MG4 Reduction Gearbox Oil Leak

[AndyL61]

Just a quickish post as I've finally done the diff oil change today, I took a few pics along the way but any questions just fire away.

It was pretty simple just remove the undertray with a million fixings, remove the square drain plug, drain the fluid (& measure) then replace drain plug. Remove the 17mm hex fill plug and refill oil with desired measurement then replace fill plug.

the only issue I came across was my suction oil filler & funnels were useless so after getting oil all over the drive , I went and bought a 1l laser mini pump from Halfords which I was super impressed with & had it refilled in about 2 mins from underneath. I've ran out of time as it started throwing it down but I'll get the undertray back on tomorrow but it's done.

soo.......I wasn't surprised to see some evidence of oil leaking underneath but I'm pretty confident it's not recent & was probably from when they fitted the breather or before and filled it with whatever amount of oil then, they were pretty vague on details at the time and it seems impossible to speak to a tech!

basically the oil was black & filthy as expected, I drained exactly 650ml out but I'd say there was probably another 50ish ml came out in drips and on the drain plug etc. As can be seen on the cardboard I left for a while & whatever is clinging to gears inside etc. so I reckon I've had 21k of pretty spirited miles with around or just over maybe 700ml in the diff.

What did suprise me initially was the state of the magnetic drain plug which had shavings all over it, after speaking to a couple of very trusted mechanic mates they've assured me that's relatively normal on any manufacturer first diff change, most of it during the first couple of k whilst it's being broken in and nothing to be worried about & there shouldn't be much on the next one etc. After a bit of research I'm not too worried about this as it seems there right.

basically the oil imo needed doing, possibly it's working harder not having the 900ml in or maybe I'm just anal with oil & it would have been fine forever but I feel alot better with it having fresh oil on there, I'll be doing this every 20k as bar the undertray it's a very simple job tbh & reckon it should be done alot sooner than the 72k I believe MG recommended .

I put a tad over 800ml back into the diff, I half expect to get a little leak whilst it may find it's 700ml ish level again or maybe that's all they filled it to when the breather was fitted? I'll keep an eye on it anyway and see what happens.

thanks again Macadoodle for the tips etc. Pal.

I intend to change my oil at about 20k so you've reassured me that it really needs doing at around that milage. Thanks . Fireblade in the background? Nice.

 

[Macadoodle]

Good stuff spence, thanks for the pics and details. I think I drained just over 600ml in a couple of mins with the original breather so it would seem that the mod lets around 50ml extra stay in there.
Your swarf looked about double but I had only 10% of the mileage so I doubt that there's anything to concern you there.
The gear teeth do their final polishing break in when the car is in service.

Having seen Maverickz motor pics I'm a little more relaxed about oil level in this box, the ring gear and I think both gears on the intermediate shaft sit really low in the casing so will continue to lubricate all the gear teeth even at a very low oil level I would guess, I would be ok with 750 ml I think, but possibly no less.
This wee puddle of oil has to work hard though, I think timely changes might be cheap insurance if you plan on keeping your car, 40k might be sensible intervals.

 

[Ian Key]

Interesting that the service plan says to change the transmission oil at 96000 km (60000 miles) under certain conditions.

 

[Lucky5]

After 550 miles mostly on the motorway from new it seems we are still oil tight, so at least that is a positive…..or it’s nearly empty

 

[siteguru]

So far so good for me with breather mod MK2 (and/or low oil level).

 

[wiz043]

uk buyer sells mg4 after problems - Google Search

Let's hope this does not become a regular happening. Covers just about everything that has been stated here.

 

[Ian Key]

uk buyer sells mg4 after problems - Google Search

Let's hope this does not become a regular happening. Covers just about everything that has been stated here.

In my opinion 90% of the problem cars are among the first deliveries probably caused by the factory still learning how to build them and the supply chain supplying substandard parts thinking they could cut corners or the specifications not being strict enough.

Cars built from December 2022 seem comparatively fault free although they might need a couple of software updates depending on how diligent the dealer is.

 

[Retsiba]

In my opinion 90% of the problem cars are among the first deliveries probably caused by the factory still learning how to build them and the supply chain supplying substandard parts thinking they could cut corners or the specifications not being strict enough.

Cars built from December 2022 seem comparatively fault free although they might need a couple of software updates depending on how diligent the dealer is.

Seems like a rational viewpoint to take about problem cars being amongst first deliveries and factory still learning how to build. It does seem most of the 23 builds don't have as much issues based on feedback from owners.

Where it fails on closer examination is that MG has had other EV builds and yes whilst they may be cheap value /budget cars they haven't been as problematic as the 4.

And also makes one think of the Mulan, Chinese version. Do they have similar problems?

 

[KH11]

I haven’t purchased an MG4 yes, I suppose I have been waiting while a lot of the issues have been ironed out on the newer models. So I will be actively looking round the September area. I have found this site useful though and I had a visit to my local dealer the other day and whilst I told the salesman I wasn’t ready to take the plunge yet. He was more than happy to show me an MG4 Trophy and explain things.

I am currently driving a Vauxhall Corsa Griffin and initially couldn’t make my mind up what I would be buying next. Initial thoughts was a Hybrid but if I am going to move from a manual to an automatic I have come round to going full electric.

 

[siteguru]

You need to edit your forum profile.

