2.5 ton rockwells

[73redblaze]

iv got a chance to get a pair of rockwells for a good price but im kinda reluctlant becuase i dont know that much about them. what do i need to look out for? i would need a new t-case, drivelines.... trany?? see i know nothing about them but i like the strength

 

[shaun89]

if u want to make them street legal (at least in CT) u have to put brakes at all 4 corners, which i have heard is a lot of money. and one of my buddies has a 70s f100 with them under there and he kept his original tranny and T case from when it had 1 tons under it.

 

[sloth]

You do not need to change the tranny or t-case. The drivelines will most likely need to be modified just like any axle swap.

Here is some other info:

* They are big. The top of the chunk sits almost 10" above the axle tube. Clearance with things like oil pans can be problematic.

* The only ratio is 6.72:1

* WMS-WMS is 79.5" with the hubs out, 69.5" with the hubs in (it is very difficult if not impossible to run disc brakes with the hubs in)

* Stock distance between spring pads is 31.25"

* Wheel bolt pattern is 6 on 8.75"

* Hub nut is 3" - OTC part number 1907

* The axles can be flipped left to right to put the chunk on whichever side you require. If you flip the steering axle left to right, you should then swap the knuckles left to right.

* The chunk can be spun 180 degrees for better driveline angles/clearance. 4 of the housing studs get reused, you need to drill and tap the other holes using the chunk as a guide.

* They have very massive/heavy drum brakes; a lot of people remove them and either run a pinion brake (cheap) or discs at the wheels (expensive).

Here is a pinion brake kit from a CK5 vendor:
http://www.diy4x.com/brakes.htm

There are kits for discs that are around $1300:
http://www.differentialeng.com/TwoHalfTonMilitaryRockwell.htm

There is a DIY disc brake conversion very similar to the above setup using Ford B700 rotors and F550 calipers but it still comes out to $600-$800 per axle once you collect all of the parts and do some minor fabricating and machining:
http://www.pirate4x4.com/forum/showthread.php?t=408046

There are also 8 on 6.5" wheel hub conversions so you can use smaller and more common wheels and brakes:
http://www.pirate4x4.com/forum/showthread.php?t=732246
http://www.ouversonengineering.com/

* The type of brakes used along with hubs in or hubs out will dictate what size wheel with what backspacing you can run.

* The axle shaft joints can be either Bendix (ball and socket), Rzeppa (ball and socket) or Spicer (u-joint). The u-joint style are considered more desireable because they used better materials.

Alloy aftermarket 1.62" 16-spline shafts and 2.0" 47-spline shafts are also available from Ouverson Engineering at http://www.ouversonengineering.com/

* Hydro steering is usually required

* Axle wrap can be a problem if you run leaf springs

 

[AJMBLAZER]

I think sloth covered most of the technical points but I will add to make sure that they are in fact Rockwell axles.

I've seen numerous times someone calls some other HD truck axle a Rockwell. Even the old GM 2.5 ton axles from WWII and post war 6x6 2.5 trucks have been represented as Rockwells. They are not and are significantly weaker, like Dana 60 territory.

 

[sloth]

Very good point! I didn't even think that he may not have been referring to top loaders.