Are you going to weld a big nut to the new filler plug, before you put it in ? Jules

Not a bad idea. Earlier in the thread someone mentioned wrapping a bit of PTFE tape around the threads before fitting the new one so I was going to try that. I'm just not sure if the resistance comes from the threads or from the flat underside of the cap head. If it's the latter then the PTFE won't have any effect. I suppose if could be a combination of both, in which case PTFE would be of some help.

As there isn't an O-ring on the cap I could just reuse the old one?? Either way I think I'll put a very thin smear of copper grease on the underside of the cap head, PTFE on the threads and copper grease on the head to stop it corroding.

There may be a good reason not to do this so please don't take my word as gospel, if I were going to remove the cap for the first time I would remove the AT controller, cover the electrical connector with gaffer tape or similar, put wet cloths all around the fill cap to keep the transmission case cool (and protect other components) and then get some heat on the cap from a blow torch (ideally with MAPP gas). I think it was the heat of the welding that broke the hold so it might not be necessary to break out the welder. OBVIOUSLY there are safety concerns around using a blow torch in an engine bay but I hope we're all grown up enough to manage those risks. 2010 Freelander 2 HSE TD4 Auto

Just thinking ...
I'm not sure putting a copper grease between steel and aluminium is a good idea based on my limited knowledge of chemistry. Maybe a silicone grease would be better.

The filler plug is a bad design - a torx socket facing upwards for all the muck to collect and corrode the splines in something that gets really really tight - almost designed to fail


Anyone tried an impact driver on the filler plug ? Jules

Silicone and rubber the love affair that is forever

jules wrote:

Just thinking ...
I'm not sure putting a copper grease between steel and aluminium is a good idea based on my limited knowledge of chemistry. Maybe a silicone grease would be better.

The filler plug is a bad design - a torx socket facing upwards for all the muck to collect and corrode the splines in something that gets really really tight - almost designed to fail


Anyone tried an impact driver on the filler plug ?

CaptainBarnacles wrote:

Not a bad idea. Earlier in the thread someone mentioned wrapping a bit of PTFE tape around the threads before fitting the new one so I was going to try that. I'm just not sure if the resistance comes from the threads or from the flat underside of the cap head. If it's the latter then the PTFE won't have any effect. I suppose if could be a combination of both, in which case PTFE would be of some help.

As there isn't an O-ring on the cap I could just reuse the old one?? Either way I think I'll put a very thin smear of copper grease on the underside of the cap head, PTFE on the threads and copper grease on the head to stop it corroding.

There may be a good reason not to do this so please don't take my word as gospel, if I were going to remove the cap for the first time I would remove the AT controller, cover the electrical connector with gaffer tape or similar, put wet cloths all around the fill cap to keep the transmission case cool (and protect other components) and then get some heat on the cap from a blow torch (ideally with MAPP gas). I think it was the heat of the welding that broke the hold so it might not be necessary to break out the welder. OBVIOUSLY there are safety concerns around using a blow torch in an engine bay but I hope we're all grown up enough to manage those risks.

jules wrote:

Just thinking ...
I'm not sure putting a copper grease between steel and aluminium is a good idea based on my limited knowledge of chemistry. Maybe a silicone grease would be better.

I have read all of the replies to your dilemma, this is what I would do, purchase a new plug from a main dealer and measure the thread shoulder from the top surface to thread width.
Carefully drill an eight’th drill bit hole all around the lip surface, use a hoover possibly a Henry type as it has quite a good suck, as what your looking for is to release the pressure between the surface and the gearbox case, removing the outer rim and then possibly the centre part of the plug might unscrew? If not Cross threaded?
Sounds bloody awful but it might solve the problem.

Or? Buy some metric taps drill down the centre of the plug again using the hoover again to suck up the particles and then re tap a smaller thread using grease to hold the cuttings and re tap a new thread with a bolt of suitable size and a copper washer. End of the day it’s a filler plug.

I once had a similar problem with a transfer gearbox on a Mercedes unimog level plug/filler where the owner/farmers son had rounded off a 14mm Allen level plug, I drilled out the centre and re tapped a new thread and fitted a 13mm head bolt as the level plug, it never leaked and never failed. The vehicle is now ploughing up some field on the Isle of Man and every year since I get a Xmas card from the owner, some 45 years ago and it’s still ploughing.
No harm in trying.

Use tapping fluid when tapping, you get a much better quality tapped thread. Use a 'taper' tap. Not intermediate or bottom tap unless the hole bottoms out. Also a Sutton tap, not Chinese rubbish.

When tapping, half turn forward then quarter turn back & repeat. More critical the smaller the tap. Procrastination, mankind's greatest labour saving device!

