I had a similar problem towing my 57 Splittie with my 66 Splittie, using an
adjustable (hinged V) towing frame.

It developed a horrible weave which started to push the rear sideways on
each swerve. Letting go of the wheel, if I remember correctly, fixed it for
me too (this was back in about 1986 or so).

Tongue loading is not adjustable when towing this way.

But then, swingaxle VW vans are awful for towing; had the rear pushed also
by a 37 Chev coupe I towed with the 66; no oscillations this time, just
refusal of the Chev to track correctly around corners or under brakes (down
a long grade).

Andrew Grebneff
165 Evans St, Dunedin, New Zealand
<andrew.grebneff@stonebow.otago.ac.nz>
ph   64 (3) 473-8863
fax 64 (3) 479-7527
84 VW Caravelle GL (to be fitted with SVX engine & Porsche G50 trans) RWD
87 Corolla 1.8 DX CE80 diesel sedan FWD
89 Corolla 1.8 DX CE96 diesel van/wagon FWD
89 Corona 2.0 D Select CT170 diesel sedan FWD
92 Toyota Estima Lucida (=Previa) 2.2 turbodiesel RWD