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Transmission with Overdrive - Which Oil to Use

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gonzo

Jedi Knight
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Apologies for raising an old subject, but i need clarification on forum search findings:

For those running Original OD Transmissions, which oil do you choose to use? I use Castrol GTX 20W 50, same as for engine, but ready to make a change to RedLine MT 90 based on forum discussions / stories. MT 90 and Castrol GTX on shelf ready for action. Any suggestions would be appreciated. GONZO
 
If 20/50 was good enough when they built it , its good enough now . Why change
 
30 wt. non detergent
 
Thanks. My old standby, Castrol GTX 20/50, will go in the trans like before. Last time I used 30W non detergent was in my '65 Corvair Corsa air cooled boxer engine, so I understand the rationale here. Gonzo
 
Same as engine 60 W Valvoline VR1
 
Some thinking behind the choices - 30 non-detergent vs 20/50 GTX - has to do with the metal used in the synchros.
Yellow metals - bronze, brass - use the non-detergent 30 wt. (earlier cars - side shift and some center shift).
Steel - 20/50 engine oil. (Later center shift).
 
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I was pretty sure that the Healey manual calls for 30w motor oil. Non-detergent would also be the smarter choice. I would concede that some modern oils such as Red Line as advertised might provide smoother shifting especially in colder weather but I agree with Healey Nut if what ever was spec'd when the car was built and of coarse if there have been no perceptible incidences of failure then the original stuff is what I use. My car usually doesn't get fired up when ambient temp is below 50*F.
I also have OD. :smile:
 
This is a discussion that seems to come up quite frequently with quite a variation in oil use type. Although, as British_Recovery has indicated, metal types used in the transmission should be considered when selecting lubrication oil for the trans/OD, I would also extend that NON-Detergent oils were recommended by Healey to allow metal debris to fall out of oil suspension and collect in the pan. Detergent oils were designed to keep debris in suspension and eliminated through the use of a filter as in the engine. Since there is no filter in our trans/OD, keeping debris in oil suspension can only present an extended risk.

As for oil choices, I use Redline MTL synthetic which is more of a gear type oil with similar viscosity to a 30W engine oil. Although synthetic oils have a greater probability for finding a path to leak out, I have found little fluid loss over the years and have enjoyed smooth reliable shifting and OD responsiveness. Although others may prefer using engine oil or even Automatic Transmission Fluid. As I see it, the construction of the Healey transmission/OD is the stimulant for their non-detergent recommendation and although others may used the same OD and recommend different lubricants, it also conforms to the requirements of their transmission as well as OD.

My thoughts,
Ray(64BJ8P1)
 
I switched to Redline MT 90 over 10 years ago. I love it. It is true that it leaks out no mater what you do. It can be had on line or Ebay for a more reasonable price. Check Summit Racing too. Use a drip pan if you don't already. The stuff is SLICK! I get about a 3-4 inch drip in about a months time. (The mystery is why the dip stick never shows any loss).
 
No mystery. A teaspoon of oil will keep your spot on the floor fresh and shiny for months. If only oil evaporated like alcohol. Fires would be more likley but we wouldn't have those gol darn spots....
 
I use Penrite Gearbox Oil 40 which I believe is an Australian product. As Ray says, I think it best to avoid multigrade detergent oils. I went for the slightly heavier weight because of the warm Queensland climate, where I live.
 
Redline recommends MT-90 GL4 (according to my notes - I've standardized on Redline for all the 'vintage' transmissions and differentials we own). They recommend it for Spridget 4 speeds, AH 3000 o/d transmissions, as well as the replacement Datsun and Toyota 5 speeds. Doug
 
tahoe healey said:
(The mystery is why the dip stick never shows any loss).
Click to expand...

I have long wondered the same thing. I have three drip pans under my BN2, end to end. I get puddles of at least three different fluids there (the car apparently leaks fluids that I don't even add!), and the quantity would suggest that I need to add this and that, here and there, more often than not. However, year after year, no loss shows on the dip sticks.

How they do it, I'll never understand.
 
I noted that some use Red Line MTL, as I do, and some use MT90. I looked into the differences and found that the MTL and MT-90 are both GL-4 gear oil and differ in viscosity with MTL providing 70w at low temperatures and close to 85w at high (SAE 5w30/10w30 engine oil) while MT90 performs through a 75w - 90w range and meant for warmer climates. Since I do drive my Healey until the snow and ice show up, I use it through a more diverse temperature range then most and find the lower viscosity of the MTL will maintain the smooth operation of the Trans/OD on cold days as it does during the hot NJ Summers.


Happy St. Patrick's Day,
Ray(64BJ8P1)​
 
Forgotten that OD equipped transmissions has TWO drain plugs, or perhaps I had never noticed! So this time the entire trans and OD were properly drained by pulling both plugs. Followed by fresh oil (Castrol GTX 20W 50). Shifts nicely- Red Line MT 90 next fluid change.

On a related subject, using 1st gear on take off now and holding each gear a lot longer with the 3.5:1 rear end installed. Holding 4th gear doing 60 / 65 MPH @ 3000 RPM. A few more runs with the GPS are needed to determine how far off the speedometer is, but at the moment it's looking like 5 to 7 MPH under. I'm liking this new ratio and a fresh rebuilt diff. GONZO
 
Hi Gonzo, when you say "holding 4th gear doing 60/65 MPH @ 3000 rpms" do you mean straight 4th or 4th with overdrive.
Thanks.
 
vette said:
Hi Gonzo, when you say "holding 4th gear doing 60/65 MPH @ 3000 rpms" do you mean straight 4th or 4th with overdrive.
Thanks.
Click to expand...

That's straight 4th gear without engaged OD. The 3.5:1 rear ratio allows to hold 3 and 4 gear longer on the same stretch of roadway which used to demand 4 gear OD. :eagerness:
 
I have used 20w-50,10w40, GL4 gear oil, and probably a few other things in my old 100 and other old British car with overdrive gearboxes. I have never noticed much difference, except some of the thicker stuff felt thicker when I used to drive year round in extreme temps.

What I have read has convinced me that a straight weight non detergent is a better choice in a gearbox than multi-viscosity detergent oil. I have been using that more as GL4 has become harder to find.

I like what I read about the Redline products, but most everybody says they have a propensity to leak. My gearboxes all seem to have a similar ropensity. Putting the two together has not seemed like a good idea.
 
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