Mondial 3.2 Differential - Help

I redid the diff seals on my 1988 Mondial 3.2 last winter, and despite meticlous attention to details and following the lead of various Fchat threads, Birdman, etc. the seals leaked anyways, actually worse than the original seals I replaced. The right one notably more leaky, not extreme but still weeping and flinging gear oil onto the header leaving a burnt oil smell in my garage after a ride.

So I am at it again.

Can a pro confirm if the right side seal is supposed to be a depth different than in the picture? I also note the diff hub surface looks very nice, I had sanded it lightly as noted in the threads. No wear grove from the original seal. I used the Hill seal installer, so the seal should have gone in nice and straight.

Also, can someone re confirm the same silicone sealing around the diff hub bolt and splines is necessary on the left side? I did that last time, but just emulated the approach in eg. Birdman for the right side diff seal hub, made sense from what I could see. I have not found any thread dealing with the right side seal installation.

What am I missing? I am not even sure I want to remove the seal I had put in, there is no sign of any damage. It should be sealing. Maybe just resand the hub seal surface more thoroughly, maybe I did not sand non directionally enough? Or did I just get some bad seals?

I don't want to do this over again!
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Did you check the ID of the seal and the OD of the hub? Even though everything looks great, if there isn't enough distortion of the seal's mating surface, you will have a leak.

 

I did not measure these things, but I did test fit the seal over the hub originally and it seemed snug enough.

From the factory, did these seals weep a bit until the break in, ie. I only put on less than 1,000 km since I did the seal job, maybe takes longer to seat the seal?

 

The figure in the 308QV/328 WSM shows that the RH lip seal should be driven in against the shoulder in the housing:
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That said, where yours is riding on the hub diameter doesn't look like it should be an issue (but fully seating the lip seal would be better -- if your housing does have an internal shoulder). Any chance that the lip seal that you got is "directional" and is mounted in the wrong direction of rotation? Andy (tuttebenne) recently mentioned that David Feinberg (www.sarasotaitaliangarage.com) sold an upgraded "double lipped" diff seal so you might consider trying that:

https://www.ferrarichat.com/forum/posts/148239688/

Maybe also try to get a finer, more non-directional, surface finish on the hub OD. Maybe it's just the lighting in your picture, but it sort of looks like a bit of a RH screw thread flavor that would push fluid out when the hub rotates in the forward direction.

 

How much axial play do you have on the axles ? if to much play, hubs can open the seals more then needed.

 

Good question, will investigate this, thank you.

 

The differential seals in the 308/328 transaxle were never much of a problem so something is wrong. I can't remember the last one I replaced. As you can see due to the length of the sealing surface on the output flange there is huge latitude in seating depth of the seal. One thing you never do is seal the OD of the seal. Ever seen a factory do that? Do it their way for best outcome. As Steve suggested, make sure it is not a directional seal going the wrong way. I also agree I really do not like the condition of the seal surface. Polished is a better word than sanded. Also make sure that the trans is not over filled and the breather is unnobstructed. Is it possible it is leaking out from behind the CV joint? The bolt/washer needs a good amount of sealant oozing out to prevent that.

 

I did indeed coat the outside of the seal, based on the Birdman tutorial, but I get that the rubber exterior of the seal should seal fine on its own.

I am going to put in a new seal, and dress/polish the sealing surface on the flange. I will also check for unusual run out of the spline. Should the flange have some grease on it when assembling, or should his be dry? I get conflicting info. online, some say the seal surface needs to wear in dry to break in, others like Birdman grease the flange sealing surface, which I would expect was common practice, but the new seal compounds may be better off installed dry?

As far as I can tell the seals are not directional, there is one Ferrari part number for both sides, 125078.

 

The spline wobbles around some. It is in fact the side gear of the differential. Dont see how it could have a run out issue. If needed for lubrications sake I do often use some silicone grease on the seal outer. Check the breather and oil level and generous sealant on bolt and washer or it will pour out of the hollow shaft and around the splines.

 

Got it, thank you.

 

That's true -- that the design intent was to use the same non-directional lip seal on both sides, but sometimes errors get made in the supply chain. Usually directional seals have a little arrow molded on them on the outside surface to indicate which way the shaft should rotate, and would have little angled ribs molded on the inside of the outermost lip that contacts the shaft surface that would tend to redirect any lubricant dragged by the shaft rotation back towards the "wet" side (and, conversely, pump it out to the "dry" side if used with the wrong rotation direction). You've probably got the right thing, but just wanted to suggest that you give any new lip seals a close inspection even if from a usually reliable F parts source -- a lot of unreliable humans are involved in the process .

 

Great insights, will check the new seals closely.

I am thinking the problem may simply be that I did not sand the sealing surface carefully enough, have resanded with 800 grit and then 2000 grit in a circular omnidirectional way. Not quite polished, but not really any meaningful sanding strakes either. Combined with a new seal, will see how that goes.

 

These are the new seals. Also, a close up of the output flange sealing surface as finish sanded with 2000 grit.
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The little "key" mark is in the same direction on both.

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I have the old seal out, and I measured the inset to the inner shoulder at 14mm deep. The seal is about 10mm, so if the seal was pushed in right to the inner lip, that would inset the seal in the casing quite a bit at 4mm. I don't recall the original (I presume) seal being in that deep last I did this, more like flush with the face of the casing ie. not inset much at all.

I can't find anything in old threads that is clear on this left hand side, nobody has a picture of what is normal.

Are you sure I should install the new seal in that deep? Would also make it harder to remove if god forbid I have do do this again in this lifetime.

I appreciate any further perspective on this.

 

Yes -- fully seated (about 4mm recessed) is how it's shown in the WSM figure (see post #4).

Just drill, or punch, a hole in the old seal, drive in a sheet metal (or drywall) screw to have something to grab onto, and pull to remove an old seal (not my photo, but this is the idea):

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Here is the only pic I could find from an old Fchat thread on this right side seal...no idea if this is correct.




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Here is a picture of mine with the seal out....
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Looks about right. There's a pretty big chamfer on that particular example so it doesn't look set in so deep, but, from the outside face, I'd call that ~4mm recessed.

 

Thank you very much for the greater certainty on this.

And, yes I removed the seal using the drill and screw approach as you suggested. A bit unnerving to drill in there, I wish there was a useful seal puller, I bought one that looked good but it could not grip the lip properly, and that spline gets in the way of many types of pullers. So the old drywall screw method and prying out seems the way to go.

 

Don't disagree. Many slide hammers come with a small "hook" end attachment that can also be used to jerk a lip seal out without needing to make a hole (even with the center splined shaft in the way).