• The Roadster Factory Recovery Fund - Friends, as you may have heard, The Roadster Factory, a respected British Car Parts business in PA, suffered a total loss in a fire on Christmas Day. Read about it, discuss or ask questions >> HERE. The Triumph Register of America is sponsoring a fund raiser to help TRF get back on their feet. If you can help, vist >> their GoFundMe page.
  • Hey there Guest!
    If you enjoy BCF and find our forum a useful resource, if you appreciate not having ads pop up all over the place and you want to ensure we can stay online - Please consider supporting with an "optional" low-cost annual subscription.
    **Upgrade Now**
    (PS: Subscribers don't see this UGLY banner)
Tips
Tips

BJ8 overdrive stops working after a while driving

Airwave

Freshman Member
Country flag
Offline
Hello I'm new in the Forum. I already read out a lot of good hints, which I really appreciate a lot.Now, as something strange happens when driving, I'm just wondering if someone can help.

Since the mechanic replaced the clutch plate the O/D doesn't work properly anymore, right after starting the cold engine it works perfect (Switch in & out), but after a certain while when heated up the Switch is not responding anymore. Has anyone any idea what could cause this phenomenon ? It doesn't seem to be wobbled contact because driving the next day the O/D works again but sets out again, Groundhog Day. Before the O/D did work without any problems.
 

oxford

Jedi Hopeful
Offline
Hi
Drive the car to warm her up. Then if you turn the ignition on but don't start the engine, put the car in first or third and flick the switch, you should be able to hear the solenoid clicking on the gearbox. Don't get confused with the relay click which isn't as loud. If you don't hear it it means the problem is electrical.
That's a start.
Matthew
 

BJ8Healeys

Jedi Warrior
Country flag
Offline
Hello, Airwave, and welcome to the Forum.
I do not believe there is a connection between your replaced clutch plate and the symptoms with the overdrive. Nor is the temperature of the engine directly related to those symptoms, but the temperature of the oil in the gearbox/overdrive could cause those symptoms if there are internal problems with the overdrive.
My first thought was that you are experiencing the same symptoms I did years ago. My O/D worked fine when its oil was cold, but once the oil heated up and I had to shift out of O/D it would not re-engage again until the oil cooled. In my case, the problem was a severely scored bore in the accumulator. That is a cylindrical aluminum part in the overdrive that has a piston with steel piston rings in its bore. Oil pressure from the O/D pump causes the piston to move back in the bore against a heavy spring until it exposes holes in the bore walls. These holes route the oil to the operating pistons to engage the overdrive. A scored accumulator bore causes too much leakage of the pressure (especially as the oil thins out at higher temperature) so the piston is not pushed far enough back to expose the holes. Some claim the accumulator can be removed and replaced without removing the gearbox and overdrive, but I've never done that.
The critical issue is that the O/D has to generate about 450 psi to operate properly and anything that prevents that will prevent the O/D from engaging.
Good luck with it!
 

Michael Oritt

Yoda
Gold
Country flag
Online
Matthew

Welcome to the forum. One of the first things to learn is that while a lot of us know a little a few of us know a lot. Steve Byers is one of those few.
 

CLEAH

Jedi Warrior
Country flag
Offline
Mine recently did the same thing. Worked fine until hot. Eventually, however, it stopped working altogether and did not work when cold. It was the relay in the engine compartment that was the problem in my case.
 

vette

Darth Vader
Country flag
Offline
Hello Airwave, and welcome to the forum. I''m going to make a suggestion based on the principle of "what was done last". i'm wondering if when the transmission was out for the clutch job that maybe some trans oil was lost. Check your fill stick indicator and refill if necessary.
 

Keith_M

Jedi Knight
Country flag
Offline
What kind of oil is in the transmission? The consensus seems to be that 30 wt nondetergent oil is best.
 

Bob_Spidell

Yoda
Gold
Country flag
Offline
...The consensus seems to be that 30 wt nondetergent oil is best.

Not necessarily. 30W non-detergent is what was recommended in the manual when the cars were built last century, and is still an acceptable lubricant (though getting harder to find). I use Redline MT-90 in both my BN2 and BJ8. I put it in the BJ8 to see if the OD would be a bit more responsive--it was--but was surprised by smoother shifting in the gearbox. The downside is a bit more leakage.

