78' SWB upgrade ideas/help

[Johnny Roadkill]

I have daydreamed about the GQ chassis with a G60 body but I think in Oz it would be registered as a GQ and it would be a struggle to meet ADRs...
If you download the G61 manual on this forum it has all the info on MQs including which motors and bodies have which ratios, choosing a ratio comes down to engine rev range, tires and intended use.
The locker options are aftermarket - autolocker or ARB airlocker. H233B rear diff is all good for a locker but not sure about H260 rear since spline counts changed between G60, MQ GQ and GU. Some MQ rears have LSD but may need a rebuild after 35 years.
I agree totally, an adapter plate sounds easy but only if you've got access to the tools or cubic dollars to pay a shop, lol.
If you find a Mark's box get ALL the bits that go with it including shift rods, etc. Then it mates to the original shift lever no worries, at least it does behind a P motor...fairly simple fabrication if you need to alter the lengths for a different motor, but you're probably going to have to use the original bell housing anyway. The transfer and gearbox hang off the back of the P motor bell housing with no mounts to the chassis. Tailshafts are different for the Mark's box, I'm pretty sure you need to swap front and rear over to account for the extra length of the box in a MWB, a SWB may be different since the rear shaft will be 300mm shorter.
The original manual for installing a Mark's box is on the web, maybe even on this forum ?

Hope that helps,
D

[Bluey]

Yer way too much red tape ):
Ok i'll see if i can find that and check it out, might come in handy..
Yes the LSD would probably need a re-build after 35 years of service lol.
Are the Mark's boxes very strong? or would i need something built a bit tougher if i used the Isuzu engine? (around 350 Nm) lol
Can't find anything anywhere about any Nissan gear boxes mating up to the Isuzu engine anyway. lol need to do alot more research yet.

[Johnny Roadkill]

The Mark's box is based on a light truck box internals and while they are getting long in the tooth they are pretty tough and can be rebuilt.
The only failure I've heard of on the net was behind a worked 350 Chev being driven hard over big obstacles.
I had a look at a G60 for sale last year with a mild 350 fitted with a Nissan light truck box and 35" tires, and the owner said he went to that box after blowing more than 1 standard 3 speed - the 3 speeds are pretty bulletproof themselves so he must have been giving them a hard time and the truck box survived what he was dishing out.
Cheers,
D

[Bluey]

Fair enough mate (: Do the 5 speed boxes have a model number or anything? i can't find anything anywhere, they are just know as MK 5 speed? :s surely they have some sort of number to know what box it is? lol
Also can't find any information anywhere about adapting the Isuzu engine up to any kind of nissan box, I really don't wanna spend all that coin to find out i can't use it or spend even more trying to build adaptors haha. I"m thinking i might look into a cummings 4BT motor, only downfall is they are extremely heavy apparently :s but they rekon there's adaptors for plenty of trannys for those, pretty common in their day but i'm not sure about now... more research to do.

[Johnny Roadkill]

I'm not aware of a part number for the Mark's box, they just have the company name embossed on the left side...someone posted a list of rebuild parts on here a while ago and the Nissan box number the parts come from. They aren't the same box as the MK 5 speed, but they may share some internals.
The 4BT is a solid motor, and heavy, but the standard P motor is nearly 300kg anyway. When John Rooth ( ex 4wd action presenter ) tried putting a 4BT in his 40 series Tojo "Red Truck" he aborted the swap, partly because of the height of the motor - needed a body lift to clear the bonnet - and he and his cronies have plenty of knowhow and workshop facilities at their disposal. He settled on a 350 Chev which was easy and cheap by comparison - just costs more to run, haha ! V8s in G60s usually seem to involve a bit of firewall modification for clearance though.
I've heard about Nissan/UD 6cyl FD6 motors in Land Rovers, bulk torque but no revs like the Cummins. Another member on this forum told me his dad had a Perkins 6cyl diesel in a G60. The 4cyl FD46T and matching super wide range 6 speed would be crazy good but they don't come cheap. So there are plenty of options but like you say you want to know what's involved before laying down the folding stuff, lol.

Cheers,
D

[Johnny Roadkill]

I think I should also say that after looking at all these dream options for my project, reality dictates that with the time and money available my plan is to stick with rebuilding the P motor, using the Mark's box I have and MQ diffs and brakes. I'd love to go diesel but an SD33T will probably need a rebuild anyway and I'd rather have a car to drive than an unfinished project for years to come. I figure if my mate's techo petrol Prado can cross rivers the super simple electrics in a G60 shouldn't be too hard to protect.
Cheers,
D

[Bluey]

Oh yes i know ol' mate Roothy haha been following his new truck "Milo 2" build. I have seen/heard a bit of his old red truck, but i didn't know he originally wanted a 4BT lol. Yer been looking into it and they are very big motors height wise and even across too i believe, which brings me back to the Isuzu. Smaller and lighter then the Cummings hmmm..
So the does the original 3 speed have the same bolt pattern as the Marks/MK box?
I was looking at a SD33 too but they are like rocking horse poo. if you do find one it's in pretty bad shape or the owner wants way too much coin for it. My theory is that the 4 cylinder diesels will be cheaper on rego, and if travelling outback it's usually easier to come by diesel then petrol. plus diesels tend to be more reliable and very little electronics to get wet/have issues with. As long as you seal up the distributor best you can. my mate at work used to have a Landy with a Holden conversion and he built a splash shield for the dizzy after he conked out on his first creek crossing haha.
My next thought was to look into UD truck engines and see if any of those are worth looking at. because really i'd like to keep it as Nissan as possible. So many options, and it's hard to work what would match what easier with less work without seeing it done already...

[Johnny Roadkill]

Yeah, as far as I know he still has the 4BT and hasn't given up on idea...
The Mark's box bolts straight up to the P motor bell housing in place of the 3 speed but the MK Patrol box won't - it bolts up to a P40, SD33 or L28.
Cheers,
D

[Bluey]

hahah bit of a blonde moment there sorry, yer forgot the P motor is different to the P40 lol my bad.

[Bluey]

So been doing allot of thinking and researching and whatever else, and for the moment i think my best bet is to keep the P motor as there is hardly anything wrong with it, why throw away a good motor? and just go for a Marks 5 speed, If i'm able to find one in good enough condition that is. Plus I also own an XE falcon that I'm considering doing a Barra engine swap with, so i would have a fairly new 250 cross-flow to bolt up to the Marks later on should anything happen, that's if i can find an adaptor for that also.

Anyway I remember reading somewhere that there are two different sets of ratios? is this true? and can you tell just by looking at the box which one is which without having to turn the shafts and counting?
Secondly, what is involved in the conversion? is it only tail shafts and linkages for leavers?
Where there any common issues with them that I should look out for?

I would appreciate any input you may have, and any other information that I is relevent.

Thanks
Bluey