle is going to be an issue.

 

[EricLar80]

Your signature line says you have a Dana 60. Why in the world would you downgrade to a 9 inch?

If you are going to run a true-trac, then you really want that 60. If you are going ARB, you also want the 60. If you are running anything other than a Detroit or a Spool...you want the 60.

The 9 inch carrier is too small to hold a decent locker.

A junkyard 60 with Torino Big Bearing Ends and 35 spline semi float axles works great on 35's. I'm moving back to drums on the rear next ttime.

Keeping the 60 isn't a cheap option when you consider the cost to rebuild/reseal, new gearset/locker, etc. It has the caddy rear brakes on it, which stop fine but the parking brake doesn't work. Beyond that, the challenge I have found is fitting a traction bar in next to it. It is original Bronco width (58" WMS), or close to it, and the pumpkin is so wide that fitting a traction bar in there is challenging. Can't went on the pumpkin easily because it is cast... It also hangs down lower, is probably heavier, and makes the driveshaft shorter.

 

[toddz69]

Thinking about buying a new rear 9" differential as part of my resto. If you were starting over, what would you build?

I do know that I want rear disc brakes that have a working parking brake. Debating 35 spline axles, semi-float and a truetac. I am willing to spend on upgrades so long as they have function; I don't need flashy upgrades. I definitely don't want to deal with leaks.

Considerations:
- Full floater 31 spline or semi-float with 35?
- 1350 u-joint or 1310?
- Which brakes?
- Truetrac or ARB? (I have arb in the front)
- Anything else I am not considering?

I don't break stuff like others do due to my smaller tires and less aggressive 'wheeling trails but I do like nice stuff . I had one of the Warn full-floaters for a few years but got rid of it due to leaks. 31 spline semi-floaters in a Currie HD housing have done just fine for me since then with 33s and 35s.

However, if $$ was less of an object, I'd probably go with some sort of a Currie housing and do their 35 spline floater with the JK disc brakes on the ends. Slightly larger version of the Explorer discs so the e-brakes work. Not as sexy as Wilwoods but better from a practical/$ standpoint. Maybe a 1350 u-joint but 1310s work fine for me. Definitely Daytona pinion bearing support and a nodular case. ARB since you already have the plumbing for the one in your truck. Tru Hi-9 as Bowsher noted if you have driveline challenges. And a 3.0 Atlas to finish it off.

Todd Z.

 

[Yeller]

for full out silliness the 10" stuff is the bomb but comes at a cost. There's a reason many have switched to a 14bolt. As for welding on the cast, its not as difficult as has been made out to be, I can coach most anyone with a 200+ amp MIG and oxy fuel or MAP gas torch to weld on it successfully. For myself unless money was no object, 14 bolt, but for pure brute strength and sex in steel, Gear Works 10", housing and full float for the win.

Todd thanks for not being in the 5:1 atlas camp, even for the hardest of wheelers its not needed and usually a hinderance. 3.0 for 4r70, 700r4. Now that we are starting to use 6 speeds, 2.0 is my choice. C4 needs a 3.8, more and your just getting in your own way. the 4.3 and 5.0 were developed for manual transmissions and power glides.