Acoustic insulation ARB TPMS 3xARB air compressors After cooler Air tank On-board OCD pressure air/water cleaning Additional 50L fuel Carpet in doors ABE 2x1kg Waeco 28L modified fridge Battery 4x26ah Solar 120w Victron MPPT 100/20 DC-DC 18amps 175amp jumper plug Awning 6x255/60R18

Discovered that plumbers PTFE tape gets eaten steering fluid (nicely taped threads were leaking after a year), but then it's not like the filler plug is constantly in contact with the oil like the steering fluid lines would be... Was surprised as it's supposed to have some pretty good hydrocarbon 'resistance'.

jules wrote:

Just thinking ...
I'm not sure putting a copper grease between steel and aluminium is a good idea based on my limited knowledge of chemistry. Maybe a silicone grease would be better.

The filler plug is a bad design - a torx socket facing upwards for all the muck to collect and corrode the splines in something that gets really really tight - almost designed to fail


Anyone tried an impact driver on the filler plug ?

Grue wrote:

Discovered that plumbers PTFE tape gets eaten steering fluid (nicely taped threads were leaking after a year), but then it's not like the filler plug is constantly in contact with the oil like the steering fluid lines would be... Was surprised as it's supposed to have some pretty good hydrocarbon 'resistance'.

That is surprising ! I thought that PTFE was impervious to almost everything.

I'm starting to think that I'll keep my old filler plug with a 32mm nut welded on and just remember to free it up every so often (maybe every engine oil change) so it doesn't bind too tightly. Of course if it does the I have all that meat to torque it around with instead of just the piddly torx drive. 2010 Freelander 2 HSE TD4 Auto

Sunday afternoon I was at a loose end so decided to build a mock gearbox filler plug scenario, plus I had an old gearbox casing from a previous project with the thread being the same as a landrover Freelander 2 auto box filler plug,(previous merc unimog days) rummaging around all the junk I keep found three old filler plugs from the auto gearbox oil change challenges of my landy, so I put the old plug plus copper washer into the gearbox casing to a torque of 7Nm then carefully drilled out the Torx area of the plug to accept a flat copper washer but without penetrating the plug cap, and then placed a black cloth below the plug, put plenty of grease onto the drill bit plus a hoover nozzle near to the drilling and put a neat hole through the plug, bearing in mind the wall thickness of the plug was tiny, again using a new tap I managed eventually to tap a small thread into the plug, tried a 13mm head short bolt and copper washer to 5Nm. Seating flat onto the plug top. Using a pressure washer no water penetrated the plug and seal.
Due to the grease and hoover there was no swarf or particles of drilling on the black cloth. Scene inside the landy gearbox.
But serious care while all this was ongoing. It’s just a workshop rig not actual.

Part 2, Yes, so I placed another plug into the same case, 7Nm, marked the plug with a thin black marker and dot punched the circumference of the plug, snapped off an eight’th drill bit to the thickness of the plug shoulder and drilled the dot markings all around the said circumference, prized off the shoulder and the inner plug I was able to unscrew by hand.

The first attempt I would be very happy indeed although care with the new bolt and sealing.

Many years ago I was part of the Lombard RAC rally as backup mechanics but not competitor mechanics, we kept the whole season going with many engineering scenarios where portable lathes were in the back of many merc G wagons, re manufacturing anything that was constantly ongoing, many stories are now happy memories, nothing is impossible even knee high in mud with water gushing down your back trying to keep everyone on track,

Brilliant work there DavyBoy, you totally engineered the heck out of this problem

I'm not sure I'd be comfortable using the first method just in case anything dropped into the box but it looks like your 2 pronged solution of grease and vacuum was very effective.

The second solution really does prove the point that it's the mating flat faces that bind up and not the threads.

Ahh, the glory days of rallying. I used to go and see the Lombard RAC at Chatsworth (up in the woods above the house - amazing!), Clumber Park and Dalby Forest when I was a kid back in the 80s. Man, those were the days We're off to the Wyedean Rally this weekend as it's just up the road. I've never been before but I gather it's a good one. 2010 Freelander 2 HSE TD4 Auto

Hi, yes a severe gamble either way, the second option is more likely to be the solution, bit of a thought though hopefully it’s not cross threaded, I remember watching some formula Ford chaps doing some repairs to one of their competition cars and time was the essence, everything was air powered and they just went straight in spinning every bolt and cap into place. Hopefully the guy who installed your filler cap originally hand fitted it then the proverbial an air or battery tool to tighten, it seems this is the norm within workshops, I remember well my first service at the Landy workshops they spun out the threads on the air filter box with some tool, the threads were none existent.
Anyway lessons learned with dealerships.

Yes the Lombard rally’s were very indeed entertaining, we were the back up, of the back up team sponsored by a private investor, the money was excellent let alone their allowance of vehicles we chose, we also supported the medics as well, a very close friend who unfortunately isn’t with us now due to a brain bleed(not connected with the sport) he was Colin McRae’s 2nd back up team leader, when they were working flat out, my friend was the night shift or the s++t shift workers. Those days were absolutely insane and out of control but in reflection they were the best days I ever spent, apart from being a forensic vehicle inspector for the police. Now there’s a story! Or three, enjoy your weekend!