GM 6.2L 420hp and 10-speed

jfortenbery wrote:
On long hills (or should i say slight upgrades), it would shift (in tow mode) from 6th (2,300 rpm) straight to 4th gear (3,800 rpm) skipping 5th altogether. AND, a GM V-8 just don't sound happy to me at 3,800 rpm. This was a Silverado w/ max towing pkg and 3.42 gearing.

2300rpm sounds like 5th gear to me. That 5.3L can sing all day long at 3800rpm for 300k miles. :) I have same trans, 3.73 gears though. 5th gear for me is about 2200-2500rpm at 65-72mph. One gear downshift is 2900-3300rpm. So I think your trans is going 5th to 3rd gears. This is very typical of our engines/trailer combos for nearly any hill larger than an overpass. I would recommend locking out 5th and 6th gears for your old combo. Keep it close to 3000rpm the time so it dos not need to downshift as often.

The 6.2L/10-spd with smaller gear spacing would do better. However, if you lose the same amount of speed in the new 8th gear, the trans will still skip a couple gears get that engine up to 3500-3800rpm to hold your desired speed. So you should pay attention to how often the trans shifts even with new truck. Start to limit the top gears. I recommend targeting 2500-3000rpm for flat highway cruising with any naturally aspirated engine. And that 6.2L will also live 300kmiles at 3800rpm.

marpel, The 5.3L and 6.2L both have AFM. I'm not hearing of issues with it in the last 10 years. Look up used 5.3L/6.0/6.2L GM trucks with >200k miles. I bet you find a lot.