Lock-out possibilities?

[magellan]

I've been contemplating this one for a while. I'm guessing that being able to disengage the front hubs on our '97 XJ has to be worth 1-2 mpg. One-piece axles with lock-outs would definitely be stronger than the MJ axle disconnect. I'm thinking about taking an XJ non-disconnect HP Dana 30, cutting the steering knuckles off at the welds and replacing them with Scout Dana 44 knuckles. I should be able to use the XJ inner axle shafts with the Scout stub shafts and all Scout parts from the knuckle out. This setup would give me bigger brakes, lock-outs, tighter turning radius and 5 on 5.5 bolt pattern. I'll swap in a Scout Dana 44 rear to match.

 

Steering linkage will require some minor modification. The only slight problem I've found is that the HP Dana 30 tubes are smaller OD than the Dana 44 tubes, so I'll have to make spacer rings to go between the tubes and knuckles.

 

Anybody done anything similar? Know of any potential problems I'm not seeing? Is there an older style Dana 30 or Dana 44 knuckle that had the same tube diameter as the HP Dana 30? I lean toward using Scout axles because I have piles of them, but a CJ Dana 30 might be a better donor for the knuckles.

 

Thanks

[magellan]

I did a little more measuring on axles tonight. The MJ/XJ HP Dana 30 has 2.5" axle tubes. Scout Dana 44s use 2.75" tubes. I measured an early Scout II axle shaft and it's 2.5" diameter.

 

Front axle U-joints are the same for MJ/XJ, CJ, and Scout II Dana 30. Scout Dana 44s use a different (I assume bigger) part number. Scout Dana 30 and Dana 44 knuckles and disc brakes are the interchangeable.

 

Scout Dana 30s are hard to find, expecially with disc brakes so CJ axles may be a better donor for this swap.

 

Anyone got a CJ Dana 30 that they can measure to verify the 2.5" tube diameter?

 

How do CJ disc brakes compare to MJ/XJ brakes?

[camjeep3]

if you have piles of d44s.... why not just swap in a whole new front end? i would think doing all that work would be about the same(maybe) as swapping the 44 in the front :dunno: and then you have manual hubs and a stronger axel all together

[magellan]

Scout Dana 44s have a passenger's side pumpkin and low pinion. The right spring perch is cast into the pumpkin. It's not a simple axle swap and for my purposes I don't need a stronger front differential. I would like to have lock-outs, bigger brakes, and a 44 rear.

[Pete M]

spinning the axle shafts around in a circle takes a miniscule amount of gas compared to moving a 3000lb+ vehicle down the road. I'm not trying to rain on your project, but I doubt you'll see an improvement. :dunno:

[mvusse]

I saw no measurable decrease in mileage when I did my CAD delete. Conversely there won't be a measurable difference gain from getting lock outs.

[Incommando]

I did a little more measuring on axles tonight. The MJ/XJ HP Dana 30 has 2.5" axle tubes. Scout Dana 44s use 2.75" tubes. I measured an early Scout II axle shaft and it's 2.5" diameter.

Front axle U-joints are the same for MJ/XJ, CJ, and Scout II Dana 30. Scout Dana 44s use a different (I assume bigger) part number. Scout Dana 30 and Dana 44 knuckles and disc brakes are the interchangeable.

 

Scout Dana 30s are hard to find, expecially with disc brakes so CJ axles may be a better donor for this swap.

 

Anyone got a CJ Dana 30 that they can measure to verify the 2.5" tube diameter?

 

How do CJ disc brakes compare to MJ/XJ brakes?

 

 

Some of your meaurements are a little off maybe? The front axle SHAFT diameter is probably not 2.5" unless maybe you are measuring where the bearing runs ...the tube may be...

 

IIRC, the advantage of the modern axle is the lower rolling resistance of the unit bearings vs. the multiple tapered bearings in the other set. I have seen write-ups for people pulling the front drive shaft to try to improve mileage to no effect. I would think you can do this project if you want to, but if you are doing it strictly for the economics you aren't going to realize a profit for years if at all, especially if you consider your time worth anything.

[Bounty Hunter]

IIRC, the advantage of the modern axle is the lower rolling resistance of the unit bearings vs. the multiple tapered bearings in the other set.

I'm sure that's a huge difference in rolling resistance :roll: And at a definite compromise of strength.

 

Find an 80's Waggy front axle, it has a stronger housing than a Scout d44 and the diff will be on the correct side. Add the brackets and call it good. Then swap in an Isuzu Rodeo d44 in the rear and you'll have disc brakes and 6-lug at all 4 corners.

[magellan]

Some of your meaurements are a little off maybe? The front axle SHAFT diameter is probably not 2.5" unless maybe you are measuring where the bearing runs ...the tube may be...

