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MG MGB Technical - OD Trans. Oil Change
I was getting ready to change the oil in my OD transmission with 30 weight non-detergent as usual. Unfortunately I did not have any on the shelf only the 20/50 I use in the engine. Before I changed the oil with the 20/50 I decided to check the archive. Answers are all over the place 30 detergent and non, same with 40, some use 20/50 and one even recommended using 90. I decided to wait and get what I have been using. What is the present "definitive" oil that should be used? |
Lee |
Factory recommended engine oil - 10W40 or 20W50. |
Chris at Octarine Services |
An interesting article: http://www.quantumechanics.com/categories.php?op=newindex&catid=11 warmly, dave |
Dave Braun |
don't use 90W, it makes the box run a lot hotter. |
dominic clancy |
Dave, Great article. I will definitely stay with the 30 weight non-detergent. |
Lee Sheldon |
Not such a great article: The OD they tested was an early A type - not a D or more common LH type found on the MGs. They didn't use 20W50 or 10W40 oil to test! LH types in good condition develop 400 - 420 psi on 20W50 or ATF. Overdrive Repair Services ( the successor to Laycock) say that the LH OD will work on any oil between ATF and 90 weight gear oil - the determining factor is the box not the OD! |
Chris at Octarine Services |
It would seem logical to do what Chris posted and use the oil recommended by the maker! or is 20/50 hard come by in the States nowadays? You have to go looking for it in this country but it's still relatvely easy to get. Ron |
R. Algie |
A 20W50 mineral will become a 20W30 in no time at all, but all the viscosity improvers are now chewed up and left in the box. An engine oil contains detergents and anti wear additives. A box oil contains Extreme pressure additives which are now in a safer form since about 2000. ATF is a 5W20 and gear oils are measured on a different scale to avoid confusion, so a 80W90 is only like a 20W50 engine oil. At the end of the day most mineral oils will end up about a 30weight and it depends on whether you want cold performance and the right additives. |
Paul Wiley |
20W/50, 15W/50, 15W/40 doesn't really matter, all were recommended for both hot and temperate climates. Only cold climates (consistently below -10C/15F) used 5W/20 or 5W/30. This is for engine, gearbox and carbs. |
Paul Hunt 2 |
Lee I have the same issue. I have read John Esposito's article and have actually talked to John about this. He is still recommending 30wt. My rebuilder (not John) is recommending same oil that I run in the engine 20/50. He had my unit on a test bench and showed me pressures. With 20/50 the D type OD was functioning to nearly perfect factory specifications. Given John's reputation, I would be comfortable with 30 weight, but given my rebuilders recommendation and now Chris's, I am going with the 20/50. |
Bruce Cunha |
Hi Folks: I think the primary issue is not the viscosity, but the detergents in the oil. To my knowledge all mutigrades use detergents. The reason John Esposito recommends the 30W non-detergent is because of the foaming problems in high pressure hydraulic systems. 30W non-detergent oil is often refered to as "compressor oil". and partly used to prevent foaming. My past experience with aerospace products is that you do not want foam in a high pressure hydraulic system, which could cause component/pump high cycle fatigue, etc. I even had a Buick V6 3.8 liter hydraulic lifter(s) crash due to foam. Had to wait until it cool down to restart. Good Luck: Rich Boris 67B roadster |
Rich Boris |
After reading through all of the recommendations I decided to do the most logical - refer to the original owner's handbook that came with the car. It reads on page 64 as follows: Key to Recommended Lubricants: Engine, Synchromesh Gearbox, Overdrive, Distributor, Carburetter and Oil Can. All temperatures above -12C, 10F Castrol GTX or Castrol XL 20/50 For those of you who live in colder climates: -17 to -7C, 0 to 20F Castrolite of Castrol Super Below -18C, 0 F Castrol CR 5/20 The recommendations include other motor oils, I only listed Castrol since this has been my brand of preference. Thanks for all of your responses. |
Lee |
Timely thread. Having just turned 100k on my 79 mgb, I am about to change the transmission and diff oils. Using a Haynes mgb manual, I am looking on page 118 & 119 to find the fill plug for the oil. My car is the manual gearbox WITHOUT overdrive. Obviously I do not want to drain the oil and not where to refill the box BTW, the Haynes manual suggests using 20W50 Castrol GTX multigrade as listed on Lubricant & Fluids page. So, does anyone know where the fill plug for the transmission is located?? Thanx cheers Gary :>{D 79mgb |
gnhansen |
Gary: The fill plug on later MGBs is located on the right side about half way up. You will need a small hand pump, available at auto stores, to fill the trans without making a mess. Ray |
RAY |
I use Redline MT90 Synthetic oil in my overdrive transmission. I've studied the properties, talked to Redline and feel it's the best choice for me. |
CD Dewey |
This thread was discussed between 17/11/2006 and 28/11/2006
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