Moss Box oil leak

[Heuer]

Argh!

Just got the new 'Marston' radiator fitted, the original oil filter back in place and all seems to be well. Except on test I could smell burning oil and thought it may be from the filter assembly. But no, seems the rear seal on the Moss box has started to leak and oil is cooking on the silencers. Anybody know if the ?3.50 seal can be changed with the box in situ or has it got to come out?

[christopher storey]

David : this subject has come up for discussion in other threads, and the consensus seems to have been (albeit in relation to all synchro boxes) that with a bit of luck, and ingenuity, it can be done in situ. It may be necessary to undo the prop shaft at both ends to drop/move it out of the way as far as you can , since the main difficulty seems to be getting adequate access to the output shaft large nut. This thread (and a link to another thread contained in it) may help:
http://etypeuk.com/forum/viewtopic.php? ... r+oil+seal
http://etypeuk.com/forum/viewtopic.php? ... 646522aed5

[Heuer]

Well remembered Christopher. I did a search on 'Moss box seal' and nothing came up. Anyway I may as well give it a go and see how far I get! Sounds fiddly and knuckle scraping though.

[Heuer]

Actually my biggest interest is in seeing why a gearbox restored 1,000 miles ago has failed. Over-filling?, poor repro seal?, forgot to replace the original seal? I am taking bets

On the plus side I intend to refill with Red Line MTF which seems to get excellent reviews on J-L and championed by Jerry Mouton who drives his car hard.

[hastylane]

David,

In my experience, it could well be a pitted output flange and the new seal is running over the pitting. The original type of seals had a felt dust seal in the oil seal and the modern replacements do not and the modern seal can run in a different position to the original. The felt seals dried out eventually and then absorbed water which in turn led to corrosion on the seal diameter.

If it is this then you can get sleeves fitted by a machine shop or alternatively get it hard chromed and ground back to the original size.

Regards

Andrew

[Heuer]

Realised there is a small flaw in my plan to replace the rear seal. I have a Motorpit so access is not a problem but I will not be able to tilt the the IRS as I can't get the car off its wheels whilst over the pit. May have to outsource this job after all :? I will ring around a couple of local companies (Ian Nuttal Racing in Nottingham and Paul Brown in Ripley) and see if they can replace the seal without pulling the engine. I have however removed the silencers and gear box support plate and I seem to think the leak could be coming from the speedometer drive. Will investigate further.

[christopher storey]

David : I would be surprised if it is necessary to tilt the IRS . You can certainly disconnect all the propshaft bolts without doing so, and it should then be possible to move the shaft downwards - or indeed upwards - and rearwards sufficiently ( including pushing the sliding portion as far back as it will go on its splines ) to get clearance at the front for access to the nut. from either above or below . However, the speedo drive sounds promising - from memory there is a O ring which seals the drive housing and if this has been displaced/trapped during the gearbox rebuild/installation then it may be your answer

[Heuer]

Good tip Christopher. I have tried removing the speedo drive from below but I can't get enough purchase on it. I will go in from above tomorrow and check/replace the O ring. I will then refill the box and leave it overnight to see if any oil seeps out. If it does it must be coming from the rear seal as the speedo housing is above the oil level. If that is the case I will give it a go at displacing the prop shaft. When I drained the oil I measured 1.30 litres whereas the capacity is 1.42L. Looks like it has been leaking a while from the baked on oil on the top of the silencers so I figure it has lost 0.2 of a pint in 1,000 miles.

[andrewh]

Who rebuilt the Mossnbix David? I have mine done but not used yet. Rebuilding Moss boxes is a contradiction in terms really as you cannot do a full job as the synchro are not available so it at be a compromise anyway

[Heuer]

No idea Andrew without checking the receipts. Amazes me there are so many of these out there but no one makes the synchro's. On the other hand the synchro's for the 4.2 box are rubbish as well. Mine (on the OTS) failed after 5,000 miles and I went with a T5. Something to do with the hardening of the synchro rings I am told. Everybody complains but no one does anything about it! SNGB?