 

IIRC, the advantage of the modern axle is the lower rolling resistance of the unit bearings vs. the multiple tapered bearings in the other set. I have seen write-ups for people pulling the front drive shaft to try to improve mileage to no effect. I would think you can do this project if you want to, but if you are doing it strictly for the economics you aren't going to realize a profit for years if at all, especially if you consider your time worth anything.

 

Given the context of the post and the fact that it was being compared to two other tube measurements, I believe everyone else figured out that "shaft" was a typo.

 

With a front axle disconnect, at best the left axle shaft and side gear always spinning, the carrier is stationary, the spider gears are spinning at axle speed, and the right inner axle shaft is spinning at the same speed as the left axle but in the opposite direction. If there's enough viscous drag in the side gears and spider gears to overcome the friction and viscous drag in the carrier, the carrier could rotate at a low speed and the right axle shaft would spin slower than the left.

 

Without a front axle disconnect both axle shafts, the carrier, ring gear, pinion, and driveshaft spin together.

 

The advantages of a modern axle with unit bearings and no lockouts are:

1) It's cheaper because there are fewer parts.

2) It's cheaper to assemble.

3) It's more compact.

4) Your mall crawler's front axle stays lubricated even though 4wd is never used.

5) People who are two dumb or lazy to lock the hubs will buy the 4wd vehicle they didn't need to begin with.

6) I believe repairs are supposed to be cheaper because unit bearing replacement requires less skill and supposedly less time.

 

Economics aren't the only factor driving me to consider the swap. I've hated front axle disconnects since a broken shift fork left our YJ stranded in 2 feet of snow. Also, I've never been impressed with the braking power of our XJ or MJ. Neither vehicle has ever been able to lock all 4 brakes on dry pavement with 30x9.5 BFGs and the brake fade is terrible. The Scout brakes could always lock 31s. My intention is to get bigger brakes on the front and use Lincoln discs on Dana 44 rears.

 

I'm sure that's a huge difference in rolling resistance :roll: And at a definite compromise of strength.

 

Find an 80's Waggy front axle, it has a stronger housing than a Scout d44 and the diff will be on the correct side. Add the brackets and call it good. Then swap in an Isuzu Rodeo d44 in the rear and you'll have disc brakes and 6-lug at all 4 corners.

 

I agree with your :roll:. Internal friction of any type of rolling element bearing in good condition is going to be far less than the frictional and viscous drag of turning a hypoid gear set in 90W gear lube.

 

The Waggy axle swap might have some merit, although I prefer the 5x5.5 lug pattern. What makes it stronger than a Scout 44? Scout has the only 8-bolt spindles I've found, but I've never been into a Waggy axle.

 

I saw no measurable decrease in mileage when I did my CAD delete. Conversely there won't be a measurable difference gain from getting lock outs.

 

That's interesting. I might not be surprised by an unnoticeable difference between lockouts and the disconnect, but I would expect a noticeable difference between a non-disconnect axle and either of the other options. Did you check the mileage on individual tanks, or was it a running average over several tanks? My mileage fluctuates by 10% from tank to tank just due to variations in where and how I'm driving, but I see pretty consistent numbers out of a 5-tank average.

 

I need to rig an electric motor to an axle and use the current draw to determine how much horsepower is being lost to back-drive a front axle. That's definitely worth doing before I convert an axle.

[Pete M]

if you want stopping power, I suggest the late model dual-booster swap. :thumbsup:

 

Feel free to measure and theorize til your hearts content, but spinning those parts in their tight little circles just does not constitute a significant gasoline draw in any way. that was a theory back in the day (hence the introduction of the CAD, auto hubs, etc), but they all fell by the wayside because they did not produce anything worthwhile (they did produce a lot of headaches for us owners of 20 year old trucks with 20 year old vacuum lines though :fs1: ). it sounds like a good idea, but just didn't measure up. heck, you might lose any theoretical gain just by the increased weight and wind resistance of the bigger axles. :dunno:

 

Nothing wrong with swapping in better axles for more strength though. :thumbsup: and don't forget better gearing. :D

[mvusse]

I saw no measurable decrease in mileage when I did my CAD delete. Conversely there won't be a measurable difference gain from getting lock outs.

 

That's interesting. I might not be surprised by an unnoticeable difference between lockouts and the disconnect, but I would expect a noticeable difference between a non-disconnect axle and either of the other options. Did you check the mileage on individual tanks, or was it a running average over several tanks? My mileage fluctuates by 10% from tank to tank just due to variations in where and how I'm driving, but I see pretty consistent numbers out of a 5-tank average.

 

I need to rig an electric motor to an axle and use the current draw to determine how much horsepower is being lost to back-drive a front axle. That's definitely worth doing before I convert an axle.

 

I keep a running tab on my fuel consumption, so that is averaged over many months and countless tanks.

[magellan]

I keep a running tab on my fuel consumption, so that is averaged over many months and countless tanks.

 

That's what I do, too. Most people don't.

 

Based on your experience, I'll believe there's no mileage gain to be had.

 

Thanks.