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240 M46 Overdrive Low Pressure Symptoms (Relief Valve Shims)

The flat was eliminated on later production OD's and even though I suspect it doesn't make a difference I always align the slot with the passage in the housing.

The reason I suspect it doesn't make a difference is that there's a recess in the sleeve where the slot is cut so oil can flow all the way around the sleeve.

pump-body-j-type.jpeg
 
I received the analog pressure gauge and connected it to the test port of my overdrive (Had it made with a custom 8' hose)

While driving in 4th gear, the gauge read 0psi. While driving in 5th gear (overdrive) the gauge averaged about 100-125psi.

Should the gauge read 21psi in 4th gear (as specified in the Volvo manual), or does the OD test port only provide the engaged OD PSI and does not provide the gearbox pressure?

Would the missing shim from my overdrive account for the very low psi in the OD?
 
I measured the shims inside the overdrives...
The '84 overdrive, which is currently on my wagon had a .76mm and .25mm shim...Missing an additional .25mm shim, which was broken.
The '82 overdrive, which originally came with the wagon, had 2x .25mm shims.

I thought both overdrives would have the same number and thickness of shims since they both came from D24 240 Volvos.
Do '84 overdrives require more shims than the '82 ODs due to the different design?
 
VolvoScout said:
Would the missing shim from my overdrive account for the very low psi in the OD?
Click to expand...
Not likely. The shims were used to "tune" the pressure between the different load profiles (turbo vs. non-turbo vs. diesel), and lining materials (asbestos vs. non-asbestos), all of them between 400 - 600 psi IIRC.

The shims thicknesses range from 0.5mm - 12.0mm, giving pressure rise from 12.1psi - 170.6psi.


VolvoScout said:
Should the gauge read 21psi in 4th gear (as specified in the Volvo manual), or does the OD test port only provide the engaged OD PSI and does not provide the gearbox pressure?
Click to expand...
Not sure what you're asking here. You quoted the greenbook, and are now wanting someone to tell you that's not how it works?
 
I swapped the shims in the relief valve.
It now has 2x .25mm shims rather than the .25 & .76mm it had earlier today.

I also swapped the relief valve inner sleeve/cylinder with the sleeve from my '82 overdrive because the o-ring was considerably thicker.

Now I don't register the 100-ish PSI that I was getting earlier and it doesn't feel as if the OD is even attempting to engage.
The solenoid is receiving power and clicking.

I swapped the new solenoid with an older one with no change in results.

From reading the following link, it would seem this may be a pump issue?
https://static1.squarespace.com/sta...a2/1560385143542/J+Type+Overdrive+Part+IV.pdf

And if this document is accurate...if no pressure can be obtained than the overdrive must be removed and rebuilt?
https://volvo1800pictures.com/document/mish/Volvo Overdrive Diagnostics and trouble shooting.pdf
 
With the ball, spring and seat removed, should I be able to push the pump plunger or should it be unmovable while the car is parked?
 
I swapped out the pump spring, seat and ball and pulled out the the sleeve to clean and inspect.
Then I removed the Relief valve and filter and solenoid again and blasted everything with compressed air in case there was a dirt blockage somewhere.

Still reading 0psi in 4th gear and Overdrive still not engaging.

The OD did successfully engage a few times a couple of weeks ago...

Where should I go from here?
 
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Is there anything else I can do to diagnose/repair the overdrive while it's on the car? (before I have to consider removing and rebuilding it...again)
Overdrive feels as if not building any pressure (gauge confirms, and does not read any pressure)
 
Either there's an internal leak or the the pump isn't making pressure. The only thing I can think of to check would be to see if the the pump plunger is moving when the output shaft is turned. If not, the woodruff key for the pump eccentric may have sheared. If that's the case the overdrive has to come off.
 
Can't help thinking that we are overlooking some important clues-- Didn't you register at least some pressure before swapping some parts/ making modifications? Sorry I have lost track of the before/after configurations. Unclear. When troubleshooting you need to be systematic and document each step and its results.
 
hiperfauto said:
Either there's an internal leak or the the pump isn't making pressure. The only thing I can think of to check would be to see if the the pump plunger is moving when the output shaft is turned. If not, the woodruff key for the pump eccentric may have sheared. If that's the case the overdrive has to come off.
Click to expand...

Is this the correct process for checking for pump movement?...I will have to jack up the rear of the car so that the rear-axle is free floating, drain the transmission, remove the OD inspection cover, remove the pump plug and inspect for pump movement as I spin the driveshaft by hand?

I don't recall seeing a woodruff key inside the overdrive, where is the pump eccentric located?

After installing a new clutch, pressure plate and swapping the transmission, the overdrive kind of worked (only in the Mornings and only the first time it was engaged.) After about a week it pretty much stopped full engagement and felt as if it was building pressure, but not enough to engage. This past week, I connected the pressure gauge and read 0psi residual in 4th gear and only read about 100psi with overdrive engaged. Now, after part swapping, I am reading 0psi residual in 4th gear and 0psi with overdrive engaged.
 
Yeah, that's what it's going to take to check the pump for movement.

The woodruff key is under the eccentric on the main shaft of the transmission.
 
Inspected the OD again today.
The pump does move with the drive shaft.

So I assume this means one of the internal o-rings is not sealing correctly? (probably the actuating pistons?)
 
The nuts for their hold-down bars have a very low torque spec. If you reefed on them maybe they broke?
 
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