Hi Laurent, Good question. I was reading the early 1850 workshop manual just now and in the General Specification section it lists the steering turns lock-to-lock as …
3 - Earlier models.
3 3/4 - Later models.
3 1/2 - nominal 1975 onwards.
So it looks like 3 different rack and pinions.
The 1850 Parts book July 1973 gives 4 listings for the pinion.
( 2 types but no ratios listed )
TKC0462 RHS ( Rimmers list this )
The later parts book just list the pinion as NSS.
…. which is given as a Toledo pinion ???
Why are the LHS and RHS pinions different but the rack itself is the same ?