Safety, Emergency and Recovery Equipment on our Oka

Apart from the usual recovery gear (jacks, towropes, hub adaptor, spade, sand mats etc) we also carry a range of safety gear and emergency equipment.


An article on our Recovery and Maintenance Equipment can be found here.


An article on our Safety and Emergency Equipment can be found here.


An article on Snake Bite Treatment notes and first aid items can be found here.

Fixing the Leaking Steering Box

As we travelled the rough roads across the Gulf Of Carpentaria from Burketown to Booroloola, we noticed a drip of red oil from the power steering box. Checking the hydraulic fluid level revealed that the level had gone down about 1 inch. There was nothing that could be done on the side of the road except to top up the reservoir and carry on, mindful of the fact that on a Oka, the power assistance for the brakes also comes from the same hydraulic power source as the steering, so a loss of hydraulic pressure could be quite serious.

By Booroloola the leak had got worse and was traced to the seal around the input shaft on the top of the steering box. After a long search, we bought a 4 litre can of fluid from a mechanic in Boorloola, the last fluid in the town it would seem.

[Note: After doing this fix, it appears that that a major steering failure from a leaking seal on the input shaft is unlikely, unless the reservoir runs dry].

Red fluid oozing from the steering box.

On the stretch from Booroloola to Katherine, the leak stabilised but it was still losing about 250 ml a day, but what was worse was that the fluid dribbled down the outside of the steering box and was then liberally sprayed by the wind over the chassis, springs and eventually down the side of the Oka where of course the dust stuck to it, creating a sticky mess. We covered the steering box with a modified wine cask bladder to stop the dispersion of fluid but something permanent needed to be done, which could only happen after got home a month later.

The Fix

The steering box fitted to later Oka's (or as an Oka mod to replace the earlier Kirby-Bishop steering box) is a TRW TAS-30 box made by TRW Torfinasa, Spain. You won't find much data on this model which was fitted to a number of European small trucks. However, it is similar in style and operation to other TRW TAS series boxes so information on the TAS-40 to TAS-85 range is quite relevant.

The TRW identification label.

There are a number of useful TRW articles on their website which document the process of replacing the input shaft seal on a TAS series steering box. Even though none of them specifically relate to the TAS-30 steering box fitted to Oka's, these are the most relevant:

TAS Series Service Manual TRW1108 (more detail than you'll ever need)

Service Procedure TAS100 (On-vehicle repair procedures)

Input Shaft Resealing Instructions TRW800 (Useful descriptions with colour photos)

Replacing the input shaft seal can be done without removal of the steering box and takes the best part of a day, once you have the bits and understand the instructions. There is no need to remove the pitman arm or any other components under the vehicle

In a nut shell, you'll need to:


1) remove the radiator grille and LHS headlight frame, and unplug/move aside any cables which will get in the way,


2) remove the steering column shaft, including the lower UJ. (You can do this without removing the steering wheel housing by slitting the rubber boots to remove them and gluing or clamping them back together later. The metal top clamp and foot can also be cut to aid removal and refitting. Refer to our blog entry here for some details on this),


3) prepare for some fluid spillage (you might loose half a litre or so, it doesn't sound much but it can spread a long way),


4) thoroughly clean the top of the steering box,


5) remove the dust/dirt seal from around the input shaft, it's just clicked into a groove on the input shaft,


6) remove the internal circlip (or flat spiral spring clip in our case) from its slot above the seal,


7) temporarily replace the lower UJ on the input shaft and loosely fit a pinch bolt,


8) disconnect the hydraulic return hose from the steering box (it's the larger fitting and marked "R", see the photo below to ensure you get the correct one) and quickly cap the return outlet to avoid fluid loss,


9) quickly plug the end of the return hose,


10) tie an old piece of towelling around the shaft to contain any expressed fluid,


11) spin the engine for a few seconds but don't allow it to start (disconnect the wire to the fuel cut off solenoid on the injector pump). This builds up pressure in the hydraulic system and pops out the seal. Refitting the UJ prevents it shooting skywards. When you hear a "pop" as the seal pops out, stop spinning the engine immediately to reduce fluid loss.


12) remove the UJ and towelling and the old seal. The old seal was not damaged but the sealing lip had completely worn down (compared with the new one) and was barely making contact with the input shaft.

