Leaking transmission output seal?

[Peter Cripps]

In the noisy gearboax thread, Paul mentioned that "the output shaft oilseals often leak".

I think I have this problem. Symptoms are that gear oil seeps out of the join between the inner CV joint and the transmission output. Not much, but there are always a few drops on the garage floor in the morning.

Looking at the parts manual, it seems that the output seal can be replaced with the transmission in place. If I'm understanding the setup correctly, I will have to get a tool to undo the special castellated nut on the end of the output shaft?

Any advice or comments? Thanks,

Peter

[Huib]

If oil leaks out of the joint between inner CVJ and flange, it is not the seals that are leaking. If seals leak the oil would be on the outside of the flanges.

If oil comes out of the CVJ, the leakage is between the half axle and the inside of the flange. The half axle is the shaft coming out of the differential. On S2 the flange is put on the half axle and then fastened by bolting a steel disc on it with two M6 bolts going into threads in the half axle. Under the steel disc is a thin copper disc to avoid leakages. If there is play on the splenes, which there usually is on S2/3 cars the M6 bolts will snap and oil will leak around the steel disc and the copper disc. You wish you had S1 flanges and CVJ's.

The way it is usually solved is to use the thickest Locktite on the splenes and not over torque the M6 bolts to allow movement. With play on the splenes and the Locktite it is virtually impossible to get the flange at exactly right angles with the half axle. If you do this on a gearbox on the bench and drive the input shaft with the electric drill, it looks like the flange is totally out of balance. You would expect to feel vibration when driving the car. In practice I have never actually felt the vibration.

[Peter Cripps]

Huib,

Thanks as always for your very detailed reply. Just to make sure that we're talking about the same thing, here's a picture of where the oil seeps out:



If I understand you correctly, I can apply the fix you describe simply by unbolting the inner end of the driveshaft, dealing with the M6 bolts and Locktiting the splines?

Incidentally, I see that the CVJ boot has "FIAT" moulded into it ...

Thanks again,

Peter

[Huib]

Yes. It is the M6 bolts. Oil leaks into the CVJ first and then out of the CVJ.

Don't forget to light some candles, say prayers and hope for the best when fixing the problem. The remains of the broken off M6 bolts are usually easy to remove. If very lucky a left hand drill is enough.

I don't remember if you can get to it by just unbolting the inner CVJ from the flange.

Note that it is the right hand side. The M6 bolts as well as the 6 Allen key M8 bolts have a tendency to turn themselves loose because of the rotation. When assembling the mating surfaces of the flange, spacing ring and CVJ should be absolutely free of grease. Also any threads. Torque the M8 Allen key bolts well and lockt the M6 bolts with red Locktite, medium strength.

[P. de R. Leclercq]

A Evolution Engineering, it was our policy first to throw away the normal M6 bolts - even if they hadn't broken, which they often do, and replace them with 12.9 grade socket cap screws. We used then to anneal the copper discs (heat them red-hot and let them cool naturally) so that they would seal better.

As for Loctite on the splines, well of course this would prevent slack etc., but having once spent an entire day (unsuccessfully at that) endeavouring to extract a Loctited driveshaft from a hub on a Jaguar XJS (Jaguar recommended the use of Loctite) I am now very reluctant indeed to use Loctite on splines - just in case I have to take the bloody thing apart again! The attempt, as a matter of interest included a good part of a bottle of acetylene, a 20-ton press and a very large hammer, none of which of course, had any effect at all. So if anyone wants an XJS rear upright with driveshaft, including a clapped-out pair of wheel bearings, they know where to come!


Paul

[Huib]

Did the 12.9 grade M6 bolts hold?

I have used those on a number of occasions but wondered if they would be strong enough to transmit the power to the wheels and found it difficult to decide between a solution aiming at holding the thing in place with stronger bolts or allowing some movement to avoid breaking.

I also thought of drilling an M14 or if possible larger hole in the shaft and use a larger bolt.

[P. de R. Leclercq]

Well, of course they are only there to keep the output flange in position, the drive being tranmsmitted by the splines. We had no trouble with them - we used to use red Loctite sine you obvioulsy cannot use tab washers. My own retaher old-fashioned preference is for stainless steel lock wire.

Paul

[Peter Cripps]

Very interesting discussion, thanks Paul and Huib.

Now I know what to do when I finally get around to fixing the leak. However, as Italian cars go, it's not a big deal - as I say, just a few drops after every run. So it may be a while before I get in there and attend to the now-famous M6 bolts.

Peter

[P. de R. Leclercq]

I have thought a bit more about this. Whilst I prefer not to Loctite the splines, I would be inclined perhaps to coat then with high-quality (usually black) silicone sealant; this would prevent oil escaping along the splines if they are a little worn.

Paul

[foggy]

Hi Huib,
I have this exact problem with an HF I've just rebuilt the engine on, I ran it up the road and back (2 miles) and when I got back there was oil dripping on the floor from the nearside drive shaft, on a very close inspection the drip was coming out of the joint in drive shaft coupling and I couldn't understand how? now after searching I find this thread, do I have to completely remove the drive shaft or can I do it just by undoing the six allen bolts and lowering the shaft?
Thanks,
Tony.