• Hi Guest!
    You can help ensure that British Car Forum (BCF) continues to provide a great place to engage in the British car hobby! If you find BCF a beneficial community, please consider supporting our efforts with a subscription.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

Transmission with Overdrive - Which Oil to Use

Share this page

I have used 40 weight non detergent ever since I had overdrive issues several years ago. Works best in my OD and when going through the trouble shooting, hooked up pressure gauge, etc, and have stuck with the 40 weight. I get mine from Amazon.
 
I used 20W-50 motor oil for many years with no problems, then tried Redline MT-90 hoping for a little quicker OD engagement when hot. It felt like the gearbox shifted a little smoother and since I wasn't looking for/expecting that I don't think I had 'confirmation bias.' Yes, it does tend to escape to the ground a bit more. Just had a discussion about this with David Nock, and he prefers MTL; I may try it next time. I just rebuilt the gearbox and OD, and at almost 200K miles both were in fine fettle except the usual wear from a ham-fisted driver grinding the gears, so just about anything we're liable to use should be fine.
 
I too used Castrol GTX 20w/50 in the (engine &) gearbox for decades, but when I had to succumb to buying a *store bought* overdrive unit for my side-shifter xmsn__I didn't have the NLA parts laying around to fix it__I turned to Quantum Mechanics for a reconditioned unit.

As per John @ QM, if I didn't use 30w non-detergent oil, the warranty was void. So nowadays, the trans has 30w non-detergent (Shell?) oil in it, along with a couple bottles on the shelf. To put everyone's mind at ease, it too is seemingly self-replenishing, confirmed by the oil-soaked piece of cardboard under the car, at the dipstick still at the MAX line...

... how it does it, we'll never know ;)
 
Randy is correct if you've had your gearbox rebuilt. Steve Day confirmed it. Use what your rebuilder tells you, otherwise your warranty is void. Same for engines.

BTW, I use VR-1 SAE 60 in mine. Otherwise, it leaks out faster than I drive. It definitely slows down the shift into OD, but I have the uprated accumulator so that's not a problem.
 
I use the Penrite 20/50 but notice that when the oil is new I have to be careful changing from first to second when starting off at the beginning of the day, as I can end up grinding the gears. once warmed up a tad there is no problem and as the oil becomes 'older' ( I guess that the properties are changing) the problem goes away.

:cheers:

Bob
 
tahoe healey said:
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).
Click to expand...

I will venture a guess splash and thermal expansion of the oil. ?
 
Clearly we're all over the place. Straight 30 non-detergent or multigrade detergent engine oil will do the job of lubricating the transmission and making the OD function, but it's good to remember that the oils recommended in our cars' manuals were developed before the advent of antibiotics and other new-fangled inventions.

I use Redline MT90 in the transmissions in all cars except for the Ginetta. In the Healey (Toyota five-speed transmission) as well as the two Elvas (MGA 3-synch's) the Redline oil produces smoother and faster shifts and in the MGA boxes it eliminates a lot of the "notchiness" that older British transmissions seem to develop. (The Ginetta has an all-steel dog box and I use Amsoil Severe Gear GL5 oil which has better anti-shearing properties--the same oil I use in the diffs of all the cars.)

Yes, Redline does tend to leak, but so do all BMC engines so no big deal. BTW the Toyota box does not leak even with Redline--wonder why....
 
Last edited:
Back
Top