The cost of SWEPCO is similar to AMSOIL and Redline the problem is it only seems to come in 4 litres so it would cost a whopping £78 to replace the oil and put half of it away for a ‘rainy day’ any views on Redline and AMSOIL as the next best option?
Sorry. I have no personal experience of Redline or AMSOIL products with regard to the steel synchro question I'm afraid, although - obviously - both brands have great reputations.
SWEPCO 201 is (off the top of my head?) I believe 80W/90, and is made from old dinosaurs. I'm told by those who know better than me that synthetics are not suitable for the steel synchros. Neither are friction modifiers.
It is kind of contrary to expectation, but you don't want an oil that is too 'slippery' here. The Porsche-patent steel Servo synchros employ
steel baulk rings (we should be talking about
baulk rings rather than synchromeshes) and - as their name suggests - they rely on a draggy/baulking action in order to smooth the correct meshing of gears. Anything that smooths that baulkiness (as in friction additives for LSDs to quieten plate chatter) is the opposite of what is required. If anything, the more modern gear oils, synthetics and the like, are too good for the baulk ring system to work properly...
Just as an aside, Nissan supplied the north American market HLS30U Datsun 240Z and sub-variants with 4-speed FS4W71-A and FS4W71-B transmissions with brass Warner-patent synchros because it was felt that the more positive, deliberate shift action required of the FS5C71-A and FS5C71-B transmissions as supplied to Japan and the rest of the world would not be to the taste of the average American customer.
Nissan saw the Porsche system as being more 'sporty' and the Warner system as being a little more on the leisurely side. A matter of taste perhaps, but the Porsche system boxes are designed to have a slightly 'baulky' shift action that requires a certain amount of positivity. Like a rifle bolt action, for example.
Nissan's Sports/Race Option A and B type transmissions were almost always fitted with the steel synchros, if that's a clue to the shift feel.
) so will look at AMSOIL - why are you preferring AMSOIL?