The theory on ND oil is that--since it has no detergents or dispersants--it allows swarf to sink to the bottom (presumably building up a layer of sludge). The MT-90 keeps wear metals--mostly brass--in suspension, though I've found they are so finely ground they don't cause a problem (at least, in the 75K miles or so that I've been using it).
 

roscoe

Jedi Knight
Silver
Country flag
Offline
IMG_20170717_074822949-1.jpgI agree that Steve is spot on. Although there are alternate explanations for your issue, since it seems to work well when the oil is cooler it is likley an oil pressure problem. Likewise,there are several spots in the OD unit where oil pressure can be lost. I've added a photo of a simple tool you can make or have made. All you need is a spare cap that goes on the selector valve, which is easily accessible with the gearbox tunnel off. A 600 psi pressure gage and a tad of welding skill. You remove the cap, drill a small hole in the top and install the cap with the gage. Go for a drive, making sure you are not going to get anything caught in the spinning driveshaft, and watch the pressure gage. I'll bet you see the oil pressure slowly drop to less than 300 psi as the oil warms up. Once the pressure drops off below the pressure needed to actuate the OD clutch the OD will drop off. I don't recall what the drop out pressure is but when i put my car on the road I found that the seat for the small ball bearing used with a spring for the oil pressure relief valve was badly pitted and would not allow the valve to ever close, thus not allowing pressure to ever build. I lapped the seat (for hours) and voila!
 
Last edited:

Keith_M

Jedi Knight
Country flag
Offline
Not necessarily. 30W non-detergent is what was recommended in the manual when the cars were built last century, and is still an acceptable lubricant (though getting harder to find). I use Redline MT-90 in both my BN2 and BJ8. I put it in the BJ8 to see if the OD would be a bit more responsive--it was--but was surprised by smoother shifting in the gearbox. The downside is a bit more leakage.

The theory on ND oil is that--since it has no detergents or dispersants--it allows swarf to sink to the bottom (presumably building up a layer of sludge). The MT-90 keeps wear metals--mostly brass--in suspension, though I've found they are so finely ground they don't cause a problem (at least, in the 75K miles or so that I've been using it).

I agree there are other oils that will work. I think I remember reading somewhere that detergent oils can foam and cause pressure in the overdrive to drop. My (not clearly stated) point was simply that one might try a different oil to see if that's the problem.
 

Bob_Spidell

Yoda
Gold
Country flag
Offline
Good point on the foaming. When my relay failed my OD disengaged randomly, so if an OD gets quits consistently when hot it's likely low pressure. A different fluid may help, but won't fix the underlying problem. I believe MT-90 is equivalent to 40W or 50W gear oil.
 
OP
Airwave

Airwave

Freshman Member
Country flag
Offline
Hello all again :smile:

Many many thanks to all of you for your excellent hints and advices, much appreciated !!

I performed easiest tests first as adviced and found out that it is obviously an electro mechanical device problem. It's likely the Solenoid.


Again, many thanks for your help, btw I also found this helpful techical overdrive description (added link eventhough I believe that all of you already know this pdf anyway):

https://www.healey6.com/Technical/Tech-OverdriveTroubleshooting.pdf

airwave

PS Low oil pressure problem; I'm using gear oil: SAE 40 and engine oil: 20w50 motorex
 

Michael Oritt

Yoda
Gold
Country flag
Online
Airwave--

I am glad you found your problem.

At the end of your post you say you are using "gear oil", a term which seems to be used loosely.

Make sure you are using an oil that has a GL4 rating which is compatible with yellow metal, such as the synchro rings in your transmission. Many "gear oils" are designed to be used in differentials or transmissions without brass, etc. parts and have a GL5 rating which has higher sulfur and phosphorus contents and will, over time, attack these parts. For more information go here: https://www.widman.biz/uploads/Transaxle_oil.pdf
 
OP
Airwave

Airwave

Freshman Member
Country flag
Offline
Thank you Michael :smile: as a fact my overdrive (false oil pressure for the Solenoid?) stops working when engine is warmed up, do you think it also might be becuse of the used SAE 40 gear oil ?
 

RAC68

Darth Vader
Offline
Hi Airwave,

Welcome. A while back there was a discussion on the effects of using thicker oils in the Overdrive and gearbox. Although gear oil and even Automatic Transmission Fluid are recommended by some manufacturers, my understanding is that a 90W gear oil (equivalent in viscosity to a 40W Motor oil you indicated using) could be a little thick to exit out of the small openings of the accumulator and cause an increase in pressure as the car continues to operate in OD. So, instead of OD loosing pressure as it warms, it is building pressure to a point that it will keep it actuated and will not release even when switched off until the pressure slowly diminishes.

As a check, I would change fluid to one having less viscosity before doing anything. I personally used 30W non-detergent oil for many years and switched to Red Line MTL about 10 years ago. No problems with 30W non-detergent but it was getting difficult to find a good brand.

