Porsche Enthusiasts Club Forum

It is currently Thu Mar 28, 2024 11:34 pm
Classic Line Insurance


All times are UTC [ DST ]




Post new topic Reply to topic  [ 9 posts ] 
Author Message
 Post subject: Final drive oil filler stuck
PostPosted: Thu Jun 22, 2017 7:56 pm 
Offline

Joined: Sat Apr 15, 2017 8:38 am
Posts: 49
TIPEC membership: 0
Help. I realised today that I have no idea how much oil is left in the final drive box, after leaking since before I bought the car, so decided that even some was a deal better than none. The filler plug is a 17mm AF female steel socket with what looks like ½" BSP male thread. I sourced a chunk of 17mm hex stock ensured it was seating properly and prepared to undo. I stopped my efforts at the limit of what my torque wrench can handle. It seems a bit worrying to be souzing it in WF40, but tried that. Has any one else had difficulty with this? Any bright ideas? I wondered about extracting the road speed sender and feeding oil in through that. Is this feasible? For that matter how is one supposed to pour oil uphill?


Top
 Profile  
Reply with quote  
 Post subject: Re: Final drive oil filler stuck
PostPosted: Fri Jun 23, 2017 10:08 am 
Offline

Joined: Tue Nov 06, 2007 12:22 am
Posts: 1468
Location: Stratford-upon-Avon
TIPEC membership: 4635
Useful to state model and year, as in this case there may be differences in access around that area depending on exhaust layout etc, and differences in the fill plug. On my MY91 I'm pretty sure is was a 10mm allen so finding suitable socket was easy.

You're doing exactly the right thing in removing the fill plug first - better than discovering it's stuck/rounded after draining, as you've discovered!

How are you driving the 17mm hex stock you said you'd sourced? I would invest in a good quality 17mm allen socket for this task - you really don't want to round out the fill plug. If you can't find a socket then you could try a 17mm allen key, with a length of pipe slipped over the long end. There's a risk of not being square to the socket and rounding it, so a better approach with 17mm allen key is to put a 17mm spanner over the short end, insert in fill plug and slide spanner up to diff casing. Then slide a pipe over spanner for leverage. That way the 17mm key is kept nice and square in the plug. But best would be a 17mm socket and a couple of feet of 1/2" breaker bar.

The 17mm hex plug does get very tight if not been removed for years/ever. WD40 is a dispersant not penetrant so won't be much use, and best not to use your torque wrench to undo as it will at best damage it's future accuracy, and at worst break the mechanism. Try to get as shallow head a breaker bar as you have behind the 17mm allen socket, with the car nice and high so there's room for a long bar. I've had success with heating the plug first with a small blow torch, also on another occasion a 3/4" impact ratchet was narrow enough to fit in there with an impact allen socket. With either method apply a proper penetrant (I like PB Blaster but unavailable in UK - PlusGaz is an alternative or 50/50 mix acetone/ATF).

For filling you have couple of options. I used a garden spray pump from B&Q for about £15 which is very handy (just remove the flexible tubing from the lance as you won't be spraying the roses after running gear oil through it). Another reason for asking for model and MY is there was a technical bulletin regarding different fill levels that applied to auto transmission after certain serial number. The other - slower - option is gravity feed by rigging tubing to gear oil bottle and tieing the bottle up in the rear wheel well so it's above the diff.

_________________
928 S4 Amazon Green 91MY


Top
 Profile  
Reply with quote  
 Post subject: Re: Final drive oil filler stuck
PostPosted: Fri Jun 23, 2017 10:57 am 
Offline

Joined: Sat Apr 15, 2017 8:38 am
Posts: 49
TIPEC membership: 0
Stratford shark,
thanks for the tact, one tends to assume every one knows your car, however its a late 1984 auto so transition to some 85 model year details. the plug is plainly steel with a female 17mm. I had an old 17 mm locking wheel nut key which yielded the very good fit hex head, I cut off the outer sleeve which was probably mild steel and then ground the required hexagon on the resultant stub. the bonus was i can grind it to fit in an impact socket, ie its a hexagon not bihexagon, so I can get heavy with it. I have a 3/4" drive breaker bar but the 1/2 to 3/4 adapter makes it too long to fit between the back of the battery box and the casing, I have bent the 1/2 inch tommy bar before and really would like to avoid spoiling the set.
I think heat sounds the most promising approach, so I'll try that next. the great thing is I have a good pit so access is really easy. I also saw one comment on lie where the owner gave up and removed the whole cover, though how that helps I'm not sure as one still has to hold on the the cover even on the work bench, and we are applying quite a load to it!


Top
 Profile  
Reply with quote  
 Post subject: Re: Final drive oil filler stuck
PostPosted: Fri Jun 23, 2017 11:35 am 
Offline

Joined: Tue Nov 06, 2007 12:22 am
Posts: 1468
Location: Stratford-upon-Avon
TIPEC membership: 4635
I didn't even know the earlier cars had a 17mm fill socket, but just goes to show about MY info!

