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BJ8 Overdrive Stays Engaged

Scot

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My overdrive will stay on after deselecting it and will come out of it sometime later. It is not consistent.

I decided to use Norman Nock's book where he suggests this issue may be due to the valve aperture becoming clogged with foreign material such as sand particles, etc. The valve was straight and not bent and all looked fine. I cleaned the valve out with some wire and noticed nothing abnormal; the same with the other components. I performed static checks on all the switches and have ruled out electrical issues since the car will go into overdrive all right.

Anything else to check while the tranmission tunnel is out of the car and I have good access?

Any advice appreciated!
 

DerekJ

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The overdrive will not disengage solely by the dashboard switch, you need to depress the throttle as well. The throttle switch can be eliminated so that the dashboard switch will directly engage and disengage. Most competition Healeys have this modification.
 

gonzo

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Agreed. Throttle switch on my BJ7 is just a relay actuated directly from dashboard switch. Depress clutch, flip switch off accompanied by throttle blip to disengage OD. OD response is immediate.
 

John Turney

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Most likely it is the throttle switch. It may be out of adjustment if a throttle blip doesn't work. A much rarer cause may be too much wear on the overdrive clutch ring, causing it to engage too far, but check the throttle switch first.
 
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Scot

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Thanks for the answers guys! I actually took the throttle switch out of the car. Cleaned all the contacts, hooked up and tested it with a voltmeter for the proper engage/disengage position. Unless I'm not getting the sequence just right in the car while driving, the overdrive will not disengage even with blips of the throttle farther than the 1/3 depression called for. Overdrive isolator switch is clicking as well as operating solenoid. Only other component is the relay. Could a bad one cause it to stay engaged?
 

Bob_Spidell

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Not common, but relay points can stick. I had a failing O/D relay, but it would disengage the O/D at random. I took it apart in a hotel room and filed the points, it worked fine until replaced and I kept it in the spares box.
 

Bob_Spidell

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Here's an experiment to get more info. Note I haven't done this myself--at least not lately--so if anyone sees a flaw in my logic pipe up:

Get on a straight, traffic-free piece of road. Get into 4th/overdrive in the normal way at about 50-60MPH. Put in the clutch, put the gearbox in neutral, flip the O/D dash switch to 'Normal' (off) then rev the engine. This should isolate all the electricals from the O/D. Then put the gearbox back into fourth and let the clutch out gently (give it a little gas if necessary); if you're still in O/D as evidenced by engine RPM vs. speed the problem isn't in the electricals (it isn't likely, but not impossible that the solenoid is stuck in the on/up position). If you're still in O/D the problem is in the O/D itself: either the operating valve is stuck open or, as John suggested, the O/D cone clutch is embedded too far into the brake ring (that's all I can think of, anyway).

Have you tried fresh fluid? If the operating valve is sticking it might free it up. How many miles on your car? Has its fluid been changed regularly (20K miles or so for dino fluid; synthetic can go longer). I pulled my O/D at 205K miles and the cone clutch lining was still serviceable.
 

Bob_Spidell

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A further comment. You do not have to dip the clutch when activating/deactivating the overdrive.

No, but I do. My reasoning: Unloading the drive drain, just a little, esp. when engaging--I've always done it when disengaging, for smoothness' sake--should put less wear on the O/D clutch. Done just right, all you notice is the change in engine/car speed. Note you don't have to use your clutch to shift gears, either, but it makes shifting a bit smoother (I've had to do it a few times when my clutch cable failed).

Another opinion: https://www.quantumechanics.com/
 
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Scot

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Bob,
I will try the road test when it stops raining here in Seattle!
I had the lay gear replaced a few years back due to a faulty first gear. It received new fluid then. I have gone back and forth on the type of fluid over the years. The overdrive always performed well no matter what was in there! There is 20w50 oil in there now so its probably time to do a change.
 

vette

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I know some trans/OD have used 20/50w oil but I don’t think Healey specs ever called for that. I’m almost sure that Healey specs call for straight 30w. I have been running straight 30w in my BJ7 trans/OD for at least 20 years now at over 100,000 miles with no issues. I also do not use a throttle switch. Just run your dash switch thru the original OD relay according to the original schematic. The only thing you have to be careful of is to not drop it out of OD when decelerating, that will jar the driveline. So the solution to that for normal driving is to use the clutch whenever shifting into or out of OD. Then there is no shock to the driveline.
 

Bob_Spidell

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Bentley reprint of 100-6/3000 shop manual:
 

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vette

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Bentley reprint of 100-6/3000 shop manual:

I can't argue with that but. I have a copy of the original Austin Healey 3000, MKS I and II Driver's Handbook which is where I got my info. It shows no more than 20w/30 for engine and trans. Unfortunately my scanner is caput right now so I can't scan it into my PC.
 

Bob_Spidell

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re: "The 100's service manual (BN1) calls for 30 weight."

True dat. But, multi-vis oils didn't become generally available until the late 1950s ( > WHAT IS MULTI-GRADE OIL? | TransDiesel < ). Had they been available earlier, the service manuals would likely have recommended it (apparently, even BMC could change with the times). As another poster mentioned, any decent oil will work in our gearboxes. I've used MT-90 in both my Healeys for many years and miles and follow an 'extended change interval;' i.e. whenever I think they really need one and I get ambitious or have to pull the gearbox, usually going 30K miles or more. Norman Nock used to recommend changing every 15K miles (he also recommended filing, cleaning and adjusting fuel pump points every 10K--anyone do that?).

