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Can overfilling Diff fluids damage anything


Well-Known Member
Apr 10, 2021
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Hi All,

I changed both diff oils at 53800 miles from a garage. Later oil was dripping from drain plug and was wrong oil so on 22Apr22 at about 56500 miles changed it at another garage. This time also they filled wrong spec along with overfilling. 10 liters instead of 6.1 liters. I didnt bother much and started driving but now oil is dripping even from rear diff fill hole. Didnt go under and check the front one though.

Will overfilling diff oil have any knock-on damage on other parts? Did anyone here experience any damage due to such overfilling?
Andy I too feel so. I explained a lot about why I am changing it and gave them a printed manual, exact quantities, specs, and also a link to the Project 200 video of how to change it. For some reason, they did it wrong again and charged me 395 for doing it wrong. I won't go back to them to waste my time. Ideally, Landcruiser should not visit garages so often.
How do you over fill a diff ? it has a fill hole and an empty hole so you would have to remove the diff or turn the truck upside down to put too much oil in ? They charged you for 10 litres because nobody sells 6.1 litre bottles . Those of us who do it ourselves will keep the 3.9 so next time we only haveto buy 5 litres .

I leaking diff plug is usually due to laziness , either they didn't change the consumable crush washer or they didn't tighten it enough .

There is recommended oil and 10 dozen other options , so long as its diff oil it really doesn't matter though if needs must and you had to get it home i suppose engine oil would do no harm in the short term .

Because you are learning all this stuff Raj your over thinking it , a cruiser is no different from any other car you have ever driven in most respects but stands out from the rest because of its toughness . Neglect it ,batter it , abuse it and it will still get you home when nothing else would .

Every other vehicle you trusted because you never thought about it . This forum can and does turn us all sometimes into mechanical hypochondriacs but you have to bare in mind most of us are in our way restoring vehicles crowding 30 years old . Enthusiasts fix things that aren't broken because we want our trucks to last another 30 years , and sometimes just because we can .
What Shayne said. Can't really see how they have materially overfilled the diffs - either not tightened or not renewed the washer.... or possibly used thinner spec oil, but I doubt that one. I also agree you are likely over-thinking everything now - as I mentioned on a previous thread, Cruisers aren't materially different to any other big 4x4 and in terms of wear-and-tear, any other 20 year old vehicle.
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Raj, all these chancers see you as a nice person, mistake kindness for weakness, and take the pi55. You have the basic equipment to do this stuff, you just need a bit more confidence.
Remember, help is just a click away should you get stuck. Good luck.
My first road trip of any kind was to Romania and the evening before we left I noticed a leak , if i remember correctly it was coming from the seal between front diff and propshaft flange .
Too late to do anything other than put some transmission leak stop in the diff and hope for the best away I went .

Had a bit of a bump in Brussels i think it was , couldn't open the bonnet and decided not to put much effort into trying as there was nothing dripping underneath the truck and only a few thousand miles to cover if i was to reach my destination , lap the Transfagarin , climb mountians , charge through forests and rivers , and get home again . And so i hooked the trailer back up and carried on .

She never missed a beat and i never did fix that seal because it never leaked again .

What but a Cruiser could do that ?

Thank you all. As long as it’s not over filled and doesn’t go in breaking any seals inside it’s fine. I can tighten the plug.
I asked specifically for this oil as it’s the only GL5 spec with correct viscosity. They added 70w80 probably from their drums and charged for 10 litres at 8.90 per litre. Rest is labour n extras
That's expensive innit? I got the stuff from roughtrax (75w90 gl4/5) sitting on the shelf waiting to be used. Can put the same stuff in front diff, rear diff and transfer box - keeps it simple and about 35 quid for 5L
Synthetic is always dearer , curious to note i couldn't find Toyota synthetic at the same spec ?
75w90 gl4/5)
I saw GL4/5 spec but manual says only GL5. Could be that I am overthinking but looked for oils that has only GL5+. This oil only gets changed only every 5 years/50K miles
Well for what it's worth I took my unfinished job to Bexhill Gearboxes in Hastings (as recommended on this forum). Correct fluids supplied by me. Everything now works: 2nd is smooth again, no more grumbling noises, and the rear diff works.

As a different perspective I do get the argument for DIY, but I'd rather timebox something with a professional than create myself a never ending 'project'. When I consider DIY I think of what could realistically go wrong and if I have the facilities to deal with that outcome - unexpected tools / snapping a bolt / needing to support a very heavy item / needing more than one pair of hands / needing a part that is out of stock or has a long lead-time. It's not a case of 'cannot' but more a case of 'potential avoidable grief'. Unfortunately this relies on a competent garage as a premise, which is where it appears to have recently started going wrong for at least Raj and me!

edit: and whilst changing the diff oil is very easy for routine maintenance, the dilemma is when there is already a suspected problem then what if a load of glitter comes out when the oil is being changed.
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Then you know theres a problem before catastrophic breakdown , to ignore the glitter and topit up without saying anything ensures you will be returning to the garage for a much more expensive repair at a later date .
Then you know theres a problem before catastrophic breakdown , to ignore the glitter and topit up without saying anything ensures you will be returning to the garage for a much more expensive repair at a later date .
Indeed, if the garage is lying to you about all being well then the whole premise it is out of the window. Hence recommendations, or shames, in my opinion are necessary. But I'd be surprised if a garage ignored the glitter when they could use that to justify the immediate upsell of much more work e i.e. the kwikfit model.
I guess the point is that whether you change your diff oil yourself or get a garage to do it, either way if there's nasties in the drained oil, you're looking at a bigger job at some point in the near future.

Personally I tend to split the jobs between DIY and paying someone, purely depending on what it is and whether I can be arsed or not ;-) But joking aside, something like changing diff oil is an easy job, unlikely to be any drama in actually doing the work, so a garage charging the thick end of £300 in labour is frankly daylight robbery. Might as well just get a mask and a gun to complete the effect.
ut I'd be surprised if a garage ignored the glitter when they could use that to justify the immediate upsell of much more work
I think it depends whos doing the job. If its just a wage slave, they might not give a toss! Just get it done and get it out.

I agree with Dave, for 300 quid you could do the job and buy yourself a nice compressor or sommat for future jobs.... :)
Raj, I've found the garage of your dreams. I was making some notes in the search bar earlier and accidentally googled '200 570'. Try it.