[There is actually not a lot of pressure behind this seal in normal operation, the real hydraulic pressure is directed to the steering rack pistons during a turn operation, or is simply returned to the reservoir (unless the return port is blocked, as when the seal is being forced out). So I think there was little risk of a major steering failure unless the reservoir ran dry.]

13) clean up the top of the steering box and reinsert the new seal, spring side downwards, grey side upwards. (This requires a special tool, plus some care to avoid inserting the seal too far. You can easily make a suitable tool, see notes below).

14) fit the new circlip, ensuring that it is fully in its slot,

15) reconnect the return hose and tighten fully,

16) bleed the system if required (it has an automatic bleed function so manual bleeding shouldn't be required if you follow the instructions and don't loose too much),

17) run the engine and check for leaks, and then grease and refit a new dust/dirt seal, it clicks in a groove on the input shaft with the lip in a slot on the top of the box,


18) refit the steering column, rubber boots, headlight frame and grille,

19) do a road test to exercise the steering box (carefully, the brakes are hydraulic powered as well as the steering), check for leaks and recheck the reservoir level. Do this several times over a few days.

What you need

1) An input shaft seal kit seal kit. I acquired this kit (part number TAS75/C1) from the local TRW importers, Complete Steering Australia Pty. Ltd, Phone (03) 9369 2659. They were familiar with the Oka steering box and the seal kit was around $80 delivered. This sounds a lot but it contains the seal, dust/dirt cover and new spring clip, plus a couple of other items not needed for this fix, and it's difficult to source from elsewhere.

Input Shaft Seal Kit.

2) 2 hydraulic fittings, a Ryco S56-12 or Pirtek AU-12 male plug, and a Ryco S65-12 or Pirtek AW-12 female cap, or equivalent (about $5 each). Hydraulic pressure is used to force the old seal out and these are for temporarily capping the return outlet on the box to create internal pressure, and plugging the return hose to prevent fluid loss.

Cap and Plug for the blanking off the return outlet and hose.

3) A special tool for inserting the seal. You can buy one ($US36 from the USA plus freight, assuming the J37073 is the correct size, or around $A100 quoted locally), or you can quite easily make something similar, as it's only a stepped cylinder. The TRW manual warns against using a socket to insert the seal since if you go too far it won't seal, and might require removal and disassembly of the steering box to recover it, which is a big job. However you can use a socket if you adapt one to prevent this from happening.

A long socket modified to avoid inserting the seal too deeply.

4) A couple of litres of Automatic Transmission Fluid (Dextron 111 or equivalent) to replenish the reservoir.

Modifying the seal insertion socket

You'll need a fairly deep socket, long enough internally to surround the input shaft plus a bit, and small enough in diameter to just fit inside the seal housing. A long, 1 1/8 inch A/F, or metric equivalent would suit. To that you can fit some clamps to prevent the socket from penetrating too deeply. Only 4.3 mm depth is required. You may notice that the clamps I used are actually some old Oka saddle clamps from drive shaft rear UJ's, which I opened out a bit and bolted across the socket. You could easily make some similar clamps using 3mm steel bar. I did try hose clips but they are not wide enough to sit on the seal housing and are not flush on their lower edges.

About 4.3 mm depth is required, no more.

After removing the circlip from above the old seal, I "calibrated" the modified socket by locating it over the input shaft and nipping up the clamp bolts while it was resting on the old seal. That gives it the correct depth. Make sure the clamps are then securely tightened as you don't want them to slip up during insertion of the seal and overdo things. It's better to leave things a little short than to drive the seal too deep.

Inserting the new seal

Follow the instruction above, or in the TRW documents. They are similar but I've added some practical tips. These photos may also help.

Old seal exposed after removing the circlip (or spiral spring clip in our case).

The return hose and outlet plugged.

Using the socket to insert the new seal.

(The socket was calibrated this way too with the old seal in place)

It was a little bit squeezy wielding the hammer above the inlet shaft (a slightly shorter socket would have been better), but it doesn't need too much force, and it's a good thing anyway if it prevents the seal from going in too far. In my case the seal didn't go in quite level so I had to tap the socket on one edge to level it up. The seal must only be inserted far enough for the circlip to fit fully in its slot.

