365 and 512 gearbox how do I tell the difference

Just changed the oil on the gearbox/diff of my 365 Boxer. The workshop manual says it takes 7.75 litres of oil plus 0.25 litres of additive, so 8.0 litres in total. My gearbox took 9.0 litres of oil which is the amount the 512 needs. So how do I tell from the outside if this is a 365 or a 512 gearbox.

My car is the last right-hand drive 365 made and supposedly the second from last 365 boxer of any type. It occurs to me it may have a 512 gearbox in it from new, as these cars were constantly being developed. It has a cable clutch (as per 365 rather than the 512's hydraulic system) and is low miles at 18,000 miles. It has not had the gearbox changed as the factory confirms the gearbox number is the original one.

I drained the box from both drain points (but did not drain the idle gears) and then sqirted in 8 litres of oil using a pressure gun (looks like a big grease gun/syringe type thingy, you suck up the oil from the conatiner and then squirt it into the gearbox filler under pressure by pushing the plunger). I had bought 8 x 1-litres of the Mobil 1 SHC oil and put all of this into the gearbox. You basically keep filling the gearbox until oil comes out of the drain hole and at 8-litres none came out. I put my little finger in the drain hole and could not feel the oil level. I re-read the gearbox section in teh workshop manual and saw the part about the modification (see below **) and realised that if I could put my finger in the hole then no modification had been carried out, which in turns means that the gearbox should be full up to the drain hole after 5.75 litres have been put in - you add the last 2 litres from the idle gear filler.

As my car has been well maintained I reasoned that the gearbox modification should have been done and then it occured to me that maybe the gearbox was a later gearbox did not need the modification. I then thought that I had filled many gearboxes and back-axles over the years and they are always filled until the oil level reaches the filling hole. I went and checked the level again - I had driven the car about 5 miles home - and thought I would add some more oil until it reached the filling hole and also decided to measure how much it took. It took just under another litre (0.9 litres to be exact because I used a measuring jug to see the exact amount). Considering the workshop manual says that the idle gears hold 100ml this makes the capacity of the gearbox 9 litres, which is what the 512 owners hand book states is the 512 gearbox capacity. Hence my original question.

BTW, I use Mobil 1 SHC 75W-90 synthetic oil which is really excellent. Expensive oil but works a treat.

** - For those that don't know the modification refered to above consisted of permanently inserting an upturned curved open-ended tube into the filler hole so that the oil level was reached at 7.75 litres rather than 5.75 litres.

Simon, it's very good that you have the update, as it was found on the 365BB's that the original fill specs was inadequate (too low) and they were burning up gearboxes.

Now to your real question. We never took the books fill specs as the definative answer. Just like engine oil, you fill and check till the thing reads full (regardless of what any possibly hastily conjured print may say). The printed matter is full of mistakes, mistranslations and ommisions. They are to be used as a guide but not relied upon for every conflicting situation.

The ways tell the two castings apart are either visual comparison or by the type # punched into the casting with the number stamps.

Wish I could be more specif about the differences but I really can't rember having both side by side and making notes.

HTH's and welcome aboard.

I hope you'll feel free to help us all by posting all the info you can on the 365BB's so we can all learn together.

Regards, JRV

The car is going to the Ferrari Owners Club national concours in early July. This will give me a chance to comapre the gearbox with some other 365 and/or 512 BBs. If I can find the differences I will post them here.

I will certainly keep posting info on the car. I've also got a 1977 400 so I'll put stuff up on that as well.

Simon