Lock out hubs for a 02' 4x4?

[JaMan]

Well I'm convinced that the front axle on my 02' is the reason for my less than spectacular fuel milage. It has the vaccum hose to the diff pumpkin(bear with me because I'm no drive train specialist) this means the axles turn all the time right? So is the a kit that will disconnect the hubs or the axles? A simmilar truck in a 01' gets 4-5 miles per gallon better with the different front diff. Is it sjust my version thats creating more drag? Or am I crazy. Would a full synthetic oil in the front axle help alot or would it be insignifigant? Sorry so long but I'm scratching a bald spot on my head trying to figure this out.



Jared

 

[Fishin Guide]

Well I'm convinced that the front axle on my 02' is the reason for my less than spectacular fuel milage. It has the vaccum hose to the diff pumpkin(bear with me because I'm no drive train specialist) this means the axles turn all the time right? So is the a kit that will disconnect the hubs or the axles? A simmilar truck in a 01' gets 4-5 miles per gallon better with the different front diff. Is it sjust my version thats creating more drag? Or am I crazy. Would a full synthetic oil in the front axle help alot or would it be insignifigant? Sorry so long but I'm scratching a bald spot on my head trying to figure this out.



Jared

If you have the vacuum hoses and the "bump" on the axle, you have the CAD system. It's exactly the same as the '01 you noted. There are parts moving inside the axle tube all the time, but they have no direct link with the driveshaft until it is engaged,



So, can you turn the driveshaft when the truck is stationary? Is there bind on pavement when turning? If it's disengaged, your milage issues are most likely elsewhere. Could be a dragging brake. Too much toe in. Gearing/ vs tire height and width. Or your truck just doesn't get great economy. Also, there could be issues with the fuel and or air system.



It can be tough to diagnose. But do the easy stuff first and see if it helps.



Dave

 

[bmoeller]

There is a conversion kit for Dodge and Ford trucks, so you can use locking hubs. Got to have deep pockets, though. They don't give the kits away.



http://www.dynatrac.com/products_freespin_dodge.html

 

[NVR FNSH]

A simmilar truck in a 01' gets 4-5 miles per gallon better with the different front diff.

Either your trucks aren't that similar, somebody doesn't know how to calculate MPG, there is something very wrong with your truck or you drive with your foot on the floor



Brian

 

[nps]

... or you drive with your foot on the floor



Brian

Don't we all?

 

[JaMan]

The truck with the better milege gets 21mpg but it is a auto with taller tires and a 410 ratio rear and this is hand calculated on a 200k truck driving 70mph with a corrected speedo. The front diff is the older version with out the vaccum hose as stated earlier. My truck is a 02' with the vaccum hose and I comb every thing on the engine and fuel and air system religously, and driving 75mph I get 16 and at 65 and an egg on the pedal I can squeeze 18. 6mpg. Could be some toe in? tires haven't made much difference the three sizes I've run are 315=15mpg, 305 and 285=16mpg and also stockers only saw 16. 5 mpg ave. So I have been looking for parisetic losses such as un needed drivetrain turning and I will look in to the brakes but I have changed them several times and never any noticeable dragging issues.

So in my setup the wheels spin the axles and the diff all the time and the driveshaft is engaged with the vaccum and the t-case stick? So with lock outs the wheels will free wheel?



Thanks Jared

 

[JaMan]

Just looked at ad Bmoeller linked to and holy crap those are

high, is there a cheaper alternative?



Jared

 

[benhall]

Correct me if I'm wrong, but I thought for the 02 models they did away with the vacuum mess and the front axle turns all the time. I plan on doing this conversion in the future, but while I have mine torn apart, I will be adding an ARB locker and bumping up the the 35 spline/1. 5" axle shafts.



Ben

 

[NVR FNSH]

Jared,

I'm calling BS on a auto truck w/4. 10s getting 21mpg at 70 mph. Is the engine stock or has it been modified similar to yours? My truck has 4. 10s and 315s - I turn 2000 rpm at 66 mph. I have an old VA box and the best I've ever gotten is 17 mpg. With your truck pushing ~500 hp do you really expect better mpg?



Regarding the Dynatrack manual hub kit: My dad has been told by a trusted shop that they have had customers state the efficiency improved ~1. 5 mpg with the change over to the manual hubs.



Your front axle has a sliding collar on the long side shaft, passenger side, that connects/disconnects that wheel from the differential via the vacuum motor. The short side shaft turns the spider gear in the diff but the front drive shaft should not be turning. When you put the t-case shifter in 4wd the vacuum motor slides the collar locking the pass side axle shafts and the xfer case is shifted into 4wd sending power to the front end.



The manual hub conversion would allow the front wheels to spin w/o spinning the axle shafts reducing the drag to just the wheel bearings and the brake pads riding on the rotors.



Brian

 

[steved]

In the CAD trucks, I doubt you would see much if any mpg gain from the dynatrac kit... the non-CAD trucks benefit the most since they are also turning the front driveshaft... the CAD trucks only spin a short shaft on the passenger side and the spiders on the driver side with the R&P stationary.



And from 94 to sometime in 02, all the D60Fs had a CAD... somewhere is 2002 they eliminated the CAD in the 2500s/3500s, which as far as I know, is still the case to present, including the newer AAM axles...



steved

 

[Fishin Guide]

The only advantage to selectable hubs for me is the fact that you can ditch the unitized hubs. but the friction gains are minimal.



Dave

 

[JaMan]

The auto truck has a Superchips tuner with Jammer 1's and a 4" exhaust with a HTT manifold. It got 18. 5 before I installed the mild bombs. These are a good milage combo but It just made me think that I could do better and with fuel at $2. 75 a gal. anything will help. Thanks for the info on the front diff and the freewheel setup but that's a lotta money so I guess I'll have to pass on that setup.



Thanks Jared



Jared

 

[KHelfrich]

it sounds like you have the non cad axle cause you say that the 01 dosent have the "vac line" going to the diff and that your 02 has the "vac line" going to the diff



i think what your calling a vac line is actually the vent line on the cad axles the vent goes into the cad unit on the non cad axles the vent line goes in the diff cover



look at the long tube "passanger side of the pumpkin" your axle should be one peice and smooth the 01 axle has a cad unit in the midle of the tube looke like about a 9" long sleve over the axle tube



ken