Im sure the 3:73's make it much more pleasant to drive. I dont know how much weight you tow but for anything heavy, 37's are crap. Im guessing your max PSI for the 37's is about 65. Not good for a heavy load.

 

10k towing. 80psi max tire pressure. Will be swapping tires in the near future and was thinking of a 65psi load E. Interesting take.. and yes it's definetly more pleasant to drive.

The trans took a couple days to find its shift points after the install. The truck stays closer to the peak of the torque curve during driving which I've noticed more than anything. Especially highway.

 

10k towing. 80psi max tire pressure.

At least your running the "F" load rated Ironman All Country MT's and not the "E" rated. I would not downgrade the load rating if you buy different tires, especially on an F250/F350 SRW.

 

I’m running 35.1” tires and stock 3.55 gears. The slightly oversized tires takes me to a 3.44 gear reduction. I’d love to throw some 3.73s or 3.90s to get some more giddy up but I cannot justify $3500 for something that’s not broken.

 

The load rating on the E is still more than the axle rating of 6100lbs. Why do you feel it's necessary?

I've been looking at the toyo rt trail. 3860lb e rated 65psi. Trying to get them in 37 13.5

 

axle rating of 6100lbs.

Because the axle rating is extremely conservative on an F250 and certainly more capable than what is listed on the cab sticker. I think your year model has the exact same rear axle as an F350 SRW. The F350 has better springs with a much higher GAWR. I think about 7000+. Springs, excepted, it is the same differential. I would rather have the higher load rated (12 Ply Rated) tires.

 

I bet your steer axle has about @4800+ pounds (assuming its a diesel) on the tires before you even hook up a trailer with a WDH, etc. There is no way I would run 40 PSI in the front tires.

 

40s was for rear. That is what makes the biggest difference in unloaded ride quality.

55 front, 45 rear. That gives approx 5500 and 4500 lbs respectively per the load chart.

 

Not too long ago I swapped the stock 3.31s for 3.73s. I wanted the stock acceleration back. I haven't seen much from people who have done this for 37s so I figured I'd post for those of you who are wondering. Noticeable: taking foot off the brake at a stop the truck starts rolling much faster. Easier to get rolling up a hill also. Haven't towed with it yet but I can tell it will be better off the line also. Freeway rpms are about 2-300rpms higher. Fuel Mileage is about the same, better around town, little lower on the freeway. Went with ford oem gear in the rear and dana in the front. Essentially a factory style swap. Carrier for the axle is the same up to 4.10 so no need to swap that. I have e-locker and no issues there also. Just needed new ring and pinion. I didn't pay the cheapest shop, I went with a shop that I felt was competent. Also threw a mag hytec diff cover on the rear. I'll post a closer up pic later of the fit and finish of the cover. Did the 500mi break in and had the fluid changed, all went smoothly. Was it worth the money? It's not a hands down "wow the power" moment, but it does feel more like a monster truck with the extra power available and the bigger tires. If you can afford the extra $, I would do it again. View attachment 793151

Do you want to sell your 3.31 gears and how much?

 

Pay shipping.

Pinion got a little water on them when it rained as I was bringing them home. Otherwise 56k mi and they look great

 

Hope you shim them just perfectly or else they’ll howl all the time.

 

FWIW, Tasca lists the same springs for the 250 and 350 SRW.

Would going to 3.55's have made the ECU think everything is still stock and kept your freeway RPM around the stock range?

 

FWIW, Tasca lists the same springs for the 250 and 350 SRW.

Would going to 3.55's have made the ECU think everything is still stock and kept your freeway RPM around the stock range?

3.73s with 36s is roughly the same ratio as 3.31 on 32s. I'm running 37s which is a little lower on the rpms. I chose to error slightly on the lower rpm side otherwise I was thinking of 4.10s for the towing low end power. 3.55s wasn't enough of a difference to justify the price. I noticed the difference with the 3.73s but it's not a huge difference. 3.55s would have kept the rpms even lower and not achieved the desired result. If I had the 3.55s stock I wouldn't have regeared, it's just not enough of a difference for the 3000$...

 

Going to 3.73 is on my plate, just wondering if I should just skip right to 4.30. do you wish you went deeper?

 

Not at all. Freeway rpms at 85 are pushing 2k. Plus the carrier is same until 4.10/11. You will be paying even more to go higher than 4.10. The 3.73 put me back in the stock range and I used factory parts for the swap. You could go 4.10s and have the same experience parts wise. It would take off faster but be screaming on the highway.

 

i was looking at 3.73 for the same reasons as you, to stay with a 'stock' ratio. not sure if it even matters.

 

If you are towing heavy frequently, or are using the low end power often, the obvious choice would be a 4.10. I split my driving among all different scenarios, thereby necessitating a good balance between low and high. It definetly gives the truck a more manageable drive around town. With the 37s I was slow at the lights and everyone would race in front to cut me off. Now I'm able to stay with the flow of traffic without sticking my foot in it. The towing is better, but I just locked out 5th before and it was fine.

 

Welp, just ordered 3.73s. hope I can find time to install them.

 

Sick. What brand?

 

Dana

 

I have the factory 4.30's on 37's. Love it.

 

What's your rpms on the fwy?

 

Around 1650 at 70

 

What year and options? 350/450 dually?

 

2016 350 srw platinum crew short bed.
Just checked @80 mph it's 1830 rpm

 

4.30 shouldn't be stock on that. And the rpms you show are close to what I'm at with 3.73s. Are you sure your at 4.30?

 

It was an option. Unless the data i pulled off forscan is wrong. I'll try check manually.

 

just realized there are two different ring gear sizes for the d60 for our trucks. was it the 9.75in d60 or the 10in for the 'super' d60

i thought all F2/350s from 2005 up were 'super' d60

 

Should be super 60.

 

I ordered the OEM equivalent so I should be good but why these sights even show the other version is just confusing for no reason

 

Original owner? You can change all that with forscan

 

Second owner. Will change it when I figure out what it is. Or not since it runs awesome as is.

 

Figured out that it's 3.55's in my truck

 

No reason to change those for 37s. Not enough of a difference to go 3.73s. Although if you tow heavy you could go up to 4.10s and still use stock parts with the original carrier and have an inexpensive swap. I wouldn't touch what you got if it were me.

 

Yeah, I'm good it lights up these tires like nothing I can imagine if I had stocks on or lower gearing.