Firstly I'm based in the UK and am more familiar with the 75, but as you are aware they are almost identical mechanically so I'll venture an opinion. I'll talk in hours rather than currency as the Aus labour rate is likely to be different to ours, and tell you the parts you'll need so you can interrogate any quotes you get to make sure they are doing a proper job.
Firstly I would like to know if it is an expensive procedure to have the cambelts changed?
It's not difficult at all - if you are at all competent wielding a spanner then this is one to do at home IMO. Budget 3-6 hours if DIY (Taking your time and cleaning everything nicely), I would be surprised if a mechanic would quote more than 3 hours.
Parts needed should be:
- Cambelt (Singular - there's only one)
- Tensioner rebuild kit (Oil seals etc)
- Fresh engine oil
- *Auxiliary belts* (Optional, but they'll need to come off so you may as well for the cost)
- *Cam Cover Gaskets* (Optional - If doing this yourself. A good mechanic is unlikely to take off the cam covers)
- *Waterpump* Optional but well worth it - these aren't the most robust of designs and often fail, and you need to remove the cambelt to change them! So do it now.
Also the car has the usual 2nd gear grind syndrome. Is this best fixed with a replacement gearbox out of an Alfa 75 or is it cheaper to just replace the syncro?
IMO it will be more cost effective to replace the syncro than to replace the entire box with a 75 unit, unless you really want an LSD. Likely problems with the 75 box:
- Unless rebuilt it will probably have a weak 2nd gear syncro anyway.
- The LSD will need adjusting which won't be cheap (If you can find someone willing to do it). If you don't adjust it you'll likely not get the benefit.
- Not sure that the new box will talk to your speedo without a bit of thought.
The Alfa transaxle is well designed for maintenance IMO, with the ability to easily remove the Mainshaft/pinion shaft assembly all held together by the intermediate flange. This bundle can then be handed over to you friendly specialist for replacement syncro's and bearings if needed.
Unfortunately, the above scenario only becomes easy once the exhaust, is out of the way, the prop disconnected, gearbox mounts disconnected, and the front of the transaxle dropped (The Bulk of it stays on the car) and the clutch pack removed.
Again, if you are at all competent at DIY, the most cost effective way of doing this is to do the donkey work yourself and hand over the Mainshaft/pinion shaft assembly to your specialist.
How long this takes really can vary, depending on what has seized solid and what breaks. I'd estimate anywhere between 6-12 hours for DIY removal and reinstall of the Mainshaft/pinion shaft assembly (That is in and out, taking your time and being the first time you've done it) and 1-2 hours for the shop to replace the actual syncro in the Mainshaft/pinion shaft assembly.
Time for the shop to get the assy in and out would again depend on what's seized. I'd estimate between 4-6 hours depending. Then, again, 1-2 hours for the shop to replace the actual syncro in the Mainshaft/pinion shaft assembly.
Parts you'll need (From memory, and it's been a while!)
- Syncro (It's common to swap 5th gear and second gear syncros instead of getting a new one, unless 2nd is totally hammered).
- Intermediate flange sealant (If they do this wrong it'll weep gear oil)
- Gear oil
- *Optional* (but not really) new gearbox mounts - unless changed in the recent-ish past, your's will be knackered!)
- *Optional* New clutch - inspect yours whilst you are in there as the clutch pack will be out!
If you want to have a go yourself, post back and we'll advise you further and point you in the direction of some on-line info.
If you do get a mechanic to do it for you, I would suggest going to a reputable Alfa specialist that knows the vehicle, otherwise it can go very wrong! E.g. rotating the engine the wrong way can make the belt jump, screwing up the timing and potentially destroying the engine, and the fact that turning the prop turns the engine(!)
Also the prop and associated components should always be marked before removal and be replaced in the same orientation or you are likely to get an out of balance and hence viby driveline!
A specialist will know this sort of stuff, not sure about a normal backstreet garage.
Good luck, hope this has gone some way to answering your question, maybe someone will be along soon who is in Aus and has had similar work done recently and can give you the dollar amount they paid..