transaxle: mineral or synthetic oil

Most important to use hypoid and NOT helical gear oil in BB. Helical only good for 246/308 series.

Shell, Castrol, Agip all do very good 75w90 hypoid transaxle oils. All these are compatible with limited slip diff too.

 

i use Amsoil 70-90 synth Race 2000 and no need to add LSD additive or mess around with such things. Naturally there is a HUGE amount of info on tranny fluid in the ARCHIVES.

 

I use RedLine synthetic gear oil in my BB512i. I used synthetic gear oil in all 6 of my previous Ferraris as well.

 

Thank you for making that distinction. Learn something new everyday!

 

The original specification for the 512 was Agip Rotra MP 80w90, but here in the UK we generally use Shell 75w90 transaxle oil.


MW

 

vincent -- I don't know if there are any "persistance" differences between the two, but if this is an issue for you -- you're not driving your BB512 enough . Seriously, if this is an issue wouldn't you have the same problem (to an even greater degree) in the engine? Can you clarify "three crowned wheels"? -- are you referring to the three helical transfer gears?

Since I'm in an area where the winter temperatures get a little lowish, I definitely prefer the 75W90 synthetic over the 80W90 conventional (and can notice the difference when the garage temp gets down to ~40 deg F).

Just to clarify Phil's previous point:
GL-4 = OK (even preferred for syncro life) for systems with helical differentials
GL-5 = required for systems with hypoid differentials

 

Oh boy, here we go again.

Ferrarifixer says Hypoid for the BB and Helical is only good for the 246/308 series.

91TR says, GL4 is okay for helical and GL5 for Hypoid

I have read repeatedly through the 100's of threads on this site concerning the correct gear oil for a 308 transaxle and each thread is adamant about using GL5 NOT GL4 in the transaxle.

Is the transaxle helical or hypoid on the BB, the 308.

 

DJ -- I'm trying to say the same thing as Phil (but just adding the API ratings for clarity):

GL4 = helical diff = 246/308

GL5 = hypoid diff = BB

It's not a huge problem to use a GL5 in the helical diff systems -- it's more that with the helical diff you have the option to use GL4 or GL5; whereas, on the hypoid diff you're limited to the GL5.

 

Thank you again for the clarification, now if I only knew the difference between a helical configuration and hypoid.

How do these relate to a conventional differential like in a Chevy or Ford?

(I would research this but I am at work)

I am currently running Redline 75/90 NS with 2 oz. of LSD additive. Perfect performance and shifting.

 

The general rule is that if there's a 90 deg angle required between the engine crankshaft axis and the driving wheel axis it will use a hypoid diff gear set -- although there are exceptions, like a 348, where they have a (straight) bevel gear set between the engine and gearbox to do the 90 deg turn and then have a helical (spur) gear set diff to drive the wheels.

If the engine crankshaft axis is parallel to the driving wheel axis (e.g., 246/308/328), a helical (spur) gear set is most commonly used.

So to answer your (trick ) question -- on longitudinal-front-engine, rear-wheel-drive F and C the diff is a hypoid gear set; whereas, on transverse-front-engine, front-wheel-drive F and C the diff is a helical (spur) gear set.

 

They both feature a helix tooth pattern. The 246/308 layout has the crown gear parallel to the driving gear, whereas the hypoid BB layout has the driving (pinion) gear perpendicular to the crown gear. Also offset (the centre line of the pinion NOT in the centre line of the crown gear).

...Am I correct or did I just mess that whole thing up?

 

I wish there was a "live" function to this site, where I could see someone posting while I'm typing...

 

Peter! You're just saying this to mess me up aren't you!

Seriously, I think I know what you are saying but I am not sure because of terminology. I am used to the terms ring and pinion but am at a loss when 'crown' is mentioned.

I think 8 X 10 glossys and a few exploded diagrams are in order.

 

Crown gear =Ring Gear?
246/308 has a pinion (drive) shaft parallel to the Ring (Crown) gear centerline.

512BB has the pinion(drive) shaft perpendicular (90 degrees) to the Ring(Crown) gear centerline.

Yes?

I have pictures of a 246 box at home, I'll figure it out.

 

IME F uses "crown gear" = "ring gear" so they describe things as "pinion and crown" rather than "ring and pinion" (whether it's a helical spur gear set or a hypoid bevel gear set)

This is a helical spur gear set (note the pinion axis is parallel to the ring gear axis) -- in theory, the teeth engage only in a "rolling" action against each other:

 

And this is a hypoid bevel gear set (note the pinion axis is perpendicular, and offset as Peter mentioned, to the ring gear axis). The teeth engage in a combined rolling and sliding action -- it's the sliding action that requires the GL5 rated lube:

 

Thanks Steve,
While we were away I found a picture of the 246 box with the spur set exposed. Logical for the configuration.

So I am curious, if the BB is hypoid I am assuming the TR is also? It wouldn't seem they would have enough room beneath the engine for a crown(ring) gear of sufficient diameter.

Sorry to drag this out but it's new stuff! I like new stuff!
This discussion of helical/hypoid also explains the different lubrication requirements. I would love to get AEHaas on this to explain the finer differences in the oils.

 

You're right on both counts:

1) TRs have a hypoid bevel gear set diff, and

2) the size of the ring gear is one of the reasons why the TR engine has to be positioned higher than is really desirable.

 

Anyone know why the pinion is offset in hypoid gearsets? Noise?

 

Less noise and better smoothness are the main reasons, but (IIRC) the teeth on a hypoid bevel gear pinion are also beefier (and therefore stronger) than the teeth on a straight bevel gear pinion of the same ratio.

 

Thanks very much for the illustrations and descriptions. I feel smarter already! Great stuff!

Wondering if they could have used the "T" configuration transaxle on the TR to reduce height? Hmmmmmmmm..........