Many Safari owners found the rear leaf springs to be too soft for towing or
hauling.
Back then, my options were:
1) add rubber or steel spring spacers for coil suspension, very cheap and
easy to install, not an option for leaf spring Safari's;
2) recurve the leaf springs or add a leaf, I forget the cost, but then you
rode high in the rear when unloaded;
3) get air shocks, getting up in price, but there seemed to be a question
about premature failure in winter/salt conditions;
4) get airbags CDN$300/pair CDN$1-200 installation (discuss more below);
and/or
5) weight distributing hitch, unlike options 1-4 it moves weight off the
rear axle, but is useless when hauling cargo without a trailer.
For options 3 & 4 you can add an onboard compressor to make it really sweet.

Since I visit Home Depot like every other week-end, I choose option 4.  The
Airlift bags I had installed were
http://www.airliftcompany.com/­ridecontrol.htm
However, the version made specifically for the Safari cannot be installed
IMHO exactly according to Airlift's instructions since it is too cramped for
the chassis.  Also with rear air, the line runs very close to the support
bracket.  I gave up trying to install it myself and had a pro truck
suspension shop install them for me.  They installed the hard-to-do
driver-side really well, but the easy passenger-side not so great.

To make a long story short, I left on a 15,000 km trip and had two Air bags
fail.  One bay ruptured right away because the installation on one side was
soo tight that the lock nut couldn't be properly tightened down.  It came
loose and allowed the bag to drift towards the tire and poof.  The second
bag I lost after hitting a pothole at ~100km/hr, the plastic air fitting was
right against the frame and the compression forces cracked the fitting.

After I got home, I switched the air fittings from plastic to brass ($5) and
strapped simple plastic wraps to make sure the air bag couldn't slide
towards the tire.  For the first trip the air bags were headaches.  After I
applied my simple fix, I had them for another 5 years problem free and put
another 15,000 km on them without any problems towing or hauling. See pics
of the simple fix
http://www.ofoto.com/I.jsp?c=1­1kqtb9x.and0kz9&x=0&y=rw6ba5

When unloaded and level, you measure the distance from the wheel rims to
the fenders for future reference (for me it was the distance between my
thumb and middle finger or 9").  After you add your load you simply add air
to raise the back-end, and bleed off some if too high. I used an ordinary
bike pump, or portable air compressor, or justed added air at the next gas
station.  I had two hidden air fittings attached to the rear bumper close
enough to the side so you could keep and eye (and fingers) on the rim-fender
distance. I normally had to do this only once unless I dramatically change
the weights on a trip or was driving extensively without the trailer
attached.  When unloaded, you can bleed off air to relevel.  During winter
and over time they do lose a bit of air just like your tires.

For my towing setup it was a little more complicated.  The trailer is
3000-3200lbs loaded.  So with 300+ lbs on the hitch ball, I found the
regular passenger tires to be too soft at the rated max of 35 p.s.i.  The
soft tires and short wheel based generated considerable side to side sway -
enough to make the kids in the back ill.  After I upgraded to LT215/75R15 (I
think the size is right) - truck tires with several side plys, I was able to
pressurize the tires to 50 p.s.i.  and the problems went away.  Now I never
have considered the Safari to be a mini-van, but rather a mid-sixed van
(like the Aerostar) and I never expected anything resembling car-like
handling.  Well after these mods, the van definitely rode and handled even
more like a truck.

If I had another Safari, would I add air bags again?  Definitely (I pick up
lumber and concrete frequently), but I would also check out Firestones' air
bags http://www.ride-rite.com/ which are installed where the rubber jounce
is, well away from the tire, but perhaps a more difficult install (don't
know.)

BTW, either air bag choice means the vehicle can't be lifted by the frame
for extended periods or the bags may over stretch and rupture.  So each and
every garage visit I make them write "after-market air suspension,
axle-stands must be used to support rear axles" on the work order.

Hope this helps,

Dan
Ottawa, ON
04 Envoy XL
99 Coleman Westlake