159 3.2 Q4 Transfer box - Alfa Romeo Forum
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(Post Link) post #1 of 8 Old 18-05-16 Thread Starter
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159 3.2 Q4 Transfer box

Anyone ever had one rebuilt, had one apart, or indeed, got one going spare?

Rear propshaft output shaft bearing on mine has noticeable play and rumbles nicely when driven when lifted in the air, so I'm about to remove what looks like most of the front end to get it out.
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(Post Link) post #3 of 8 Old 22-05-16 Thread Starter
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Having baulked at spending large amounts of cash on something secondhand that may be just as bad as my original, I dismantled the transfer box today.

Pretty simple unit, nothing complicated. What was upsetting was the amount of metal flakes in there - lots n lots. All bearing on the two shafts look pretty okay - I'll check again after proper cleaning tomorrow, but I think for the sake of a few quid in bearings, it'd be silly not to change them.

The output pinion bearings though! The large one behind the pinion gear looks fine on the rollers, the outer cup looks worn but not badly - maybe "used" is a better description. The one behind the output flange - knackered! Major spalling on the rollers. Unusable. Outer cup not excessively worn though.

This bearing looks to be expensive - 20 quid including postage! ;-)

Gear teeth all look pretty good, with nice even wear patterns.

So, good clean of the casing tomorrow, heat it up to drop the old bearing cups out, maybe drop the new ones in if I've got them, and onwards and upwards.

Timing chains on the V6 next week . . .
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Garage
Any chance of some pictures of the insides? Would be interested to see how it works and for future if I have problems?
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(Post Link) post #5 of 8 Old 22-05-16 Thread Starter
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Wrong way up - the output to the rear diff is the bevel gear you can see top left.

As you can see - pretty simple.
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(Post Link) post #6 of 8 Old 12-06-16 Thread Starter
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Well, a few weeks later and ZF in the UK finally tracked down someone who had technical responsibility for this power take off unit. And they state there are no service manuals produced and no spare parts. The only way to source a replacement unit would be through the vehicle OEM.

But as every bearing in it has part numbers from the manufactures, and the same with the seals, and its not exactly a complex unit, I don't think it's exactly a problem. The knackered output flange bearing is 16 quid. The one other end is 20. Seal a couple of quid. I just hoped I would get the method and numbers for setting output shaft bearing pre-load. However, all is not lost. The day job sees me designing all sorts of things, part of the current work load involved speccing rather more expensive bearings (couple of grand!) and bearing manufacturers are delighted to assist in suggested set-up, so I can feel a phone call coming on on Monday.
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(Post Link) post #7 of 8 Old 08-08-16 Thread Starter
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I think I know what caused the bearing to fail - loss of pre-load caused by the collapsible spacer holding it in place being deformed.

The out put shaft has a large taper roller bearing sat behind the bevel gear, a really good interference fit on the shaft, which at this location diameter is slightly bigger than the rest of the shaft - it means the bearing clears the rest of the shaft and only has to be pressed onto it's location, not the full length of the shaft.

Next comes the collapsible spacer, then the bearing behind the output shaft (obviously the shaft is inserted in the case before the last bearing). The spacer sits on it's own location diameters, the final bearing inner race butts up against the spacer. The other end of the spacer butts up against the shoulder of the first bearing location diameter on the shaft, rather than against the first bearing inner race. And over the course of around 90,000 miles, the loading on it has hammered it slightly over the shoulder - losing the bearing pre-load.

I've reassembled it with some stainless shims to spread the force a bit, and to allow me to crush the spacer a little more on setting the rolling torque of the shaft. A similar arrangement in the Lancia integrale box uses a rolling torque of around 1Nm, further reading around backed up this typical figure, so that's what I used, plus a bit for the drag of the oil seal on final tightening.

It's taken me a while to get it all back together, as I decided to change the timing chains while the engine was out, blast, paint and underseal the sub-frame, blast and powder coat various brackets, battery tray underside brackets etc, remake the bumper.under tray mounts that bolt to the lower radiator mounts and sort out sheared screws etc.

I bought the timing chains, guides, tensioners, gasketc, from GM Parts Direct in USA - slightly delay due to them not sending one of the guides, but all sorted and changed easy enough.

I then spent a week in Bogota (some Alfas floating around over there) and so only managed the first test run yesterday - 34 miles of silence - no timing chain rattle, no bearing hum :-)

Bit early to say its done and dusted, but fingers crossed . . .
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(Post Link) post #8 of 8 Old 1 Week Ago Thread Starter
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The request thread for a transfer box reminds me to update this - still fine, silent, etc.
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