SL, SLE, SLE2 ,SLT ????? what's the difference

[rolling rolling]

Hi There

We are looking to buy a used 2006-2008 GMC 3500 diesel dually. We were pretty much
decided on the SLT model, which is as far as we know the top of the range.
Is there anyway on the web were I can look up the different standard features you get with the different models.

SL
SLE
SLE2
SLT
It seems like the SLE2 has leather interior like the SLT. But then alot of the dealers that run ads on the web often put the wrong model number. Need to get in clear in my head what I'm getting for my money.
GMC's website only quotes current models .

Thanks for your help

Alan

[chevychase]

Sl - standard - sle - mid level - sle2 , and slt just about the same. Slt comes with heated leather seats , and mirrors .
But you can order for sle2. All about the options. But slt is top of the line.