Hey Dave, I think we've chatted about this before, I'm in the midst of doing the same thing. I picked up a used front axle with 3.73 gears and have put 3.73s in a 14-bolt 9.5" axle. My weak constitution causes this project to be dragged out. Too hot outside now, so I'll probably have to wait until September at the earliest to complete it.
3.73s will give you that extra capability on the steep grades and less downshifting on overpasses and small hills. Someday I'll either supercharge the 5.3 or put a 6.2 in it so it will be identical drivetrain wise to my pickups and be even more capable and fun!
I'm curious to see what the 3.73s will do for my 60-foot times at the drag strip too.
Don't "think" the steeper gears will affect mpgs if at all. As it stands now, my truck gets better gas mileage going 77-78 mph than 70-73 mph, it likes the additional load on the engine. I had a Pontiac that was the same way. Of course, once the 14-bolt is under my truck and broken in, I'll start all manner of testing and share it with y'all here.
Thanks, I appreciate this input and will definitely be interested in hearing your feedback after the 14-bolt install. I'm still a little torn, see below.
If it helps, towing a 7500 lb camper (large wind sail) with the 6L80 with 3.42 gears, I find 4th gear is about 2800 rpm at 65 mph. It's the sweet spot for towing with these rigs, in my opinion, and it will run that way all day and require very few shifts around here until I get to the mountains. Then I'll need 3rd once in a while and it's about 3800 rpm to hold 65. I don't bother with 5th because it's constantly dropping out of it.
This, with a modified 6.2L. I would expect a 5.3 to spend a lot more time in 3rd with 3.42 gears, so I suspect the 3.73 gears would be more beneficial for a 5.3 rig than a 6.2. That extra 250 rpms might just be enough to keep it in 4th much more.
Yep, exactly my thoughts about towing in 4th gear. My calculator is showing 2800 at 65 mph in 4th, too. If I wanted to tow in 5th, 3.73 would be a no-brainer. But if I tow in 4th all the time, I'm still thinking 3.42 might be best. The 2800 at 65, flat or minor hills, seems pretty good to me. Then I drop it to 3rd for the steep grades, and I'm at 3400, 60 mph. On flat or slight downhill, I could still go to 5th some times - 2100 at 65.
My trans is tuned to only allow TC lockup in 5th and 6th. So to me the question is answered by what gear I want to tow in. Mostly 4th, I think 3.42 work work OK. Mostly 5th, 3.73 seems like the way to go. AFAIK, my 200k rig is on its original trans and TC. So it seems like 4th would be the way to go?
A week ago I rented a small travel trailer (3500 lbs) for a family reunion. Only 300 miles round trip, no huge mountain passes. But I used it as a trial run and while driving thought about where I'd be at in various scenarios with both 3.42 and 3.73.
BUT -- I'm not discounting all the guys that are saying 3.73. The double jump idea makes sense, and I've definitely wondered if I really want to go to the expense and trouble for a pretty small jump. I've been busy in June so haven't made any purchases or progress yet, but I'm thinking I may buy the 14-bolt 3.42 rear this week. It would be expensive to do the conversion to 3.73, but still may. Someone said just go with a 10-bolt if I want 3.73, but for some reason I'm seeing the cost of those substantially more than the 14-bolt in my area - go figure! But on the front, I can pick up a 3.73 unit a little cheaper than a 3.42 - double go figure!
thanks for everyone's input.
