Some OKA questions from a newbee

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31 Oct 2012 20:39 #1 by dandjcr
dandjcr created the topic: Some OKA questions from a newbee
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Pete Fox
Member
Posts: 140
Hi All
First post here. I am looking at purchasing a MultiCab Oka and while I have a background in things mechanical, the specifics of Okas seem to be a bit of a dark art. so I have a few questions
This Oka is a 1995 Multi, 390k on the clock and appears to be in very good condition. It has a full service history from Alltrac 4wd. It was purchased from them new and all service work has been done there. Engine has not been rebuilt.
A few questions:
The transfer case has been changed for a Nissan one. The Nissan ratios have been changed to lower ratios with gears form Marks Adapters. Anyone have any thoughts on the reliability of this conversion?
I have read a bit about heavy duty 35 spline axles. Is there a problem with the std. axles? Is the conversion done to both front and rear? Approx. cost ?
The springs and shackles seem to be a bit of an issue. Exactly what are these issues and what should I be looking at on the Multi I am looking at?
The main reason for purchase is the extra space available with the multicab, and still have a tray. I don't intend to load this thing up (GVM) but it will be towing a Kimberley Karavan (about 2.2 tonne) so the GCM will be up. What are member's thoughts on the on road performance when towing.
Anything else I should look closely at? Inspection is next week.
Thanks in advance for any input

Peter Fox

October 11, 2011 at 8:31 AM Flag Quote & Reply

joseph baz
Member
Posts: 331
Hi Peter, a full service history is a good start, Nissan transfer cases with lower gears seem to last very well, Mark's 4wd makes the gears to the same or a bit better than OEM and the lower gears give you a much better engine braking, 35 spline axles are the way to go with the OKA weight, as far as cost it's all relevant to what you want.... just 35sp Dana replacement, 4340 chrome moly (my choice) full floater from Anthony Natolli, shackle pins... David Hallandal has a good kit, there is also a 1" pin conversion the same as the NT model.... as far as towing I can't help you there, David Hallandal has a beautiful trailer that he tows behind, maybe send him a PM, hope this been of some help.
Cheers, Joe
October 12, 2011 at 7:44 PM Flag Quote & Reply

Dean & Kaye Howells
Member
Posts: 79
G'day Peter,
As the proud owner of an LT multi-cab I'll try to address some of your concerns.
Your mechanical background will hold you in good stead as the OKA is a very simple machine and most work you will be able to do yourself if you're so inclined. At first glance they may seem a bit quirky but underneath they are really basic and easy to work on.
The engine is an old technology 4 Litre turbo diesel from Perkins. About as low tech and reliable as it gets. The only departure from 'normal' here is the non waste gated turbo which is really more suited to a constant speed application such as a marine engine or a pump than a vehicle, but that's the one Oka chose. Another difference is the water pump which is engine rather than belt driven, a good design feature. Also a bit 'different' is the 'hydraulic over hydraulic' (my terminology here) braking system which uses the engine driven hydraulic pump for the power steering and the brakes instead of a more conventional vacuum or air over hydraulic system. Again, in my view, a good design feature. By different I mean different to your average 4WD, though the Nissan Patrol does have an engine driven hydraulic pump. Great engine, rock solid and reliable. Not exactly power packed but heaps of torque. Good for half a million K's or more if looked after.
The original clutch had a ceramic clutch plate, very heavy duty but a bugger to use especially if it's been driven by someone who was used to 'slipping' it a bit. With a bit of luck the one you're looking at will have been changed to an organic (conventional) type.
The gearbox is a fairly standard 5 speed full synchro (5th. overdrive) gearbox from Spicer, strong and reliable, nothing fancy.
Don't know much about Nissan transfer cases but they're supposed to be pretty tough. My only concern here would be that when fully loaded and towing your Kamper it's carrying around twice its design load which would tend to worry me a bit. But as I said I don't really know much about them.
The gear linkage is mechanical and can get a bit sloppy as the gearbox end rose joints wear but easily fixed. The original transfer case had cable linkages, don't know what this one has.
I replaced my 32 spline rear axles with 35 spline and at the same time replaced the rear diff centre for a Dana/Spicer LSD, had to change the side gears and bearings anyway so went the whole hog.
For reasons only known to Oka my front axle inner axles were 35 spline whilst the outers were 32 spline. I changed the outers to 35 spline which meant upgrading the FWH's as well. At the same time I upgraded the front diff centre to a Dana/Spicer LSD as well. For costing and very good advice the best person to speak to is Paul Nott (East Coast Oka) on 0418 125 428.
The reason I upgraded the driveline was for toughness and to make it even more unbreakable than normal as we do some fairly remote outback driving and strength/reliability is vital. Probably a bit of an overkill but certainly made it very capable off road.
Leaf springs tend to flatten out and need re-tensioning from time to time and it can be a bit of a fiddle to get the truck sitting level as the RHS of the Oka is heavier than the LHS. My original spring bushes were this horrible grey fibrous 'erkot' material. Replaced them with brass/stainless bushes and new shackle pins when I had the springs retensioned. Had a new front RHS main leaf made out of 8mm steel to replace the original 6mm leaf. This extra rigidity compensated nearly perfectly for the extra weight on the front RHS. For the rear I had the RHS main leaf free camber increased 10mm to compensate for the extra weight. Had the work done at Moorabbin Spring works in Melbourne, they did a good joband it cost around $1000.
The shackle pins are 16mm in dia. and have been known to fail under harsh conditions. I'd consider changing the pins and their hardened side washers and nylocks as a matter of course and keep the old ones as spares. There are mod kits out there to increase the pin size but at $1000 a kit I dont know if it's worthwhile. I'll probably upgrade my 'drive' shackle pins to 20mm as these are the ones (four off) that are (comparatively) more likely to fail as they do the most work.
Oka road performance when towing.................................................Hmmm. To use the term Oka and performance in the same sentence is probably an oxy-moron. Easy towing as the Perkins is a very forgiving high torque engine but performance, no.
Hope this helps.

