Overdrive Oil Info.

[Guest ron]

I came across this on an MG forum, it's of less relevance to TRs but worth bearing in mind if you're experimenting with gearbox oils.

The recommended oil for an MGB gearbox is 20/50 engine oil, during a gearbox oil change the gentleman in question filled his box with Castor GTX 20/50 'high mileage formula' he then found that the previously OK overdrive wouldn't work, he then did the obvious thing and drained the oil which he described as 'foamy brown green stuff' He flushed and filled with normal 20/50 and the OD worked fine!

Ron

[Rhodri]

Ron, I believe it is the detergent part in the oil that causes the foaming, which, as you rightly imply, prevents the pump from building up the high hydraulic pressure needed for the overdrive to function.

[Tom Fremont]

Ron, I believe it is the detergent part in the oil that causes the foaming, which, as you rightly imply, prevents the pump from building up the high hydraulic pressure needed for the overdrive to function.

 

Precisely why Quantum Mechanics advise use of 30W Non-Detergent for TR gearboxes

[F69]

Gents,

I have read this thread with interest and totally agree with what Rhodri has to say about the detergent effect, however, and I appreciate what Tom says, but I have always used standard EP90 oil in my gearbox ( fitted with A type overdrive unit ) and also in the rear axle unit and never had a problem. There you go, having said that, no doubt it will drop off next week.

[jemgee]

At Malvern a couple of years ago the guy from Overdrive Repair Services recommended using Duckhams Q20/50 - and they should know (or else he's trying to drum up more business!)

[RogerH]

Hi Richard,

I hope your gearbox doesn't drop out otherwise we are all up the swannee. There has been a lot posted about

what is best and what isn't. Clearly as Ron has indicated Castrol GTX is one to avoid because of the detergent foaming.

However I thought Duckhams was a high detergent oil (probably not though).

The original manufacturer/designer of the overdrive issued a warning stating DO NOT USE EP oils. However a few years later Triumph state DO use EP oils (probably the oils improved so as not to seperate under centrifugal conditions).

 

Thus you can use ancient non-EP gearbox oil or modern EP gearbox oil or anything that is moderately slippery (old shampoo etc) but not Castrol GTX - you have been warned!!!

 

 

Roger

[tr3timme]

Over decades, now, Duckhams 20/50 has always kept my O/D box working perfectly. I'll stick with it.

Tim.

[ianhoward]

Greetings...

 

I know lots has been said on this subject already... I too have been advised to used good old Duckhams and use it to good effect. However, Last Autumn I had a fully refurbished G/B and J-Type O/D fitted to my Good Lady's GT6 (they wished to fit it as some small mods were required etc.) When I mentioned 20/50 in the G/B and O/D he guffawed profoundly! Said he had never heard of it! That was a Triumph place near to TR Bitz... Suffice to say the unit has also worked fine with the Gear Oil he filled it with.

 

Regards

[Bob Stubbs]

My 6 recently came out of Racetorations after some winter work and part of that was working on the gearbox (with A type overdrive) and diff. Both were refilled with Millers CRX 80W90. There's no noticeable difference in how the overdrive unit performs.......it still kicks in smoothly with no delays.

[Andy Moltu]

There used to be concerns that the EP additives were potentially damaging to some of the gearbox/OD components. I'm not sure that applies to current gear oils.

80w/90 gear oil is probably the nearest thing to the original gear oil. If you can't get hold of a brand which is recognised to be safe in classic gearboxes & overdrives such as Millers or Penrite then strait SAE 30 oil is a safe option - can be got from oil stockists or agricultural merchants. It doesn't mean that the other brands are not safe in classics just that the manufacturers don't bother to state one way or the other.

 

There are a couple of problems with using multigrade engine oils - the foaming which has been mentioned and also the use of viscousity enhancers (I think that's the term) which are not ideally suited to the shearing forces applied in a gearbox. These get broken down & the oil's nature changes and may well lubricate less well over a period of time.

[heliguy]

I "borrowed" this thread from the TR Forum, an article written by the quantumechanics guy, the overdrive "guru's" on this side of the pond....