Just a thought,
Ray(64BJ8P1)
 

vette

Darth Vader
Country flag
Offline
I have to agree with the proponents of the correct oil theory. If it is not low on oil then the wrong oil could be the problem as well. My belief is that you can get too thick of an oil. I still use 30w motor oil with no troubles with the trans or OD.
 

John Turney

Yoda
Silver
Country flag
Online
I have to agree with the proponents of the correct oil theory. If it is not low on oil then the wrong oil could be the problem as well. My belief is that you can get too thick of an oil. I still use 30w motor oil with no troubles with the trans or OD.
Actually, I use SAE60 in mine, but I have the uprated accumulator.
 
Similar threads
Thread starter Title Forum Replies Date
AUSMHLY BJ8 Overdrive Oil Passages Austin Healey 2
S BJ8 Overdrive Stays Engaged Austin Healey 35
AUSMHLY BJ8 Overdrive Accumulator Spring Tube Austin Healey 1
AUSMHLY BJ8 Overdrive Pressure Loss Austin Healey 11
AUSMHLY BJ8 Overdrive Oil Pressure Austin Healey 14
S BJ8 Overdrive Issue Austin Healey 7
S BJ8 Overdrive issue Austin Healey 10
BJ8Healeys For Sale Rebuilt BJ8 overdrive unit for sale Austin Healey Classifieds 0
M Overdrive In-Op AH BJ8 1967 Austin Healey 11
4tecdog BJ8 Overdrive oil leak Austin Healey 6
S Overdrive solenoid problem on a BJ8 Austin Healey 3
D Overdrive problem when raining - bj8 Austin Healey 23
S BJ8 Sputtering at High Engine Speed and in Overdrive Austin Healey 36
davidb BJ8 Overdrive Austin Healey 16
P Mysteries under the BJ8 transmission tunnel, speedometer cable, overdrive and gerabox Austin Healey 1
AH67 BJ8 OverDrive Austin Healey 5
M correct gear oil for bj8 trans and overdrive ???? Austin Healey 5
M overdrive bj8, smoked Austin Healey 1
D BJ8 Overdrive Switch on gear leaver top Austin Healey 2
R BJ8 overdrive intermittent Austin Healey 11
bighealeysource overdrive not disengaging right on my BJ8 Austin Healey 7
Ed_K Overdrive solenoid rubber piece on a BJ8 ? Austin Healey 2
specialsports Help Healey BJ8 overdrive just stopped working? Austin Healey 5
A BJ8 Overdrive Austin Healey 3
Steve P. Value of Healey BJ8 overdrive? Austin Healey 2
1 BJ8 History Trace Austin Healey 7
Patrick67BJ8 Wanted Looking for a used BJ8 switch panel. Austin Healey Classifieds 5
D BJ8 Top Installation Detail Austin Healey 3
B BJ8 Rear Backrest Hinges Austin Healey 4
S Wanted WTB: 3.5 ratio diff/pumkin for '67 BJ8 Healey 3000 Austin Healey Classifieds 0
AUSMHLY BJ8 Trans Cover Carpet Austin Healey 7
nitro BJ8 Engine Design Austin Healey 1
AUSMHLY BJ8 Carpet and Snaps Austin Healey 2
Overdrive45 BJ8 Interior Trim Austin Healey 8
nitro BJ8 Production Year Austin Healey 6
WHT BJ8 Rear Seat Surround Drain Tube Grommets Austin Healey 0
B BJ8 Seat Sliders Austin Healey 4
B For Sale 1967 Metallic Golden Beige MKIII BJ8 Numbers Matching - The Real Deal Austin Healey Classifieds 0
F Wanted BJ8 Engine Block Austin Healey Classifieds 1
BoyRacer For Sale BJ8 disk wheel hubs, spindles & calipers Austin Healey Classifieds 0
AUSMHLY BJ8 Rear Seat Squab Austin Healey 0
AUSMHLY BJ8 Differential Oil Change Austin Healey 6
S SOLD!! For Sale 1964 AH 3000 MkIII BJ8 Phase 1 Austin Healey Classifieds 2
Patrick67BJ8 BJ8 Factory Hardtop Rear Window Austin Healey 6
AUSMHLY BJ8 Clutch Pressure Plate, Old vs New Austin Healey 4
AUSMHLY BJ8 Clutch Fork Bush Replacement Austin Healey 5
AUSMHLY BJ8 Cylinder Head Installation Austin Healey 6
LAW75 BJ8 Brake Lines Austin Healey 2
AUSMHLY BJ8 Clutch Pressure Plate Brand Preferences Austin Healey 3
BoyRacer For Sale BJ8 spindles & disc wheel hubs Austin Healey Classifieds 0

Similar threads

Top