It is tight in there and I recall having to try different combos of socket/adapter/breaker to find something that would fit behind the battery box. A 1/2" breaker shouldn't bend - the spec torque is less than 30Nm i.e. not much, so it's only corrosion and habit holding it in. Mine went with a great crack when it budged!

Am impressed by your improvising with locking nut key, but you may end up with something that is not a perfect fit at one end or other, so increasing risk of damage to plug. At risk of being boring I would get a 3/4" 17mm socket (just checked and there is good quality BGS item on ebay for £12.99) and use your 3/4" breaker, or go the allen key/spanner/pipe route. Will delay you by a few days, but damaging the plug could hold you up for a lot longer!

Removing the cover is something I had to do on a damaged plug on the transmission pan. I know it sounds as if you still have to hold it when applying torque, but the thing is having access let's you get more creative with things like chisels to get things moving, as well as find ways of wedging the cover between objects so you can get some torque on it too. If you go that route you will need to renew gasket too.

Is the car running? I think the WSM says to get the transmission up to temp to make it easier to remove the plug, because of the different expansion rates of aluminium case and steel plug. Nothing to lose trying that first, but local heat should achieve similar effect.

_________________
928 S4 Amazon Green 91MY


Top
 Profile  
Reply with quote  
 Post subject: Re: Final drive oil filler stuck
PostPosted: Mon Jun 26, 2017 10:23 pm 
Offline

Joined: Sat Apr 15, 2017 8:38 am
Posts: 49
TIPEC membership: 0
Well, thanks for the moral support and advice. I welded the hex plug into the socket with the cover in place, the weld ripped before any movement so I took the plunge and drained best part of three litres of oil before removing the cover. Bother, the original mission was to check the oil level hadn't dropped due to leakage. It was nigh on full so I need not have worried after all.
I bolted the removed cover to a large lump of steel angle in the vice then welded the plug all round. I then applied a four foot extension and braced my self against the bench and pulled. It came quite gently, but it came all the same. Now I need a new plug, I'm tempted to machine a different style with a gasket seal. Thread looks like it's M24 fine, pitch is 1.5


Top
 Profile  
Reply with quote  
 Post subject: Re: Final drive oil filler stuck
PostPosted: Tue Jun 27, 2017 12:19 am 
Offline

Joined: Tue Nov 06, 2007 12:22 am
Posts: 1468
Location: Stratford-upon-Avon
TIPEC membership: 4635
Good result - those bolts always succumb in the end!

Correct level or not, your diff will benefit from fresh oil.

_________________
928 S4 Amazon Green 91MY


Top
 Profile  
Reply with quote  
 Post subject: Re: Final drive oil filler stuck
PostPosted: Tue Jun 27, 2017 11:09 pm 
Offline

Joined: Sat Apr 15, 2017 8:38 am
Posts: 49
TIPEC membership: 0
Who'd have thought a plug could be such a pain, my OPC says the replacement is listed but not available, subject to design change, but still the same part number, order from Germany£5. Well that's ok, and what must be the cheapest Porsche part ever, a gasket £ 1.80. Except again back order from Germany. I wanted it sooner so I have a sheet of gasket ins so cut my own. Easy enough. The plug is more of a pain, they are available for MB transmissions on eBay, but for now I turned off the lovingly comprehensive weld of yesterday and revealed enough slightly munched hexagon to still be functional though the tapered thread slipped in the chuck and damaged the thread a bit, I dressed it up best I could and wound on some PTFE tape, and eased it in. Went in quite nicely, but scheduled for replacement ASAP.


Top
 Profile  
Reply with quote  
 Post subject: Re: Final drive oil filler stuck
PostPosted: Tue Jul 25, 2017 8:10 pm 
Offline

Joined: Sat Apr 15, 2017 8:38 am
Posts: 49
TIPEC membership: 0
Post script
The new plug arrived, turns out the modification is a change of hexagon. It's now 14mm female, otherwise no change.


Top
 Profile  
Reply with quote  
 Post subject: Re: Final drive oil filler stuck
PostPosted: Tue Jul 25, 2017 8:56 pm 
Offline

Joined: Tue Nov 06, 2007 12:22 am
Posts: 1468
Location: Stratford-upon-Avon
TIPEC membership: 4635
Isn't it amazing how mission creep can take over the simplest 928 job?

At least you now have comfort of knowing there is a perfect fill plug in the diff, with no damage to the hex for when you next need to change the oil.

_________________
928 S4 Amazon Green 91MY


Top
 Profile  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 9 posts ] 

All times are UTC [ DST ]


Who is online

Users browsing this forum: No registered users and 10 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group