I have a 1963 MKX with the DG 150 2 speed transmission with the direct drive lockup torque converter “3rd gear”. When driven on the highway I feel a shudder or a slight hesitation almost like a misfire condition. I have replaced spark plugs, spark plug wires, cap and rotor. I am using the pertronix with their recommended coil. Timing is set at 10 deg and the centrifugal advance is free and the vacuum advance seems to be working.Carburetors have been adjusted and the plugs are showing a slight tan like they should. I am thinking that since this transmission is equipped with a lockup converter as the third gear, it has worn causing the surging at highway speeds. Anyone have any experience with this issue?
I have the DG250 in my ‘63 Mk2 - so have some familiarity. I think that the lock up feature is managed via a solenoid controlled valve. This could be playing up? I will have a look in my workshop manual to see if there is a fault diagnosis that might attend your issue. Paul
Does it do it when moving or when pulling away? I had an issue with my DG box shuddering when pulling away and it turned out to be propshaft alignment which is critical on these.
The workshop manual shows how to check this and adjust and if its out it can make a massive difference. I altered the centre bearing height of mine by around 15mm and it went from shaking my teeth out pulling away to smooth as silk.
I was absolutely amazed as it was suggested by a UK DG gearbox specialist and I thought yeah right like that’s going to make much of a difference but it does!
I had the same experience and similar remedy, in my '72 XJ6. Now bullet proof even if I stand on it from a stop. The OP’s issue is at highway speeds though. Paul
The issue is as soon as the converter locks in around 35 miles an hour, I have added a shudder fix additive and it has improved the clunk sensation when the converter locks but the sensation is still present. Another issue is the relatively high engine rpms these engine spin at 70 mph, how in the world did they drive them on the European Autobahns? I am seriously considering using Johns Cars adapter and adding a GM 700r4. I plan on using this car for fun excursions and loath the thought of the little 3.8 spinning at 3500 rpm for hours on end.
3500 rpm is just above the peak torque IIRC (3000rpm)?
Oh and I believe when the motorways in the UK opened up they started loosing engines 