Hey guys, first post here. Trying to figure out my gears/locker combo for my '05 Excursion (6.0). I'm running 37" tires (ProComp Extreme AT) and have AFE intake, MBRP 4" exhaust, SCT tune with custom tune, and Edge Juice (set at 0, so the attitude controller is only used for monitoring).
I've pretty much decided on 4.56 ratio, and a True Trac in the rear. I can't seem to find a True Trac part number for the one that goes in the rear of an Ex. From reading posts on here I assume they make one for the F250, so I assume they make one for the Ex. Any help pointing me in the right direction on that would be appreciated.
Also, is the front axle a d50 or a d60 on an '05 with the diesel? Is the rear a 10.25 or a 10.5?
When you buy a master install kit, does that come with inner and outer diff seals and bearings?
This truck sees 98% on road driving, so I assume the True Trac is probably the best limited slip for me. If not, please let me know your thoughts on other options. Thanks.
Do you know what gears are in it now? If all you do with it is highway driving i would look in to 4.10/4.11 whatever gos in it. Lower gears are going to kill your mileage. I know you have 37" but i have 35" and 4.10 gears at 65MPH I'm doing 2300RPMs.
Good luck.
Great info guys. Thanks. That seems to be a good price on that True Trac. I'm turing 2000 RPM at 70MPH right now with 3.73s and my 37" tires. I've wondered about whether I should go with 4.56 or 4.30 since it is mainly a street driven truck. Originally I thought I would go up to 38" tires, but I'm liking the fact that my truck doesn't scrub when I do a full lock turn and enter a driveway. So, that's why I thought I'd get 4.56 in case I went up in tire. Leaning towards staying at 37 though I wished they made a 37x15.50 Toyo MT.
I know theres a calculator somewhere on the internet that will help you with finding the gears that would work for you. It compares your gears with tires.... and shows what RPM youll probly be running. That would be my only concern, RPM with lower gears.
I've seen the tire/gear calculator, but thought that was pretty much for gas engines. I figured it would be different for diesels, but I will search that a little more.
fordtruckman150, I think you're pretty much thinking the same thing I am, but since I want to leave my tire options open for later down the line I'm thinking of going with 4.56. I'm right on the cusp of needing one or the other, so I think I'll see if I can find the calculator psdmike is talking about and see what kind of difference in RPM I would have between the two.
If you are making good power or ever plan any more power stay with 3.73 unless you are towing heavy even then 4.10s is the most I would go. You are going to kill your mpg with 4.56. They are what most run with 40s when there's no heavy towing. Since an X can not legally tow over 10K doubt full you will need it. You want those gears to not so tall to let that turbo work.
You have a D50 and 10.5 rear. If you go with 10.25 gears you have to do the pinion bearing and race, so basically a master kit. Find a salvage yard with low mileage ford 4.10s out of a 10.5 and you only need a basic kit.
Thanks for the info TARM. I don't tow regularly, but would like the option in case I have to tow something heavy. My friend has a cigarette boat, so I might end up towing that on the rare occasion that his truck isn't in service. I've got a buddy running 4.10s in his X and he only has 35" tires. Still gets 14-15MPG highway. Another buddy had an 03 X and ran 38s with 4.56 gears and got 18MPG highway with nothing more than a programmer, exhaust, and intake. Wouldn't 4.56 with my 37s get me back into the factory range for RPM, etc.?
One note about my original post, I'm only turning 1750 RPM at 70 MPH, not 2000 RPM as I originally stated.
FWIW, i had a 7.3 with 38's and 4.56's and hated it on the highway doing anything above 65mph (2000rpms). I went to 4.30's and that seemed pretty good for what i used the truck for (mostly highway road trips, no towing). I even added 40's later on with the 4.30's and it still seemed fine for what i used it for. Pretty sure with the 40's and 4.30's I was doing 2000rpms at 70mph using the GPS.
Hmmm, well it's sound like maybe 4.30 is what I should go with. I'm at 1750 RPM at 70 MPH and 2000 RPM at 80 MPH currently per GPS. My speedo seems to be about 10 MPH at those speeds. I'm still debating on whether to go up to 38s, or just stay with my 37s. The 37s are starting to grow on me since they don't scrub at all, and I have no shaking or bad ride qualities even at 80-90MPH. I love the look of 38" TOYO M/Ts, but I doubt they will give me near as smooth of a ride as the ProComp 37s do. So, maybe that should really tell me that staying 4.30 as the max gear is the best solution. While I know my RPMs will be higher at 4.30 than say a 4.10, I would think the mechanical advantage that the gears will give me will help keep the gas mileage in a respectable range.
Yep the 40s is the break line for the 4.30 and 4.56s. The thing you have to account for there is that increase in rolling mass and weight. You simply can not assume a 1:1 relationship when you are going from a 100 total per tire weight with 35x12.50 @ 3.73 versus a 200 pound per wheel @ 40 with 4.30. 400 total weight versus 800lb. Doubling the weight has to be factored in. The issue is not so much cruising as it is stop and go / take offs etc.. If you are running more air and bigger injectors it makes getting the setup to be clean a bit harder.
I personally felt a 4.30 would be close to perfect for a 40x14.50x20 for me but a few people that have a good amount of experience have said 4.56 may end up being a better fit. I think it comes down to the terrain and type of driving you do. I live in the hills and mountains of Va. Not in the super steep grades but everything is hills. Now if I was in south or north tx La Ga Al or the shore are of va 4.30 would make more sense.
FYI: If you go to the top tool bar banner of PSN look two from the right and you will see the link button to the sites calculators. There are tire and gear calculators along with others on that page. Do not forget on the tire cal to multiple your gear ratio by .71 to get your final ratio in OD if you have an auto tranny. Most guys that have added power and are running 31-35 can get better times running 3.55 instead of 3.73 from what I have read. For DD highway driving not racing etc you want your rpms to be 1800-1900 for the speed you honestly typically cruise at. Now a days that seems to be 70 on average. The more power you make the more you can afford to go lower on gearing, within reason.
This is what I would run:
31-33: 3.55
35-36:3.73
37: 4.10
38: 4.30
40: 4.56
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Related Threads
?
?
?
?
?
Ford Power Stroke Nation
2.5M posts
107.4K members
Since 2007
A forum community dedicated to Ford Power Stroke owners and enthusiasts. Come join the discussion about diesel performance, modifications, EGR deletes, troubleshooting, lift kits, tires, wheels, maintenance, and more!