The circlip located in its slot above the new seal.

After putting the new circlip in, I removed and replaced it a couple of times to ensure that it really was fully in the slot. You don't want the seal popping at the wrong moment and distributing fluid all over the Oka and road, and leaving you without steering or brakes. If the circlip is not quite in its slot, put the socket back on top of it and tap it down gently until it seats properly.

Remove the plug and cap from the return hose and quickly reconnect to the steering box, to reduce fluid loss, and tighten fully.

To aid the bleeding process, and before reconnecting the steering column shaft and lower UJ, I ran the engine several times briefly as per the instructions, checking the reservoir level in between. Ensure there are no more leaks, from the input shaft or return hose, then grease and refit the new dust/dirt cap. If all is OK, then you can fit the lower UJ and steering column shaft.

The seal and dust cap in place, with blue grease under the cap to keep out water.

Replacing the steering shaft

The steering column shaft can be replaced without disturbing the steering wheel housing but needs to be manually compressed and expanded as it's fitted to the splines at each end. It's better to leave all the pinch bolts off until the shaft and lower UJ are in place. Being able to slide the shaft up and down the spines makes fitting it a bit easier. Ensure that the steering wheel is aligned with the front wheels in the straight ahead position before assembly.

The lower UJ back in place with safety locknuts fitted.

I fitted Nyloc nuts plus extra locknuts to the UJ bolts to ensure they never, ever work loose.

When refitting the steering shaft, according to TRW, the UJ's should be in phase to avoid cyclic binding. I never knew I suffered from cyclic binding but apparently it can occur where there are 2 or more UJ's in the steering shaft and they are out of phase.

"Steering column assemblies with more than one universal joint (cardan type) can cause a cyclic binding feel or torque variation at the steering wheel if the u-joints are not in phase with each other".

I presume being "in phase" means that the UJ cross shafts are parallel, like in this photo, but they don't explain. (Note: the urethane bush clamped to the siding shaft is to reduce steering column rattle, which works well and could easily be installed at this point, see this article).

Steering shaft with UJ's in phase, I think.

Replacing the rubber boots and steel framing brackets is easier if they are first slit/cut up the back. You don't then need to slide them over one end of the steering shaft where they get in the way of reconnecting it. The steel clamps should hold them in place but they can be super-glued if you need to, or as I did, hold them together with nylon tie-wraps.

Rubber boots, slit up the back to aid assembly.

(They were cleaned before reinstallation)

I also fitted a leather boot to the the lower UJ to protect it from the worst of the dust and water.

Leather boot to protect the lower UJ.

GARP, The Great Axle Reconstruction Project (Part 2)

Intro

In GARP Part 1, I described the events leading to disassembly and repair of the front axle. GARP Part 2 describes the reassembly process.

Hubs and Spindles

Following on from Part 1 which was initiated by a front end vibration, I have now cleaned up the spindles, removed the diff inner oil seals and checked the bearings for fit on the reground spindles. The shells are a tight fit, or rather, they need accuracy in location or they will jam sideways. Once correctly located the bearings slide and rotate very smoothly. Of course, once the bearings are tightened up the shells shouldn't move or rotate on the spindles anyway.

I removed the rear hub oil seals, using an inside gear puller pressing on a steel bar placed across the hub, but before replacing them, I tried the hubs and bearings on the reground spindles, temporarily reattached to the steering knuckles. This is to ensure they can be correctly assembled without jamming when the hub is offered up to the spindles. Had the inner bearing jammed on the spindle, it would have damaged the new oil seal when the hub was removed.

If the bearings are jamming, smoothing the spindle with some fine emery cloth and careful cleaning with WD40 will help, as will a smear of oil on the bearing surfaces. Older bearings will fit slightly easier than brand new ones.

If the hub and bearings can be successfully located on the spindle without jamming, a new oil seal can be pressed into the rear of the hub, by gently tapping around the edge with a heavy hammer until it's flush with the hub casing. Don't knock dirt from the back of the hub into the bearings.

Oil seal inserted into the rear of the hub.