 

[KH11]

There didn’t seem to be a way of putting down anything other than a MG car but when I get one it will be the MG4 trophy so I put that

Right I think I have found the edit hopefully it will show none MG now. I hadn’t spotted that when I registered.

 

[maverickz]

Seems like a rational viewpoint to take about problem cars being amongst first deliveries and factory still learning how to build. It does seem most of the 23 builds don't have as much issues based on feedback from owners.

Where it fails on closer examination is that MG has had other EV builds and yes whilst they may be cheap value /budget cars they haven't been as problematic as the 4.

And also makes one think of the Mulan, Chinese version. Do they have similar problems?

Yes, Mulan has the same leaking issue.
But seems not that many.

 

[tsedge]

In my opinion 90% of the problem cars are among the first deliveries probably caused by the factory still learning how to build them and the supply chain supplying substandard parts thinking they could cut corners or the specifications not being strict enough.

Cars built from December 2022 seem comparatively fault free although they might need a couple of software updates depending on how diligent the dealer is.

Mine was built late November and has no issues so far.

 

[AndyL61]

Don't know my build date but car was with the dealer late Jan so I estimate late October / early November build. No leaks so far over 3k miles.

 

[bowfer]

I intend to change my oil at about 20k so you've reassured me that it really needs doing at around that milage. Thanks . Fireblade in the background? Nice.

Not a fireblade.
CBR650F.

 

[Cocijo]

Just a quickish post as I've finally done the diff oil change today, I took a few pics along the way but any questions just fire away.

It was pretty simple just remove the undertray with a million fixings, remove the square drain plug, drain the fluid (& measure) then replace drain plug. Remove the 17mm hex fill plug and refill oil with desired measurement then replace fill plug.

the only issue I came across was my suction oil filler & funnels were useless so after getting oil all over the drive , I went and bought a 1l laser mini pump from Halfords which I was super impressed with & had it refilled in about 2 mins from underneath. I've ran out of time as it started throwing it down but I'll get the undertray back on tomorrow but it's done.

soo.......I wasn't surprised to see some evidence of oil leaking underneath but I'm pretty confident it's not recent & was probably from when they fitted the breather or before and filled it with whatever amount of oil then, they were pretty vague on details at the time and it seems impossible to speak to a tech!

basically the oil was black & filthy as expected, I drained exactly 650ml out but I'd say there was probably another 50ish ml came out in drips and on the drain plug etc. As can be seen on the cardboard I left for a while & whatever is clinging to gears inside etc. so I reckon I've had 21k of pretty spirited miles with around or just over maybe 700ml in the diff.

What did suprise me initially was the state of the magnetic drain plug which had shavings all over it, after speaking to a couple of very trusted mechanic mates they've assured me that's relatively normal on any manufacturer first diff change, most of it during the first couple of k whilst it's being broken in and nothing to be worried about & there shouldn't be much on the next one etc. After a bit of research I'm not too worried about this as it seems there right.

basically the oil imo needed doing, possibly it's working harder not having the 900ml in or maybe I'm just anal with oil & it would have been fine forever but I feel alot better with it having fresh oil on there, I'll be doing this every 20k as bar the undertray it's a very simple job tbh & reckon it should be done alot sooner than the 72k I believe MG recommended .

I put a tad over 800ml back into the diff, I half expect to get a little leak whilst it may find it's 700ml ish level again or maybe that's all they filled it to when the breather was fitted? I'll keep an eye on it anyway and see what happens.

thanks again Macadoodle for the tips etc. Pal.

Excellent update. Do you have any concerns at how dark the oil is? My experience is that the oil is usually much cleaner when drained. I also understand that there is no service item listed by MG to change this oil, which is a concern given the running in swarf and Colour of the oil after only 20k miles.

 

[Les burrows]

Spence 7788 only just seen your pictures and thank you for them great help so if you don’t mind I have a couple of questions.
1 You said you removed the under tray from the car to do the oil so how was your tray before you removed it in regard to any bulging that many of use haveon our cars and if it was bulged did it fit any better when you put it back on

2 Can you give me a picture or a link to the laser pump you say you got from Halfords to help with refilling I have look on there website but found nothing.

3 And I hope you don’t mind and please don’t think I’m stupid with this, but I took a screen shot of one of your pictures to mark up what I’m sure is the drain plug is that correct? So could you please mark the filling plug for us here.
Many thanks again for your efforts it is much appreciated by all of us here.
Les

 

[Cocijo]

A good tip is always remove the fill plug first. If this is seized and you’ve drained the oil you’re in trouble.

 

[Ayoull]

A good too is always remove the fill plug first. If this is seized and you’ve drained the oil you’re in trouble.

I'm sure the dealer would just role it over to refill

 

[AndyL61]

Spence 7788 only just seen your pictures and thank you for them great help so if you don’t mind I have a couple of questions.
1 You said you removed the under tray from the car to do the oil so how was your tray before you removed it in regard to any bulging that many of use haveon our cars and if it was bulged did it fit any better when you put it back on

2 Can you give me a picture or a link to the laser pump you say you got from Halfords to help with refilling I have look on there website but found nothing.

3 And I hope you don’t mind and please don’t think I’m stupid with this, but I took a screen shot of one of your pictures to mark up what I’m sure is the drain plug is that correct? So could you please mark the filling plug for us here.
Many thanks again for your efforts it is much appreciated by all of us here.
Les

View attachment 16829

Halfords pump .