 

Topic of the month for June 2005 – Overdrive oil recommendation

 

Gang – I apologize for not writing an article for some time, but between the rough winter and everything else going on, it was impossible!

 

I want to express our experience and opinion on the topic of the proper oil for use in the Laycock de Normanville overdrive units. We constantly get into discussions( and sometimes heated debates!) with British car owners on this subject. This month’s discussion will invariably get some interesting responses as it seems to be a rather emotional (and not necessarily logical) discussion item for British car overdrive owners.

 

Let’s start out with history. Historically even the recommendations from various car manufacturers are confusing. Some say to use multi grade oil (MG manuals), some hypoid oil (Triumph manuals), some non detergent oil and some even recommend automatic transmission fluid! No wonder everyone is so confused!

 

Many years ago (in a land far, far away (OK it wasn’t that far away or even that long ago)) we ran an experiment on overdrive oil. We rebuilt an A type overdrive unit and initially ran it with 30 weight non detergent motor oil. When spun up on our test bench at 1,000 RPM, it reached a normal pressure of 400 PPSI. When shifting the pressure dropped to 300 PPSI and quickly recovered to 400 PPSI. All was right in the world of overdrives.

 

We then drained the oil and replaced it with 10W30 multi grade oil. When spun on the test bench, initially it tested fine. However, after a few minutes of running, the oil pressure dropped to 300 and when shifting, to 200. Upon observation of the internals of the operating overdrive we found bubbles developing in the oil pump body and oil pump output passage. We surmised that the detergents in the oil were causing the oil pump to cavitate, and develop air bubbles as it pumped.

 

We then drained the oil again and replaced it with 90 weight hypoid oil. This time the oil pressure jumped to 600 PPSI! When shifted, the pressure dropped to 450 PPSI, which made the shift immediate and harsh. After a few minutes of running the oil pressure actually began to climb even higher. (Which made no sense since we thought the oil would thin out and the pressure would drop). We finally shut it off at 750 PPSI as we did not want to damage the unit. Even though the overdrive unit was now in the non overdrive position (solenoid disengaged), the overdrive was now stuck in overdrive and would not come out. The higher pressure had driven the sliding clutch member so hard into the brake ring that the clutch return springs could not return it to the non overdrive position. A tap on the brake ring with a hammer (the universal overdrive release tool), shifted it back into the direct drive position. After running a number of these test with the same result we found what was happening. The oil holes in the accumulator sleeve are very small. The 90 weight oil was so heavy it could not escape from the accumulator chamber as fast as the oil pump could pump new oil into it. So even though the accumulator piston had passed the oil hole relief position, the pressure continued to build up because the oil could not leave the system as fast as it was being pumped in. The accumulator piston actually bottomed out in the sleeve (similar to coil bind on valve springs). When removed we found the accumulator spring had been compressed and was no longer useable.

 

After replacing the spring, we then tried automatic transmission fluid. We saw the same results as we did when we used the 30 weight non detergent oil.

 

We then tried synthetic oil and the unit also worked OK although it began to leak from all sorts of places it had not leaked from before.

 

Based on these tests we have since and continue to recommend the 30 weight non detergent motor oil as the best oil to use in the overdrives.

 

Some other experiences with customer overdrives over the years have reinforced this choice. For example, we found a Jaguar compact overdrive with a broken accumulator piston and bent spring when it had been used with 90 weight oil by the owner. When the piston and spring were replaced and the unit filled with 30 weight non detergent oil, it functioned normally. A customer LH overdrive unit that was filled with 90 weight oil "pulsed" between direct drive and overdrive without even being switched on electrically. When the oil was flushed and replaced with 30 weight non detergent oil the unit worked normally.

 

Other noted problems with overdrives filled with 90 weight are excessive wear on the oil pump plunger wheel and the eccentric cam, probably due to the higher pressures developed. Also the clutch lining seems to be more deteriorated in units with 90 weight oil than those with 30 weight oil.

 

The use of non detergent 30 weight oil does not seem to affect the transmission parts or function. Bearings, synchros, gears and hubs do not seem to function any less effectively with the non detergent 30 weight oil as with 90 weight gear oil.

 

So there it is gang, our scientifically based rationale for using and recommending 30 weight non detergent oil in Laycock overdrives. I welcome further discussion and feedback on this topic by anyone interested. As always, thanks for reading this article!

