I know this has been tossed around here in one form or another. I am not sure what the best gearing would be in a 250 PSD for my situation. I am looking at an 07-08 model (I know, two different engines). I drive a silverado z71 extended cab short bed with a 5.3l and 3.73's running on 285/75r16 tires now. I want to upgrade to a diesel next.

Anywho, I use my truck as a tool and do pull with it. I don't pull all the time, only on occasion. Many times when I do pull it is long-distance, but not too much weight (under 6k). I do pull rental equipment on occasion - TLB, excavator, etc probably hitting the 8k mark. No highway driving with the equipment though.

The silverado does fine everywhere except the long distance hauling category on 3.73's. I think if I had 4.10's it would be fine.

That said, upgrading to a diesel I have a TON more torq at my fingertips to take care of the slack I see now.

My question, therefore, is what gears should I look for - given this will my daily driver (good MPG's) as well as a tow rig on occasion? 3.55 to me seems too low, 3.73 seems fine, and 4.10 seems a little high... but based on my current truck on 3.73's makes me want to go with 4.10's.

Any thoughts?

Steve

 

I've got 373's in my 250 and when hooked to a heavy horse trailer it has no problems at all. My dad's dually has 410's with the same 7.3 PSD and it doesnt seem to pull any better than mine but mine gets better mileage. I don't think you'll see any benefit to the 410's unless you pull really heavy but 12,000+ lbs is no problem for my 373's.

 

The 3.73 will give you better mpg than 4.10s obviously, and unless your are pulling huge loads you don't need 4.10s. However, if you do plan on upgrading tire/rim size 4.10s could be worth it.

 

I see. So far no one has mentioned the 3.55's, so I am guessing those are not in the cards.

Does anyone have them? What are your driving characteristics/environments?

I might up the tire size and lift at some point. When/if that happens the truck will be in for an overhaul in ths suspension anyways so might as well swap gears while I'm at it. That shouldn't be too hard, I've re-built an axle before. Realistically, though, in the near future I am going to keep it stock.

Steve

 

I think we need some heavy haulers to chime in. I would think 3.73 is your best choice. And I dont thnk 3.55's are offered by ford.

 

I've done a lot of reading on mpgs and gears in the 6.0L forum and the majority of information says if you keep it under 65-70 you'll get better mileage with the 4.10s than the 3.73s. I know this sounds wrong, but it puts the engine in a more efficient rpm range. You'll definitely get better towing mileage with the 4.10s. I had 3.73s with 35s and have a set of 4.30s waiting to go in. 4.30s with 35s will put me about 5% lower gears than stock tires with 3.73s.

 

3.55 is not avaliable from the factory. I tow about 13,000# (fifth wheel) with my '06 F250 and it does just fine. For the loads you are talking about 3.73 will do the job. A friend of mine has an F350 with 4.30 gears and it pulls the hell out of his toyhauler (about 14,500#) but sucks when not towing. Running at 70 mph he is turning about 2200 rpm. Really bad for economy. I would not go any higher than 4.10 if you aren't comfortable with 3.73.

 

Thanks for all the info. I wish I knew what the ratio was in the 350 I drove, I ran up some good road time in that rolling up to 25k lbs. Even in the hills of Pittsburg, PA, it had enough power. Could have been 4.10's or 4.30's.. not sure exactly.

I thought 3.55 was an option when I did the "build your own" thing on Fords site (or whatever they call it). I seem to recall selecting anything between a 3.55 and 4.30.

Anywho, it sounds to me like 3.73's are the way to go. Unless more people can back up the 4.10 theory... The engine will be turning faster with 4.10's. If the torque is +/- 10lbs between the RPM at 70 on 3.73's and 4.10's but the RPM is up 100 on the 4.10's wouldnt the 3.73's be the better choice? Very close torque at less RPM? Maybe we can get some real values and play with the numbers

Steve

 

3.55 were an option on the early model PSD (1994 and up)
Now, the choices are 3.73, 4.10 and 4.30 that is if you want to stay with factory gears.