D30 Opinions

After reading JZEBER's thread on his D30 build, I have pulled mine from the shed and have been looking to build it.
It is a D30 out of a 1972 CJ-5 with drum brakes. It needs to be re-geared from 3.73's to 4.88's. My plan is to re-gear myself and add a ARB air locker and convert to disk brakes.
I'm looking for opinions/facts:
Question 1. Can I use my current disk brake set up that I installed on my D27?
Question 2: Can I use the same knuckles that are on the axle or are there disk brake knuckles?
Question 3: Can I use the drum brake spindles or should I swap out for disk brake spindles?
Question 4: Is it worth the extra $$ to upgrade to the 30 spline axles while I'm re-gearing?
Like the title says opinions, thats what I'm looking for.
Thank you,
Rob

 

1, Yes
2, same knuckles with the D27 setup or get disk brake knuckles and use them but since you already have functional brakes, why?
3,Yes and yes
4, depends on the case and whats available.

Best narrow track Dana 30 iteration questions

 

#1 A direct swap over of your disks brakes is likely.
#2 Disk brake knuckles have longer spindle studs than drum brake knuckles. Otherwise the same.
#3 Disk brake spindles require different inner seals and inner bearings. Outer braings are identical. Disk brake spindles have a stronger "stepped" design.
#4 Chromoly axles shafts with larger universal joints is a decent upgrade.

 

Just swap your brakes on and run it once you re-gear it. Don't forget the inner axle seals when you have it all torn down.

 

Yes. I forgot about that. Thanks.

 

How big of a tire are you running? In my opinion, upgrading the axle shafts probably isn't needed in most cases. If you are running 33" or smaller, I'd run the 27 spline shafts and probably be fine for most stuff. Chromoly is typically hard.... Which transfers energy into other components, while softer OE shafts allow for some twist without breaking and is easier on other components. When chromoly does break, it can break sooner than a less hard shaft will because it is brittle. I don't think chromo shafts are all they are cracked up to be. Give me a gun drilled OE shaft over a hardened chromo shaft almost any day of the week. Dana 30 components are still relatively small inside, I prefer to keep my likely failure point in the U-joint as opposed to rebuilding a diff or replacing R&P.

 

ARB Locker and 30 spline? , My opinion would be Yes on the chro-mo shafts. With a Powr-Lok up front then maybe the OEM 27 spline might be OK.......
Most Chro-mo kits are 30 spline inner and 27 outer. and also come with the larger 5-760X Joint which most times will not fit the early 27 spline axles without some grinding which may weaken the axle beyond the benefit to change to the stronger U-joint.

https://www.summitracing.com/nv/parts/aly-12129-arb/overview/year/1972/make/jeep/model/cj5

Some Info:

Off Road Truck Axleshaft Facts - 4-Wheel & Off-Road Magazine
Axle Steel Grades: Carbon vs. Chrome-Moly

 

Personally I'd just start with the original axle shafts then swap over to a large joint chromoly shaft IF and WHEN you ever break the original.
Like Tarry says a 27 spline side gear shaft is certainly acceptable with Powr Lok but 27 splines may not hold up to a locked differential.
As far as the weak link goes.... I like the idea of running soft grade drive flange bolts. It's Very cheap and easy to access those bolts.

 

Decide on the spline count before you buy the diff case, otherwise you are either stuck with 27 spline inners or you'll need to replace the locker to move up to 30 spline. Having said that, I've been running cromo 27 spline axles in my D30 with 35" tires and a locker and I've never had an issue. I did have to open up the hole in the knuckle slightly to get the larger u-joint to go through. 5 minutes per side with a grinder.

 

Thank you for the replies, keep them coming.
I am running 33's on it at this time. No plans to go bigger, but we all know how that changes.
After some research and help from 47v6's thread, I figured out the brake thing.
Still deciding on 27 or 30 spline shafts.

 

I've never broken a 27 spline inner stock shaft with 35's and a V8. Could I? Sure, but it always fails at the U-joint if it's going to so far. That said, if you've got a 2 piece ARB, you can swap the side gears from a 27 spline to a 30 spline. The gear set isn't cheap, but it is do-able. I've got a set of stock 10bolt/Dana44 shafts that I had Carl Jantz cut to Dana 30 width and spline to 30 spline, and a 30 spline ARB to go in it. Time will tell if they hold up. So, D44 joints, 30 spline shafts that are OE shafts cut to D30 width. Haven't gotten the Jeep back on the road yet to bother installing those parts yet however.