Build just starting 720 V6 3.8 manual 4x4 dual cab with king cab tub

[Ben.db89]

Hi there!

 

I'm new here. Living in Australia, owner of a tired 720 dual cab ute (can't complain after 553,000 km with a petrol engine). I bought it for $600, just had to change the carby and it has been on the road and in the paddock for two years, every single day. It eventually became too small and too weak to do the job so I bought a 6.5 tonne hino truck. So now the ute is off the the road and I can start working on this crazy project I've been thinking about for over a year.

 

I want to build a 4x4 720 dual cab with an extended chassis to take a king cab tub. And power it with a buick 3800 and a manual gearbox. On top of that, I want dual battery system, air conditioner, power steering, front winch, and a lot of little details.

 

I want it as quite and discrete as possible and as close as possible to the factory suspension height of a 4x4 (I don't like the look of the oil sump of the buick engine when it comes to that.) What I want is towing power, low rev torque, some guts to overtake with half a ton in the ute and a trailer, and being able to go thru the paddock.

 

 

 

Here is a list of what I have so far:

 

-Complete 720 dual cab 2wd with a L18 4 speed gearbox and a tow bar

 

-Complete 720 king cab 2wd with a L18 5 speed gearbox all pulled apart accept for the tub and body still on the chassis

 

-Buick 3800 n/a series 1 engine I believe (1993 Holden) with auto transmission ecu and wiring (and 4 speed auto gearbox out of a VN Commodore but that's irrelevant as I insist on manual transmission)

Plus a couple of spare heads, covers and accessories and parts from a second engine that threw a rod.

 

-Lots of patience and a fair bit of tools.

 

-A friend who builds race cars and rebuilds Z series Datsun's. He can find me virtually any part I want.

 

 

 

Soon to come (just have to pick up):

 

-T5 gearbox with bellhousing from a Holden Commodore that had an ecotec 3.8l engine. Hopefully I'll get the flywheel and clutch with it but I don't know if that fits a series 1 buick.

 

-two 4wd chassis, one with just suspensions and front diff, the other with suspensions, rear axle and transfer case (I like that transfer case as it is a divorced transfer case but I'm not sure it can handle the torque of a V6 3.8l engine)

 

-Some time and money

 

 

 

The plan at the moment is to strip both vehicles and both chassis, sort out the parts that are still in good condition, and work on the chassis and suspensions first. I only got the engine and gearbox because the first one was free and the second one only $250

 

Any advice is welcome. I'm just starting, it's going to be a long and slow project but I'll be coming back every now and then with some updates and some questions.

 

Thanks for your time

 

Ben

[datzenmike]

Is one of the 4x4 frames a long wheelbase? Two and four wheel drive frames are very different but in  a pinch you could lengthen the 4x4 frame behind the cab.

[Noflers]

Awesome! I was obsessed with those GM 3800 engines at one point too, haha. 

Welcome,

I'll be following.

[Crytek89]

It certainly sounds like a rather ambitious project - can't wait to see some progress photos!

 

Any chance of having the original photos of the truck uploaded prior to digging into it?

[Lockleaf]

T100 tcase should handle the 3800 torque pretty well for a good while at least. It's an extremely overbuilt box for the truck.

 

I'm building the same truck you are, but we never got the dual cab here in the US, so I'm building my cab as step number one. I need a third cab right now in order to make more progress. I'm excited to see how you go about it vs the directions I decide to take.

 

Have you seen the white dual cab long bed? It's the only one I've seen.

 

[wayno]

This is not a long box/tub in the photos below, nor do I believe it is a regular cab box/tub, I believe it is a kingcab box/tub, I have a long box on my 720 diesel, and it has almost a 30 inch skirt between the cab and the rear wheel well opening, the box/tub in the photos below has barely a foot long skirt between the cab and wheel well opening so I believe it is a kingcab box/tub.

T100 tcase should handle the 3800 torque pretty well for a good while at least. It's an extremely overbuilt box for the truck.

I'm building the same truck you are, but we never got the dual cab here in the US, so I'm building my cab as step number one. I need a third cab right now in order to make more progress. I'm excited to see how you go about it vs the directions I decide to take.

Have you seen the white dual cab long bed? It's the only one I've seen.

[Lockleaf]

Wayno, I agree entirely. I'm building a dual cab with a king cab box like that pic. I believe Ben is as well.

 

I misused the term long bed. It's a "long bed" when on a dual cab, as compared to a stock dual cab bed and I've gotten in to the misleading habit of referring to it as such. It sounds odd to call it a dual cab king bed...? :)

[Ben.db89]

Hi.

 

Thanks for the attention already.

 

 

datzenmike,

 

The 4x4 chassis where king cab so, yes, long wheelbase. What I have in mind at the moment is to cut the best one as far back as I can (just in front of the front spring mount of the rear axle) and cut the chassis of the 2wd king cab as far forward as I need, that'll give me the length for the build and all I should have to do is relocate the rear cab mounts to fit the dual cab and probably the transfer case cross member.

 

After all that, I might even have enough chassis/parts to build a second one, king cab, all factory specs this time.

 

Noflers,

 

I don't even really know why I prefer that engine. I've been offered a KA24,didn't take it. And the other day I picked up a RB30 for free too, didn't even consider using that in the Datsun even though it's a nice engine, I swapped it for some parts for another project (non car related)

That GM engine just has got something the other don't.

 

Crytek89,

 

I do have some photos and I'll be taking plenty more. I'll upload a few tonight.

 

Lockleaf,

 

I always hoped that transfer case would work. After all, some people chain two of them to build some rock crawlers. Though someone told me the other day that some only have a 1:1 transfer and no reduction. I how the one I'm picking up has got reduction.

