4WD Toyota Coaster Build up

Thursday, Feb 11, 2010 at 16:31

Life Member TourBoy, Bundaberg

Why build one when Toyota make one you ask?

Well the factory Awd Coasters are mainly used in the icy areas of Japan and production is limited to around 20 per year. Apart from them being a grey import, they may have rust issues from salting of the roads.
The 2 biggest problems that I can see are that they don't have much ground clearance and a lower than normal side door entry. The main problem in my view is the independent suspension and portal hubs from the mega cruiser. The mega cruiser was never imported to Australia either so I would hate to break anything and expect to get parts that month.

The transfer case is that of a dyna and can be full time or part time 4wd and has low range but isn't connected so you can't engage low unless you have linkages made up.

I was going to make one for myself after I failed to find a suitable 2nd hand one to purchase. During many enquiries to many fellow EO members I realised that finding an ex tour coach that is regularly serviced and put over the heavy vehicle pit every 6 mths was the go as it wouldn't have been off road (2WD) and generally would be in much better condition than any ex 4WD tour bus that had been flogged to death anyway.

I have since had many enquiries from others interested in owning one as the last one was built approx 8 years ago and now no one does it. So I will be building a few if anyone is interested.

So I hunted around and found this

I have decided to use NPS300 Izuzu diffs as they are still in production and are readily available as are spares. The previously built coasters usually had ford Dana 70 diffs but these are becomming scarse and expensive.
The transfer case I decided on is a bullet proof cast iron gear driven New Process 205 from a F series truck. These are cheap to rebuild and are virtually indestructable behind a big block V8, so the old 1HZ won't kill it. A lot of Oka's use this transfer case. The early Coasters used a Rockwell transfer case but they are expensive and are noisy on the road.

I am intending to keep the Toyota engine and gearbox with transmission brake and mount the transfer case "divorced" from the gearbox via a small drive shaft.
I will be using the standard Toyota Parabolic rear leaf springs and mounting the rear diff under the springs.

The front will also have leaf springs as the earlier coasters with coils suffered from some issues and most were converted back to leaves. Reliability is everything. I am trialling a set of Mitubishi Canter front springs to start with as I want it to ride well, if they are too soft I will add another leaf.

Here is a pic of the rear diff in place

The front is mocked up but not installed yet and then will be the transfer case and shafts. Hopefully I will be able to reuse as many standard toyota bits as possible and am also putting in a brand new radiator at the same time as it was tired anyway.

Ok here is an update, the front is basically in only a few adjustments to be made before all welded up. The air cleaner assembly will probably need to be relocated to the passenger side to allow for the steering arm to have more room. This will make fitting the snorkle easier too.

The exhaust will have to be re-routed past the transfer case as there was a muffler right where the transfer case will be fitted.

Another update.
Diffs are in and ride height adjusted to suit, transfer case is in, linkages and lever are being made, brakes are hooked up and fluid changed, shock mounts are going to be made this week to use coaster shocks.
Driveshafts have been measured and are going to be made modifying 2 of the originals and the front will have a new complete shaft made up. Only problem is the driveshaft mob are going on holidays for 2 weeks...d'oh.
Steering will be made this week, replacing the isuzu arm that has welded tie rods for a custom made arm utilising 2 x screw in coaster tie rods for easier maintenance and replacement years down the track.
Still thinking about air cleaner box mount and won't decide on a final solution until the steering arm is sorted out. I may even use a bull bar mounted remote donaldson type filter.

Another update,
The steering box will have to be replaced with a Hino truck unit as the coaster although being very similar to the hino unit works the opposite way. At the moment the vehicle is steerable but to turn the steering wheel to the right makes the bus go left, A bit freaky when reversing and I seriously doubt that Qld Transport will like it that way...lol I don't want to go down the route of an idler box and more linkages which will make for more serviceable items down the track so a new box it will be. This will make it one shaft from the steering box to the link on the diff...simple.
A polished alloy bullbar will be grafted to the front this week.
Still can't set up the air cleaner until the new steering box is sorted out.
Tail shaft bloke still on holidays until the 15 March.
I made a couple of mods to the transfer case linkages to make it a bit smoother as the NP205's are firm to shift at the best of time. The housing of the divorced transfer case does hang down a bit low for rock hopping and so I may put in either a Mitsubishi or Isuzu transfer with cable or vacuum operation next time instead of linkages, but it works OK anyway just a personal thing and the NP205 is generally stronger than the jap units.
Still have to get new shocks to replace the toyota items and a new set of tyres rather than the rough riding MRF's. and also snorkle when the air cleaner is sorted out.
New radiator is in and grass guard fitted to the bottom for protection.
On the rear axle, as I'm going with single wheels, the inner stud holds the wheel on as normal but we've machined the inside of the wheel nut to enable it to be placed on back to front and fit over the chamfer of the inner wheel stud so that it also locks the inner wheel in place. Just a piece of mind thing and it has the advantage that if anyone wants to put on duals in the future, all you have to do is take off the outer nut, turn it around and put it on as you normally would with dual wheels.

The new truck power steering box is being fitted, the driveshaft fella is back from holidays and hopefully will have them finished today, that only leaves the bullbar, air cleaner assembley, snorkle, a set of new shocks and some better than MRF tyres Modification plate, HV inspection and rego.

UPDATE. 26/3
Well we were all set for an end for the conversion today and to bring the coaster home.
The bullbar went on, the snorkle was manufactured and fitted, new air cleaner assembly installed, power steering filled up, new radiator topped up, recovery bottle re-installed, steering arm modified slightly to avoid rubbing on the tyre on full left lock and she was fired up for the first time in nearly 2 mths. We then flexed the suspension on a simple ramp and all is good nothing is hitting anything else and I think that this thing will have close to 1m of wheel travel.

Then I took it for a drive and the transfer case that I bought is crook so back in the workshop she went. I called my supplier and he said no worries send it back and we will send out another. So maybe the end of next week and more $. I had even organised a pit inspection for this afternoon...oh well. The bump stops for the front hadn't turned up anyway so they can be done next week too. It seems to ride really well and the brakes feel stronger than the originals.

Update 27/4/10
Brought it home on Friday. Still needs a few things tidyed up and the mod plate put on for rego but it won't be done for a couple of weeks.
Went back to duals on the rear as I was told it wouldn't pass a roadworthy on singles. My mod plate engineer said it would be ok as the tyres as a single still exceed the vehicle load rating but I'm not taking chances so back on with the duals. There is still a little bit of driveshaft noise (similar to gearbox rollover noise) just off idle but all the small busses of most makes do that. That is Ok just a bit annoying if you aren't used to it. Most of the custom 4wd's and trucks make a lot more noise than this thing does anyway and all of the time.

I am waiting for the transfer case operation control cables to arrive so they can be fitted as well.

Update 5/5/10
All work on the conversion is completed other than a retractable step for the side door and I took it to the Heavy vehicle inspection mob this arvo for them to do the roadworthy tomorrow sometime.
The FTS700 Isuzu transfer case operation cables work well and other than a gearbox rollover type noise when taking off from idle, there is only minimal noise from the drivetrain. It is much quieter than all of the factory 4wd trucks I have driven.
So hopefully I can get rego on it tomorrow arvo if there is time. woohoo

Update 6/5/10
Passed the heavy vehicle inspection with flying colours and now has 12 mths rego.

It will make a great coach or motorhome.

2010 Isuzu FTS800 Expedition camper
2015 Fortuner
Had 72 cruisers in my time
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