L31MaxExpress
I'm Awesome
Owning two G1500's with 3.42's, I can't disagree that a lower gear in the diff would quite likely help. But it does require buying and installing the parts, and as stutaeng noted flashing the ECU.
Both of my G1500's are cargo vans and their everyday payload is maxed out, plus a stack of ladders on top that will act like a sail. I live in Colorado where there's lots of up and down and significant elevation gain. And you're correct, they don't spend a lot of time with the TQ locked. One lost the trans at 154k, the other at 155k. I currently have 110k and 70k respectively on the rebuilts. Neither have the external cooler. With an every day heavily loaded 4L60E, 150k is probably a reasonable expectation of the trans lifespan. Here on the forum and a friend with a Suburban, it seems some folks are well north of 200k with their original 4L60E's. Somebody has to be doing something right.
As I have continued to preach, keeping the fluid bright red may be the most important part of the equation, and I'll find out if that contributes to longer life of the trans.
Did you break the 4L60E's before or after you deleted the PWM?
First 60E failed at 38K, completely factory. 4L65E had the PWM deleted. It lasted 40K. Both transmissions broke hard parts. The 60E had a smoked converter clutch and the torque converter was blued from heat. The paint on the reman S10 converter was still perfect on the 65E leading me to believe it ran much cooler.
Suburban is not putting the constant load on the trans that a van does. Van has a bigger frontal area and more weight.
His hightop and the fact it is a conversion van is probably getting him up near the GCW with 4-6 people and baggage in the van. I know with the standard low top roof, 6 adults, our bags, a couple of coolers and some camping gear my 97 was over max GCW. Empty van with a 1/2 tank of gas, my 97 scaled 5,800 lbs. GVW was 7,100.