Marina diff drain plug

[jammmorris]

Hello,
My minor has a Marina rear diff. I want to drain the oil and replace it. I can't find a drain plug and I can't find anything online or in the Haynes manual I have for a Marina about a drain plug. It just seems to have a filler plug in a similar place to a minor halfway up on the back. Does anyone know how you drain a Marina diff please?
Thanks

[Bill_qaz]

Either suck out with syringe or vacuum pump or remove rear cover to allow you to fully clean out. Remove two lower cover bolts may drain out oil but will need a while.

[philthehill]

If you have a Marina diff you must have a Marina rear axle casing which does not allow you to drain the axle oil in a similar way to the Morris Minor 1000 as the Marina rear axle casing does not have a drain plug.
You cannot remove the bottom bolts to enable you to drain the axle as they are headed studs fitted from inside the axle banjo.
The Marina axle casing does not have a rear cover. The axle casing is one piece.
All you can do is suck the oil out through the filler plug.

[jammmorris]

Many thanks for the information. Seems an odd design?! I've just ordered an automotive syringe/vacuum pump following your advice and will try to get it out that way!

Cheers

[Bill_qaz]

Either suck out with syringe or vacuum pump or remove rear cover to allow you to fully clean out. Remove two lower cover bolts may drain out oil but will need a while.

Sorry for duff info as Phil is the bmc guru, I thought the image online was shown as a marina. Ref https://tasteslikepetrol.net/2021/07/pr ... e-service/
I'm sure Phil will ID it

Screenshot_20240101-191351_Chrome.jpg (101.34 KiB) Viewed 52211 times

[philthehill]

Having done a comprehensive search I am certain that the car with the axle featured in the link above is the Australian version of the Morris Marina.
Quite a few of the drive chain components were changed possibly for use in the Australian environment.
The axle looks to be a MGB unit which does have the removable plate on the rear of the axle banjo ex factory.
It also has a revised handbrake cable compensating arrangement which is totally different to the UK handbrake cable compensating arrangement.
The Australian Morris Marina parts list shown in the link gives the game away.
Here is a link to the history of the Australian version of the Morris Marina:-
https://www.aronline.co.uk/cars/leyland/marina_/

[jammmorris]

Thanks as always Phil for your dedication in helping to find the answers to problems.
Thanks for your time and input too Bill.
Best
Andy

[Blaketon]

Rather than start a new thread, is the Marina axle compatible with the Minor? In other words, are the half shafts the same size (Wheel size different but not sure on wheel stud PCD)? My car has standard half shafts and whilst I don't do quick starts, it has 77bhp, not the 48 it had when it was new. I know Midgets and Marinas used more powerful engines than Minors (I'm not necessarily talking B Series and I don't know whether the 1.8 Marinas used a different axle; higher geared I am sure) but I don't know whether they had stronger steel than the 1098 Minor half shafts. If so and if they fit, it could be cheaper than getting special half shafts.

[philthehill]

The Marina rear axle is compatible with the Minor though the track is about 2" wider.
My Ser 2 had the Marina axle fitted and it was a good modification.
To fit the Marina rear axle the axle mounts of the Marina axle need to be modified which is a relatively easy job.
The Marina wheel PCD is 3.75" so Marina wheels or similar (for example Triumph) have to be used.
The half-shaft arrangement is totally different to the Minor and yes they are stronger so can transmit more power.
The same axle was used on the early 1800cc MGB and gave no problems.
The Marina diff has a ratio of 4.11. The Marina diff and carrier are much stronger than the Minor diff. Special tools are required to remove the crown wheel assy.
The diff pinion flange is different but can be overcome by fitting a Marina prop-shaft flange to the rear of the Minor prop-shaft. I have several spare Marina prop shaft flanges if anyone requires one. They are interchangeable with the Minor rear prop-shaft flange.
Full instructions (with measurements) for fitting the Marina axle to a Minor are given in the Owen Burton booklet 'Marina to Minor'.
The one downside of using the Marina axle is that it is a heavier unit than the Minor axle so the un-sprung weight is increased and I do not like un-sprung weight so still use a Minor axle in my car but it is an upgraded Minor axle with half-shafts capable of transmitting 178bhp. My experience has been that the diff fails before the half-shafts.

[jammmorris]

Following on from my earlier question I'm just checking a couple of things if anyone has any thoughts please.

1. I unscrewed the diff drain plug on the back (only one there is) and I didn't anticipate oil would flow out. I thought it would be below the level of the drain plug? It was only a trickle but surprised me. I topped the oil up by syringing some in but it kept flowing out whilst I quickly screwed the plug back in. I thought that if I have put too much in it will just release through the breather at the top which I checked was clear. Is that correct?
2. Whilst under the car I thought I'd grease the universal joint on the prop. I spun it round 360 but there isn't a grease nipple. I assume it's a Marina prop? If so does that not require greasing? The Marina Haynes manual isn't very helpful on rear axle maintenance.

Thanks in advance.

20240111_202936.jpg (1023.24 KiB) Viewed 49957 times

20240111_211303.jpg (1.15 MiB) Viewed 49957 times

[philthehill]

The plug pictured is the filler/level plug and not the drain plug. There is no drain plug for the Marina axle.
It is not uncommon for a small amount of oil to flow out of he level plug when the level plug is removed. Just let the excess drain out and re-fit he level plug.
The breather on top of the axle is to release the pressure built up by churning oil not to allow excess oil to escape.
If you have a Minor gearbox the prop-shaft shown is a Minor prop-shaft with a Marina rear flange fitted. The flange PCD is different so a Marina flange has to be used. The Marina prop shaft is a three piece unit with flanges at either end.
Not all U/J have grease nipples. So long as the operation of the U/J is smooth and has no play then there is no problem.

[jammmorris]

Thanks Phil. Yes its a minor gearbox.
So can I just clarify if the car is on level ground I should remove the filler plug till excess oil has mostly drained out and that's the correct level for that diff? I may have put too much in yesterday. Does it matter if it's a little over filled? Still learning!
Thanks again.

[philthehill]

If the car is on level ground - remove the filler/level plug and let any excess oil drain out. Re-fit the filler/level plug.
That is the correct rear axle oil level. It does not help the oil seals if the oil level is above that which is specified.

[jammmorris]

Very helpful thanks Phil.