From Finnish scrapper to four-wheel drive – my T3 Syncro conversion

In spring 2025 my rear-wheel-drive T3 became a Syncro – four-wheel drive with diff locks front and rear. All the running gear comes from a Finnish Syncro panel van that I bought as a donor and stripped.

In this post I show what sets a Syncro apart from a 2WD, which parts I refurbished and how I got the front axle, gearbox and tank into the 2WD body. At the end you'll find part numbers, suppliers and the links that helped me most.

Donor vehicle and my T3 side by side in the barn — Left the stripped donor, right my T3 – just before the parts change sides

How this post is structured

The donor vehicle
What sets a Syncro apart from a 2WD
Preparation: refurbishing everything
Front axle conversion step by step
At the rear: gearbox, tank and filler neck
Pneumatics and electrics
Registration
The result
Update: switching to selectable four-wheel drive
Parts and suppliers
Thanks to the Syncro community

The donor vehicle

The donor is a Finnish T3 Syncro panel van, built in 1990, with the 1.6-litre JX turbodiesel (69 hp). Cosmetically it was finished, but the Syncro running gear underneath was complete – and that's exactly what I needed.

The Finnish donor Syncro on a trailer — Collecting the donor: lots of rust, but everything that makes a Syncro is there

I have a translation of the Finnish vehicle documents – handy as proof of where the parts came from.

What sets a Syncro apart from a 2WD

A Syncro is more than a 2WD with an extra front axle: the frame, floor and rear differ in several places. VW sent part-finished bodies without certain frame panels and without a front axle to Steyr-Daimler-Puch (SDP) in Austria, where the four-wheel-drive conversion was done. These are exactly the differences you have to recreate yourself when converting.

Area	What's different on a Syncro
Front axle	Axle carrier bolted to the frame; its own steering box plate; reinforcement plates in the frame; its own springs, shocks, anti-roll bar, wishbones, hub carriers, brakes and drive shafts; 6N front differential with lock; brake lines routed differently; shift housing and linkage
Rear gearbox	AVK gearbox with diff lock; different gearbox mounts; brackets for the skid plate, clutch line and coolant pipes
Tank	70 l plastic tank at the rear; filler neck at the rear; tank support plate
Other	Propshaft, pneumatic lines for the diff locks, switch panel

Removed steering box plate — The Syncro steering box plate (251803935B)

JX engine and AVK gearbox on a pallet — JX engine and AVK gearbox from the donor

Skid plate brackets with a template — Skid plate brackets – I took their position with a template

Removed 70-litre plastic tank with the old tank sender — On the Syncro, the 70 l plastic tank sits at the rear

Filler neck panel and other Syncro panels, freshly painted — Filler neck panel and other panels from the donor

Preparation: refurbishing everything

Before anything went into the bus, I stripped, de-rusted and overhauled every donor part.

Front axle

Removed all relevant parts
De-rusted the axle carrier, sandblasted the axle components
Repainted everything
Pressed in new rubber bushes, ball joints and wheel bearings

Wishbones, hub carriers and brake calipers before sandblasting — The front axle components before sandblasting …

Freshly painted hub carriers and wishbones hung up to dry — … and freshly painted

Tank and propshaft

Overhauled the tank sender, replaced the tank hoses, cleaned the tank
Overhauled the propshaft: new universal joints, a new flex disc (Hardy disc) for decoupling, repainted

Gearboxes

The front differential (6N) got a new viscous coupling (since replaced, see the update), and I got the diff lock working again.

Front differential taken apart on the workbench — The 6N front differential taken apart

I had the rear AVK gearbox rebuilt by TH Parts & More: new bearings and synchro rings, seals, a reinforced synchro hub for 3rd/4th gear and more. Including shipping, that came to around €2,300.

Note: the gearbox comes back without oil. Both gearboxes got new oil and new seals.

Front axle conversion step by step

The biggest job was the front axle: a 2WD lacks the mounting points for the Syncro axle carrier, so 2WD panels have to come out and Syncro panels go in.

1. Cutting out the 2WD panels

First, the panels that only the 2WD needs come out.

Three 2WD panels cut out, lying on the floor — Surplus 2WD panels

2. Opening up the frame

The frame is cut open so the reinforcement plates for the axle carrier fit inside.

Frame cut open after removing the 2WD panels — 2WD panels removed and the frame cut open

3. Welding in the reinforcement plates

Reinforcement plates for the front axle carrier in hand — Reinforcement plates for the front axle carrier

Reinforcement plate welded into the frame — Welded in

4. Fitting the steering box plate

I welded in the steering box plate and additionally fixed it with four M12 bolts.

Fitted steering box plate, painted black — Steering box plate fitted

5. Front axle carrier mount made from flat steel

For the front mounting of the axle carrier, I welded in flat steel and additionally fixed it with eight M12 bolts.

Prepared frame with red primer, ready for welding — Frame prepared

Front axle carrier bolted onto the flat steel — The front axle carrier sits on the flat steel

6. Re-routing the brake lines

On a Syncro, the front brake lines run in a different place, so I re-routed them.

New brake line at the front of the frame — New front brake line

7. Adapting the coolant pipe bracket

To make room for the propshaft, the bracket for the coolant pipes had to be modified.

