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Gearbox oil is foamy

Posted by isaacjames24

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Gearbox oil is foamy #1
isaacjames24 Isaac C. Olympia, WA, USA 1971 MG MGB GT	Posted: March 06, 2013 04:55PM Registered: 1 year ago Posts: 73

I just checked my gearbox oil level and it's foamy. Very foamy. So foamy it's reading far above the FULL mark on the stick. I just changed the oil in it to Valvoline VR-1 20w-50 (same as I use in my engine) about a month ago. I was talked into using Royal Purple previously and drove with it in there for a few months. I hated it and so did the gearbox! Don't do it!!
Anyway, the car sat out in the cold rain for the last week (long story) so I warmed it up for about 5 minutes and then checked the fluids before I went on a little cruise. That's when I found the frothy gearbox oil.
Thoughts on the subject?

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Re: Gearbox oil is foamy #2
MKulka Matt Kulka Charlotte, NC, USA	Posted: March 06, 2013 05:01PM Registered: 3 years ago Posts: 64

Does it look like a milkshake? If so, that's moisture in the oil. Since it sat out in the cold and rain, I suspect it's condensation. I would take the car on a run, long enough to get it warm and stay warm for awhile - an hour maybe? Then check it again. I'll bet that allows the moisture to evaporate and the oil to come back to normal.

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Re: Gearbox oil is foamy #3
isaacjames24 Isaac C. Olympia, WA, USA 1971 MG MGB GT	Posted: March 06, 2013 05:08PM Registered: 1 year ago Posts: 73

Thanks Matt! Sounds logical to me. I was thinking it probably had something to do with it sitting outside. Looks like I'll have to go on a drive....strictly for the benefit of the car, of course! If only I could get my wife to believe that...

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Re: Gearbox oil is foamy #4
ohlord Rob C North of Seattle, N.W., USA 1971 MG MGB "Bedouin 2"	Posted: March 06, 2013 05:12PM Registered: 1 year ago Posts: 1,839

It is most likely overfilled after the fluid change. They are more prone to aeration if even a bit above the full line.

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Re: Gearbox oil is foamy #5
ingoldsb Terry Ingoldsby Calgary, Alberta, Canada 1971 MG MGB	Posted: March 06, 2013 05:24PM Registered: 9 years ago Posts: 9,752

If it is above the fill mark, then I suspect it is being beaten into a froth by the gears.

I would change it (and I would go to a GL-4 gear oil such as Redline MT90) and check the level carefully.

Terry Ingoldsby
terry.ingoldsby@DCExperts.com

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Re: Gearbox oil is foamy #6
ohlord Rob C North of Seattle, N.W., USA 1971 MG MGB "Bedouin 2"	Posted: March 06, 2013 05:31PM Registered: 1 year ago Posts: 1,839

Castrol 20/50 wt

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Re: Gearbox oil is foamy #7
rdgreen Robert Green Adelaide, Australia 1975 MG MGB MkIII	Posted: March 06, 2013 05:37PM Registered: 1 year ago Posts: 735

Here we go!!!!

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Re: Gearbox oil is foamy #8
isaacjames24 Isaac C. Olympia, WA, USA 1971 MG MGB GT	Posted: March 06, 2013 05:48PM Registered: 1 year ago Posts: 73

You guys are welcome to discuss fluids-types all you want smileys with beer

But the foam has settled and the fluid level is a gnat hair below FULL. I'm off for a drive!

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Re: Gearbox oil is foamy #9
mimssandi Roger & Sandra Hobart Mims, Fla, USA 1962 Triumph TR4 ~ For Sale ! ~ 1968 Triumph TR4A	Posted: March 06, 2013 05:50PM Registered: 3 months ago Posts: 197

Water can get into the tranny from the shift lever area. Leave it in the rain with the top down and water runs down the shifter and finds its way into the tranny. Light brown foam is water.

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Re: Gearbox oil is foamy #10
GILMGA Gil Dupre Chattanooga, TN, USA 1962 MG MGA 1974 MG MGB GT	Posted: March 06, 2013 06:10PM Registered: 6 years ago Posts: 7,300

Maybe you should use non detergent oil. devil smiley

Gil

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Re: Gearbox oil is foamy #11
gooser Drake Myers Danville Va, USA	Posted: March 06, 2013 06:43PM Registered: 5 years ago Posts: 6,915

In reply to # 2306145 by GILMGA Maybe you should use non detergent oil. devil smiley

x2.

