matemike

My wife and I are looking at getting a new expedition. The 3.5 ecoboosts and 6R80 seem like a good pair. A couple bolt ons and a tune ought to make the thing pretty peppy for a mom-mobile.

One option I'm considering is the 3.73 rear end Instead of the standard 3.15.

I know the 3.73 will have more torque, be the better hauler, accelerator from a stop, etc. and I know to have all that we will get slightly fewer mpg's (dont care). But which of those two rear ends would have the better 60-80 acceleration time? That's both of our MAIN concern. My theory is that the 3.73 will have the faster acceleration from a dig no doubt, but that being said it should be more torqy in all 6 gears. Is that right?
If anything it'll cruise at highway speeds in 6th at a few hundred more RPM's so it'll be that much closer to the power band at all times.

matemike

C'mon man.
I realize this is primarily a GM site; of which I have one. (see sig) I really enjoy all of the know-how I've gained from this site.
I thought this gearing question was a good all around question but I still decided to post in the ford section since it specifically references an Expedition.
Can a moderator move this simple rear gear question to the general discussion section?

Just wondering if lower gears give good acceleration from a highway roll the same way they do from a dead stop or slow roll.

Vortec350ss

iTrader: (20)

Unless the 3.15 gears catch you perfectly at the top of a gear when you mash the throttle the 3.73's will step all over the 3.15. And part throttle or half theottle will be absolutely no comparison. With the ecoboost unless you are seriously trying to get away from someone you won't have to go WOT to get from 60-80 briskly.

If it's acceleration you want the 3.73 is a no brainer.

matemike

It is primarily acceleration I want.
Thanks for clarifying that the lower gear should still rip better than the higher ones in 1st through 6th and at all common speeds.

I was worried for a minute remembering a 2009 GMC ECSB with a 5.4L and 4L80 with 3.73's. I found myself making some dangerous passes in the 70-80 mph range. More than once I stepped on the gas to get around someone and the engine revved but the truck barely increased speed.
Thinking back I worried; was it the 3.73's that were tapped out for engine speed on the highway? But now I figure that truck was just simply underpowered for my taste.

madmann26

iTrader: (7)

Ditto on what Vortec said.

Some of what you want is in the tuning as well. Depending on how it's tuned with the 3.73's, it's entirely possible to have it grab 3rd @ 60 or 80.

It would definitely **** and git...lol.