GT6 Diff oil

[Alex Lowe]

Hi all

With all this free time figured time to change the diff oil whats the best Technic for this on the MK3 GT6 and what type of oil should be used?

 

[johny]

Unless you're very lucky and someone has installed a drain plug in your diff removing the old oil isn't so easy. Assuming you don't want to remove the complete unit then sucking the oil out with a tube fed through the fill hole would be about the only other option....

[Mjit]

I've got one of these - https://www.machinemart.co.uk/p/cgg500-500cc-oil-suction-gun/

Certainly used it to suck the old oil out of a big saloon diff but have a feeling the tube might be a bit big and stiff for the smaller diffs.  Should be bodgable though with some smaller diameter, flexible plastic tubing and some duct tape.

 

[Pete Lewis]

as there are no contaminants in a diff and sucking wont lift any sunken particles it really does  not need changing hence no designed  drain plugs

even 50 years on

but if it gives peace of mind in this lock down its a good job to amuse for a while 

Pete

[dougbgt6]

I topped mine up a couple of years ago, I can't remember having done it before in 40 years, didn't get much in, not half a cup full. I think I used gearbox oil EP90?

Doug

[Pete Lewis]

yes EP90  GL4  not GL5 

pete

[poppyman]

Also check the breather is clear, it might stop an oil leak, don't ask me how i know that........
 

Tony.

[yorkshire_spam]

1 hour ago, Pete Lewis said:

as there are no contaminants in a diff and sucking wont lift any sunken particles it really does  not need changing hence no designed  drain plugs

even 50 years on

but if it gives peace of mind in this lock down its a good job to amuse for a while 

Pete

Pete, I respectfully disagree. If the diff oil is of unknown "heritage" then I think changing it is well worth it.

This is what came out of mine when it had it's first change in 2012.

Mostly dirty water. Clearly the "seals" just weren't sealing and over time it had drawn in moisture. 

That said I don't change mine as a part of a service or anything like that, only when I've had the diff apart. The rest of the time it just gets the level checked and topped up if needed.

[Mjit]

I only tend to change the diff. oil when buying a 'new' car.  It could be fresh.  It could be the oil it left the factory with.  It could be GL5.  It could be 50% oil/50% sawdust. The fact it only took a cup of oil to top it up could be because it's only lost a cup in 40 years...or in the 40 miles between a pre-collection top-up and getting the car home.

I now KNOW it's fresh EP90/GL4 oil and is starting its life with me at the top of the filler plug.

[Pete Lewis]

i wasn't condemning oil changes more why theres no designed drain plug 

please feel free to change oils in anything when ever you fancy ,  

Pete

[Colin Lindsay]

I had a garage day a year or two ago for the local TSSC - topups of gearbox and diff oil, grease the handbrake cables, that sort of thing. Some of them were quite low on oil and one at least was bone dry; you'd wonder where the oil goes, or how it gets out, once below the levels of the seals.

I use one of these to extract old oil - works on the gearbox too. Lidl sold them a few years back for about £11.99. You can drain a sump through the dipstick tube - very handy in some moderns - and it also works on brake fluid if you're emptying or flushing the system. No matter how good the oil was back in the day it wasn't designed to last decades, so regular changes do no harm, provided you can get genuine GL4 - I had to have five litres specially ordered in, but it has lasted a while.

 

 

[yorkshire_spam]

9 minutes ago, Colin Lindsay said:

I had a garage day a year or two ago for the local TSSC - topups of gearbox and diff oil, grease the handbrake cables, that sort of thing. Some of them were quite low on oil and one at least was bone dry; you'd wonder where the oil goes, or how it gets out, once below the levels of the seals.

I use one of these to extract old oil - works on the gearbox too. Lidl sold them a few years back for about £11.99. You can drain a sump through the dipstick tube - very handy in some moderns - and it also works on brake fluid if you're emptying or flushing the system. No matter how good the oil was back in the day it wasn't designed to last decades, so regular changes do no harm, provided you can get genuine GL4 - I had to have five litres specially ordered in, but it has lasted a while.

 

 

I had one very similar... it couldn't cope with the viscocity of gear oil, fine with engine oil though. When I tried it on diff oil it drew too much current and the wires caught fire. Not my finest success story when it comes to car mechanicing! 🙂

 

[Colin Lindsay]

I haven't tried it with petrol yet...

[daverclasper]

I got mine out with a large plastic syringe off Ebay (1 pound, delivered) and some silicon hose.  I tried a small diameter hose at first, as not lots of room to feed down, though it struggled, was ok with one a bit bigger. Ran the car to get oil hot first

[ahebron]

I fit drain plugs to my diffs whenever they are out of the car

[Colin Lindsay]

I should... the perfect time for it, and I can't get near the drills or equipment I need... but at the rate my Estate is losing oil I reckon it'll drain itself.

[ahebron]

When I went to drain the oil from the rear diff on my Amarok I was surprised to find it has no drain plug so removed the back plate, some rear diffs have a drilled through bottom bolt hole to help drain them but not these. Front diff has a drain plug even though it is right prick to remove and refit the fill plug and fill.

[Nick Jones]

2 hours ago, ahebron said:

I fit drain plugs to my diffs whenever they are out of the car

Me too...... Small chassis diffs are undersized, especially for the 6 cylinder engines and have limited oil capacity. One fast run across Europe and the oil is cooked. Change mine every 2 years. Been using Redline Shockproof, which seems to hold up better, possibly because it does help the diff to run cooler as they claim. My IR gun readings seemed to show this, but it wasn’t good science.

Nick

 

[Pete Lewis]

if you consider the horses are all processed by the diff its not unusual for the things to fry eggs 

Pete

[GT6M]

Its no a hard job t,drill the diff for a plug,

And, regardless of use, change yer oil every year,

oil is cheeper than a diff

Olde diff oil, full of water, car not used much is a recipe for disaster

most diffs I get exchange are useless due to water  / contaminants int oil

eating away the parts that sit in oil when not in use,

no just the CW / P, but bearings, inc half shaft,ns, totally shot at.

 

And, as Nick says, a long run will fry the oil,

the Comma stuff is total sheite, goes black after 500 miles of high speed use

plus when its hot, its like thin pish

 

Use 140 Penrite fully synth pro gear  oil, it last alot longer

dont go black,   an end up like thin pish

me self, 2-3 times a year, depending on where I been, what been doing.

 

Dont change yer oil, then dont expect the surcharge that likes of Rimmers, Moss,  charge                 to be given back,

its getting that bad, as no much left to re use.

[Colin Lindsay]

Hello Marcus - you were quiet for so long I thought the corona had got you!

I agree, treat the diff oil like any oil and change regularly. I don't care how good the oil is that was used forty years ago, it was never meant to last this long and I personally know of cars that have been owned for over twenty years and the diff has never been touched. 

Even if you can't drain the diff, then putting a lot of fresh oil in and waiting while the excess drains out, hopefully taking a lot of the old oil with it, is better than nothing.

 

[johny]

Don't forget that average annual mileage figure given for classic cars and that even then most are just pootling.....

[ahebron]

Oils cheap. Diffs aren't.

[poppyman]

I have to say, i have started using 140 gear oil in my Triumphs, they seem quieter and one in particular hardly leaks now  

Tony.

[johny]

28 minutes ago, ahebron said:

Oils cheap. Diffs aren't.

Triumph obviously weren't too worried though and I don't think back in the day diffs failing was an issue...