720 dual axle under a D21?

[Telkwa]

Has anyone tried bolting a genuine Datsun 720 dually rear axle to a D21?  D21 is the name for the next generation after the 720's, I think. 

 

I have an '81 Heavy Duty truck, originally sold as Cab & Chassis.  I don't have the time/expertise/desire to fix up the 720 cab so was wondering if moving the axle to a next gen truck might be a better option. 

 

Or even the next-next gen truck if that were possible.  The Frontier came after the Hard Body, correct?

 

Driveshafts can be cut and modified.  I'm mostly wondering about spring hangers, brake lines, and other "devil in the details" booby traps.

[Lockleaf]

Not sure it's worth the effort. The axle itself is narrower than on a D21, though I realize this matters less on a dually setup. The biggest reason though is that the dually setup was nothing more than an extra leaf spring or two in the spring pack and a set of adapters that widened the rest end enough to fit two tires. It wasn't actually a heavier duty unit.

[Rjawm]

I know that 1995 and up D21 has an antilock setup you'll have to work around.

 

I'm currently swapping a Toyota rear end into a 1995 D21 and am trying to determine what route I'm going to take.

 

I'd normally just go with deleting it but as I'm building it for my son, I'd like all the safety features to be working.

[bananahamuck]

If the springs are different width and don't line up with new truck,,  we have just welded a 1/4 inch plate on top of perch added a brace (farther in or out depending) measured for the hole and redrilled it,,,  spaced the distance you need... You will have to notch new plate for U-bolts.

 

 

But most of all a measuring tape is your friend and i have seen some seriously stupid shit done lately because builder couldn't use a simple measuring tape..

[Telkwa]

I hadn't thought about antilock.  Can antilock be disabled by pulling a fuse or some other similar work-around?

[Stoffregen Motorsports]

ABS usually has nothing to do with the axles. It's a system that's usually a part of or piggy backed on to the master cylinder. There may be a speed sensor or two on the rear axle, but those can either be left as they are or a plug machined and installed to get rid of the sensor.

 

Now if you want to put a non ABS axle into a truck with ABS, again, there may be wheel speed sensors. If you do not use them, you could possibly trick the system by using a transmission mounted speed sensor.

 

In older ABS systems, they are not usually part of any permanent electrical system which means that you should be able to remove the system and replace the master with a non-ABS unit.

[datzenmike]

Not sure it's worth the effort. The axle itself is narrower than on a D21, though I realize this matters less on a dually setup. The biggest reason though is that the dually setup was nothing more than an extra leaf spring or two in the spring pack and a set of adapters that widened the rest end enough to fit two tires. It wasn't actually a heavier duty unit.

 

It was way more than just an extra leaf and rims. The axle does not support the vehicle weight and is fully floating and can be removed without removing the brake drum. The axle does not have the wheel studs either. These are on the brake drum (also much different) that is turned by the axle. The axle housing is also different from the 2wd in that IT carries the load on a bearing but does share the spring location and U joint.

 

There were D-21 Cab/Chassis trucks available.

[Lockleaf]

I stand corrected. Man there is not much info online about full floating c200s. I found a couple blips but now I want more. So disregard my earlier post

[datzenmike]

There was a Camper Special or HD option, at least with the 620 and that probably was just heavier springs, 3 core rad ... just enough stuff for carrying an add on camper. I think the '79 the last year 620 had a Cab?Chassis option that was carried over into the 620. Not even sure if it had the dual wheels, probably not. So the Camper option may have slowly morphed over into the Cab/Chassis.

[Stoffregen Motorsports]

I wonder how wide that dually axle is. If it's a floating design, and the width is similar to single wheel width, it may make an awesome upgrade for the single wheels HD crowd.

[Lockleaf]

Stoff, try sending a PM to wayno. He's not on here very often anymore but he has like three of those axles so he could measure one and answer your question.

[Telkwa]

I measured across the tires.  Inside edge to inside edge.  44".  This measurement would give you an idea of whether the tires would clear wheel wells and or frame parts.  The tires are standard issue 14".

 

Measured to the outside edges of the spring perches.  By "spring perches" I mean the flat plates welded to the axle housings that the springs bolt to.  I pulled a tape all the way across from outside edge to outside edge.  40.5" across the spring perch thingies.

 

Measured to the inside edges of the axle at the point where the axle housing bolts to the back of the hubs.  45.5"  If anyone wants more numbers let me know...