C4 vacuum modulator piston?

[FLStang]

Which way does the damn thing go in?

I can put it inb either way, and I have found references to it posted by others online, but nowhere does it say which way it should go: fat end first, or skinny end first.

The tranny never worked (probably why the previous owner parked the car) and I don't know if it was in correctly when I tore the tranny apart.

So, a simple question. Which way does the modulator piston go?

Jan

 

[brianj5600]

Most things are skinny end first, but I will verify. If it went fat end first, the smaller parts could not block the big hole required by the big end. Clear as mud?

 

[brianj5600]

Now that I think about it. Only one end will accept the rod. Turn it toward the modulator. The other end is too flat to keep the rod in position.

 

[brianj5600]

How do the rings look towards the end of the pump? Those are what seals to the forward clutch. Also how does the area look that they ride on in the drum thingy? Bad seal here = no forward gears.

 

[FLStang]

Now that I think about it. Only one end will accept the rod. Turn it toward the modulator. The other end is too flat to keep the rod in position.

piston goes in either way, and the rod still fits, and the modulator still screws in the same.


Rings on pump "looked fine" but having never seen new rings, I can't tell if these were ok or not. The bore they ride in looks ok, to the untrained eye. I could get new rings, but I read some people complaining about new rings sealing much worse than therir old rings, so they had to put the old ones back in.

Wouldn't leaking rings also affect reverse? When pressure drops all throught the system?



jan

 

[brianj5600]

There are 2 pairs of rings. Each pair of rings has a feed hole in between. The valve body only supplies pressure to both drums in 3rd gear. In reverse the VB supplies oil to the direct only. With now oil being fed to the forward drum, it would not have any affect on reverse. If the forward drum leaked it could lower pressure to the direct in 3rd gear.

 

[FLStang]

Well, I figured out the modulator valve. It goes in fat end first, leaving the skinny end sticking outwards, ready to accept the pin.

The orientation was obvious once I saw the bleed holes, and moved the piston back and forth by hand.

I went and got new rings for the pump too. The 2 new big ones closer to the pump were fine, but the skinny ones at the end didn't fit the bore they're supposed to slide in, they were too large in diameter. I reused the old ones and called it a damn day. Am not taking it apart again. Next step is garaging the damn thing and saving money for another tranny. I've had it. The PO trashed it real good, who knows what all is wrong with it. The whole car was raped by a dumb teenager, shoulda known to expect everything to be trashed.


(For example, he "rebuilt" the carburator, didn't use any gaskets anywhere, promptly had an engine fire, burned the paint off the hood and all the wiring in the engine bay....)


Jan