Automatic Gearbox Pressure

[Pawel66]

I am just about to install back the gear box after it has been refurbished. As the refurbishment is being done in another town, I will receive te gear box and we will install it in the car ourselves. Then we would like to attempt tuning it in.

I have gone through Ignition System information, Linkage Tour as well as Gear Box Adjustment information. Realize the sequence and what I need to have working before getting under to fix the gearbox. Almost all clear.

One topic is not clear to me, though: if the pressure at idle, vacuum off, is different than 4bar (say: not drastically, just off, e.g. 3 or 5) - is there a way to adjust it? I saw clues in the posts, but I am not sure - diaphragm adjustment (how, where?), solenoid rod length adjustment (how exactly?).

Could you shed light on this?

I am asking now, just to have, potentially, the solution if issue arises rather than nervously ask for it later... Season is passing by and I just drove it a couple of times before gearbox (hydraulic clutch) fell apart.

Best,

[ja17]

Hello Pawel,

There are only three external adjustments on these gear boxes. The reverse gear band adjustment, the modulator pressure adjustment and the linkage rod adjustment, which also changes modulator pressure.

Before making any adjustments, make sure that the engine linkages are correct, the transmission fluid level is correct (check with warmed-up with engine idling). Make sure that the vacuum line to the modulator from the intake manifold is secure at both ends. Engine timing should be correct since timing will affect engine vacuum and transmission modulator pressure. Engine vacuum should be around 15psi.

 ***Make sure that the transmission linkage moves at all three positions. Minimum voltage at the solenoid is 10.8 volts.

Connect pressure test gauge to the modulator test port on the transmission. For the modulator pressure, disconnect the vacuum at the engine, engine should be at idle with engine linkage at rest Next move engine linkage above idle so that the transmission solenoid moves to the center (rest) position. The engine vacuum is still disconnected. The modulator pressure should now read 41.24psi. You can adjust this reading by turning the small modulator adjustment screw, after loosening its lock nut. (one turn of the adjustment screw equals 2.1 psi.).  Now check the modulator kick-down pressure. With the vacuum pressure still dis-connected, engine linkages just off idle,  reach under the accelerator pedal and depress the kick-down switch. The transmission linkage should energize to the "front" position. The modulator pressure should reach 65.41 psi.  ******(Early BBB 27-8/5 and 27-0/1).  Adjusting the length of the rod on the automatic transmission, should adjust the kick-down pressure up to specs. Re-check the modulator pressure at the other two positions. Re-connect the vacuum line and test drive the car. Some minor adjustments for shift quality can be made during test drives by adjusting the transmission linkage.

[Pawel66]

Joe,

Thank you, very clear!

So I guess the "small modulator adjustment screw" is the same we use for shift quality adjustment.

I think the only item I am missing on the picture in Technical Manual is location of the pressure measurement port. Hope we will recognize it...

Many thanks for reply again!