Hallo aus Amerika! Ich bin ein neues Mitglied und helfe einem Freund bei der Arbeit an seinem 1975 c304. Ich bin ziemlich aufgeregt, dass ich an so einem einzigartigen Fahrzeug arbeiten kann. Wir machen einen Mercedes-OM603-Turbodiesel-Swap sowie vollständige neue Verkabelung, allgemeine Aufräumarbeiten usw. Ich habe viele Projekte in der Vergangenheit durchgeführt.

Meine erste Frage, die ich habe, ist, wie die vakuumbetätigten Differentiale so betrieben werden, dass das Vakuum beim Abstellen entlastet wird. Hat jemand eine Art Diagramm, das dies zeigt? Ich bin verwirrt, wie ein einzelner Magnet das Vakuum von drei separaten Kreisläufen entlasten kann.

ps, ich spreche nicht viel deutsch und benutze einen übersetzer ... würde es mir lieber sein, wenn ich nur englisch spreche ?!

Here is a picture:

https://imgur.com/a/vs4ZR2W

https://www.c303.de/c303-pdf/service/section4transmission2.pdf

Fig 40-7

Willkommen hier im Forum... 
Schön das ihr den Weg hierher gefunden habt.

Wenn der Motor aus ist (Vakum Out) Allrad und Differenzialsperre ON
Wenn der Motor Läuft (Vakum ON) Kein Allrad , Differentialsperren Out
Nach dem Motto Safety First 

Goggle

Welcome here in the forum ...; D
Nice that you have found your way here.

When the engine is off (vacuum out) 4WD and differential lock ON
When the engine is running (Vacum ON) No four-wheel drive, differential locks Out
According to the motto Safety First in the field;)
The valves only allow the vacuum to be checked.

Greetings Küppi

Zitat von: kueppi am 4.Februar 2019 17:22:29

Willkommen hier im Forum...  Schön das ihr den Weg hierher gefunden habt. Wenn der Motor aus ist (Vakum Out) Allrad und Differenzialsperre ON Wenn der Motor Läuft (Vakum ON) Kein Allrad , Differentialsperren Out Nach dem Motto Safety First  Goggle Welcome here in the forum ...; D Nice that you have found your way here. When the engine is off (vacuum out) 4WD and differential lock ON When the engine is running (Vacum ON) No four-wheel drive, differential locks Out According to the motto Safety First in the field;) The valves only allow the vacuum to be checked. Greetings Küppi

Nonono!
T-case & diff-locks operate differently, passive-on/active-off vs passive-off/active-on

Engine-Off = No Vacuum = Allrad/Vorderachs-Zuschaltung/Frontaxle-Engagement & NO axle-difflocks !
Engine-On = Vacuum = Hinterachs(en)Antrieb/Rearaxle(s)-drive & (still) no axle diff locks


The way I understand the question of OP, is 'what forces the locks (front vs axle) in either position, when vacuum is off (front-on/axle-off)'.
Which is, IMHO, in both cases, a metal spring....:))

Zitat von: yitzac1990 am 4.Februar 2019 15:56:4

Here is a picture: https://imgur.com/a/vs4ZR2W

Cool to see the surface-differences between regular steel (top body panels & doors), vs the alu-zinc plated steel (lower body).
How was this effect triggered?
Sand-blasting, wire-brush, or chemical peeling?
(looks as if the regular steel still has the white undercoat, so sand-blasting is less likely?)

Vielen Dank an alle für die Antworten! Ich denke, die Hauptfragen, die ich habe, sind:

1. greift die Vakuumquelle an den Front-Diff oder ist der Front-Diff an der Atmosphäre angeschlossen?
2. Sperrt die Vakuumquelle den Front-Diff oder ist der Front-Diff in der Atmosphäre gesperrt?
3. Sperrt die Vakuumquelle die hinteren Diffs oder sind die hinteren Diffs in der Atmosphäre gesperrt?

Was die Körperunterschiede angeht, wurde die untere Hälfte des Körpers tatsächlich von meinem Kumpel gemalt und die Farbe getestet, die er zu malen wählte. Als er es kaufte, war das Ganze wie die obere Hälfte gefärbt. Die untere Hälfte besteht aus Stahl und die obere Hälfte aus Aluminium (Aluminium-Zink?). Außer der Kabine (oben und unten) besteht alles aus Stahl.

