1986 720 "Heavy Duty" dually rear axle

[Telkwa]

I have one - well, two actually - genuine Nissan heavy duty dually axles.  These things are geared really low.  I've rowed thru all 5 gears within 30 seconds of leaving the driveway.  Venturing onto the interstate is not a pleasant experience. 

 

Is it possible to change the final ratio?  I've never worked on a differential, but if parts are available I'd pay someone who knows what they're doing.

 

Here's a shot of the i.d. plate under the passenger side hood hinge - Next to "TRANS.,AXLE" it appears to say "FS5W71B  CA46"  So that means the differential is a CA46?  I had always thought the "heavy duty" cab & frame truck had its own axle, but maybe the only thing that differentiates this axle from a billion other Nissan axles is the dually rims?

 

[datzenmike]

EN720 is the Heavy Duty option and came with single rear tires and 1,500lb. rating  or the Cab/Chassis option and 1,700 pound carrying capacity with dual rear tires.

 

CA46 is a C200, or 200mm ring gear with a 4.625 ratio. This is a Salisbury type differential case where the gears are bolted directly into the housing and cannot be removed as a unit. C200s (but with the different housing and different axles) were also used in the later 720 4x4s and used a 4.11 ratio. I suppose they, (crown and pinion) could be swapped into your axle but a shop with all the gauges and someone who knows how to set the proper lash would be needed. The 4.625 is needed on the Cab/Chassis because of it's intended use of carrying a heavy camper van or commercial cube body on it. If you are not carrying any loads then a 4.11 would work.  

[Telkwa]

Thank you for the most excellent response.  I think that messing with the differential is a non-starter.  Maybe an eight-speed transmission? :thumbup:   

 

The original papers were still in the glove compartment when we bought it.  The Owner's Manual says the Cab & Chassis (EN720WA) has a 1200 lb. payload and the Heavy Duty (EN720) has a payload capacity of 2,050 lbs. 

 

There's an asterisk next to the payload ratings.  Following further down the page, the asterisk explains that payload "includes load, occupant and equipment (air conditioner)".  Air conditioner?

 

Anyway, add two people and it appears the Cab & Chassis isn't even a half-ton.  I was sure ours was the Cab & Chassis, because it had a U.S. made lift-gate bed on it, but a paltry payload of less than a half-ton seemed ridiculous.  The manual doesn't seem to agree with your data, so I'm still unsure whether this thing is a half-ton truck or a one-ton.

 

I realized later this afternoon that the axles are different than a billion other Nissan differentials in at least one aspect.  They have huge hubs at the wheel ends.  I seem to remember someone telling me years ago that these were a "floating axle bearing" design.  Or something like that.

[datzenmike]

Yeah gross vehicle weight cannot be exceeded by law. The GVW may be on your paper work because it is a Cab/Chassis. Lets say it was 4,500 pounds*. Go to the local land fill where there is a vehicle scale and weigh your truck full of gas and you in it.... say 3,350 pounds. The difference is what you can legally carry....1150pounds.

 

* (just a guess I don't know)

[harlow426@msn.com]

I've got 2 chuckle a little bit reading the above. I have (on a regular basis) had 2000lbs<one ton>of scrap steel in my standard 82-85 720s. Yes 15" whls tires w/LT load rating and overload air bags. I once had 3060 lbs<one and half tons>(accidently kinda) of steel in the truck and drove 60 miles(95deg weather,windy rough road) with out incident(rear axle 4500lbs/front 1660lbs on scale). I wonder what I could move with the "heavy duty dually" rear end......

[datzenmike]

Arial font and size 14 works best here.

 

 

There is virtually no upper limit to what you can haul on these trucks. Doing it safely is the thing. It's easy to exceed the braking and handling and that scares me when I see an example coming towards me on the highway. In 2004 there were 60,000 trailer related accidents. My 620 has Ford F-150 leaf springs on all four corners and 33 x 12.5s. It weighs about 3,600 pounds with me in it and I have probably hauled close to a ton of wet fresh cut fir on it. Handled fine but I went easy... brakes were sluggish. I just don't recommend it. If someone stepped out in front of me....

[wayno]

I have been needing the same thing, I have one with the 460 gears also as a backup rearend, my current one has 437s, and the damaged one has 437s also, but that one has a bad carrier, so I need a carrier for it, but I have not a clue where to get one, I was hoping that the 2wd version with the same housing was the same, but when I ask I never get a responce.

[Xnke]

C200 rear ends can use the R200 ring and pinions; but I am not sure if the carriers can be swapped over. H190 rear ends and R190 carriers can be interchanged; it's often done to get the H190 limited slip or air locker options into the 240Z's that got the R190 Nissan Comp diffs.

[Bill.D]

What is the lug pattern on the dually you are talking about..I have nissan dually rear-end I have no idea what year it is but I do know it cam out of a nissan pickup..it seems the lug pattern is 6on170 which from my research has never been use before or after.. I wand to put 15 in tire on it but can't seem to find anything that will fit. Any help would be appreciated 

[wayno]

On 6/22/2021 at 6:48 AM, Bill.D said:

What is the lug pattern on the dually you are talking about..I have nissan dually rear-end I have no idea what year it is but I do know it cam out of a nissan pickup..it seems the lug pattern is 6on170 which from my research has never been use before or after.. I wand to put 15 in tire on it but can't seem to find anything that will fit. Any help would be appreciated 

 

6-170mm sounds about right for the Nissan dually wheel pattern, but I have never heard of it in 15" rims, I have 14" rims and I like it as I can keep my flatbed decks low, my deck is 30" off the ground so i don't have to lift shovel loads of debris very high.

You might want to check the lug pattern and size of the Toyota dually trucks, they had heavy duty trucks with dually rims on the front so maybe they had 15" rims, otherwise I would find/buy 14" radial tires, I have used them for 20 years without tire issues and I have loaded my trucks up way past the dually axle capacity.

 

The 1985/1986 Nissan 4wd trucks had the C200 rear axle in them(single rim/wheel), them carriers will work in the C200 dually axle as i have done it.