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Re: Gearbox oil is foamy #12
dipstick Kenny Snyder La Center, Washington, USA 1941 Ford N-Series 1958 MG MGA 1500 Coupe 1970 MG MGB GT 1971 MG MGB 1992 Nissan 300ZX Z32	Posted: March 06, 2013 11:23PM Registered: 4 years ago Posts: 589

Consider checking the gearbox breather cap to be sure that it is clear to vent.

I doubt that rain water would get into your GT transmission, unless you leave the sunroof open.

Transmission oil hot generally runs 250 - 275 degrees (put your hand on it if you don't believe) and any moisture will boil off and pass out thru the vent.

The MGA/MGB transmission gears are designed to throw off mass quantities of oil in order to get that oil into the upper channel on the left side of the inner case that feeds the front cover, thus there will always be some "foam" on the dipstick on hot shutdown.

Be safe out there.
Kenny

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Re: Gearbox oil is foamy #13
MCCT Charles Tisdall Auckland, New Zealand 1967 MG MGB	Posted: March 07, 2013 02:54PM Registered: 4 years ago Posts: 1,120

quite a common issue..I replaced my oil with Penrite non detergent ..made big difference

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Re: Gearbox oil is foamy #14
GILMGA Gil Dupre Chattanooga, TN, USA 1962 MG MGA 1974 MG MGB GT	Posted: March 07, 2013 03:03PM Registered: 6 years ago Posts: 7,300

Ha. Non detergent oil doesnt foam.

Gil

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Re: Gearbox oil is foamy #15
Wachtmans Wouter Strodijk Overveen, Netherlands 1974 MG MGB "The Bee" 1974 MG MGB "The Bee" 1974 MG MGB MkIII "The Bee"	Posted: March 07, 2013 04:12PM Registered: 1 year ago Posts: 110

A descent quality oil does not foam! It is water that makes it foam. Water cannot enter the tranny; even when you leave the sunroof open, water cannot run down the shifter into the tranny, that's BS; there is no opening whatsoever to the tranny over there! It could be either the Royal Purple does not match with the oil you replaced it with, or your oilcan has collected water. Don't run your MG until you get the clue! It will ruin your gearbox.

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Re: Gearbox oil is foamy #16
GILMGA Gil Dupre Chattanooga, TN, USA 1962 MG MGA 1974 MG MGB GT	Posted: March 07, 2013 07:52PM Registered: 6 years ago Posts: 7,300

I use sae30wt non detergent in all my transmission and have since 1965. John Esponito who refurbishes transmission recommends it especially in OD transmission.

Gil

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Re: Gearbox oil is foamy #17
ourmg George Heissenberger Victor, New York, USA 1973 MG MGB "OUR MG- The Old Girl" 2006 Mini Cooper "Greta's Mini"	Posted: March 07, 2013 09:03PM Registered: 7 years ago Posts: 2,814

After you have tried all the things suggested above, make sure you don't have anti freeze in the oil/ oil in the anti freeze, I had foamy oil in a previous car and it ended up being the head gasket.

"OUR MG" Glacier White 1973 MGB, owned since 1983. Factory hardtop. Member MG Car Club Western New York Centre
"Beer is proof God loves us and wants us to be happy" - Ben Franklin

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Re: Gearbox oil is foamy #18
isaacjames24 Isaac C. Olympia, WA, USA 1971 MG MGB GT	Posted: March 07, 2013 10:11PM Registered: 1 year ago Posts: 73

Thank you everyone for your comments! I really appreciate the advice. After my drive yesterday, I checked the gearbox oil when I got home and it was smooth and clear! No foam and sitting nicely at the FULL mark.
I think I will switch to a non-detergent oil in the gearbox next time. It seems pretty logical option. However, I wouldn't call Valvoline VR-1 "cheap" oil. It may not be the highest of the high-end, but it's certainly not pond scum in a Dixie cup. I'm pretty happy with it in the engine.
Thanks again everyone!

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