There probably isn't much when you're in overdrive. The gear ratio is pretty high, something like .7:1 I think. You will need to shift into 3rd if you want engine braking.

 

My experience with my 3.5L and trans in various gears is as follows
D...... is of course "overdrive " so its ineffective truck just freewheels
3....... doesnt seem to produce any drag below 55-60 so thats ineffective for most hills in SE PA.
2........Will provide braking but only at 25-30 and the rpms are a bit high for my liking so i use it sparingly with a great deal of actual braking.
1........Crawls.

So overall I dont find it to be a very strong attribute personally

 

I use 2nd gear on one of the roads here where I live. From the crest of the hill I drive about 30mph then just allow gravity to take over and it usually maxes out between 35-40 just nicely (35mph zone). No braking over the 1/2 mile descent. I would not suggest driving much faster than that (i.e. Do not use 2nd gear on the highway).

 

I do gear down into drive and sometimes second when on paved roads and descending a hill and there isn't the hold-back that I think should be there. There are also times when off road and in 4 low on a steep down hill descent in 1st gear and it feels like I have to stand on the brakes.

The brakes are in good shape, its just lack of hold-back.

I havd a s-10 blazer w/ a 4.3 auto, and it performed well in down hill descents when using lower gears, and _ have a '99 2 door tahoe that performes great. The Colorado just doesn't seem like the i5 is generating enough compression. Has anyone else experienced this with their Colorado or Canyon. Is it a computer programing issue?

 

Compare the gear ratios of the Colorado and your S-10 and Tahoe and I bet you'll find your answer.

It has nothing to do with the "compression" of the engine (matter of fact, the I5 is actually likely higher compression than the 4.3L in the S-10 or whatever's in the Tahoe...although that's really not relevant).