Eine lustige Tatsache - mein Vater lebt tatsächlich in Hamburg, meine Großeltern wie in Kiel, und ich war schon zweimal dort und kann es kaum erwarten, wieder hierher zu kommen!
_______________________________________________________

thank you everyone for the replies!  I think the main questions I have are:

1. does vacuum source engage the front diff, or is the front diff engaged on atmosphere?
2. does vacuum source lock the front diff, or is the front diff locked on atmosphere?
3. does vacuum source lock the rear diffs, or are the rear diffs locked on atmosphere?

As far as the body differences, the lower half of the body was actually painted by my buddy, testing out the color that he chose to paint.  When he bought it, the entire thing was colored like the top half.  The bottom half is steel, and the top half is aluminum (alu-zinc?).  Except the cab (top and bottom) is all steel.

A fun fact - my father actually lives in Hamburg, my grandparents like in Kiel, and I have visited twice, and cant wait to go back!

Zitat von: yitzac1990 am 4.Februar 2019 21:23:28

Vielen Dank an alle für die Antworten! Ich denke, die Hauptfragen, die ich habe, sind: 1. greift die Vakuumquelle an den Front-Diff oder ist der Front-Diff an der Atmosphäre angeschlossen? 2. Sperrt die Vakuumquelle den Front-Diff oder ist der Front-Diff in der Atmosphäre gesperrt? 3. Sperrt die Vakuumquelle die hinteren Diffs oder sind die hinteren Diffs in der Atmosphäre gesperrt? Was die Körperunterschiede angeht, wurde die untere Hälfte des Körpers tatsächlich von meinem Kumpel gemalt und die Farbe getestet, die er zu malen wählte. Als er es kaufte, war das Ganze wie die obere Hälfte gefärbt. Die untere Hälfte besteht aus Stahl und die obere Hälfte aus Aluminium (Aluminium-Zink?). Außer der Kabine (oben und unten) besteht alles aus Stahl. Eine lustige Tatsache - mein Vater lebt tatsächlich in Hamburg, meine Großeltern wie in Kiel, und ich war schon zweimal dort und kann es kaum erwarten, wieder hierher zu kommen! _______________________________________________________ thank you everyone for the replies!  I think the main questions I have are: 1. does vacuum source engage the front diff, or is the front diff engaged on atmosphere? 2. does vacuum source lock the front diff, or is the front diff locked on atmosphere? 3. does vacuum source lock the rear diffs, or are the rear diffs locked on atmosphere? As far as the body differences, the lower half of the body was actually painted by my buddy, testing out the color that he chose to paint.  When he bought it, the entire thing was colored like the top half.  The bottom half is steel, and the top half is aluminum (alu-zinc?).  Except the cab (top and bottom) is all steel. A fun fact - my father actually lives in Hamburg, my grandparents like in Kiel, and I have visited twice, and cant wait to go back!

I think you wanted to distinguish between front/axle/diff-lock, center/frontwheeldrive and rear/axle(s)/difflock.

Axle diff's: no vacuum = open/disengaged; vacuum = locked/engaged

Center: no vacuum = engaged; vacuum = disengaged.


Also, what you might not yet have discovered, is that there is also a pressure sensor in the brake circuit (located just above your right-side lower leg, cq above gas-pedal), that *also* engages front-wheel-drive, by switching off (electric) vacuum (electric valve, in rear cabin, behind rear heater).

Poor man's ABS....:))


Only roof is aluminium, all sides are steel, just like the doors.
Originally normal steel, later upgrade{*} is steel with a coating of alu-zinc (similar concept as normal zinc/galvanising).

*Normally*, the upgrade/conversion from regular steel to alu-zinc was done 'as needed', meaning lower-panels first, upper panels not always.
Even differences between floor & sides exist....just 'as needed'.

{*} both military & civil, all done in military workshops, just as most of the rear bodies were build there in the first place (Volvo only delivered cab/frame); some rear bodies by special companies, like firetrucks.

Nicht sicher, ob ich richtig verstehe ... was meinen Sie damit, wenn Sie Center sagen? Die 3 Bedienelemente sollten vordere Differenzialsperre, hintere Differenzialsperre und vordere Differenzialsperre vom Verteilergetriebe sein, richtig?

Wir haben diesen Druckschalter tatsächlich bemerkt, aber ich glaube nicht, dass er an irgendetwas angeschlossen war. Wir dachten, es war nur etwas, das von einem früheren Besitzer hinzugefügt wurde. Wie funktioniert dieses System / diese Schaltung?

Danke für die Information!
________________________________________________________________

Not sure if I am understanding corrently... what do you mean when you say center?  The 3 controls should be front diff lock, rear diff lock, and front diff engagement from transfer case, correct?

