Are Ferrari differential internals common to anything else?

Hey all,

Anyone know if the diff of the 308-348 is the same/similar to anything else out there?

Like spider gears & shafts, etc.? . . I bought some thrust washers one time when I tore one down and the guy implied "they're just ZF parts" .. is the same true of any hard parts in there?

I've hurt mine but it had a lot of end play and wear on the spider gears/shafts (think that's the term?) when I put it together which I could never get a tolerance on (clearance seems like .004" factory and .006" with wear on dia's ... .022" end float though .. Yikes!!! . . . a ton when you wiggle the CV joint if they're loose) . . if these are F parts only I'll use a spare and shim the assembly to minimize end float with the gear wear .. . anyone know what I'm talking aobut?

I'll post some pics .. . someone might recognize the diff assembly for a P car or something????

thanks & cheers.

 

end float I'm referring to is the "sun gear"/output shaft that the flange bolts on .. end float relative to the diff housing itself.


I'm not referring to end float of the diff itself in it's bearings.

cheers

 

G50 or 915? .. . thanks . .you knew this would happen

 

or non 911 variant?

 

is there a possibility the "sun gear"/output shaft I'm referring to lurk's in P car diff's somewhere??????? friend ?

 

I have a couple spares already but each of them seems to have pretty significant end play on the shafts, the driver side specifically. I looked at measurements I've taken over the years when I've had diff's apart and they all had wear on the shafts and gears. This failure makes me want to "tighten" this area up, so if there's some stout Porsche parts or aftermarket race parts to put in there I'd sooner do that than just destroy my inventory.

What I'd like in a perfect world is new spiders, spider shafts, and output shafts. Or possibly an entire diff that I could machine for bearings and the gear? Even if this cost a bit more than just replacing the guts of my diff I'd be okay with that since I'd no longer be destroying the factory pieces .. see I care .


cheers

 

The output shafts are what I'm concerned about since that's what I've seen a lot of wear on with the diff's I've pulled apart (on the gear teeth of this component). That piece has the spline built into it but makes sense wouldn't be unique to Ferrari. But like I posted, I would luv to run a new diff that I just modify for the 308 bearing and gear arrangement.


cheers

 

I don't like that

 

I swear it's way tighter on one side of one of the diff's I have .. . . I'll measure it with an indicator and get a number . . .thinking like .01" when all snug .. . that end play is compounded by the gear wear .. if there all new might only be .01 .. .022" where I assembled and had .002-.003 wear on all the spider shafts on the diff's I've had apart . . . I guess the end play is all relative but I think I could shim it down to like .004/.005" and that'll capture everything tighter and not break any teeth again.

 

you're right .. . other side doesn't have any studs or anything to crash into even with a ton of slop so no washers needed ... there's a reason for everything I find . .. and under normal driving forces the spiders push the axle shafts out ... but there's no reason one side should be looser than the other . .. I've come up with load reasons in my head why the driver's wears more than the passenger and swapped them from left to right one one gearbox .. . tightened it up nice for a while.


I think there's a benefit to hand fitting this area . .. factory clearance on the spider to shafts was .004" ... that seems like a lot but might of been necessary for gear clearances at initial assembly ... . sorry for taking up bandwidth .


cheers

 

Thanks for the info Verrel!!!! ... bet he can answer some end float questions intelligently also.


I was just talking with my one of dune buggy buddies. He converts his diff's from 2 spider to 4 spider and this end float I'm referring to on the output shafts was something he specifically shims out. The punishment his little Corvair diff sees on the dunes is way beyond what I do. I think a brand new diff would only have a few thou end float .. when I was chatting with him on the phone, he set his up at .002-.005" back in the 80's "the last time he did his" ... I mentioned the .02-.03 I've seen and he said "you're asking me why it broke LOL?" ... not to mention worn CV's aggravating the problem.

cheers

cheers.

 

yeah they can . . . but I am also seeing MASSIVE wear on the output shaft teeth and the spider shaft bores and shafts . . . probably has something to do with why the 348 diff is "open" with the same diff . . never would've made it off the showroom floor with the extra power otherwise .

the diff that's in my car right now had not too much wear on the teeth but wear on the spider shafts and bores . .. . looking at my notes it had about .02" end float when I assembled her. From the experience of others this seemed acceptable ... even called the local guru to get an actual number for it but was told "there's a lot of slop there" . . . but 350 hrs of fun later something has failed in there . . I found a piece of tooth on the magnet . .pulled the sump cover off and luckily nothing else got touched . . . my gut feeling is if I would've shimmed this down to .005" this would've never happened. I think I've found another forum where I can get in depth analysis on issues like this hopefully ... principles should be pretty universal once you get down to this level .. don't matter if it's a Ferrari or a Dodge.

cheers,

Sean

 

Brand new parts available from my typical parts guy for "not the end of the world" pricing and used pieces available too if budgets are tight. I'd like to have a brand new set just so I know what they measure from factory and see how much end play I end up with. Like I said in the initial post, I did meaure some wear on the parts but had no experience and with all the other "balls in the air" I didn't want to get into diff analysis. No spec's in the WSM either. It was way tighter than the diff that came out of my car and It's not a common failure. And it seemed like there's quite a bit of clearance on the spiders & shafts from the factory which adds to what is probably considerable clearance between the gears which guys who work on these cars all the time observe. There's a thrust washer in there from the factory that I've seen the ear busted off on a couple of diff's (small soft metal part). I remember thinking that the end float could almost pull the thrust washer tab out of it's hole on some diff's I've seen. Worn out CV's didn't help with it all either . That thrust washer is specifically the feature that compensates for this end float, although different thickness aren't available, I don't think??? I didn't specifically ask that. If not I was just going to improvise something.

No matter what the model of car, seems like a smart thing to minimize this end float. I gotta quit thinking about this and get some work done!!!

cheers

 

Passenger side had .012 end float, driver side had .025". One of the pics shows the excessive wear I see on the output shaft teeth. Another pic shows the wear I've commonly seen on the spider shafts. Also pictured is the infamous "preload" spring and the thrust washer with it's retaining tab broken off. Also note the 2 different style bolts that were holding it together . . original "ground shank" Ferrari bolts and some "12.9's".

Enjoy . . was fun after cutting rock all day

cheers
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chime in if these internals look common to a specific other car/model.

 

Been told it's the same as a G50 and this guy has beefier internals. I'm waiting to hear how much end float the Porsche guru's set 'em up with . This guy commented the excessive wear is a lubrication issue so definitely going to Redline for gearbox oil. I'm thinking his opinion is based on running this diff hard in Porsche race cars so that makes me feel good .


cheers

 

Be nice to have a number. "A lot of end play" to mechanic #1 may not be "a lot of end play" to mechanic #2.

 

the output shafts are different though . . .bummer.