'74 S3 Gearbox Noise

Hi folks, again...
So nothing has broken per say, but there's a new noise rearing its head and I'm not too sure what it could be.
The gearbox has it's fair share of whines but I'm used to those, recently ( started after a long run) there has been a new kind of gurgling/boiling/bubbling noise coming from the gearbox area when throttling off completely, it started as a very occasional noise that only appeared say leaving a motorway, now though I only have to drive up the road. Otherwise the gearbox is pretty sound so far as I can tell, the only minor thing is an occasional momentary judder pulling away from a stand. Maybe worth mentioning, I know that whatever seal goes between the main and transfer box is shot, so the transfer box is full of oil and the main drinks the stuff. Does anyone have any ideas?

Hi Wilson. I have the same problem with my 1977 gearbox in that the oil leaks from the main box to the transfer box then eventually onto the road. We should replace our seals really but easier said than done. Your judderering sounds clutch related and I have no idea what the bubbling/boiling sound might be. However, I learnt soon after getting Compo that it's usually best to completely ignore any noises that sound strange otherwise the landy will spend the the rest of your life in bits.

Col

In the end you will have to change the seal because the main box will often be runing with a low oil level and something on the mainshaft will start to run dry. I've repaired my box in the past and I don't recall it being that hard a job. The worst part is getting it back in place, aftert hat its just lots of nuts and bolts. I agree re traying to avoid takeing it apart and the risk it stays apart. I now always do a specific job, plan it and set a deadline. Its too easy for things to get out of hand and turn into a rebuild. Re the box, drain it and see what comes out - metal etc and you can take the top cover off and look around but its hard to see much. I would satry by assuming the noise is not the box if its working OK and look at things like mountings, propshaft, the tranny brake etc but if you narrow it to the box then fix it ASAP before it gets worse. Bearings and seals are cheap but the gears and shafts can get expensive.

The seal can be changed with out removing the gearbox by taking back cover off gearbox that supports the main shaft. Worth a shot if bearings are ok .
If your noise is on the over run check rear diff for oil and check propshaft joints are ok.

From bitter experience any unusual noises from a gearbox are expensive and labour intensive. My old collie bitch used to be a keen gearbox listener but she has become deaf in old age- once she became so frightened by the noises that she wouldn't get in any more till I changed the box-

These things are usually very difficult to diagnose from an owner's written description; everything that others have suggested above are all good, here is something else for you to think about: you mention an occasional judder on starting off, this could be broken damper spring/s in the clutch plate which could also make a noise similar to the noises you describe. Sometimes, but not always, you can hear them rattling at idle if you listen near the bell housing.