Modified bracket under the floor of the vehicle — The modified bracket at the bottom of the picture

8. Fitting the axle

Front differential on the axle carrier, ready to fit — The front differential on the carrier, ready to go in

Fully assembled front axle with brake disc and yellow shock absorber — The assembled front axle

View from below of the complete front axle — And from below

At the rear: gearbox, tank and filler neck

At the rear, the Syncro needs new gearbox mounts, a tank mounting and a filler neck in a different place.

Gearbox mounts with weld nuts

My gearbox mounts sit on M8 steel weld nuts. On paper, press-in nuts would have been enough:

An M8 steel press-in nut holds approx. 6,000 N.
The gearbox weighs approx. 50 kg; engine and gearbox together approx. 130 kg.
The gearbox hangs on six M8 (8.8) bolts. With a load of approx. 65 kg, that's around 10 kg per bolt.

I still went for weld nuts, because the weight sits on a 4 mm shoulder. A weld spot on each nut also stops it from turning.

Prepared holes for the weld nuts in the chassis rail — Holes prepared

Weld nuts inserted, not yet welded — Nuts in place …

Fitted gearbox mount — The gearbox mount fitted

Skid plate and small brackets

The skid plate bracket fits existing holes; I drilled one new hole and fitted a press-in nut.
The brackets for the clutch slave cylinder line and the coolant pipes are bolted on.

Rear with engine, gearbox and skid plate fitted — Rear with engine, gearbox and skid plate

Tank mounting

De-rusted and painted the engine bay and tank area and added insulation mats
Prepared the tank support plate for the tank straps, spot-welded it at 8 points and riveted it at 4
De-rusted the tank straps and gave them several new coats of paint
Fixed the tank strap mount in the engine bay to the panel with an M8 bolt, as original

Fitted tank support plate, painted black — The tank support plate in place

Freshly painted engine bay from above — The freshly painted engine bay

Tank filler neck

I cut the filler neck panel out of the Syncro, fitted it into the body and welded it in. Then: filler, sanding, paint. I drilled new holes for the filler pipe and breather lines, resealed everything and secured the lines. A YouTube video on fitting the filler neck helped me a lot.

Filler neck panel fitted into the side wall — Fitting the filler neck …

Welded-in filler neck with visible weld seam — … welding it in …

Side wall around the filler neck filled and primed — … filler, sanding, paint

Bonded-in filler pipe under the vehicle — Bonded-in filler pipe

Parking heater

The conversion also meant the parking heater had to move: it now sits under the driver's seat, and I changed the Y-piece in the fuel line. I show what that looks like in the post about the parking heater.

Pneumatics and electrics

The front and rear diff locks are engaged pneumatically, which needs its own lines and an air reservoir.

Laid the pneumatic lines for the rear and front diff locks
Mounted the air reservoir under the vehicle on threaded rods, as original
Laid the wiring for the reversing light, rear diff lock, front diff lock and tank sender
Replaced the old power wire to the tank sender with a new one
Fitted the switch panel for the diff locks

Fitted switch panel with diff lock indicator below the radio — The switch panel with indicator for the diff locks

Registration

After the conversion the bus is technically a different vehicle, so several points have to be entered in the registration documents:

Four-wheel drive: two driven axles instead of one
Updated weight
Updated axle loads
Updated braking performance
Note "Syncro conversion"

The result

The 2WD Westfalia has become a Syncro with diff locks front and rear – and now it can tackle gravel and forest tracks too.

The finished Syncro Westfalia with the pop-top raised in the woods — Roof up, spare wheel on the back – we've arrived

Update: switching to selectable four-wheel drive

The bus no longer runs with the viscous coupling but with selectable four-wheel drive. The reason: I had set up the viscous coupling incorrectly and it was too stiff. Instead of redoing it, I switched to the selectable four-wheel-drive unit from mybusparts.

The swap is simple. The new housing replaces the old one; according to the seller, all parts are new apart from the inspected and overhauled housing. It comes with a gasket, vacuum line, Y-piece, bracket, cable ties and the valve and switch to operate it.

Old housing with drive flange next to the new housing with blue actuator on the workbench — Left the old part, right the new one

The selectable four-wheel drive fitted to the vehicle

In November 2026 the price was €1,299 plus a €550 core deposit. You get the deposit back when you send in an original, unmodified housing.

Parts and suppliers

Most of the Syncro parts came from the donor. The body panels missing on a 2WD are available new from these suppliers:

Part	Part number	Available from
Steering box plate	251803935B	th-bus.parts – repair panels
Front chassis rail reinforcement plates (2WD to Syncro)		Tygrys Syncro
Tank reinforcement plate (tank support plate)	253801551	TK Carparts
AVK gearbox rebuild		TH Parts & More
Selectable four-wheel drive (replaces the viscous coupling)		mybusparts

Thanks to the Syncro community

I couldn't have done this conversion without the people in forums, Facebook groups and on YouTube. Countless photos of original vehicles showed me what it should look like in the end. Those pictures belong to their creators – so I'm linking to the sources here instead of showing them:

The Gray Bus (YouTube)
Mark Halligan – Syncro conversion (YouTube)
Video on fitting the filler neck (YouTube)
2wd goes syncro
TheSamba: thread on the 2WD-to-Syncro conversion
Facebook group on the Syncro conversion

And what was left of the Finn was collected by the tractor.

Empty donor body on the front loader of a red tractor — The stripped donor body on its final journey

Questions about the conversion? Get in touch – I'm happy to help.