Isuzu npr 4x4 conversion

[Outdoort]

Copy and paisted from ih8mud as im getting zero responses there. Hoping a few folks here can help me. I wouldnt be opposed to inporting the nps stuff but i figure it would cost way too much to do so.​

Through some reasearch, looks like a ford super duty front axle and possibly a sterling 10.5" rear would be a good combo.​

So i just bought this Isuzu npr. 1988. It has the 4bd1t with an automatic transmission, but i have everything i need already to convert it over to manual transmission except the shifter and linkage.
So thats what im probably going to do is convert it over to manual with the factory msa-5d.

This truck can be a little bit of a project truck right now and i really want to convert it over to 4x4.

Need some help with what would be the correct parts to source.
Ive seen the thread on expedition portal about rc trucks and their conversion and a few people posted about how they think its a dana 60 axle and a nv 271 transfer case.

I just need some guidance from a few knowledgeable people out there on what dana 60 i should be looking for and from what model truck and year????

I guess there were several versions of the dana 60 and i just dont know what i should be looking for from the junkyard.

This swap needs to be price sensitive, so nothing crazy, but i plan on possibly turning this into a mobile welding rig or just a nice flatbed for my fabrication shop. No crazy wheeling, just a nice 4x4 for general use. I may have the truck loaded down here and there with some heavy weight.

Do i need to swap the rear axle out as well? Do both axles have to have the same gear ratio?

I can figure out the rest as i go along, i just need the correct parts first and that may take a bit of time. Also thinking a divorced transfer case. Its got a 150" wheelbase.

Thanks guys
​

Friday at 4:56 PM

 

[charlieaarons]

It sounds like you don’t have any experience with this sort of thing. The rear differential ratio must be either the same as the front or 1 to 2% “shorter“ i.e. numerical higher. THe divorced transfer case is not a bad idea with the long wheelbase . Perhaps a NP 205. Recommend putting in a rear locker if you go into the rear differential at all or even if not. The automatic lockers like Detroit/NoSpin work well with long wheelbase. If funds permit an ARB front locker if go into the front to change ratio. Exact choice of axle depends on transfer output or vice versa.
Be sure you have worked out what ultimate tire size you want to use before picking gear ratios in differentials.
Avoid Dana 60s with unit bearings

 

[Outdoort]

Charlieaarons, yes i have no experience doing this sort of thing. But im a experienced welder/ fabricator that runs my own shop so i have that going for me.

Ive looked at a couple of those threads posted above already and im still looking through the rest on that list.
Thanks for sharing david!

I want to use 34" tires. I dont see using 37".
This is going to be mainly for work truck use (at least currently).

So based on 34" tires and a np 205 transfer case (just because ive read of two posters here using that transfer in there 4x4 swap what axles might be reccomended?

 

[charlieaarons]

What is the GVW and front/rear GAWR and tire size of the vehicle? Current diff ratio?

 

[Outdoort]

This is all i got. I have no idea of the rear axle ratio and id love to find out. I dont know how to either. Even a call to the dealer is no luck

 

[Outdoort]

I have a feeling the rear axle ratio is not what i want it to be. Havent done the calculations, but just want a nice cruise speed of 70mph at the optimum rpms.

Ive already rebuild one of these 4bd1t engines and its pretty straightforward. Very simple engine design. Since new axles would mean a re gear for my new rpm range being a lot lower that stock on these npr 's im gonna use a td04hl turbo as there pretty cost effective and it will give me more boost and hp in my rpm range.

 

[C p weinberger]

I Have done some research over the last 12 months with the same idea in mind. I liked the Mitsubishi FG 4x4 setup but was not happy with the engine/s performance. So I looked into NPR conversion to 4x4.
My impression from research:
You had a hard time getting a response on I8mud because very few people have done this conversion or interested in it.
As far as I know, no private person in the US has done a low cost 4BD NPR Conversion to four-wheel-drive and has Posted information on their success.
There is a post on here about an NPR conversion with a Cummins and another with a gasoline engine. But these are different animals. As far as I’m concerned, I don’t want to follow in anyone’s footsteps until they have proven it will Function In a practical/ hostile environment.
Rebelzilla Is cool, but there’s very little practical stuff for the average guy there trying to do a low cost build.
Look into the Land Cruiser/ 4BD Engine swap forums, There was a guy on there who makes adapters, he buys manual transmissions just for the bell housing, They would probably have the shifter and cables as they’re not usable for them.
D60 will work, but which one?
If you want to avoid unit bearings, you have to go older. How much weight do you want to carry? Mitsubishi uses a centered front differential, with a stepped frame. I’m not sure what NPS uses. Do you need a passenger or driver side drop front diff? NPR uses a dropped front axle, so you’ll need to raise the spring height quite high to clear the oil pan. Snow-fighter King pin D60 had the highest rated weight capacity before unit bearings.
Don’t forget to upgrade braking capacity to match your weight.
Cross over steering seems to be the way to go to Help eliminate bump steer.
Earth cruiser and ATW expedition camper builder websites both offer good perspective on their build techniques.
NP205 if very good choice, available in both driver and passenger side drops, but has poor low ratio, if you really want to go slow you can get lower gear set. If you center the transfer case you might be able to use the same size front and rear driveshaft.
Are you going to stay DRW. It makes it all easier. Once you get into SRW you have problems with finding rear wheels/ tires rated for that axle with the correct backspacing.
Cab-overs Are Known For their poor ride, if you are driving extensively Offroad an upgrade to shocks is recommended and place close scrutiny on your choice of leaf packs.
My 2 cents
Good luck
Chris

 

[javajoe79]

Going the route you are planning, for simplicity I would do the divorced T case if you have enough room to do that. Or a different transmission swapped in with accompanying T case. NV4500 trans perhaps? I am using a D60 from an 02 Superduty as that is what came with the truck. It's a high pinion and already a 4:10 gear which was ideal for my tire size and transmission. I am thinking that you'll need a lower rear gear if you are increasing tire size or the truck will be terribly slow. I have an old NPR in back of my shop with a 4bd1 in it if you are interested.