[marvmul]

A very interesting article ! Without such experimentation, one can only guess when an overdrive doesn't work or is damaged. When would one be able to conclude that a wrong oil is the culprit?

[Guest ron]

I've got 20/50 in the MGB gearbox and Castrol EP80 in the TR6 and I can't feel any difference in operation of their respective overdrives, same slight delay engaging, same smoothness of take up and release, I try to select the oil nearest to what the maker originally recommended, personally I think the gearbox is the governing factor in which oil to use not the OD.

Ron

[Don Elliott]

I have used Valvoline 20W50-R (the R is for Racing) for the last 16 years (94,000 miles) in my gearbox with overdrive in my TR3A and I'm satisfied with it. BTW, the specs. for this oil quote that it has double the Zinc and Phosphorus needed for flat tappet engines etc. where high contact pressures occur like in a gear box.

 

And the overdrive specialist Quantumechanics recommends SAE 30 straight Non-Detergent as was produced in 1955.

 

http://www.quantumechanics.com/categories....ex&catid=11

 

He explains why you should not use 90 Hypoid. But he makes no reference to high pressure contact points on the faces of the gear teeth which need additives like those found in Valvoline 20W50-R.

 

In the first 80,250 miles from new, I ruined the gears 3 times in the gearbox of my TR3A using SAE 30 non-detergent as was recommended in the Triumph manual at that time. In the last 94,000 miles since using the Valvoline 20W50-R, the gear wear is as expected.

 

Why did I select this oil ? When I was doing my total body-off restoration from 1987 to 1990, I came to the point when I was ready to fill the gearbox/overdrive with oil so I asked Ken Gillanders, a good friend who runs British Frame and Engine in Temple City, California. He raced and dragged his TR2 back in the 1950s and was featured with his 1980 TR8 in the recent "Triumph World". He told me to use Valvoline 20W50 - but make sure to use the "R" for Racing designation. I countered with all the usual things I knew about, like the detergent is too slippery and the cone clutch will slip, etc. Won't it foam which would make a problem too ?

 

He convinced me with his answers and told me to go ahead and use it. He had been using it for several years back in 1990. It was good advice.

 

Don Elliott, Original Owner, Montreal, Canada

TR Register member since 1987.

 

http://www.britishcarforum.com/bcforum/pho....php/photo/1977

[john.r.davies]

Anyone who has a copy of the TRaction Tecnicalities CD-ROM disc will find further discussion of this subject under "TR 2-6 transmission oils".

That includes a quotation from the Laycock overdrive manual where, as I have not seen that document I can only say that it alleges," It is essential that an approved lubricant be used when refilling, preferably a straight mineral oil with a viscosity between SAE 30 and SAE 50 with no EP additives".

However, the author of that item (Ian Gibson) did not state which Laycock manual or its age. Is this advice relevant to later overdrives?

 

And the article quoted above, of the test-bed overdrive trial. That overdrive was let down by the size of the holes in the oil pressure accumulator, that were "too small" for Hypoid 90 and allowed the clutch to over-pressure. That detail could have been changed easily in the several later versions of the Laycock overdrive, so that experiment can only be true for the 'A' type.

 

John

Edited April 28, 2007 by john.r.davies

[graeme]

Sorry to drag this up, but while searching for info on OD gearboxes, I found the above document from Quantum Mechanics.

 

If they used 90 weight oil in the OD I am not surprised they experienced problems. 90 weight oil is NOT EP80/90, it is high viscosity steam cylinder oil, its like treacle and will only work at high temperatures.

 

EP80/90 is virtually the same viscosity as SAE 30 engine oil.

 

Cheers

 

Graeme

[Andy K]

A bit off topic, but I can't get my Technicalities CDs to work any more. Don't seem to like XP or W7. Any suggestions.

 

Oh, and I've used Duckhams Q, Halfords Classic 20/50 EP90, EP80/90 and ATF in my O/D gearboxes and they have all worked fine. The most important thing seems be making sure there is the right amount of whatever you decide on in there!

 

Andy K

[RonA]

Mine seems to work OK on W7