F78 Fourtrak DIFF Level Plug Problems


Thought I'd change the front diff oil today. Easy job, three hours later!! The level plug was well seized. Tried heating it up, all to no avail, and eventually the inevitable happened and it was well and truly rounded off!

Ended up taking off the cover, clamping it up in a workmate (the workmate grip plugs have handy grooves in them, ideal for gripping the cover really well without distorting it) and then with my 15 stone holding down the workmate a large pair of stilsons finally did the job. Unfortunately the stilsons wouldn't bear in situ.

I now have to do the rear diff and a quick check seems to suggest that the level plug is similarly seized. They seem to be made of pretty poor material and the shoulders are shallow making it hard to get a good purchase.

So has anyone faced this and found a better way than my first attempt which I don't wish to repeat if I can avoid it!

And where can I get some new, hopefully better level plugs.


Now the filler plug is off and assuming you have access to a lathe, bore out the centre and tap a 20mm hole on it. Get a shout 20mm bolt with machine the shank and underside of the head until it is perfectly flat, and skim the front face of the old filler plug. Insert the filler plug and tighten with PTFE tape or thread lock around the thread to prevent leaks, and put a cpooer washer onto the 20mm bolt and screw this into the filler plug.

This ensures the full width of the nut is useable when you come to replace your oil in the future.

Another option is to weld a 16mm nut onto the old bung and use this as the spanner size would be 24MM.

Thanks Assassin

Unfortunately I don't have easy access to machine tools but will have to organise something. I've since repeated the performance on the rear diff, but remembered my physics this time, by turning the workmate on it's side I was able to get downward pressure on the wrench, much easier, but still a pain. For the moment I have wound the plugs in with some thread tape so they don't need to be overtight to be leakproof, until I solve the problem permanently.

Presumably I could find some bolts with the right thread but with decent sized heads and adapt them.

David T

You could try getting plugs

You could try getting plugs from scrap vehicles, assuming that they aren't seized of course. The other option is to weld the head of a bolt onto your existing plugs.

Drain plug

I had the very same problem recently, the front diff went well,so thinking the back would be the same i cracked on and drained out the oil, big mistake as when i came to top up the diff i couldnt remove the filler plug !
i ended up jacking up the back of the vehicle and then undid the bolts at the top of the diff plate so that i pulled the plate away from the diff and had just enough room at the top to fit in the spout of the oil bottle and squeeze in the oil.
Not ideal but it worked.
When the vehicle was in the garage for a cambelt change i asked that a nut be welded onto the original rounded nut, and they forgot!
And i thought it was landrover owners that had all the fun.


24mm Drain Plug


This is completly of the top of my head, has any one thought that the sump drain plug may be threaded the same , after all its 24mm same as the diff level/drain plug size, as "Milner's" have these in stock, just bought one for spare. Just a thought !!!!!!!!!!!!.

Edward (ews) '92 Fourtrak 2.8 TDX

I'm sure you're right,

I'm sure you're right, hadn't thought of that. Double the magnetic pick up as well!

David T

Reply To EWS

The issue is the depth of the head of the axle drain and filler plugs, when people do not use 6 point sockets on them they easily round off. With a standard bolt the head us much deeper so putting a socket on goves much more contact area to distribute the torque required to undo it. Spreading this torque requirement over such a significantly larger area prevents them from rounding.