Re: [A/S] Grand Cherokee and Safari

["Harvey Barlow" <harveybarlow@xxxxxxxxxxxxx>]

Bob,

My daughter's Jeep is a '00 or Y2K as some prefer.  It is a 4.7 liter V8 and
has a factory installed hitch.  I don't think that hitch receiver can be
properly called a Class IV.  A Class IV is rated at 500 lbs. tongue weight
and 5000 lbs. gross weight without equalizer bars, and 1000 lbs. tongue and
10k lbs. gross weight with equalizer hitch assembly.  The Jeep is apparently
a modified Class III rated to tow 6500 lbs. according to the label on her
hitch receiver.  Small to medium-sized older Airstreams should fit just
under that upper limit.  Newer ones will not unless you stick with a lightly
loaded Safari.  An area that concerns me is the fact that a Jeep does not
have a frame.  Regardless of how strong the hitch, it is attached to sheet
metal.  If you crank up full tension on a set of 1000 pound trunnion bars
and do a lot of towing I would worry that the hitch receiver mounts could
eventually pull out of the attachment points.

My daughter uses a Reese dual cam hitch assembly which is completely
suitable.  The combination feels perfectly stable in calm weather at
moderate speeds.  The limitations, in my opinion, are engine/transmission,
short wheel base, and overall lighter duty components.  I'm not familiar
with Hensley hitch assemblies.  Their owners swear by them but they seem
awfully expensive to me.  A hitch can only compensate, to a point, for the
inherent limitations of the short wheelbase.

More important than factory horsepower rating and equally as important as
factory torque ratings are the rpm at which the engine develops peak torque.
If the engine develops say 300 ft. pounds of torque, that makes an adequate
towing motor for lighter trailers.  But, if it doesn't develop that torque
until 4000 rpm, the torque will only be available for towing at 100 mph in
overdrive or while buzzing the engine at 4000 rpm in second gear.  Most
short stroke passenger car type motors develop maximum torque at higher
rpms.  Some overhead cam engines, notably the 5.4 liter Ford Triton gas V8,
have a wide flat torque curve which makes them good towing motors for their
relatively small size.  That motor begins developing about 90% of its
maximum torque at around 2200 rpm.  Towing motors develop maximum torque at
or below top gear highway cruising speed.  The most economical operating
point for most engines is near the point where it develops maximum torque.

But, as you stated, you are fully aware that you are pushing the outer edge
of the envelope and you have towed before so you probably know how to
anticipate and avoid most potential problems.  Ultimately, the decision
comes down to whether or not you'll be happy with the combination.  If your
towing is done on an occasional basis, with an eye toward safety, knowing
the vehicle's limitations, you may find it an acceptable compromise.  Every
choice we make is a compromise based on wants, needs, cost, budget, intended
usage, how long we'll keep the compromise, and many other factors.

Harvey