Don't get me wrong, the 3.55's will be enough for the load he's pulling. I think he would be happier if he got the 3.73's though.

My cousin had a 2002 with the 3.73ls, mine is a 2001 that had the 3.55ls. Drivin the 2 around town it was obvious his took off better than mine did. Pulling his 2500lb boat around his pulled better going up hills. On the open road we didn't notice much, once we hit some steeper hills his pulled the hills easier than mine did. Mine pulled it just fine, barely knew it was back there, but his was just a little better.

2-3 MPG will never happen with a 100-150 rpm change. Going down the freeway the 3.55 probably will get slightly better mileage, but I can about guarantee it won't over 1 MPG. If it is, it won't be much. Pulling any kind of load I believe 100% that the 3.73's will get better mileage, even going down the highway. The motor just doesn't have to work as hard. Yes it will be spinning faster, but won't be working as hard. The city mileage will be slightly better too.

My truck now has 34" tires with 4.56 gears. The only time I got better mileage when it was stock is going down the highway with no load. Now that it has the gears in it, my city mileage is better than stock. And believe it or not I get about 1 mpg better gas mileage pulling my buddies 3000 pound boat down the highway than I did when it was stock. Sure the motor is spinning about 500 rpm faster, but now the motor isn't even working pulling the load. I can pull most small hills now without even shifting out of OD. When it was stock it was constantly shifting out of OD to pull the same hills with the boat back there.

 

dAM IT guys, now I wish I had the 3.73 gears!! If only I had done what this guy is doing and found this website before I purchased. There were plenty of 3.73 lsds out there. I got the 3.55 because the dealer scared me into thinking the 3.73 would kill my mileage.

Getting an enclosed trailer this fall. It will be interesting to see what its like pulling 7k pounds with the 3.55 gears. I may be forced to upgrade..

 

Look at my signature. I had the truck you have...pulled a 27ft TT around 6400lbs...did that 4 times....bought a PSD. Now it pulls the TT like a shadow.

I too wish I had been to this sooner.

Better to set a proper expectation level before pulling you 7K trailer. Take what ever gas mileage you get right NOW and divide that by 2...then subtract 15% of that number. That will be your new MPG when towing.

Can your truck do it? Sure. Would I do it every day? Hell no. See people at the campsites with some unsafe set ups.

This forum is light then it comes to the tow police...head on over to RV.Net and check out their towing section. It's brutal.

 

Don't get too upset, Robert. The gearing difference is only 5% better with the 3.73. It really isn't that much. I bet 10% of the population could tell the difference between the exact same truck with the only difference being 3.55 vs. 3.73. It's better, but not much, and that's why not much better or worse fuel economy.

To change your gearing on a 4x4 means you have to change the transfer case gears and the rear diff gears. That's in the $1200-1500 installed range. 2wd trucks are like $250 parts and similar labor. If you are really considering a gearing change, go for 4.10 for near stock sized tires or 4.56 for anything over 33" and towing. For $500, gearing is the single best investment to improve performance.

FWIW, the 20" tires are 2% smaller than stock 18's and the 3.73 tires are 5% shorter. So, you'd be actually be about 7% shorter and 7% higher engine speed with the OEM 20's than 18's and 3.55. These are for a 4x4.

 

you seem to be very knowledgable so I am sure it was just a mistype, but I wanted to point out that regearing a 4x4 involves changing the F & R ring and pinion. the transfer case gears are not touched

 

Thanks for the technical catch. My point was that the two sets of gears complicates the cost advantages for small percentage gearing changes.

 

Nice to see that my inquiry has initiated some healthy discussion....to say the least. Great to see so many folks so passionate about this stuff.

Thanks to the info on this thread we have decided to go with the 5.4 / 3/73 LS. Now that we have decided, the dealer can't find one for us. Lots of XTR Supercabs with that drivetrain combo but none that are bright red with captains chairs. Have to play the waiting game I guess.

 

In my opinion, it really depends on what you are tring to do, and what your expectations are.
I have a 97 4x4 4.6, 5 speed ext cab, 3.55 rear gear, and OE tire size 235 70 R 16. I tow a 4200 lb loaded TT, it does OK, no power house, but I would'nt expect a 281 ci small V8 to do any better!
Would a 5.4 do better, yes, it has more torgue, more HP, and more displacement. Simple!!! Is the 5.4 a better engine ????? Wow many would say, yes! More power, yes! In my opinion it is not a better engine! The 4.6 is a known to be robust! The 5.4 is known to have the spark plug spitting problem, not all engines, but too many for me to feel comfortable. if it wasn't for that the 5.4 would ahve my vote! it gets about the same mileage with more power.
But wit the right expectations, the 4.6 is a good little motor