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MG MGB Technical - HELP - Refilling O/D Fluid in Transmission

Hello,

I posted another thread about a week ago concerning the filter for the O/D and changing/cleaning it.

Tonight I put the car on jack stands and removed the filter and cleaned everything and reassembled it. There was some sludge and dirt in the magnet area - no metal chips that I could find.

However, when I took the filter cover plate off, about three cups of transmission fluid flowed out. FYI - I had the back of the jacked up higher than the front.

The car is now level and still on the stands, and when I check the transmission fluid from the fill hole on the side, it still shows it is full of fluid. So I started the car and let run it for a few minutes and then went through the shift pattern several times and turned the O/D on and off.

Now, when I check the fluid it is still showing that it is completely full. What I mean by this is that when I remove the fill hole bolt on the side of the transmission, the fluid runs out of the hole; and when I stick my finger in the hole the fluid is full to the top.

So how do I refill it from the fluid that came out when I changed the filter? Is it OK to drive? Is there a separate fill spot for the O/D?

Please help me. Thanks

Robert
Robert Browning

Sorry, I forgot to add that my car is 1973 MGB
Robert Browning

Robert. The overdrive transmission is not original to your car. Your car should have had the dipstick type transmission, not the side filler. Thus, at some point, someone has replaced the original transmission with the later model, overdrive, transmission.

It would seem that they may, also, have over filled the transmission after installing it.

You have done, everything, perfectly correct. The car should be level when checking the level of the transmission fluid. When checking the level of the dipstick type transmission, the markings on the dipstick are the indicators which we use. When checking the side fill tranny (and I have several of these in use on our cars) the method is to remove the bung (plug) and see if any fluid leaks out. (None should.) Then, very carefully (sharp threads can cut the finger if one is not careful) insert the finger, anyone which will fit into the hole and can be moved downwards slightly, into the hole and see if any oil is on the finger when removed. If you can see oil, no problem.

If you do not see oil, use an oil gun, or a pump type oiler, filled with the proper Castrol 20W-50 motor oil (or a good quality SAE 30 weight oil) and fill the transmission until the hole is leaking out some oil. (I put one of the wife's old cookie sheets, with either some paper towels or some newspaper lining it under the tranny to catch the drips.) Go have a cup of coffee, or a beer, depending on the time of day. Allow the tranny to stop dripping. Wipe off all of the excess oil from the exterior of the transmission case. Install the filler hole plug. You have, now, successfully, topped up the transmission, with or without overdrive, properly.

Again, sounds like the tranny was over filled to begin with and is now at the correct level. Good show.

Les
Les Bengtson

Les gives very good advice, I might add that we use straight 30w non-detergent in our OD gearbox. The non-detergent foams less and does not suspend the dirt to cycle readily through the gears. Just a thought.

warmly,
dave
Dave Braun

When you went through the shift pattern and turning OD on and off did you have a rear wheel raised and let the clutch out so the wheel spun? You have to otherwise the oil is not pumped round the OD to level things off. Remember ther car needs to be level when checking the level.
Paul Hunt

?? taking the filter out and cleaning will only empty the OD sump, not the passageways within the OD.

The gearbox was overfilled - the oil would have flowed by gravity back into the OD sump through the holes in the adapter housing.

Absolutely no need to do as Paul suggests.
Chris at Octarine Services

Update

After letting the car sit over night, I drove it around the block, going through all the gears and the O/D.

When I got back I checked the oil and it was low. I added about a 1.5 cups of fluid - till it was just at the fill hole - I run 20W-50 oil in my transmission.

As for Les, yes, this is not the original transmission for this car, as when I rebuilt the motor we added the O/D transmission and it has the side filler plug. What is interesting is that on my car, 1973 MGB, there is no opening on the tunnel for checking a transmission dip stick if it had one.

Other item, Paul, yes, I had the rear wheels off the ground when I was running the transmission. However, it was not until I put the car on the ground and actually drove it that the oil seem to get
dispersed.

Now, one additional item, this morning I found a small, greasy flat metal washer under my car in the area I was working. I know the bolts holding the cover plate on had washers, but are there any metal washers inside on the filter that I missed? I simply pushed the screen up onto the center post thing and then reassembled everything.

Is there a metal washer I missed or is this something extra from another repair job?????

Thanks for all your help.

Robert
Robert Browning

"Absolutely no need to do as Paul suggests. "

Well, speak as one finds. I refilled mine to the mark on the dipstick and tested it as I suggested, and was rather put out to discover the OD only engaged fitfully. Rechecked the level and it had dropped off the bottom of the dipstick. Topped up and tested again and it was fine. This also seems to have happened to Robert.
Paul Hunt

Robert,

How long after getting back did you check the oil level? I takes a little while for all the oil to settle back down into the sump of the gearbox. There are rails built into the top of the casing which catch oil thrown up by the gears, this is then fed by gravity through drillings to the mainshaft - quite a lot of oil can be in the system. Best to recheck again the next morning.
Chris at Octarine Services

Chris,

Will do.

Thanks.

Robert
Robert Browning

So what is the consensus?

20/50 wt. or 30 wt. oil for o/d? Detergent or non-detergent oil?
Steve Rechter

Checked oil level and it is fine.

Steve - Even one has told me and I have read where to only use 20w 50

Robert
Robert Browning

Makes no odds, although it should be the same viscosity as used in the engine, which is lower than 20W/50 for colder climates. Personally it just seems easier to keep one container of oil for topping up both rather than two different ones.
Paul Hunt

This thread was discussed between 25/04/2009 and 29/04/2009

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