Are Ferrari differential internals common to anything else?

So rock your output shafts in and out ... see if one feels looser.

 

You trying to get me worried now?

Hang on....

 

Can't feel any at all with the car on all 4, but the angle of attack is somewhat wanting that way. Where it is now I can't get further under it. There us certainly no excessive float decernable. Car has 85.000kms, GTSi Euro.

 

if your CV joints are good and snug definitely makes it harder ... that's a good thing. I could just reach down from above thru the engine bay and rock 'em all over before I replaced CV's.

cheers

 

I just did a simple calculation using some random figures. In a turn with a 30 foot radius to the inside tire, and a 35 foot raduius to the outside, the outside wheel only turns 7% more. But on a tighter turn, one with a radius 16 feet to the inside, and 21 feet to the outside, the outside turns 35% greater distance.

Using a 27 inch diameter tire around a 90 degree turn, the tires, or,the axle themselves in this case, would rotate 6.7 turns on the inside wheel, and 7.2 turns at the outside. IOW, the outside only turns 1/2 a turn extra. On the tighter radius, the inside turns 1.7 times to the outside turning 2.3.

While this is roughly the same distance, a tighter turn being generally accomplished at lower speed, it could be assumed the car would most likely be in first gear, where wider turns are almost always taken in a higher gear, in this case probably second. Even at light throttle, the torque available in first gear is much more than what is available in second, even if you gave more throttle in second, so the loads down at the differential could easily be double in a tighter turn. IOW, even though the outside advances about the same revolutions per turn, tighter turns are most likely putting much greater pressure on the outside gears than would be seen on wider turns. And because right turns are tighter in LHD countries, we should see more wear on on the left side gears.

 

Always good to toss some numbers around.

Was it determined where the wear on the teeth occurs? Is it in the driven direction, or the 'overrun' direction?

How much of your driving do you do at full lock in first gear though, and then with a healthy dose of throttle? A diff is supposed to facilitate this, and if it can't withstand tight turns I'd say it is inadequate. This, of course, not taking any abuse into account

I had another thought last night, but it's somewhat difficult to check on the car without taking the suspension apart: could this damage occur as a result of a force inward applied by the driveshaft due to, for instance, some collapsed busshes in the lower A-arm?

 

Many of these cars are 30 years old, and most of them have far greater mileage than they indicate, some perhaps ten times or more what they indicate. All things considered I would say they have held up quite well. And because the drive axles freely telescope lengthwise, there is really nothing in the suspension that would push or pull the side gears and create more wear. And even if it were possible, we would be seeing wear randomly spread between both sides, not just the left by itself.

Remember that the tighter the turn, the greater the differential is binding trying to slip the clutches in the clutch packs, and additional torque must be applied just to keep the car rolling. The differential chatter we have experienced or seen discussed takes a great deal of power, and its magnified as the turn tightens. If you have tried pushing your car around in the garage you will have noticed that the tighter the front wheels are turned, the more difficult, if not impossible it becomes to move the car by hand. But when the engine becomes the motive force, the torque spreads the diff side gears out against the clutches and demands an even greater amount of torque. So while you may not realise your stepping on the gas any more in a tighter turn, the added drag in the clutch packs would require additional power just to give you the same seat of the pants acceleration.

Perhaps side gear slop could become another item to determine a cars true mileage?

 

Driven direction.


As I stated before, it's very interesting that the Porsche race cars wear out diff clutches before they do this part ... so I'm told.

Cheers

 

Dug up an old thread. The splined differential output shafts (left/right) have end play, that's not my main concern. The concern I have is "wobble" or radial movement. Presuming this indicates worn shafts. What is normal or acceptable radial play? New seals will leak with excessive wobble. The current seals are 45mm, thinking of going down to 44mm. But that is only a band aid.

Has anybody had any luck with replacement shafts?

Cheers Wayne

 

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