Deano

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October 16, 2011 at 10:33 PM Flag Quote & Reply

Pete Fox
Member
Posts: 140
Thanks Joe and Deano for your replies.
I inspected OKA 266 today, was fairly satisfied and signed up subject to a couple of issues being addressed.
Interesting that the vehicle has been recomplianced in SA. The CVM and GCM have been upgraded to 6600kg and 8400kg respectively. Tyre size is also specified as 305 70R19.5.
The "Mod Codes" are given as S2, S3 and F1.
Anyone know what this means?
I'll post some photos soon.
Pete

--
Peter Fox

OKA 266 Multi-cab.

Photobucket album



October 18, 2011 at 11:45 PM Flag Quote & Reply

Peter_n_Margaret
Member
Posts: 198
Who did the Mod plate on the GVM/GCM Peter?
--
Cheers Peter, OKA196 Motorhome. www.oka4wd.com/xt196.htm



October 19, 2011 at 9:59 AM Flag Quote & Reply

Pete Fox
Member
Posts: 140
Peter
mod plate has the following stamped on it:
Australian Technology Pty Ltd. W.D.R. Potts CPEng.
From google:
Australian Technology Pty Ltd
Consulting Engineers
Telephone: (08) 8271 4573
1 Bendall Avenue
Wayville
South Australia 5034
I'll post a photo of it when I work out how.
Pete
--
Peter Fox

OKA 266 Multi-cab.

Photobucket album



October 19, 2011 at 3:40 PM Flag Quote & Reply

Dandj
Member
Posts: 367
"I'll post a photo of it when I work out how."
Peter, go to Member's Okas/Photo Gallery and click on Add Photos. Add a New Album name and click on Upload Photos... to select it/them from your computer.
It/they will then appear in the album you created for members only to see.
If you want to add photos to a post it's a bit more complex, see Hal's original note on the subject.
It's easiest to upload pics as above and refer to them in a post.
--
David and Janet Ribbans, Oka 148

October 19, 2011 at 4:07 PM Flag Quote & Reply

Peter & Sandra James Oka 374
Member
Posts: 412
As Oka re rated the Dana 60 & 70 diff housings for a higher than the manufacturers standard carrying capacity without upgrading anything, so at standard GVM they are already beyond their "limit" I wonder what was done to increase the carrying capacity to the above limits.
Short of replacing the housings with Dana 80s it would seem that the axle housings would now be way past sensible loadings.
--
Oka 374 LT Van

October 20, 2011 at 8:23 AM Flag Quote & Reply

Pete Fox
Member
Posts: 140
Well Oka 266 has done 400k taking passengers and lots of gear from Adelaide and up the Birdsville Track etc and I can't see any sagging springs, broken bolts or cracks anywhere, so I don't think the diffs are an issue.
I actually thought that Oka de-rated the diffs.
Does anybody actually know the numbers?

Pete
--
Peter Fox

OKA 266 Multi-cab.