[Heuer]

Progress I think. I checked the restoration records and they did purchase a new rear seal and speedometer O ring. After removing the gearbox top cover I found the following:
The rear seal is new and appears to be working - the shaft is pretty much dry:


The speedometer gearbox has been fitted with a new O ring and does not seem to be leaking any oil:


Oil is pooling on the gearbox support. I cleaned it off yesterday and this is the result after 20 odd miles:


I am now suspecting the selector shaft O ring. The shaft is very oily and in 1st and 3rd gear the selector lever is directly over the prop shaft universal joint. Any oil dribbling here would by spun out over the tunnel sides, which are indeed very oily.:


To get at it I need to remove the gear lever housing on the top cover (4 bolts) but can anyone advise what is involved in doing this? I am thinking of any snags or precautions. Springs, small bits etc etc The manual only talks about taking off the entire gearbox top plate.

[christopher storey]

David : you need to be careful. If you look at plate 14 in the gearbox section of the 3.8 parts list, you will see that there are 3 ball/spring/plunger arrangements, with an unspecified number of shims at the very top under the selector housing ( parts 27-30 inclusive ) and these are retained under compression between the selector housing and the top cover. It may well be that as the holding down bolts are gradually unscrewed the compression on the springs is released ( provided of course that the housing is not being held down by a sticky gasket ) but it seems to me that you need to ensure that the housing comes up gradually as the bolts are unscrewed, and does not come up with a sudden leap, and that you can gather all the bits without them flying out in all directions, noting how many shims are on each plunger

[Heuer]

Thanks Christopher

Did as you suggest and found three springs but no shims (although someone has been in here before me at some time. Gasket was completely shot so that could have been the first culprit and I won't know about the O ring until I get it out - the support washer has been peened in and never removed so after 50 odd years maybe does need replacement. Other than that the pivot was a bit stiff with old grease, someone had used a locknut to hold the gear lever in place rather than the slotted nut and I will replace the rubber bushes whilst I am in there.

Next problem - SNG don't seem to sell the gasket C13338 or at least it comes up as 'no such number' on their web site

[christopher storey]

David : You usually have to buy gearbox gaskets as a set in my experience and just use what you need out of it

Edit : just looked and a set is ENT 101 and about ?8 from SNGB

[Heuer]

SNG have the kit but is specifically does not include the top housing gasket Nor do they sell it separately However once again Andy at Hutson's comes to the rescue as he has the ENT101 kit that includes the gasket and, a part complete set out of which he will fish the C13338 and send it to me first class at a reduced price! What a guy!

Next question - what is the best way of removing the peened in O ring and its retaining cup - Dremel with care; relieve with a sharp knife/screwdriver - is only allo?

[christopher storey]

David : Glad Andy has sorted you out. The picture of ENT 101 in the SNGB site specifically shows a selector housing gasket ( 4 bolt holes at the corners and 3 in a line at the rear for the plungers )! As far as removing the Welch plug I think the only way you will get it out is to drill it and lever out with a screwdriver. Then , of course, all you need is a new Welch plug ....

[Heuer]

It is not the Welch plug Christopher - that is as the other end - it is the washer nee retaining cup seen at the bottom of the picture. Basically there is an O ring, held in place by the retainer, held in place by being peened in two spots; the oblong dents either side of what looks like the black ring.

[pmansson]

Interesting that David is planning to use the MTL in the Moss box. I use that oil in all my BMW gearboxes. My mechanic says this is the best compromise with regards to quietness, ease of operation, longevity and overall quality.
Please report on your findings after a couple of drives.

[Heuer]

I already use it in my Porsche 993 on the recommendation of other owners and it does indeed improve the synchro action. I have now fixed the oil leak so will be putting the Redline MTL in shortly. It is not cheap though, about x4 the cost of standard gear oil and only available in quarts so there will be a pint left over.

The leak turned out to be a) missing O ring on speedo gearbox, b) worn O ring on selector shaft and c) disintegrating gasket on selector assembly.

[Heuer]

My Moss box oil leak is still there. After a trip to see Angus I had quite a headache caused by fumes in the car so I resorted to fitting a gearbox gaiter from an S3 which worked perfectly and my last outing was completely fume free ....................... until I got out of the car to be met by the smell of burning oil. Having cleaned the outside of the box thoroughly when I last went leak hunting it was fairly easy to see (via a bore-scope) the leak was coming from the bottom of the rear seal:

Side nice and dry:


Bottom:


To remove the seal on the Moss box it needs to be either pressed out or possibly levered out with a screw driver. So theoretically just a matter of separating the prop shaft and slipping it off although getting it out could be difficult but my biggest concern is how to get it pressed back in correctly. There is limited access from the top and no access from below. Anybody done it?