Strut: re: your comments on the Trans holding the gear even when you apply throttle in T/H, from what I can tell this is normal operation. What I've gotten used to doing is punching the T/H button (turn it off) when you hit the flats and let the trans upshift. This is something the Ford trans will do smoothly and something the Chevy Ally I had could not do at all! (it would continue to hold the lower gear, even after you turned T/H off and hit the gas!). That said, my Chevy was an '05, so the 6 speed Ally with manual shift they now have would (should) go to the gear you want. My Ally also did surprise upshifts when going down hills in T/H -- so the grass isn't always greener, if you know what I mean...!

If I were in your shoes with the weight trailer you have and the 4.88s, I'd leave it OUT of T/H all the time unless you were going down a grade. T/H is going to keep it from upshifting for more revs in each gear, which it doesn't sound like you need until you get a heavier trailer. The rest of the trans will handle it just fine out of T/H -- try it and see what you think...

Good luck!

 

diesel_dan, thanks for the input to us new guys with the T/H. Sure makes sense to me. Looking forward to giving it a shot. Thats what I like about FTE, is guys like you come up with great ideas and input to help everyone out.

 

Absolutely, was really feeling frustrated, as if you couldn't tell. But like firehawk said.......the experience in here helps answer or explain the frustration away. Thanks guys

 

Hi,
I just drove to Phoenix and traded my '04 F350 6.0L, KR, LWB, DRW, 4x4 that got a consistant 11-12 mpg whether I was hauling or empty for a new 2008 F350 6.4L, KR, LWB, DRW, 4x4 4.10 rear end like yours.
First tank 5 mpg, second tank 6.4 mpg, both hauling my 41' 5th wheel to Albuquerque. Both trips at round 75 mph. Then the third tank 8.4 mpg, fourth tank 9.8 mpg pulling a light trailer with a Yamaha Rhino to Colorado Springs. I now have about 1000 miles on the truck. I really miss the 11 mpg my 6.0 gave me hauling the 5th wheel. I can't believe I'm only going to get 5-6 mpg now. Is this normal for the 6.4?
Also, when I needed to pass someone and put the peddle to the metal, the truck didn't down shift and kick butt like my 6.0 did. I just built up slowly. What a drag. With the 6.0 I never lost more than a couple of miles per hour on these same hills at 75 mph with the 5th wheel. The 6.4 would slowly lose speed and drop out of cruise at 60 mph and continue dropping to 45 mph by the time I topped the hill.

Do you think I have a problem truck? What do you suggest?

Thanks for your post,
Bob P.

PS Where the heck is my arm rest??

 

That may be, but the point really is to get it closer to its peak torque range. Peak is +/-2000 rpm, at 75 it is pushing 2900 rpm. If you could get it down to 23-2400 rpm at 75 that would be MUCH better. At 23-2400 rpm which is +/-65 mph I am getting +/-1.5 mpg better. I would have gone with the 4.30's if I had known this. That is the sole reason for my post.

 

Someone else mentioned this but, I think that at hwy speeds the 4.88's are so much above the peak torque range that the speed drops considerably until you reach the peak range. I pulled my trailer at 19k up a 7% grade which is about 5 miles long with my 250 (seriously overloaded, hence the new truck) but with the V-10 and 4.56 gears it pulled it but top speed was +/- 40 mph. My 450 pulled the same trailer and I was able to hold 55 mph. Not only that but I had to come to a complete stop in the middle of it due to construction and was able to accelerate to 55 mph. Now I was not able to go much faster than that because then it was outside of its powerband.

 

I just want better mileage it seams all i can get is 12 max not towing, 2005 f350 cc 4x4 6.0 diesel lariat

 

dieseldrinker: you should be posting for help in the 6.0 section. imo, something is either wrong with your truck, you have a heavy right foot, or you are a troll.

Now my recently so happily departed duracrap regularly got 12 or less when empty, it, like all the rest of them was a POS. My friend with his '05 cumapart gets around that too, you sure you don't have a 5.9 under that hood??

 

No ive had two of these trucks and my 2003 psd 6.0 got 17-18 mpg I know what im talking about and also this was my thread from the begining

 

??? mattebury started this thread, you're in the 6.4 section....

 

 

Hey guys: Like Diesel Dan said I also use the tow haul button to turn it off when coming off a hill. I will as he suggested only use the tow haul when on inclines. The torque converter will not lock up in tow haul and your mpg will suffer. Also when towing I don't use the Cruise Control as the torque converter will not lock in OD with the cruise on. So if you are on somewhat level ground try it without the tow haul on and your mileage will go up significantly...

I don't have a 6.4 but have had 2 6.0's with the tq shift.


Good luck

 

You believe it would be MUCH better based soley on engine rpms. Don't over look these factors;
1. MPG will be better at 65mph than 75mph becuse of the energy it takes to push the vehicle through the air, so a 4.30 geared truck is not likely to get the same mpg at 75mph that you do at 65mph.
2. The 4.30s don't have the gear ratio advantage the 4.88s do so the 4.30 geared truck won't be able to accelerate or maintain speed as well as the 4.88 truck no matter what the rpm.

 

just look at the name.

 

Actually I was trying to offer an explanation as to why the mpg actually is so much better. The information on the mpg/rpm/mph is from an identical truck with 4.30's and not the 4.88's that I have. As far as #2, that is quite obvious and is the reason for having 4.88's it is always a trade off, but if the power is there to provide sufficient speed/acceleration and ability to maintain speed than taller gears would be appropriate. 4.88's would be great if I lived in an area where 65 mph is the max I would ever expect to run. As I stated previously I think the 6.4 has the power to handle the heavier loads with the 4.30's. And I don't know for sure, but am willing to bet that the acceleration with the 4.30's is quite satisfactory, maybe someone with 4.30's will chime in on that.