I am not sure I posted my final impressions after replacing the rear LLS with springs from Strutmasters, so there it goes. If I already did, sorry for the repeat…
My Expy had the 4 wheel LLS, which includes conventional shocks at the rear. The shop ordered a set of replacement rear springs from Strutmasters and installed them. That took about 1.5 hours of labor. The front is now simply resting at the lower height with the torsion bars, but the truck looks fine and balanced. I drove it 600 miles, including 300 miles while towing my car on a tow dolly.
I could not tell the difference with the air suspension. Confort and towing ability (at least for that relatively light load) were not noticeably affected.
The total cost, including replacing a coil pack (not related, but done at the same time) was just about $400. The shop gave me a good deal.
That is probably an order of magnitude less than it would have cost me to have the LLS repaired at the Ford stealership, and I would still have been left with a poorly reliable system. I am pretty sure the springs wont require maintenance for as long as I have the truck.
I will put the front and rear height sensors, and the compressor, on ebay soon… The compressor is 3 years old but has been used very little, since the LLS was turned off most of the time.
The Strutmasters rear springs are a highly recommended upgrade for anyone with a 4 wheel LLS.
Didier