We actually did notice that pressure switch, but I dont think it was hooked up to anything.  We figured it was just something added by a previous owner.  How does that system/circuit work and hook up?

Thank you for the information!

...the Vacuum does lock the Axles and disable the frontwheeldrive.
The Atmosphere does turn on the front Axle.

The big red button right side in the lower dashboard is the switch for the frontwheeldrive.
It opens a Valve in the Vacuumcircuit, so the frontaxle is engaged. The same Valve will be opened by the brakepressureswitch.
The two switches on the left side of the lower dashboard (Framaxel und Bakaxel) are putting the vaccum directly to the difflocks. There must be some hoses behind the dashboard.

Zitat von: yitzac1990 am 4.Februar 2019 23:23:26

Nicht sicher, ob ich richtig verstehe ... was meinen Sie damit, wenn Sie Center sagen? Die 3 Bedienelemente sollten vordere Differenzialsperre, hintere Differenzialsperre und vordere Differenzialsperre vom Verteilergetriebe sein, richtig? Wir haben diesen Druckschalter tatsächlich bemerkt, aber ich glaube nicht, dass er an irgendetwas angeschlossen war. Wir dachten, es war nur etwas, das von einem früheren Besitzer hinzugefügt wurde. Wie funktioniert dieses System / diese Schaltung? Danke für die Information! ________________________________________________________________ Not sure if I am understanding corrently... what do you mean when you say center?  The 3 controls should be front diff lock, rear diff lock, and front diff engagement from transfer case, correct? We actually did notice that pressure switch, but I dont think it was hooked up to anything.  We figured it was just something added by a previous owner.  How does that system/circuit work and hook up? Thank you for the information!

The ambiguity/confusion in this discussion is in this 'front diff engagement', translated even worse here 'Differentialsperre vom Verteilergetriebe, as especially the latter could easily be read as 'center diff lock / Zentral-Differential-Sperre'.

Just trying to avoid this, as there is no center diff on the Volvo, only good old-style front axle engagement....;))


Pressure switch should contain 2 electric connectors & wires, switching ground to the vacuum valve, cutting out vacuum, engaging front wheel drive.

ah ok, thank you both very much!

Part of the confusion is also the fact that I believe the C304 is missing the "big red button" on the right side of the panel in front of the shifter.  So we had no idea how this system worked, and no idea how the single solenoid in the rear cabin under the side seat worked.  My friend said he "didnt know how it worked, just that it worked."

Let me confirm something else I found online:  When turning OFF the front and rear diff locks (using the quarter turn switches on the lower dash), is the vacuum relieved back to atmosphere by the switches themselves?  I heard something about an o-ring built into the switch that relieves vacuum when switched off.

Zitat von: yitzac1990 am 5.Februar 2019 19:10:58

ah ok, thank you both very much! Part of the confusion is also the fact that I believe the C304 is missing the "big red button" on the right side of the panel in front of the shifter.  So we had no idea how this system worked, and no idea how the single solenoid in the rear cabin under the side seat worked.  My friend said he "didnt know how it worked, just that it worked." Let me confirm something else I found online:  When turning OFF the front and rear diff locks (using the quarter turn switches on the lower dash), is the vacuum relieved back to atmosphere by the switches themselves?  I heard something about an o-ring built into the switch that relieves vacuum when switched off.

Yes, you can even hear the air being operated, engaging & venting (engine off makes listening easier).

Also, the condition of the system, cq all seals together, can be observed by how low the vacuum stays intact, after engine is switched off.
(I believe a perfect system can hold vacuum for several days, even a week(?))

Hello.
Normally axle diffs are open without vacuum. When you turn switch they lock by vacuum. Those are just faucets.

Middle diff without vacuum is locked. It unlocks only when high gears are selected when pressing that big red button. It is locked in low gears and locks pressing brake pedal.

Big red button only turns on middle diff lock light and gives earth to solenoid behind back seat.

Zitat von: EuGarais am 5.Februar 2019 20:5:25

Hello. Normally axle diffs are open without vacuum. When you turn switch they lock by vacuum. Those are just faucets. Middle diff without vacuum is locked. It unlocks only when high gears are selected when pressing that big red button. It is locked in low gears and locks pressing brake pedal. Big red button only turns on middle diff lock light and gives earth to solenoid behind back seat.

Nonono, *not* 'middle diff'....;))
There is no middle/center diff on Volvo C3-series....

