Thread: Using a V8 R380 in a Tdi

After a little gap due to weather and other duties, the matter has progressed rapidly. I won't go into replacing bearings and the re-assembly of the box because it was simple and without hassle. However, the next bit can cause some headache.




As you can see, this is the output shaft and the oil seal collar. The end of the shaft is threaded M12 coarse, and extends for 4cm. With a gear engaged, old clutch plate on the input shaft, the collar wound on OK - you know when to stop as the thread stops just before the end of the bore. Then unwind and put some more washers or large nuts on and continue. Generally, you get 2cm each time, and since you only have to go 3.5cm, it's a fairly quick job.

As others have stated, put the OIL SEAL on first - otherwise (like me) you'll have to take it apart and start again.

NOTE: Wrapping electrical tape around the collar and over the gap between the two sections of the collar so you can slip the seal over it and into the recess does not work. One has to try I suppose.

The piece of tube isn't regular 3mm wall tube. I found out that regular tube is either too big or too small for the combination of shaft and collar. Yet another huzzah for Edcon steel - they had a piece of thick wall tube that only needed to be cut




The (very) thick wall pipe is 50mm, and has an ID of 32 mm, which is great as it slips over the output shaft neatly and drives the collar without damage. It was 150mm long, ($10) and I used a M12 set screw 100mm with some washers to suit. You could use a shorter piece of pipe and screw, this worked for me.

Then the tunnel bolts on, and leaving the gearbox mount off the gearbox, all is ready to refit into the truck.

As for the clutch, you can align the plate without a alignment tool, just centre the plate whilst doing up the clutch bolts.A smear of grease on the splines is a very good idea and don't forget the new spigot bush.

With the mount off the gearbox, it isn't too heavy to lift - but be carefull not to damage the reverse switch which poke out the side. It even slides under the car sitting on the roadway.

Now to prove 1 person can fit a gearbox to a Disco on the street - with only a trolley jack.




For the observant, do you notice what has taken the place of the torx plug gearbox filler? It's a standard brass plug - same size as a radiator plug. I dressed the rim of the filler hole ( after stuffing a rag in the hole) with a file, and it seals well.

Up up....and away



Now some points to remember: When you lower the gearbox to remove it, you will need to support the front of the engine, so when the gearbox comes off the engine adaptor the engine doesn't drop back down and jam up against the firewall. Similarily, when re fitting, the engine has to be jacked up at the front so you can access the top studs of the engine adaptor. It's easier to do those top nuts up with a 6 point 15mm socket, with about 50cm of extension bars. That puts the ratchet near the end of the gearbox and with clearance to use it easily.

Now the hard bit.



The transfer case is a bit of a problem. After a few tries, it seemed that starting with the input pointed upwards balanced on the jack got the TC up to level. Then, I carefully rotated the TC so it was aligned with the gearbox. This is when the 200mm M10 guide bolts come into their own. Using them, from the position you see, you can slide the TC into position without damaging the TC input seal. With the brake drum/shoes, mount and input gear assembly off the TC can be handled with some degree of safety and control by the average person. Once the TC is on the dowels, bolt the rest of it together, noting which bolt goes in which hole, as if you use the long bolts in the bottom holes you could interfere with the gear assembly.

The rest is just fiddle work - especially the high/low and difflock levers. Make sure the breathers are open and not kinked, and everything is plugged in and tied down as it should.

I cleaned out and replaced the rubber on the clutch slave cylinder - there was a little corrosion, but some wet/dry paper brought it back to smooth. There is a plastic cap in the end of the cylinder that makes bleeding difficult.

I started off by letting gravity fill the cylinder, then switched to the standard method. It took a while, as the plastic cap inside traps bubbles. But having the car parked facing upfill helps, as the air bubbles eventually travel up and out.

An old 1L ATF bottle with a nozzle did fill duty, and everything else went in OK.

The last thing to do before putting the console back on is to adjust the bias plate on top of the box. Whilst you can do this before installation, it is better after a test drive.

And, as a bonus, I think I have a solution for cracked bias plates.



I've cracked a bias plate before, and it fractured at the same point as others you have seen. It seems that there isn't any adjustment for clearance in 4th. So, if the tongue is bent backward, and doesn't contact the gearstick, it should last longer.

The 3rd/4th shift is easy after a short drive, and then you can put the cover on. But even though the RAVE says you can do this in situ, on a disco you have to bend the side of tunnel up a little to slip the gearstick cover on.

Test drive results:

The V8 box has the same 2/4/R as the TDi box, and the other gears are only 5% different. 1st is .07:1 higher, 3rd is .09:1 lower and 5th is .04:1 higher.

Around town, unladen and not towing, I didn't notice any change in first - I have 31's and hill starts always need some revs up. But on the positive side, doing a right turn from a stop can be accomplished without a gear change. 3rd is a little more comfortable on suburban streets (50k) and 5th is really good cruising along the freeway at 110k. Before, it seemed that 100k was the sweet spot, now it's a bit better.

Now you know if you need a replacement gearbox, and the only one you can find is a v8, at least it will work with only one custom part.

Originally Posted by langy

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As you can see, this is the output shaft and the oil seal collar. The end of the shaft is threaded M12 coarse, and extends for 4cm. With a gear engaged, old clutch plate on the input shaft, the collar wound on OK - you know when to stop as the thread stops just before the end of the bore. Then unwind and put some more washers or large nuts on and continue. Generally, you get 2cm each time, and since you only have to go 3.5cm, it's a fairly quick job.
.. .... ..... ...

Thanks for the tip. It worked well.

One small modification that I believe is an improvement.

I welded the head of two bolts together so that one was screwed all the way into the shaft and the threaded end of the second one protruded through the washers and was fitted with a nut.

I believe that has two advantages:
The bolt in the shaft is always fully wound in so there is no chance of stripping the thread as might happen of you started with too few threads.

The longer bolt out the back allows the collar to be pressed on in one continuous operation, so that if you have warmed the collar, it has less time to cool down.

Originally Posted by langy

<snip>
As others have stated, put the OIL SEAL on first - otherwise (like me) you'll have to take it apart and start again.

NOTE: Wrapping electrical tape around the collar and over the gap between the two sections of the collar so you can slip the seal over it and into the recess does not work. One has to try I suppose.

<snip>

Been there, tried that too.

After stuffing around for far too long I ended up making a brass sleeve as an installation tool. Slide the seal onto the sleeve, slide the sleeve over the collar and push the seal home.

I stuffed a couple of seals and wasted miles too much time doing that
(I decided to replace the seals during a clutch change )

Big Jon reckons they used a big O ring in his old workshop and it does the job too.

Does anyone know a source for the QH p415 bush? About to embark on this.

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