I have an 04 - 5.4 ltr w/ 373 gears, my S/Crew is in currently for a 6" superlift suspension install which will be added to my already existing 3" body lift.

I have 35" BFG Mudds on hulk 18 X 10 wheels right now, my question is with the 373 rear will future 37" MT's make the truck feel like a slug. How much more sluggish if any will it feel.

Thanx Members.
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It won't feel sluggish, it will be sluggish. You will need 4;88's.

 

I agree.

 

you'll want bigger gears. although i think josiah has the stock 3.73s running 37s. so its do-able.

 

Will it feel more sluggish than 35s? Not really, the seat of the pants dyno isn't that accurate. More likely you will "feel" it the first time you get in the gass, because you will be expecting it to be sluggish.

I run 37s with 3.73, it's no race truck, but it moves out OK and cruises nicely. And I still beat most coffee can ricers out of the hole. If most of your travel is highway, it works fine. I think mileage and performance would be better with 4.10 or 4.56s, but they aren't in the picture right now for me. Pull a respectable 12.9 to 15 mpg, depending on the overall driving. If most of your driving is city/stop'n'go/off-road, I'd go to the 4.88s. If you are happy with current performance, you won't have issue.

 

I love my 4.88s!!

 

I'm all hwy driving 1 hour each way to work, if a gear replacement is in order which gear do you recomend, and will the gas milage go further into the dumper, with 37's and taller gears??

 

If 90% of your driving is highway (at the speed limit), I would probably go 4.56 - you will probably see a slight increase in mileage. IF you do a fair share of wheeling, Thumper's 4.88s make sense - even into low 5s. But, with a couple hours commute everyday, 4.56 is where I would go. Now if you drive well over the speed limit, the 4.1 is probably better.

Forgot to add... I witnessed the bigger difference because of tire width than tire height - the 13.5 width was 50% more tread width than the factory tire. THe difference I saw between 33 and 37 was only 5 or 6%. The programmer made up for that and then some. My experience with my SuperChips is to run tow setting for best performance/mileage mix.

 

If you do that much highway driving, I'd go with 4.56s.

I drive AT LEAST 45 minutes on the highway a day. I TRY to keep it at 70-75 for the most part and my mileage will go up. If I try to run 80+ than it goes down from my city driving. I'm getting 12.6-13 mpg consistently.

 

hah well i have 3.55 and i dont think its that bad, but its a hard choise better gas with 4.56 or more power and better take off with 4.88s hmm what to do....

 

I might add, the difference in power between the 4.88 and 4.56 will not be evident with the seat of pants dyno. Nor will the mileage be a huge difference - the difference in rpms is only 5%. The difference between 3.73 and 4.88 is a whopping 33%! Even 3.73 to 4.56 is still 30%.

Most gear ratio charts do not show OD rpms, but they give you an idea. Using 4.56s puts you back to about stock rpms and performance. If you google "gear ratio charts" you can grab the same info I'm working from.

 

What are you guys running RPM wise at 70 with stock gears and stock tires?

I'm turning 2100 RPMs at 70 with 4.88s and 37s.

 

Im not 100% sure but I think I am at like 1900 RPM's at 70, with 4.56's and 38's.

 

I'm running under 1600 - shifts out of OD all the time, not a good situation at all. 2000 - 2200 is about the best logical place to be (IMHO).

 

373 gears w 37" is do able but like everybody else said u prolly wont b to happy w it... 456 works good w 35"... which would b good w/ the 37" but the 488 would be better with those tires