 

Sorry to know you can't get a dual cab over there. There aren't many here compared to the king cab but still enough to find parts.

 

That one you got photos of looks nice. I like those round headlights and the absence of console. Not fond of the colour though. I'll stick to the metallic/silver blue I have on mine.

The only ones I've seen with an extended chassis where lowered 2wd, does nothing for me.

 

I'm looking forward to see how you go with your project.

 

wayno,

 

I was on the same page as him, and I actually have never seen a longer tub. It is indeed a king cab tub.

A longer tub would probably be nice to put on a long wheelbase with a single cab though.

 

 

I'll go take some photos and I'll see if I can figure out how to load then.

[Lockleaf]

The t100 transfer case is 1:1 in 4wd Hi, and I'm pretty sure 2:1 on 4wd Lo. Every one I've seen here in the states is that way. Couldn't be sure about yours

[wayno]

I have done something like you are going to do, I put a longbox(pre 1983) and kingcab together just for the fun of it, I also made it a dually and it is also a turbodiesel, the turbo part was done recently(last 3 years), it's always had a SD series diesel engine.

I added 16 inches to the frame/chassis by putting two different frames/chassis together cut the proper length, like what you appear to be planning to do.

 

 

 

[Ben.db89]

The t100 transfer case is 1:1 in 4wd Hi, and I'm pretty sure 2:1 on 4wd Lo. Every one I've seen here in the states is that way. Couldn't be sure about yours

That's what I thought too 1:1 hi range, 2:1 low range.

I'll know for sure in a couple of weeks when I pick the chassis up.

 

Wayno,

 

That's what I'm planning on doing indeed. Have you got any photos of the chassis build? Did you weld or bolt the two half chassis together?

[Ben.db89]

Pulling the V6 buick 3800 out of the old VR commodore

 

 

 

 

 

 

The guy I got it from threw a rod out of the previous engine, pulled it out with an excavator, managed to break the bellhousing, bend the flex paste, bought another engine and gearbox, couldn't bolt the gearbox properly on the "new" engine, bent the second flex plate and broke the housing out the "new" gearbox while putting them in the car.

At least he never finished putting it together so I'm pretty confident it's a good engine as he bought it from a mechanic.

[wayno]

It was done before I joined Ratsun, didn't take a lot of photos back then, the two frames were cut in such a way that when put together the chassis would be the correct length, then they were welded together, then more plates were added in the area where they were joined together as insurance, I never planned to use the truck to haul weight, so I didn't worry about that area of the chassis being over stressed, the truck was for fun/looks, although I do tow with it, it's very good for towing with the dually wheels.

The e-brake system is going to have to be re-engineered, it doesn't work when the chassis is extended, the angles don't work and the cables have to be extended, when they extended the chassis over here for mobile homes they extended the cables and then added a 1/4 inch by foot long piece of round metal on each side, they then looped the end of it in the proper place after it was welded onto the inside of the frame, this kept the cable at the proper angle coming out of the cross member, if you seen the extension they did on them frames you would understand why they did the e-brake the way they did it, it was a joke, I believe the only reason that they didn't fold up going down the road was because the actual mobile home structure was bolted to the frame holding it all together.

I re-engineered my e-brake system by making one like the 521 which is a center pull type, but it took me a couple tries to get one that actually worked.

[wayno]

You have to host your photos somewhere, another site like photobucket, you then need to copy the IMG code and paste it in your reply, you cannot publish them directly from you computer albums on this forum. 

[Ben.db89]

There is the old girl

 

[Charlie69]

Welcome!  We love pictures!  LOL

[wayno]

Looks like the taillights are in the rear bumper, I wonder if the stock taillight mount assemblies are behind that bumper.

There is another guy on here that just cut another dual cab apart to put a 521 cab on the frame.

Here is the thread about that one, he is in Mudgee where ever that is.

http://community.ratsun.net/topic/71111-auzzie-521-build-thread/

[Ben.db89]

Looks like the taillights are in the rear bumper, I wonder if the stock taillight mount assemblies are behind that bumper.

There is another guy on here that just cut another dual cab apart to put a 521 cab on the frame.

Here is the thread about that one, he is in Mudgee where ever that is.

http://community.ratsun.net/topic/71111-auzzie-521-build-thread/

That's the stock tail lights for the dual cab apparently, in the step/bumper. And those lights are impossible to find replacement for, except for some cheap Chinese aftermarket products.

The king cab has got the tail lights in the corners of the tub. I haven't decided what to do about that for my build. Might end up with two sets of tail lights on the ute as I'm planning on using that bumper.

 

Thanks for the link of the other thread. (Nearly had a heart attack when I saw the chopped up cab :'( )

Mudgee isn't far from me.

 

And about the park brake, I'll have to see, I really want to keep the dash mounted one, even if it mean I have to modify it a lot.

 

 

And, Happy new year.

[wayno]

That's the stock tail lights for the dual cab apparently, in the step/bumper. And those lights are impossible to find replacement for, except for some cheap Chinese aftermarket products.

The king cab has got the tail lights in the corners of the tub. I haven't decided what to do about that for my build. Might end up with two sets of tail lights on the ute as I'm planning on using that bumper.

 

Thanks for the link of the other thread. (Nearly had a heart attack when I saw the chopped up cab :'( )

Mudgee isn't far from me.

 

And about the park brake, I'll have to see, I really want to keep the dash mounted one, even if it mean I have to modify it a lot.

 

 

And, Happy new year.

 

I am talking about the e-brake cables that go to the rear drums, when you lengthen the frame they don't work right no more, angles and length are wrong.

Where the taillights are is dependent on the year of the truck, they are at the bottom 1980 thru 82, they are in the corners of the tub/box 1983 on, we got them taillights over here, they are all over the place.

[Draker]

Love me some 720 double cab.