I have a 2002 Toyota Tacoma Pre-Runner with a towing capacity of
3500lbs.It has the 2.7 4cyl.motor and 3spd auto transmision with
electric OD.I have installed an aftermarket tranny cooler.I currantly
tow a small travel trailer that when fully loaded weighs about 3200
lbs.When everything in truck bed and bodyweight is added in I'm
probably at 3800 lbs.It pulls this weight without any problem.
I want a bigger trailer though.When all weight is added in I'll be at 4500 lbs.
Will my truck handel it OK? I'm Planning on a lot of miles.

Best consult your vehicle manual and/or your Toyota dealer. But from
how I look at it, going 1000 lbs. is going to put significant strain
on your machine, with breakdown a possibility. I think you'll either
have to modify your Forerunner or get a more powerful machine (like
the Ford or Chevy biggies).

The problem I have with going to Ford or Chevy at the currant time is
fuel milage.Sure a big v-8 could tow double what I'm looking at
without a problem.I havn't got right down to numbers but at $2.50 a
gallon and rising I'm likely to save the cost of a new vehicle over a
200,000 mile stretch.(last Toyota had 260,000 and running excellent
when I sold it)Toyota will say stick with what owners manual says
witch is 3500 lbs.so as not to be liable for anything. But is there
any technical  reason any part of the drive train shouldn't handle
4500 lbs.I'd like to know what that might be..................Thanks

I believe the main concern would be structural and mechanical
integrity when it comes to vehicle limits. If your machine can pull a
weight larger than the manual indicates, it will probably be paid for
by accelerated wear and tear on the machine, engine and chassis. It
can result in increased maintenance costs, fuel consumption costs,
etc., or even the constructive breakdown of your pulling vehicle. But
I suppose that depends on the situation.

Perhaps you consult someone, perhaps a mechanic of the type who would
appear in the program "Rides" on Discovery Channnel, with more than
enough knowledge of how cars totally work and can do major surgery on
them. That is, if you know a mechanic or someone like that. I admit to
not being that.

You're right about For and Chevy though... American-made cars have
often been thirsty at the pump, and it's the Japanese I believe that
pioneer more fuel-efficient cars.

The danger is not being able to stop it, the brakes.  Sure, the
trailer has brakes too, but together with the car there is an awful
lot of inertia to be stopped.
And the cops and your insurance will look very askance at you if you
ever have to deal with them.