Also, red button (claimed to be missing with OP's vehicle) engages front wheel drive in high gear; FWD default in low range gear.

NB: the latter (T-case low range = FWD) can also complicate things electrically, as this switching is done by (mechanical) sensor & electric switching, another loop in the entire ground switching wiring.
Which sensor/switch contains 4 connectors (electrical/spade), but with rather easy to misplace colors (wire determination), and make the system go totally haywire (default lock in high range, button (or red light?) operates the other way around, in=open, out=locked)....so *if* the T-case was ever taken out, or worked on by the non-initiated, chance is significant  that the wiring in this location is wrong.

Thanks to everyone for the help, I think I finally understand how it all works.  I had no idea that engaging LOW on the transfer case would also engage the front axle.  I dont think we will wire this feature in though, as we prefer to switch everything "manually" when we want to.  I'll have to study the vacuum diagrams posted earlier to ensure our routing is all correct and clean everything up.

One more question...is that solenoid under the folding seat in the rear cabin a 12v or 24v solenoid??

Zitat von: yitzac1990 am 5.Februar 2019 22:33:31

Thanks to everyone for the help, I think I finally understand how it all works.  I had no idea that engaging LOW on the transfer case would also engage the front axle.  I dont think we will wire this feature in though, as we prefer to switch everything "manually" when we want to.  I'll have to study the vacuum diagrams posted earlier to ensure our routing is all correct and clean everything up. One more question...is that solenoid under the folding seat in the rear cabin a 12v or 24v solenoid??

Rule of thumb:
- (Swedish) military = 24v (all of it)
- civil = 12v (all of it)

Since I have yet to see the first *civil* C304/SWB/6x6/5-door, it is safe to assume yours is 24v also.
That said, the base system should already be quite obvious, by the number of batteries mounted....:))


Btw, with a 6x6, you might even consider disconnecting the 'Hard-brake=FWD' system, as it is not uncommon to have the system 'sticking' afterwards (FWD disengaging slowly, and/or with a disconcerting KLOINK), especially in/after corners.
(without powersteering, in tight corners, like hairpin roads downhill, you have another argument to keep it disengaged)

Note that this 'ABS-override' is not recommended for 4x4, even less empty, because these are already somewhat unstable under heavy braking, having very little load on the rear, so you don't want the rear wheels to lock up & skid before the front does.
(on a 6x6, the rear stability is much better, just by sheer weight, of 1m more vehicle & another axle)

Zitat von: WJM am 5.Februar 2019 21:11:4

Nonono, *not* 'middle diff'....;)) There is no middle/center diff on Volvo C3-series....

Sorry. I forgot how to call it in English.  So I called it "middle diff"

Zitat von: WJM am 6.Februar 2019 01:55:29

Since I have yet to see the first *civil* C304/SWB/6x6/5-door, it is safe to assume yours is 24v also. That said, the base system should already be quite obvious, by the number of batteries mounted....:))

Actually the previous owner of this C304 had already converted everything to 12v!  I am not sure to what extent everything was converted, but I know it was 12v.  Also, currently no batteries in it as we already disassembled all the wiring about a year ago...

Zitat von: yitzac1990 am 6.Februar 2019 13:16:28

Zitat von: WJM am 6.Februar 2019 01:55:29 Since I have yet to see the first *civil* C304/SWB/6x6/5-door, it is safe to assume yours is 24v also. That said, the base system should already be quite obvious, by the number of batteries mounted....:)) Actually the previous owner of this C304 had already converted everything to 12v!  I am not sure to what extent everything was converted, but I know it was 12v.  Also, currently no batteries in it as we already disassembled all the wiring about a year ago...

Okay, so it was crippled already, and all that for no other purpose than finding 12v bulbs & relais easier....;((
(since nearly all other electrical stuff is so Volvo C3-Series specific, *and* 12v/civil models are much much more rare than 24v/military, hence donor-parts are much more difficult to find in 12v than in 24v)
(add 24 to 12 conversions, and owners of 12v have even more difficulty finding specific parts)

Given the exotic nature of our Volvo', cq the narrow niche & steep pioneering/learning curve, it keeps baffling me to no end that people still consider 24v either a nuisance, too complicated or incompatible to the modern world.

Also, anyone having this kind of pioneering/engineering spirit must also have a keen eye for any further military exotic parts/upgrades/playtoys, be it lamps, radio's or generators, cq the really good stuff comes in 24v only.

Sorry for my pet peeving rant....;))
(from a long-time TLC-owner, where the 24v/cold-spec diesel versions are common & desireable)