Diff Carrier Rebuilding

Refer to Section 4 of the Dana 70 Maintenance Manual (available here) and the Carrier section of the Dana 60 Maintenance Manual (available here) for advice on how to do this. The front axle of an Oka is actually a Dana 60 while the rear is a Dana 70, but there are many similarities and the techniques in these manuals are relevant to both types. In fact there's a host of useful documents available from the Dana website here.

After removing the diff centre carrier, I unbolted and removed the ring gear, knocked the roll pin through and removed the cross shaft and differential gears.

Because it's a heavy item and would be seriously damaged if it fell on the concrete floor, I inserted a sturdy cable through the carrier and tied it to a roof beam so that if it slipped out of the vice whilst being worked on, it would swing clear and only hit me, not the hard concrete.

Removing the ring bolts was easier than anticipated since they should have been torqued to 130 ft-lbs (176 Nm) and Loctited too. I left four of the bolts partly in place and tapped them with a hammer to free up the ring gear, which wasn't very tight anyway. I moved the carrier from the vice to the workbench and then removed the last 4 bolts whilst holding the ring away from any hard objects. I didn't want to have to replace that as well, since ring gears only come as matched pairs with the pinion, which would have made it a much more difficult (and expensive) job.

The Ring Gear being removed.

Leave 4 bolts loosely in place and tap the heads to release the ring.

The bearing cups came away when removing the diff centre, so I put old socks over each of the bearings to protect them while this work was being done.

I tapped out the roll pin using a length of 5mm steel rod, and the cross shaft then slid out of the carrier.

Removing the differential gears looked difficult since they remained meshed together, but by turning a side gear, the spider gears simply walked themselves around to the opening in the diff and fell out. All 4 gears are seated on thrust washers which might be stuck to the carrier by oily suction.

I smoothed the rusted and pitted surfaces of the ring gear with fine emery paper and WD40 and cleaned them off with Brake Cleaner fluid.

The broken gear wheel will end up in my Museum of Broken Car Parts which is becoming quite extensive.

The diff in pieces ready for reassembly.

The Differential Gear Set.

A close up of the offending tooth.

Diff Oil Seals

Removal of the Inner Seals

To remove the inner diff oil seals I built a pusher rod made of a metre of 12mm tapped rod with a large steel washer, just the diameter of the rear guide section of the seal, bolted to the other end. A few whacks with a heavy hammer and the seals popped out into the diff chamber. Other people have used a large socket and several extension bars to achieve the same result, but I didn't have the right size socket (or sufficient extension bars). The bar needs to be at least 1 metre long to remove the LHS seal.
This bar, with a sock tied over the washer, also makes a useful tool for cleaning out the oily/muddy sludge from the axle tubes.

The pusher for removing the inner seals and cleaning out the axle tubes. 

Installing the Inner Seals

To insert the seals I used a modified 40 mm high pressure water fitting, which just fits inside the seal body, to avoid damaging the plastic parts of the seal with a hammer. The fitting will need to be cut down to about 50 mm long to allow a hammer to be swung inside the diff housing. I drilled and fitted a long bolt to the side of the plastic fitting as a handle, to keep my thumbs well clear of the hammer. A suitable socket might also work. Alternatively a pusher tool could be made up as described in the Dana 60 manual. Any rust or corrosion around the seal location should first be removed and the surfaces smoothed down.

The old seals had silicon gasket sealant smeared around their outer surfaces before insertion, presumably to keep water away from the metal surfaces and prevent premature rusting. Seems like a good idea, as does greasing the seals and guide inner surfaces to help the splined drive shafts find their location.

However, sealant on the seal casing also makes them slippery and more difficult to keep centred as they are inserted. It takes a quite a lot of effort in a confined space to insert the seals straight, since they are a tight fit, and I had to remove and reinsert one of them a couple of times to avoid fitting it crookedly. A pusher tool would certainly be more effective.

Mind the pinion gear, bearing seats and thumbs as you are wielding the hammer, damage to those would be expensive and/or painful.

Clean out all the resulting muck from the diff housing.

A pusher for removing the inner seals and cleaning out the axle tubes

can be made by cutting down a 40 mm high pressure water fitting,

which fits neatly inside the body of the seal, to about 50 mm long.

Reassembling the Diff Carrier 

Before reassembling the diff centre, ensure that the ring bolts and tapped holes in the ring gear are thoroughly cleaned and free of old Loctite.

