550 Differential Broken – NIGHTMARE, help!!!

Sorry to hear that the weak diff story that started with the Daytona is still with us. Also sorry it happened to you.

First get it appart enough to be certain what you are dealing with and make a parts list. Next, FNA has a habit of requiring you to buy complete components when in the rest of the world Ferrari will sell al la cart. Try Ricambi America or Ferrari UK and see if parts are available that way from across the water.


BTW as with most driveline failures, what you were doing when it quit was not what broke it. It was a prior event or lifetime of events that killed it.

 

From the diagram, it's a German ZF LSD. Hopefully the spider assembly (if that's what has gone) is available from the manufacturer, as there's a good chance it's a unit common with other large-capacity vehicles (big BMWs, etc?).

 

I'm sure it's unrelated, but what brand of gearbox oil were you using?

 

Probably not. My 740iL had a recall as the transmission was known to fail if the wrong gear oil is used.

 

My uncle had an old International tractor that broke an axle. He couldn't get the part because it was obsolete so he had one made. If you could find a good machine/fabrication shop they should be able to make something that would work. I guess it would depend on what actually broke, I''m not really clear on what you actually broke. I know for a fact that companies like Strange Engineering will make custom length/spline count axles for hot rods so they might be worth a shot. As I recall, they only charged like $350 for a custom made set of axles for a mustang with whatever spline count you wanted. Might be worth some research, hope that helps.

 

Do you perchance have the ZF numbers stamped on the side of the diff housing? Not sure if it will be fruitful, but you could try to search for a diff for an alternate car with the name numbers. This presumes that such a beast exists


Lou

 

Hey Eric,

Sorry to hear about your "dif"ficulties . Having just finished going through gear box troubles I feel your pain. While I had my gear box apart I rebuilt the dif too. Nothing was busted, I just atlernated the cross plates and abrasive disc, the same way they are in your car. You can read about it here, with pics even http://ferrarichat.com/forum/showthread.php?t=102751

Going by the diagram you posted your dif looks almost exactly the same as the dif in my 348. So it is pretty simple to take apart.

From what you are describing I'm gonna have to guess that the cross bracket/s, that hold the spider gears in place, is busted and you could also have destoryed the spider gear/s, maybe even the sun gear. You won't know what kind of carnage went on inside till you take it apart. I'm hoping it is just the cross bracket that is busted. The reason I think it is the cross bracket is because you are hearing noise. The spider gears are mounted on the ends of the bracket, and if the bracket is broken it won't hold the gears properly inside the cups and will alow the spider gears to disengage from the sun gear, that is the one that looks like a pinion gear that the axle flanges get bolted to. Anyway, if the spider gears disengage from the sun gear, they won't be able to apply the proper preasure against the cups, to get them to spread so that the cross plates and discs lock. Which is why the car wouldn't move even though it was in gear. It is also why you were hearing the noise.

So the only thing for you to do it tear appart the diff to see what kind of nightmare you are dealing with. Hopefully you will only have to replace the cross brackets and maybe a spider gear.

You can try calling ZF's automotive and see if they can get you what you need (847) 478-6868 or try the website http://www.zf-group.com/am/pc/pt/ampcpt05.phtml It would be best if you had the numbers ready for them when you call. Ferrari DOES NOT make any of the parts for the gear box, they are made by Zahnradfabrik so don't even bother with dealing with FNA. ZF makes the tranny so don't give up trying to get the parts you need. Like I said if you have the part number handy I'll bet they can get you what you need. If not, then Dan is your man. http://www.ricambiamerica.com/

Hope I was of some help.

 

Yeah, I'm curious to know what they have to say about it too. Please do keep us posted on it.

 

Bump.

Any updates on the status of the diff?

 

Modena engineering in austrailia makes aftermarket carriers for boxers and many other race proven parts. You can try them as well.

 

If you wanted to know the technical specifics of the diff, it is a Salisbury type differential. As to how it works, the angular gears mounted on the shafts (circled in the pic above) rotate with the diff in operation. Those four gears are the connection between the two half shafts but will rotate when the two half shafts are at different angular velocities (allowing for the differetiation... essentially an open diff).

Where this diff locks and provides its limited slip capabilities are in the clutchpacks to either side of the gears. The shafts, onto which the angular bevel gears are mounted to, stick out and ride on ramps that will put pressure on the clutch packs, locking each side up (independant of each other). The ramps may be profiled to have different locking characteristics for thrust coming from the engine and thrust in the opposite direction coming from the brakes.

The Salisbury type of differential is a pretty good style of diff (Hewland uses this style with their Powerflow diff). It's probably one of the best for a purely mechnical fricition diff as it allows for different amounts of lock from the engine and the brakes. It's much better than a Torsen style or Quaife ATB type diff that rely on on friction from pressre angles between the helical and worm gears in them (essentially an open diff with some torque biasing) and bias torque the same for both the engine and the brakes. It still isn't as good as some viscous-coupling locking diffs. Many top-end motorsports differential manufacturers (X-Trac, Ricardo, etc.) prefer using a combination viscous-coupling and clutchplate combination for maximum tuneability. That's probably the best for passively acting differentials... once you get into active differentials like the F430 has it's another story completely and much closer to an ideal situation.

If I lost you on some of this stuff, check out http://auto.howstuffworks.com/differential.htm. It has some good animations that explain a bit. The clutch type diff they have has a spring in it that provides some preload, but isn't the source of the torque biasing (a little confusing how they have it worded).

Tim