The recommendation from a lot of people is to limit the
weight to no more than 75% of what the vehicle is rated
for. That would be 3750 pounds. One problem you will run
into as well is that your vehicle has a short wheelbase that
will make it a bit unstable.

I see where "jayco1007" <ostafie@shaw.ca> contributed:

Please don't try it.  The Envoy is too tall, too short, and will not
be able to give you a safe, comfortable ride with a two-ton trailer.
The fact that a few people have survived while towing big trailers
with Jeeps (imitation and otherwise) does not make doing so a good
idea.

Congratulations for having the good sense to ask before trying it.

See the following verbiage - old but relevant.  Especially note #10:

===============

It is my firmly-held opinion that  - on average - manufacturers'
maximum tow ratings are optimistic and presume near-ideal
conditions and a fair amount of operator skill. I continue to
recommend that people buying equipment to tow (or be towed) try
to stay well *under* the maximum. I like a 75% target, on the
basis that it provides a safety/reliability/comfort cushion for
steep grades, bad roads, and emergency maneuvers.  In recent
years as the bulk of traffic has moved over to the interstate
system, I've become increasingly concerned with the number of
people who sincerely believe it is OK to drag their long long
tri-axle trailer (at 125% of tow rating) at 75 mph with their
leetl pick-em-up.

    [There is even the Hensley hitch character going about    
    like a side show barker with his video showing an    
    Intrepid hauling a 9,600 lb trailer! This is FIVE TIMES
    the tow rating, ladies & gents! The product is good but
    the marketing is near-fraudulent.]

Bottom line:  there's a great deal more to tow ratings than
power.  To get some perspective on that, consider the average
over-the-road truck. Typically 400 horsepower or less to haul
80,000 pounds.  Do your own math.

And consider this reasoning for a 75% recomendtion:

There is pretty general agreement that it is unwise and possibly
dangerous to EXCEED maximum ratings, but many of us with long
trailering experience have found that tow rating information is
often misleading - or at least not applicable to everyone.

1. The tow rating is ALWAYS a maximum figure, and is as large as the
manufacturer dares make it. They hope you will buy their stuff for
towing.  Their rating may or may not be right for you.  Every maker
has his own methods of setting tow ratings. Some are conservative
and some are ludicrously over-stated (many Jeep Cherokees were rated
at 5,000 lbs, and IMO are hopelessly overloaded at that figure).

2. MOST tow ratings (nothing personal or specific vs your brand)
do not allow for long steep grades - up or (especially) down.

3. Most tow ratings make no allowance for bad road conditions.

4. Most tow ratings are accompanied by asterisks that call attention
to special equipment "required". Your rig may not have those features.

5. Most tow ratings make no allowance whatever for emergency
maneuvers.  I assure you your vehicle WILL NOT turn or stop as
fast or as safely with the maximum load as it will with a lot less.
The difference can be dramatic. Don't believe me?  Try a few tactics
in a large parking lot.

6. Vehicle tow ratings make no allowance for the DRIVER'S "tow
rating".  No insult intended, but if you have to ask how much your
rig will tow, you have neither the experience or the knowledge to
handle the maximum load safely.  IMO.

7. One of the most-overlooked factors in safe towing is a COMBINED
maximum (GCWR = Gross Combined Weight Rating, often only found in
a towing guide) that dictates a much lighter-than-maximum TOWED load.
Most of the weight of cargo & passengers in the tow vehicle must be
deducted from the permissible towed load to find the true rating.
Some towing guides appear to gloss over this issue because the
marketing types want to put the best possible face on their product.

8. What is reasonably safe and comfortable at 45 mph may well be a
lethal weapon at 75.  Tow ratings, IMO, do NOT reflect any respect for
this hazard.  

9. An internal combustion engine loses about 2 1/2 to 3% efficiency
per thousand feet.  You can easily lose 15-18% in the mountains
unless you have a turbocharger or supercharger.

10.  Regardless of weight ratings, SUV's and "1/2'-ton" pickups are
mostly useless for serious towing.  They will handle pop-ups and even
some of the short "lite" trailers - and will haul yer big one out to
the lake if you are careful.  But competent handling of a large TT
requires a long wheelbase & short overhang.  

Someone once wrote: "You can tow anything with anything - the question
is how far, how safely?"

BOTTOM LINE:  IF you trust the experienced trailerists who have been
there and done that and don't want to go back, you will not exceed
about 75% of the rated maximum.  The number is of course not writ by
the finger of God on a stone tablet - it is merely an indication that
you should stay well below the manufacturer's maximum allowance if you
want a safe, comfortable trip.  Some say the figure ought to be as low
as 50 or 60%.  But except for a few macho braggarts, most experienced
folks agree in principle if not detail with these concerns. For
example, go to http://www.popuptimes.com/archives/75rule.asp
   
==============

Will Sill - towing trailers for 50+ years
The Curmudgeon of Sill Hill

I had an '02 Trailblazer 2WD with which I towed a 24' Mallard. I had
the same engine as you mention. I believe the tow rating was 5100 or
so, yours may be less with the 4WD.

There is also the GCWR or combination of tow vehicle/trailer which I
read somewhere is about 10,500 lbs for that Trailblazer, but not
certain of that.

The TBlazer was a fine tow rig for that trailer, but we were near the
limit. We used a weight distribution hitch which is required on heavier
towing, about 4000 lbs as I recall. That WD hitch set up was a pain and
I hated messing with it.

An unacceptable trait of the Trailblazer as tow vehicle was its small
gas tank, about 17 gallons, as I recall. Our towing range wasn't much
more than 100 miles. That lousy range was a deal killer for me; we sold
the Mallard after about six months and bought a motor home.

GM knows more about your Envoy than do the know-it-alls who tell you to
stay way below the factory ratings. The factories have too much to lose
to advertise unsafe tow ratings. The nay-sayers aren't GM engineers.

Good luck.

Dale
www.FishWisher.com