Before the ring is refitted, the new gear set must be installed, with their thrust washers, and the cross shaft and roll pin inserted. Oil all the parts well before assembly and check for smooth rotation.

Installing the Differential Gears

You'll need about 15 fingers to hold the 4 gears and their thrust washers in the right place but it's not too difficult. Insert the side gears first on their washers, with the carrier horizontal so they can't fall out. Then insert both spider gears exactly 180º apart from either side of the carrier and walk them into the carrier case by turning both side gears in the same direction. If they are not exactly 180º apart on the side gears the cross shaft holes won't line up. I found it easier to slide the saucer shaped thrust washers in behind the spider gears after the gears were in place.

Gears reinstalled in the carrier.

Once all the gears are in place, centre the the spider gear washers with a finger and insert the cross shaft with the roll pin holes roughly in line. Use a thin bar to turn the cross shaft until the roll pin holes line up and drive in the roll pin. The differential gears are now complete, assuming they all turn smoothly.

Driving the Roll Pin home to complete the assembly.

Installing the Ring GearThe ring gear should be replaced in its original orientation (not sure why, it doesn't seem to be a balanced item, but that's what the manual says) and this can be determined from the imprint markings on the carrier made by the ring. There is a cut out on one side of the ring, presumably for oil flow, which will show up as a shadow on the carrier. I also took photos of the stamped markings to confirm it's location.

The manual also suggests replacing the 12 ring gear bolts, but they are very high tensile bolts (SAE Grade 8, equivalent to metric class 10.9) and if they are in good condition and not stretched or worn, the originals could be reused. On a rear diff, which is subject to a far higher and continuous load, I would certainly replace the bolts.

[BTW, if you are excited by such things, there is a very good Australian document on bolts (and fasteners in general) available for download from the James Glen Company here, or view an on-line version here].

The ring bolts need to be tightened alternately to 130 ft-lbs (176 Nm) and Loctited. A tight fitting socket is required (hex, not multi-point is preferred to avoid rounding the corners) and the carrier needs to be securely held in a large vice, preferably tied to something substantial to catch it if it breaks loose. Vice jaws have been known to snap off. Protect the exposed bearings while doing this.

My torque wrench only goes up to 110 ft-lbs so I tightened the bolts alternately to 110 ft-lbs and then used a longer bar to turn them all a fraction of a turn more, about 25º to 30º (1/12th of a turn max.). I reasoned that this would increase the torque to around 130 ft-lbs. Don't forget the Loctite and ensure you haven't missed out tightening any bolts, 12 is a lot to remember.

Reinstalling the Diff Carrier

Fully fitted with gears, the carrier is a bit of a handful to manage under the vehicle. It has to be manoeuvred around the tie rod, the bearing cups have to be fitted and held in place and the whole assembly inserted straight and level into the housing so that the pinion engages with the ring gear and the bearing cups locate correctly in their slots. And it's heavy and makes your arms ache.

The bearing cups had previously been rotating in their housing and caused a burn mark so I applied some Loctite 641 (bearing retaining compound) to the housing and bearing caps to stop them rotating.

The differential installed in the carrier.

It took me a couple of goes before I could locate the carrier properly, but I had the bolts and bearing caps ready to go so that when finally it slipped into place I could whip in a bolt to hold it there before it all fell out again. Had the diff carrier been a press fit requiring a diff spreader to remove it, I doubt that it could have been replaced in situ and the axle would have had to be removed first.

Once I had recovered my strength and confirmed that the gears all rotated correctly, I Loctited the bearing cap bolts and torqued them up to 80 ft-lbs. The bearing caps should be replaced in the same orientation as previously. They have stamped markings on to aid identification.

Fitting the Drive Shafts

Once the diff is in and working correctly (although I don't see how it couldn't work as it's a very simple but clever mechanism), the drive shafts can be installed.

I had already cleaned them up, checked the UJ's and replaced the oil seals. I was surprised to find the short shaft UJ had a grease nipple, which worked. It must have been hidden under years of dirt and sludge and in 5 years I had never noticed it. Presumably this UJ, or maybe the complete shaft, had been replaced at some stage as the inner splines were also much less worn than the long shaft, which had no grease nipple. Fortunately there was little play in either UJ.

