Hi

Gearbox and Transfer case oils changed last weekend, I have also purchased oils for front and rear diffs to do the oil change on my 2012 4.4 Westminster.

The front and rear diffs are rusty and the fill plug on the rear diff appears to be stuck solid. it looks like someone has tried to open it before and rounded the hole for the bit.

I dont want to heat it as may damge seals, i will cover with wd40 and leave to soak for a while.

Does anyone have any experience with a siezed / damaged fill plug and how to best remove, I am wary of hammering an oversized bit into the hole as may damage the diff casing and same concerns with using a chisel on the plug.

Any thoughts appreciated.

Thanks

Tom

The diff is a big heavy chunk of metal to heat up, so if you have a highly localised heating method like induction or an oxy torch, you would be OK if you concentrated on the plug alone IMO. I'd certainly go down that route personally.

Before that though, I'd get a good cup brush on a grinder over the whole thing and see about getting a decently fitting tool into the plug and giving it a good whack with a hammer then applying a manual impact driver to it.

If that failed, I'd go for hammering in a bigger tool and trying impact again.

If that didn't work, I'd go for heat.

If none of that worked, I'd go nuclear and use a grease covered drill to put a hole in the middle and use a decent sized extractor on it, then flush the diff with thin oil before fitting a replacement plug and refilling.

If none of that worked, I'd remove the diff.

The first three options have worked for me in 99% of situations including seized drain/fill plugs. 2012 (L322) 4.4TDV8 Vogue SE, RSE, Fuji White over Arabica.
Previous V8s: BMW 645Ci, P38 4.6, P38 4.0, Merc CL500
Previous others: Honda x1, Volvo x7, Rover x6, BMW x6, Ford x1, Mercedes x2, Skoda x3, VW x2, Renault x2, Citroen x1, Mazda x3, Nissan x1, Audi x3, Kia x1, Fiat x4, Subaru x3, Austin x2, Triumph x2, Jeep x2, Hyundai x2, Lexus x1, Mitsubishi x1, Saab x2... and some others I've forgotten!

See my guide about getting the plugs undone in the wiki. You need heat, a wire brush and impact wrench.

Re the rounded plug, a large torx/star bit may help grip it. Also try the end of a 3/8"/1/2" (i can't remember which) socket bar.

If that doesn't work, a set of large mole grips and a club hammer may be your friend. Obviously have a new drain plug at the ready to replace it with. 2015 Range Rover Autobiography 4.4 SDV8

Last edited by garyRR on 11th Apr 2024 10:24pm. Edited 1 time in total

Thanks both, those ideas give me a few options to try.

Fingers crossed!

Tom