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Passat B5 Wagon 4motion Differential

212 Views 5 Replies 4 Participants Last post by  rehoward
Hello, new guy here. I am not a Passat owner but rather a fan of VW engineering. To date, I have bought a 1.8T to swap into my 1985 VW Vanagon and a 2005 Passat rear suspension (4motion) including a subframe that I hope to transplant into a Triumph Spitfire. Now onto the Passat suspension.

I chose it because it is very sturdy looking and has a low overall height. Also because it is a true 4-link suspension with CV axles and disc brakes. My concerns are these:

It is heavy, the Spitfire is not and I want to keep the car as light as possible. Any suggestions for lightening it?
The differential seems large. Does anyone know what the ring diameter is? Or how to determine the gear ratio? Or if it has limited slip or not? How much HP can it handle in a light car?
Will smaller disc brakes fit this axle if taken from another model of VW? What model? I could easily open up the center diameter of the disc if necessary.
Has this axle been converted to coil-over shocks by anyone?
Has anyone tried to narrow this assembly before?
Should I be looking for a lighter and smaller assembly? If so, what? The Spitfire will initially have 170 HP but later may be boosted to 350-400 HP so I will need sturdy axles and differential then.

Thanks for the help.
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I think you need to be in a Triumph Spitfire forum.
True. But I was hoping to find out how to identify the differential for the gear ratio or for limited slip. Apparently, few on this forum have experimented with the Passat for high performance.
Apparently, few on this forum have experimented with the Passat for high performance.
That's why there's the Audi S and RS series.
I think the lighter rear suspension was only in the S6 or RS6 where they use aluminum. There are aluminum hubs on later 4Mo, but I don't know if it was certain years or just W8 models.

The differential is either 3.889 or 4.11 and uses a torsen setup, not a true limited slip. They do have upgraded diffs that can be fitted. There is a 3 letter code on the diff that will tell you the ratio.

You can add coilover sleeves to the rear shocks, not the easiest to adjust, but they worked great on my car.

I'd expect that there are several other cars that run an IRS that would fit better in a smaller car. Maybe a late-model Golf Alltrack would be much lighter, smaller, and more efficient.

There were plenty of performance-minded owners on here, but with the last B5 built nearly 20 years ago, most moved on.

Here are the rear differential codes:
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Thanks for the help PZ.

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