 

[Themanicmechanic]

http://www.pirate4x4.com/tech/billavista/60_front/index.html
This is a huge Dana 60 info article. Pirate 4x4 is an amazing group for knowledge. I would recommend going with a ford donor for both axles so they match. I have an 07 f350 I'm parting and planning to save the axles from for something similar. The late model axles are huge, heavy duty, plentiful and 4 wheel disc from factory. The 205 will do you well too. Look into twin stick mods for it as well. Nice in a heavy truck to have 2 wheel drive low range.

 

[Britboaters]

If I may suggest, the idea of using Ford axles both front and rear is good for many reasons. However, please pay attention to the axle ratings and the weight / weight distribution of your finished truck.
F350 front axles I believe are rated at 6,000 lbs
F450 /550 fronts are rated at 7,000 lbs.
If you do some weight distribution calculations you'll probably find you're at 7,000 lb on the front very easily.
F450 rears are rated at 11,000 lbs
F550 rated at 13,600, all with duals of course.
These ratings are from the Ford spec sheets.
Hope this helps,
Bob

 

[SkiFreak]

From my experience, all of these 6 tonne trucks ride pretty hard on the standard suspension.

 

[DzlToy]

While I did not read all of the responses, I think I may be able to clear a few things up for you:

Your 4x4 conversion answer lies on a board called 4BT Swaps, a HUGE community surrounding the Isuzu 4BDx engines and other similar 4 cylinder diesels such as the Mitsubish Fuso 4D34 and the later Isuzu 4HE and 4HK series engines. There are adapters available to mate these engines (4BDx) to almost anything. (Isuzu Diesel Swapper) They are similar to the venerable Cummins 4BT, hence the popularity on that board.

Take your truck to a CAT scale and weigh it. You should see something on the order of 5500 pounds for a curb weight on a chassis cab. About 3500 - 4000 of that will be on the front axle. Depending on your intended load carrying capacity, a Dana 60 may not be enough and you may need a Super 60. BillaVista's Dana 60 Bible has ample info for you to figure out if a D60 will work. If you have the cash for a custom axle, you could call Torq Motorsports or Dynatrac and have a steering axle built to your specs.

An AAM 11.5, Dana 80 or Corporate 14 bolt will be plenty for the rear of that truck. Front and rear ratios need to match and you should research the best cruising RPM or sweet spot for the motor to run, aiming to stay in that range on the hwy. Most small diesels like to run around 1800 rpm, which is the lowest BSFC at the highest torque, i.e. the most efficient rpm. HP goes up with more RPM, but torque will drop significantly. If you dont care about fuel economy or need to drive fast, just ignore everything I said.

Suspension travel is AWFUL probably only a few inches before slamming into the bump stops on the front and not much better on the rear. If you are doing a 4WD conversion, you will either need a link suspension and coil-overs/airbags or you will need custom leaf springs, about a grand per pair from Deaver, Alcan, Atlas, Betts, etc., Leaf springs are much cheaper and simpler than links.

You will need long travel dampers, due to the lift, which will probably be at least 5-6 inches to clear the front diff. Rancho makes a 9000 series that is adjustable for compression and rebound IIRC. This will allow you to tune the ride a bit based on use or load. They are worth the money IMO.

The NV273 is a great case and will eliminate the need to run shift cables into the cab as it is ESOF. A GM NV263 is similar in design. Atlas and HERO cases will mate to just about anything if you have the cash, but they are not practical for a work truck. JB FAB makes really nice cables for NP205 cases if you want to go that route. JB CONVERSIONS makes 3:1 gear sets for the 205 if the 1.96 is not deep enough for you.

High Angle Driveline, Denny's and Tom Woods can all make custom driveshafts to fit your needs if you don't have a local shop that can do it.

The Superduty axles are an option, but the front diff is quite large and can cause interference issues depending on the amount of lift, desired tire size, cross member placement, etc. A friend of mine tried to go that route on an NPR and ended up using a GM 60 instead of the Ford 60. A Chevy 60 and 14B would be a decent combo and they are readily available and well supported in the aftermarket. You can choose your ring gear, locker, axle width, bolt pattern, spring perch width, etc. when using a popular axle like a Dana 60 because it was used in so many applications. That is not to say it is the right axle for this application, only that you should look into it.

I have not seen a 4BDx body converted to 4x4 except for a picture on Pirate from more than a decade ago, maybe even 15 years ago now. I will repost if I can find it.

Good luck and keep us posted, interested to see what you come up with.

So here is the link that I mentioned. It was on 4BT, not PBB:

http://www.4btswaps.com/forum/showthread.php?11480-NPR-on-37s-And-now-d60s

 

[DzlToy]

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