[Healeys] Russ Thompson

Charlie Baldwin mgcharlie at comcast.net
Wed Aug 9 05:44:05 MDT 2017


You have probably stepped in it by getting an oil discussion started again.

But to answer your question without adding my opinion to it, I believe 
that when someone on the list contacted Red Line, they recommended 
MT-90, which from memory is 40 wt.  Check Red Line's website:  

They make a good argument for using a gear rated oil in a transmission 
as Harold also outlines below.  As he mentions and we have discussed 
previously, it seems that the synthetic transmission oils do leak a bit 


On 8/8/2017 11:24 PM, Harold Manifold wrote:
> Mike,
> I am new to the Healey world but I am an engineer with an automotive 
> background who recently had a BN4 transmission with an overdrive 
> completely rebuilt. I could not find a consistent answer on the 
> recommended oil for the transmission. The original Healey manuals are 
> not consistent either, the shop manual recommends 20W50 and the Healey 
> service bulletins from the day recommend 30W. Coming up with the right 
> oil is further complicated by the design of a Healey transmission 
> which is two different transmissions with a common oil system. One 
> transmission is a traditional gear type with syncro rings that are not 
> compatible with the additives in modern gear lubricants and the other 
> is a hydraulic pump. I am sure there will be much disagreement but 
> these are the steps I went through to select the oil I would use:
> 1. The additives had to be compatible with brass and other soft metals 
> used in older transmissions.
> 2. The oil should be designed to work with gears and have some level 
> of EP protection. Note very few engine oils meet gear oil specifications.
> 3. The oil should have a viscosity similar 30W engine oil which was 
> recommended in an Austin Service bulletin in 1960 replacing 20W50.
> The oil that best fits all of these requirements is a 70W-90 GL4 gear 
> oil. Red Line MT-90 meets this specification as does Pennzoil 
> Synthetic 70W-90 GL4. I picked the Pennzoil as it costs less than the 
> Red Line but both should work well. Do not use a GL5 as the additives 
> are not compatible with brass. I looked into why Austin switched their 
> recommended oil from 20W50 to 30W and concluded it was for a lower 
> viscosity at lower temperatures i.e. when the transmission is cold. 
> Viscosity is another important consideration. 70W-90 GL4 has the same 
> viscosity as 30W engine oil above 35 degrees C and a better low 
> temperature viscosity. The only downside I have seen with Pennzoil 
> Synthetic 70W-90 GL4 is that it can get through even the smallest 
> openings and cracks and the transmission may leak a little more but 
> that is evidence the oil is getting every where it should. I have 
> heard Red Line MT-90 doesn't leak as much as the Pennzoil.
> For those that may doubt the viscosity claims please note that engine 
> oils and gears oils are classified differently and should be compared 
> by looking at the numbers on the can. See the attached viscosity curve.
> I trust this helps but I want to emphasize this is the oil I use and I 
> recommend you reach your own conclusion.
> Harold
> ------------------------------------------------------------------------
> *From:* Healeys [mailto:healeys-bounces at autox.team.net] *On Behalf Of 
> *Michael MacLean
> *Sent:* Tuesday, August 08, 2017 5:47 PM
> *To:* Healey List
> *Subject:* [Healeys] Russ Thompson
> Through a reference from the list I am having Russ Thompson in 
> Northridge, California rebuild my BN2 transmission.  It is a low 
> mileage (10,000 mi. approx) transmission, but I wanted to be able to 
> put it in and not have to take it back out again. Good thing I took 
> this precaution.  Russ found the overdrive stuck and would never have 
> worked.  Today he showed me the accumulator piston.  The smaller 
> center piston was scored from dirt or crap in the oil.  Russ replaced 
> it with a one piece piston from a Triumph overdrive.  There was a huge 
> spring below it.  Anyone heard of this?  He said engagement will be 
> real positive now.  Even with the low mileage, the number 2 synchro 
> was toast and will be replaced.  The other two were fine and will be 
> re-used.  All the gears showed very little sign of wear.  The reverse 
> gear had some surface rust on the teeth, but that can be blasted and 
> it will be fine.  Getting closer to having the drive train is the car.
> I know I am going to start a discussion, but Russ recommends using 
> 40wt motor oil for the transmission.  Anyone know what weight Redline 
> MTL is?
> Mike MacLean
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