I haven't gotten into my BN2's gearbox, but I don't think they're significantly different than a BJ8's (besides being side shift). I don't think multi-vis oils offer significant improvements for gearboxes like they do for engines--no top end to get oil to ASAP--though I think a gearbox and O/D would be heavier shifting in really cold conditions and, since 20W-50 is higher viscosity than 30W at higher temps the hydraulics may work a little better.

We just proved Godwin's Law of Motor oil:

"As an online discussion grows longer (regardless of topic or scope), the probability of a comparison discussion involving Nazis or Adolf Hitler motor oil--or tires--approaches 1"
 

Bob_Spidell

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I can't argue with that but. I have a copy of the original Austin Healey 3000, MKS I and II Driver's Handbook which is where I got my info. It shows no more than 20w/30 for engine and trans. Unfortunately my scanner is caput right now so I can't scan it into my PC.

The manuals reflect what was available/recommended at the time of their writing. Lubricant formulations have changed immensely over the decades; generally, for the better (except maybe ZDDP content for our flat-tappet engines). 10K mile oil changes are now routine. If you follow that recommendation strictly to the letter, you can only use oils that were manufactured in that period (I can't recall ever even seeing 20W-30 motor oil). Would you say that, since most of us were 'manufactured' in the late 40s/early 50s we should only use the medical techniques/medications available in that time period?

One difference, and it may or may not be significant--is the type of gear oil used. Most newer ones are GL-4 or GL-5, which usually contain sulfur-based 'EP' (extreme pressure) additive which may (or may not) be harmful to gearboxes/ODs containing brass or bronze. The only brass/bronze components that I can think of right now are some thrust washers in differentials and the plugs in O/Ds; my BJ8 has its originals and, after 210K miles I've had no issues. My old Ford tractors call for GL-1, which I had to special order 5g from Napa; I don't think I'll bother next time I need gear oil.
 
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vette

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The manuals reflect what was available/recommended at the time of their writing. Lubricant formulations have changed immensely over the decades; generally, for the better--except maybe ZDDP content for our flat-tappet engines--10K mile oil changes are now routine. If you follow that recommendation strictly to the letter, you can only use oils that were manufactured in that period (I can't recall ever even seeing 20W-30 motor oil). Would you say that, since most of us were 'manufactured' in the late 40s/early 50s we should only use the medical techniques/medications available in that time period?
Bob, I'm only saying what I am reading in my specific documents. I do have the Bentley manual but I have not needed to refer to it lately. When you questioned my remark about something lighter than 20/50 I had to look to see where I got the idea I was relying on. When I first bought my Healey the driver's manual is what I relied on hence where I got the idea of 30w. I have an MGB that a Haynes manual recommends 20/50 in the trans/OD so I know that some trans use it. My personal opinion, based on no scientific expertise, is that 50w is too thick for an OD. Especially in cooler temps. To me 30w seems about right for all around driving. Just my own warm fuzzy feeling.
 

Bob_Spidell

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Note the manual 'allows' 20W-50 motor oils; the '20W' indicates the oil has the viscosity of 20W oil at freezing; your 30W would be thicker. That's the whole point of multi-vis oils: thinner when it's cold--so the oil can get where it needs to be quicker* and the starter doesn't have to work as hard--and thicker when it's hot (the '50' indicates the oil has the viscosity of 50W oil when hot; not sure what temp is used; probably boiling). Thicker viscosity reduces metal-metal contact hence wear (up to a point). The only (potential) issue with multi-vis oils is they use long-chain molecules called 'viscosity improvers' (VIs). These molecules 'coil up' when cold to make the oil thinner, then 'stretch out' when hot to maintain viscosity/thickness (> A Simple Explanation of Viscosity Index Improvers <). Over time, these molecules get shortened ('sheared') in use, reducing their effectiveness. Note the 'base oil' for a multi-vis is lower than the cold temp number; the VIs increase viscosity even when cold; I think 20W-50 uses a base oil that's around 12-15W--don't quote me on that--and the added VIs bring it up to 20W.

The massive improvements in lubricants, along with better metallurgy, exotic metals in spark plugs, electronic controls, etc. is what allows many modern cars to go 100K miles without even a tune-up--which is mostly new spark plugs--and 200K miles or more without overhaul (we won't talk about timing belts).

* Edit: Both my Mustangs call for 5W-20 oil, and I go 'by the book,' but that seems 'thin' to me (thicker is recommended for racing, with an oil change after every track session). In earlier years, some would use higher viscosity oils. Well, the Modular engine uses hydraulic timing chain tensioners; some 'smarter than the average bear' types used thicker oil and, because the oil didn't pressurize the tensioners quickly enough they suffered busted tensioners.
 
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vette

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The massive improvements in lubricants, along with better metallurgy,
Thanks Bob. My only last thought on this is that I don't think the metallurgy in my Healey has changed much over the last 70 odd years. :smile:
 
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