When reinstalling the drive shafts I wanted to avoid the splined end from collecting dirt, as it was pushed along the axle tube, and injecting it into the diff housing. So I placed a thin plastic strip in the axle tube and slid the drive shaft along that and straight into the diff. The plastic strip was actually the cap from a length of Clipsal rectangular electrical conduit and acted like a thin "V" shape for the splined shaft to slide along. When the shaft had entered the diff housing but not fully engaged with the side gear, I pulled the plastic strip out of the axle tube and pushed the drive shaft home, all nice and clean.

Using a length of plastic strip to keep the drive shaft out of the dirt.

The oil seal has also been replaced.

Refitting the Spindle 

Before refitting the spindles, I levered out the old oil seals (which had broken in 2 anyway), flushed out and re-greased the needle bearings and tapped new oil seals into the back of the spindles.


Clean and grease the rear of the spindles around the needle bearing seal since the drive shaft oil seal engages that surface.

Needle bearings greased and new oil seal fitted into spindle.

Strangely, I couldn't recall the order in which the spindle, brake calliper plate and stone guard came off, so I thought "simple, I'll look it up in the manual".

Wrong. There are pictures of the axle, spindle and hub arrangements and pictures of the brake rotor and calliper, but none showing both. Eventually I deduced that the spindle is attached direct to the steering knuckle with the brake calliper plate on next and the stone guard on last. It didn't look right, due to the cranked angle of the calliper plate and stone guard, but it was logical when I thought about it.

Loctite the spindle fixing nuts and tighten them to 65 ft-lbs. Once the hub is in place you can't reach them anymore.

Refitting the Spindle, drivers side.

Grease the rear oil seal bearing surface and clean out the spindle nut threads. 

When fitting the hub to the spindle, have the greased up outer bearing and the hex spindle nut ready to go. Otherwise, when you fit the hub with only the rear bearing in place the hub might slip down the spindle when you let go.

I was tempted to put bearing retaining compound on the bearing cup surfaces to prevent the original problem of the bearing cups rotating on the spindles, but there is so much grease around that I doubt that the retaining compound could do it's job effectively. With rebuilt and reground spindles it shouldn't be necessary anyway.

The spindle nuts should be tightened to 50 ft-lbs, spun a few times to seat the bearings and circulate the grease and then backed off about 45º before fitting the lock washer and outer lock nut. Pre-loading is essential for tapered roller bearings so they share the load equally. If there is any free movement, they are too loose. On the road I check the temperature of the hubs frequently to ensure they are not getting too hot. Warm is OK due to the brake heat, but if one is appreciably hotter than the others, something is wrong.

[There are some very useful tech notes on bearing problems and installation at the Timken site here and here].

Fitting the lock washers can be a tricky task. Bend 2 tabs in towards the bearing, being careful not to go too far or you can damage the bearing cage. I used a rod formed from the tapered end cut off a tent peg to do this. Bending 2 tabs outwards on to the lock nut is even more difficult. I made a small tool using another tent pen with a sharp bend on one end (more than 90º so it won't slip off) and threaded the other end. Using a breaker bar with a hole it it, I slid the tool in behind the tabs and levered against a nut fitted on the threaded end. Once the tab has bent slightly, I used a square shank screwdriver to lever them flat by twisting it with a wrench on the shank.

[In the US, there are more sophisticated (but expensive) locking devices described here and here].

Epilogue

The rest of the rebuilding process (free wheeling hubs, tie rod ends, steering damper, brakes, wheels, diff cover/oil etc.) should be fairly straight forward, but as with any major project, check if there are any bits left over and check that everything is reconnected, tightened, greased or refilled.

On it's first test run, there was no evidence of the original vibration which kicked off the whole axle reconstruction program in the first place, and the steering seemed a lot smoother, although there's no logical reason for that other than the greased joints. I ran the Oka in 4wd for a while, but with the hubs unlocked, to allow oil to circulate through the diff components before any load is applied to it.

This has been quite a long and complex rebuilding process and ironically, there will be almost nothing to show for it at the end, except peace of mind.

However, it is not difficult or mechanically challenging or even very expensive, there's just a lot of it.