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Triumph TR3 - Gearbox Oil

This may seem like a silly question, but since I have conflicting information I'll ask the opinion of the forum. I've searched the archives, but to no avail. The question is what type and viscosity oil are you using in your gearbox? The car is a '59 TR3A W/ Overdrive. I'm working with the Bently reprint of the Workshop Manual, a reprint of the drivers manual and advice from a restoration shop. The bently reprint shows 50 weight motor oil, the drivers manual shows 90 weight hypoid gear oil (GL-4) and the restoration shop suggests 50 weight motor oil. The problem is the transmission leaks excessively, to the point that people following get a drop or two with a good bump. The underside is well rust proofed! The gearbox has been rebuilt with all new bearings and seals. The major leak is from the output shaft seal. After that the leak is from the selector shaft seals. The output flange hub body does have a slight groove where the seal runs, but before I go and replace it, wondered if the 50 weight motor oil is adding to the leaks as well. Only concern with going to 90 weight Hypoid gear oil is damaging OD. So, what is the correct oil?
Scot Stewart

I was told by the individual who rebuilt my transmission - who does this sort of thing fore a living - to use only 30W non-detergent oil.

Kieran Busch
kieran busch


Here is the story of my experience on this subject. It is a tech article I did a number of years ago, but I have just up-dated it here.

I bought my 1958 TR3A brand new. I always changed the oil in the gearbox/overdrive with straight 30 grade engine oil. At that time this was the recommendation. The gearbox in my car does not have a synchromesh first gear and at 14,000 miles (22400 kms) I had to have the lower lay shaft with its straight cut spur gear teeth plus all the bearings changed. Perhaps I was too rough or too young, but I felt it didn't last very long. After getting it repaired, I was extra careful never to take it up above 3000 rpm in first gear and I made sure that I was at a full stop before engaging first gear. I was a student in university at the time paying my own car expenses and college fees, so I had to be very careful. The same problems occurred again at 42000 miles. Before I put the car away in 1972 with 80000 miles on it, the first gear and bearings in the gearbox were damaged again. The overdrive was never a problem. All this time I used 30 weight engine oil as the lubricant for the gearbox/overdrive.

During the early 1960s, multigrade oils became available, such as 10W30. It was said that the detergents in this oil would foam and the oil would not be able to efficiently conduct the heat away. The foam would also allow the gears to touch metal on metal as the foam was not thick enough to resist the forces as the gears mesh along the contact or pitch line of the tooth face. Lastly, it was said that the detergent additive would cause the cone clutch in the overdrive to slip because it was too slippery. So I never used anything but 30 engine oil.

In 1990, after three years restoring my TR3A, and which included a complete rebuild of the gear box and overdrive once again, I called Ken Gillanders in California for his opinion. Ken has been the only registered owner of his 1955 "Red Rocket" TR2 and long ago he raced it. It is a very reliable car and Ken uses it as a test bed for new speed equipment, oils etc. He told me to use Valvoline 20W50 multigrade detergent engine oil in my gearbox with overdrive. I protested, quoting all the reasons above.

So I decided to use it and since then, I have changed the oil every 3000 miles. I have always used this 20W50 oil. I have now driven the car 60,000 miles since the rebuild was completed eleven years ago and the gearbox is still like new. The overdrive has never slipped. And I often take the engine up to 5500 rpm in first gear. The straight spur gear (non-synchromesh) first gear has never given me a problem, but I must admit that I still come to a full stop every time before engaging first gear.

Don Elliott, 1958 TR3A - TS 27489 LO
Montreal, Canada
Don Elliott

This thread was discussed on 03/01/2002

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