Photobucket album



October 20, 2011 at 9:58 AM Flag Quote & Reply

Peter & Sandra James Oka 374
Member
Posts: 412
The numbers were all on a post a few weeks ago, Oka diff housings are the one of the lightest versions available and have been uprated to the heavier versions carrying capacity from what I could find out. In normal use It probably isn't a problem as the vehicle would rarely be loaded to whatever the GVM is although tour buses might ;-))
374 has a GVM of 6 tonne and GCM of 7 Tonne, fully loaded in the present motorhome config it weighs 5.46t with pretty well even distribution front to rear. that was including both of us in the front seats, full fuel and water tanks, full clothes and food load.
--
Oka 374 LT Van

October 20, 2011 at 12:33 PM Flag Quote & Reply

Hal Harvey
Site Owner
Posts: 510
As best I could figure it out in that earlier thread, the factory downgraded the Dana 60/70 by 10% to suit the suspension chosen... from before:

>> GAWR is a combination of axle rating, springs, wheels and tyres...
When Ford used the 60 in the front of F-450s and F-550s, they rated them up to 6000lb (2700kg); so it would appear that the springs are the limiting factor.

Wikipedia says of the 70 rear: “All Dana 70 rear axles are full floating and typically have a gross axle rating of 7500lbs” (= 3400kg, which OKA downgraded to 3100kg on the 5500GVM vehicles).

It looks to me like a 5500kg GVM OKA is a 6000lb front and a 7500lb rear, downgraded 10% = 5520kg... 2450kg on the front and 3070kg on the rear (OKA say 2400/3100). <<

So by upgrading springs (and wheels/tyres if required) you could sling 6100kg on the Dana 60/70 combo for sure - but Mr Potts has evidently given the nod to 6600kg, which is a surprise.
--
Hal

October 20, 2011 at 2:04 PM Flag Quote & Reply

Peter_n_Margaret
Member
Posts: 198
Australian Technology Pty Ltd. W.D.R. Potts CPEng.
That's Doug Potts.
Well known in motor sport circles too, thanks Peter
--
Cheers Peter, OKA196 Motorhome. www.oka4wd.com/xt196.htm



October 20, 2011 at 6:16 PM Flag Quote & Reply

Pete Fox
Member
Posts: 140
OK this is the Re-rated compliance plate:



I have done a bit of digging around and the Mod Codes refer to the National Code of Practice for Heavy Vehicle modifications. Section S refers to Vehicle Ratings and Section F deals with suspension as follows:
S2 - alterations to GVM
S3- alterations to GCM
F1- fitment of alternative suspension
Documents are available here S2 &S3 and here F1
So what this means is that Oka 266 has non-standard suspension, so I'll have to figure out exactly what that means.
As 266 was a public passenger vehicle, I doubt very much that the axles have been rated beyond their design capacity, not worth the risk for someone to do that. I'll also have a scratch around and see if I can glean some numbers from the diffs.
Cheers
Pete
--
Peter Fox

OKA 266 Multi-cab.

Photobucket album



October 20, 2011 at 11:34 PM Flag Quote & Reply

Hal Harvey
Site Owner
Posts: 510
Just whack us up a photo of the rear axle & suspension Peter, preferably without the spare in the way, and we'll compare & contrast!
--
Hal

October 21, 2011 at 9:35 AM Flag Quote & Reply

Pete Fox
Member
Posts: 140
Hi guys Sorry about the time taken to post a reply on this one, however I now have an explanation of what was done to 266 to get the upgraded GVM and GCM.
What was done is absolutely nothing.
Apparently the engineer in consultation with the SA transport dept assessed that the Oka was good for the the increased ratings without modification as long as the tyres used were 305 70 R19.5. The new compliance plate was issued on that basis.
Funny that they have been registering it there with 285 tyres ever since with no questions asked. Anyway at least now I know that apart from the Nissan transfer case the Oka is standard.
--
Peter Fox

OKA 266 Multi-cab.

Photobucket album



November 8, 2011 at 12:05 AM Flag Quote & Reply

Dandj
Member
Posts: 367
This creates an interesting precedence in the case of any legal challenge.
A 20% increase in GVM is a huge amount based on no modifications or upgrade.
The tyre size on the compliance plate could be read as the maximum size allowed since a 285 tyre with a load index of 144 (Michelin XDE2) has a maximum axle load rating of 5600 kg, more than enough for 6600kg GVM vehicle. (A 305 tyre axle rating is 6150 kg).

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David and Janet Ribbans, Oka 148

November 8, 2011 at 7:46 AM

David and Janet Ribbans - Oka 148
Oka148 profile here.
Visit our technical and travel blogs: here.

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