i bought my 2003 f350 7.3l awhile back and its running 38 inch toyo mt's and i was wondering what gears i might need in the rear end to help with the weight of the tires? and if yall could tell me of any other mods i can do to help the drive train would be a big help thanks for reading.

 

I prefer the 3.73's to the 4.30's I have now. Add hp, not gears.

 

would going from a 4:10 to a 3:73 affect towing? about how much of a RPM drop would there be? right now at 80 MPH i'm at a fuzz over 2500.

 

38's are in the 4.10 - 4.56 range if you stay with a taller gear your truck will be gutless towing and suck with the large meats. what came stock in your f350? i for sure dont recommend going taller 4.88s and 44's my speedo was off 5mph from factory. keep the math close to factory specs for the best results. higher for racing and lower for wheeling.

 

i'm kinda looking for a lower RPM at cruising speeds since i drive ALOT. but if it will only drop it say 100 RPM, i won't even bother with it.

 

I have 3:73 & wish I had 3:55, but I don't pull or tow, I just want a better MPG

 

Most 7.3's came with 3.73's from the factory. A few 4.10's in the offroad packages.

I had 3.73's with 37's and loved it. Thought the 4.30's would be better, but they were not. Only place they are better is stop and go traffic around town.

 

all 3 pickups i've had, have had 4:10's. so i can't compare to anything! has anyone ever seen a dually WITHOUT the overload springs? i drove my buddies 2000 PSD with a auto. i believe it has 3:73's. i was doing 100 and was at 2400. i wish i could do that

 

so if my 7.3l from the factory came with 3.73 gears (my truck is not a dually) i should be fine with 38s then? or should i drop to a lower gear ?

 

if it were me i would for sure go to 4.10's if not 4.56's you need to do the math and see what your final drive ratio is with your 38in tires compared to stock tires and adjust acordingly to where you want your best performance. so many people think they get better fuel milage with bigger tires, THIS IS WRONG because they dont factor in the ratio change to the ground and there instrement cluster making things read all stupid. diesels can get away with a higher final drive most of the time but for the best performance do your math.