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OD sluggish when cold

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nevets

nevets

Jedi Knight
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My overdrive is sluggish, meaning when I flip the switch it can take more than a minute to finally engage. However, once the car is warmed up, say after 20 min of drivng, it engages more readily. And after it's been engaged for a while, then disengaged, then next time I flip the switch, it engages immediately, and each time thereafter (until the next time I drive the car from cold). Never any hesitation disengaging, I might add.

Any ideas about what the problem might be? The trans oil level is where it should be.
 
Nevets,
That is about how mine operates. On a cold it may take 5 miles or so to engage. I am using 30 wt non detergent oil as per John at Quantum Mechanics. Have a good day!

John
 
Mine seems to work the same whether hot or cold. It seems to have a random delay from 0 to 5 seconds on both engaging and disengaging. I haven't figured out a pattern of what might cause the delay.
 
Hi Nevets,

Mine may be broken since my overdrive seems to smoothly engage almost immediately when the switch is flipped. I only seem to have a slight delay on a cold winter morning at first start-up but I am slow at that time as well.

What fluid are you using in the unit? After using Red Line MTL for the two year, I find it performs very well with the unit sliding in and out without fuss. The drawback is, as with most synthetics, it seems to find new ways onto the garage floor. I will be changing back to 30-weight non-detergent when I find some.

I would suggest you change the fluids, if you haven’t already. Initial foaming, which dissipates as the oil warms, could be causing your problem. Additionally, oil residue or corrosion could be slowing your solenoid resulting in slow response. I would first check the solenoid’s amperage draw prior to removing the trans cover. Keep in mind that there is no fusing on the solenoid so a high draw will result in a burn. If the draw is in line with normal current operation, the plunger can still be the sticking point.

Since the unit recovers nicely when warm and performs properly when engaged, I don’t expect you will find any internal issues in the unit.

All the best,
Ray (64BJ8P1)
 
I had this problem for years until I finally took off the side cover and cleaned out the accumulator tubes. There was a lot of sludge in them. I also followed Norman Nock's tech tips about checking all the ball valves and adjusting the solenoid. Now it engages immediately all the time and stays engaged (before it would sometimes slip out of OD and I would have to come to a stop then start up again and re-engage the OD). I did all the work with the trans in the car, just removed the trans. cover.
 
When I first acquired my Healey, overdrive was not functional. Without knowing what I was doing, I did notice the solenoid was sticking. So after cleaning and making sure it was engaging, the OD worked. Since my car has been on the back burner for the last 6-7 years, OD would not engage and very sluggih after some driving. Definately one place to start.
 
Thanks for the comments and suggestions. I'll add it to my growing list of winter projects. Regarding access to thru the side cover, Tim, how big of a PITA is it? I assume it rrequires removing carpet, trans tunnel, draining the oil, new yoga positions, and a bucket of cuss words...any other cautions?
 
No, it was not that much of a problem to access the accumulator.

The accumulator is accessed through the side plate shown in this picture under the solenoid:



IMG_0729-1.jpg


The oil does not have to be drained from the transmission. Oil only gets pumped into the accumulator when the car is running. I have a BN7 so the tunnel is no big deal to remove; I understand the later models are not so easy. I did take the driver seat out of the car. I highly recommend NOrman Nock's Tech Talk manual available from British Car Specialists. It's the best $35 tech manual I've ever seen. The only problem is that it lets you know you have problems you didn't know you had.
 
Tim

Thanks for the great pic and additional info. I have a BN6, so tunnel removal should be similar as BN7. I have an autographed copy of Norman Nock's tech talk, though not quite up to date, and yes very useful. With its hand drawings and scrawled page numbers, it reminds my a little of a VW beetle manual I had called 'VW Bug Beetle How to keep your VW alive for Dummies', also very useful.
 
By the way, after you take out the screws on the side plate you have to remove some bolts to remove another plate. To do this you have to remove the solenoid activating arm, so when you put it back together you have to reset the solenoid arm position following Norman's directions.
 
Tim/Nevets,

I would suggest after removing the plate, and before proceeding as Tim indicates, you examine the area for oil and debris and test the action of the solenoid per manual directions. If sluggish, take the 2 screws holding the solenoid down and slide off the plunger. Look into the solenoid hollow and make sure it is clean, smooth, and dry (not saturated with oil). Also check to make sure there is a proper rubber bumper for the solenoid plunger to strike in its downward travel.

Reinstall the solenoid and retest for proper activation. If still performing sluggishly, proceed as Tim indicated.

Good Luck
Ray (64BJ8P1)
 
I will be changing back to 30-weight non-detergent when I find some.

Most racing oil will meet this criteria such as Valvoine VR1 etc.
I do suggest that you make a pressure test of the unit and insure it builds rapidly to about 400 PSI and holds it ..Keoke
 
Keoke said:
I do suggest that you make a pressure test of the unit and insure it builds rapidly to about 400 PSI and holds it ..Keoke
Click to expand...

Uh, you lost me on this. Whats going to build rapidly to 400 PSI???
 
The OD cam driven oil pump pumps oil which pushes the accumulator piston against a heavy spring. This should generate 400psi of hydraulic pressure which is maintained until released when the solenoid is tripped and lifts a ball valve and the oil under pressure is driven against the operating piston which engages the OD. The pressure can be measured by removing the plug at the top right side of the OD unit (where the ball valve resides) and replacing it with a threaded line to a pressure gauge which measures 500lbs. or more. Pressure is developed by rotating the wheels (presumably by jacking up the rear end and running the drive line in fourth gear). I have not done this myself.

I did have a problem of no pressure after I cleaned out the accumulator system, but it just took some time to get the pump to refill the system, sort of like bleeding the brakes.
 
Tim, Ray, et al...good stuff here. Hopefully fixing this problem will not turn into a big adventure. I'll be back with more questions once I get stuck into the project. It would be nice if all I need to do is clean out some debris from the assembly. Feel free to contribute additional information. Thanks again.
 
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