Well I bought a 99 suburban last week....I guess I was taken by just how clean it was...pristine ...and the matter of checking the gear ratio slipped my mind after looking at a bunch of abused and neglected Suburbans for a few weeks prior. So last nite I go out and do some checking on it and discover it has the 3.42 gear in it..I was honestly hoping for the 3.73...but its mine now..so...what can I expect from it in terms of towing performance?
I willl be pulling a popup camper with a slide out so its pretty heavy for a pop up camper and a 16' utility trailer which will have 4 quads on it...I would estimate at the heaviest 3500 lbs.
It has the 5.7 motor with an auto trans. and 100k miles.

 

I think you will be OK with what you are towing. I would add a transmission cooler if it doesn't have one. The 5.7 motor had good torque at lower RPM's compared to the newer 5.3.

 

I agree, I think it will be ok, but, you'll enjoy the additional MPG you'll probably get from the higher gear when you're not towing.

What you meant on that 16' Utility is, that you have dual axels...right ?

 

Correct...a 16' tandem axle trailer....I will check on the trans cooler...In the past I have removed them form the radiator and depended on a new air-to-air style cooler...didn't want to dump the transmission heat into the engine cooling system.

 

That's definitely a good point, specially in Xhot climates (like mine).
BUT, there is an advantage of having that heat (warm up) source available for the Tranny Oil. Most TOil is supposed to run between 175° & 200°. Might be a good idea to put a Temp Gauge on the output line of the Tranny, and just see how bad you need a cooler.

If I remember correctly, there's a Thematic Valve available, which totally transfers the TOil away from the Radiator into a Cooler (and then back when it cools down). You might check that out if you're really going to do something there.