Rockwell transfer case

Submitted: Sunday, Aug 28, 2011 at 14:42
ThreadID: 88735 Views:5173 Replies:4 FollowUps:9
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I recently got back from a trip through the Aurora ranges. 50km from home my front drive shaft fell off the front diff (seems it wasn't tightened up properly). I tied the shaft up off the road with a bit of wire and continued on my way. BUT with the front shaft immobilised, the transfer case eventually siezed and is now permanently in 4WD. There is a shaft running through a gear to drive the front shaft, normally these run at the same or similar speeds but without the front shaft turning the gear is stationary and the shaft at full speed. I have the transfer case out but can't seperate the shaft and the gear. So, now I need a replacement Rockwell T223. Anybody know where to find one, seems the Oka owners have bought and stockpiled them all.
Alternatively I could change to an NP205. I've read lots about the NP205 but haven't actuall laid hands on one to see if it will work in my situation. Front diff is to the right (drivers side). My transfer case is divorced from the gearbox. Handbrake is not on the transfer case, no PTO. Anybody swapped a Rockwell T223 for an NP205?

So, a warning..... don't immobilise the front drive shaft on a T223. Had I disconnected the front shaft at the transfer case, this wouldn't have happened.

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Reply By: Ozhumvee - Sunday, Aug 28, 2011 at 18:00

Sunday, Aug 28, 2011 at 18:00
In an Oka the front shaft doesn't turn when in 2wd with the front hubs unlocked so it shouldn't worry the transfer case.
The Rockwell is a bit of a bugbear with the later LT Oka owners, way oversize for the job, sucks gobs of power, generates vast amounts of heat and constantly leaks from every orifice. Plenty have ripped them out as I intend to later this year. Mine will be available then ;-)))
The earlier XT Oka's run a married NP205 straight on the back of the gearbox, quite of the LT 's have been retrofitted with divorced NP205's in place of the Rockwell.
You would be after a Chev/Dodge version of the NP205 as they right hand drop for the front output. Ford NP205's are left hand drop.
What vehicle are you driving?
AnswerID: 463726

Reply By: CH86 - Sunday, Aug 28, 2011 at 20:56

Sunday, Aug 28, 2011 at 20:56
Ahhh, that's information I need Peter, thanks. I'll start the hunt for an NP205.
Yes, I agree, the T223 seems to be overkill. It's a struggle just to roll the thing over on the floor....must be 50kg. It makes noises and seems to weep oil all over. I was surprised at how quiet and feely the bus drove with the front shaft removed. I don't have free wheeling hubs so the shaft turns all the time. That's another job.

I drive an Asia Combi bus (Korean copy of a Mazda T4100) converted to 4WD. Isuzu 4.7 turbo diesel, Isuzu 6 speed manual, Dana 70 diffs and until recently a T223 transfer case.

I wonder if the front shaft doesn't turn (even tho not driven from either end) on the Oka just through friction in the hubs and transfer case.

AnswerID: 463745

Follow Up By: CH86 - Sunday, Aug 28, 2011 at 20:57

Sunday, Aug 28, 2011 at 20:57
What high/low ratios does the NP205 have?
FollowupID: 737607

Follow Up By: Ozhumvee - Sunday, Aug 28, 2011 at 21:15

Sunday, Aug 28, 2011 at 21:15
Off the top of my head 1.96:1 springs to mind.
So you want a divorced Chev/Dodge NP205 with which size drive flanges? I just sold a fully reco'd one I imported from the US, was going into the Oka but have changed my mind and am going to fit an auto with married transfer case.
I've still got a married NP205 in the shed, has a "racetrack" bolt pattern to mount on the back of a Chev manual box, there are adapters to adapt to other trans though.
FollowupID: 737609

Follow Up By: CH86 - Monday, Aug 29, 2011 at 08:53

Monday, Aug 29, 2011 at 08:53
My T223 has a flat flange for the input and half the universal joint (bolt on joint with U bolt) for both outputs. From pictures I've seen it is the same setup as the Oka. Don't know what splines I'm dealing with until/if I get my NP205.
All this has me now thinking about trying for a transfer case to bolt directly to the rear of the transmission. I know Isuzu do a 4WD version of the truck I got my engine and gearbox from. Going to be simpler and lighter. I don't suppose there is an adapter from Isuzu to NP205!
The NP205 low ratio is a bit faster than the T223 but still plenty slow enough.

FollowupID: 737632

Follow Up By: Ozhumvee - Monday, Aug 29, 2011 at 09:26

Monday, Aug 29, 2011 at 09:26
Those "half U joint" flanges come in different sizes, the Oka uses 14XX and most of the NP205's have 1310's or flat flanges.
The input and output spline sizes are another minefield, they come is various sizes from 10 (earlier/weaker) up to 30 and 32.
I would think that the Isuzu route might be the way to go except for problems with driveline angles. would the Isuzu transfer be in the same position as the Rockwell or a lot further forward meaning the front tailshaft would be much shorter and/or steeper with greater uni angles?
FollowupID: 737633

Follow Up By: CH86 - Monday, Aug 29, 2011 at 10:51

Monday, Aug 29, 2011 at 10:51
Good point about those angles. The jack shaft between gearbox and transfer case is about 500mm long and the front output shaft is a very gentle slope down to the front diff. Hmmmm, not even sure if there is room to get a shaft from a gearbox mounted transfer case down to the front diff. Will have to get back under there when I get home. In the mean time I will do some research on the availability and dimensions of Isuzu options.

FollowupID: 737639

Follow Up By: CH86 - Monday, Aug 29, 2011 at 13:49

Monday, Aug 29, 2011 at 13:49
Isuzu tell me that there is no transfer case option for my gearbox :-(
Back to the NP205 search.
FollowupID: 737659

Reply By: CH86 - Wednesday, Aug 31, 2011 at 14:33

Wednesday, Aug 31, 2011 at 14:33
Does anyone know if the NP205 will operate if it is mounted upside down? Lubrication, breathers etc....

An NP205 with right hand front shaft is hard to find and expensive but the left hand front shaft version was used on the older F series and are more common.
AnswerID: 463941

Follow Up By: Member - Christopher P (NSW) - Wednesday, Aug 31, 2011 at 15:20

Wednesday, Aug 31, 2011 at 15:20
can you do a flip on the diff assembley????? and get your spring perches changed over to other side???\

would it ppay to rebuild your current buggered transfer???
FollowupID: 737837

Follow Up By: CH86 - Thursday, Sep 01, 2011 at 08:59

Thursday, Sep 01, 2011 at 08:59
I was kinda thinking of flipping the transfer case rather than the diff. I seem to recall reading on an Oka forum someplace that some are upside down with the selectors at the bottom.
FollowupID: 737876

Reply By: CH86 - Monday, Sep 12, 2011 at 18:48

Monday, Sep 12, 2011 at 18:48
Have been unable to source an NP205 transfer case to suit for under $5000! Crickey, that's how much my entire engine and gearbox cost and it came with a free freezer truck attached.
Now waiting on a quote to get my T223 repaired.
AnswerID: 464822

Follow Up By: CH86 - Saturday, Oct 08, 2011 at 10:14

Saturday, Oct 08, 2011 at 10:14
Finally got my transfer case repaired and it's now back in the vehicle. I've never really noticed how hot this thing gets before but now I'm getting paranoid about it. After a 15 minute drive at speed I can barely touch it, probably 50 degrees. Hope this is normal and I'm not about to have another failure. Was planning a trip to Wiluna in a few weeks and now I'm losing confidence in my vehicle. There are no bad noises and everything shifts smoothly.

How hot does your transfer case get?
FollowupID: 741169

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