Driveshafts and CV Joints

First it’s worth noting that the strength of the CVs is dictated mainly by the diameter (90mm or 100mm) and the size of the ball bearings. (Thanks to CrazyQuiff, Mk1OC and Ex-GKN ).

Working from the gearbox out, and assuming that Mk1 GTI spec is used at the least:

Inner CVs and Gearbox mounting flange options:

• Either the size of the Inner CV joints have to match the standard flanges on the gearbox used, or the Flanges on the Gearbox must be swapped to match the CVs used. I believe large block Mk1s (GTIs etc), and Diesel Mk2s use 90mm Flanges/CVs. Some Late mk1 Cabriolets, 16V Sciroccos and Mk2 GTIs (and G60s) use 100mm Flanges/CVs. Measure them if in doubt!

Driveshaft Options:

• Standard Mk1 GTI Shafts
• Late Mk1 Cabrio Shafts (Shorter than above to accommodate bigger CVs)
• Scirocco 16V Shafts (Believe same as the late Cabrio shafts)

I believe Late Mk1 Shafts Cab are identical to Rocco 16V spec, and have the larger Mk2 GTI 100mm spec CVs so will fit direct to Mk2 Gearboxes.

NB: the Mk2 GTI (100mm) CVs are not just larger in diameter, but are also thicker than the 90mm CVs. This means that they will not fit on far enough onto std mk1 shafts to fit the retaining circlips. To get round this there are a few options:

• Machine out the inner splines slightly to the CVs fit on slightly further.
• Machine the lip on the shafts down slightly.
• Don’t fit the circlips! Not ideal for obvious reasons. A few blobs of weld could be used on end of shaft to secure if wished.

The assembled shafts can also be too long depending how you machine them, so can knock on the diff depending on ride height.

Outer CV options:

• Mk1 GTI, Mk2 Diesel, Mk2 GTI (8 and 16V Identical), Mk2 G60. I believe all of these can be fitted to both types of driveshaft.

There are a few combinations of CV joints and drive shafts, what will fit is likely to be different from what is ‘recommended’ as inevitably lowering and increase of power will increase strain on the CVs.

My experience: I used Std mk1 GTI Box, Inner flanges, CVs and Shafts for the last year, but have destroyed 4 old std mk1 90mm CVs in the last 6 months, so have now upgraded to 100mm Inner (and flanges) and 16V Outer CVs on std mk1 shafts.
Soon to move to the 16V Scirocco set up.