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4.7L with 4.10's and LSD

6K views 54 replies 9 participants last post by  snrusnak 
#1 ·
I'm considering as my next mod to change my open diff 3.55 to a LSD 4.10, but would like some input on gas mileage from you guys that have this with the new 4.7L. Also welcoming input from 3.92 and 4.56 guys :) I'd like to see city and highway comparisons to my current 17-18city and 19-20hwy. I'd like to do this mod next as the 4.7 is slightly lacking power at lower rpm's. Thanks in advance.
 
#6 ·
I can't remember I'm going on the freeway tonight I'll let you know my 65mph and 70mph and maybe my 90mph depending on freeway congestion lol!
I have a detroit locker posy rear end, had it all done at once, works great lots of power whenever I need it in both wheels.
 
#12 ·
Thanks for posting that southpaw, I'm going to check tomorrow but I think at 70 I'm at about 1,500 rpm. There's not much difference there, I am going to start looking into prices to get this done...
 
#14 ·
Thanks for the input. I'm going to get the 4.11's, I was thinking about 4.56 but it'll be too much. I rarely drive highway so it wouldn't be an issue, but for those few trips a year we do across half the country it'd kill me...
 
#18 ·
4.56 for the little 287 would be great. It's a very powerful engine for it's size, just lacks the off the line grunt. The gears would help alot. The 2nd OD with the 5-45rfe allows it too while maintaining decent mpg. I'm just afraid of the 4.56 and at 75 mph being over like 2200rpm getting bad mpg. That said, my 3 speed ford with 2.42's or something like that was at 3000rpm at 65mph... and still got about 15 or 17 mpg or something like that...300 inline six.

This may help some of you decide, notice there's a huge jump from 4.11 to 4.56, this is what has me nervous:

32.5" tires at 70mph: 3.55's - 1721rpm
3.92's - 1901rpm
4.11's - 1993rpm
4.56's - 2211rpm
All in OD (5th gear)

I wish there with like 4.20's or 4.30's or something like that.
 
#21 ·
I am saving up for the 4.11's and a lsd, really excited about it and heard great reviews on the 4.11's. Maddog told me that the 4.11's are a better torque multiplyer than the 3.92's. Thats what sold me. Dont do much mudding but going to college in a country city so might go every now and then and want my little 2wd to be able to keep up with my buddies so thats why I am gonna most likely get the lsd lol If I get impatient I might just go ahead and get only the gears...not sure yet.
 
#25 · (Edited)
This has no relevance to your 2nd gen but most of 3rd gen 4.7/5.7 folks i have seen regret going from 3.92's or 3.55's to 4.10's and typically end up switching to 4.56's down the road.

I noticed a difference from 3.55's to 4.10's w/ 30" street tires but i regret not going to 4.56's the first time.
Now she is a hole shot queen cause i now have 4.88's and rear 28" drag radials full time.

IMO i would go right to 4.56 and get that 4 door beast moving. It will feel like it lost 1000lbs.
 
#32 ·
I really considered going to the 4.56 but the magnum engines already dont get very good gas mileage as it is...9-11ish city, and I was afraid the 4.56 would just make that number plummit. and I do about a hour and a half of high way driving about every two weeks when I go home to visit from college. Worried about highway mileage with the 4.56 as well.
 
#26 ·
Another thing to keep in mind for anyone racing....if you go to 4.56's this may put you in overdrive on the drag strip, which is not a good thing, you don't want to be putting alot of stress on the overdrive gears. I am not 100% sure, but right now my plan is to go 4.10's with my 32.5" tires, then at the track run a small tire like 28" or so to give me a better effective ratio.
 
#30 ·
I don't think I could do that in my truck.... My shifter has PRND then the +/- button on the gear selector to manually select gear 1-5. Also with the tow/haul button I believe it rearranges the gear ratios to the following:

Regular:
1st 3.00:1
2nd 1.67:1
2nd Prime 1.50:1
3rd 1.00:1
4th 0.75:1
5th 0.67: 1

Tow/Haul:
1st 3.00:1
2nd 1.67:1
3rd 1.50:1
4th 1.00:1
5th 0.75:1

So in that truck he shifts manually from 1-2, then manually from 2-3, then at 5k rpm he shifts down from 3-2, then at the trap he shifts up into D? How does it lock in 3rd by doing that? Is it a protective thing that will keep the engine from downshifting because of too high a rpm?
 
#35 · (Edited)
Forget what i said then as i thought you had a 3rd gen from looking at your engine specs but then saw you have a 2010.
The way i mentioned helps in keeping out of O/D so we are crossing the traps at the top of 3rd instead of it going into 4th which is a no no with our trannies.
You cross the traps at the end of 3rd then AFTER the traps is when you go back to D while your coasting down.
Light 1-2-D-2 then once you are done then back to D. All this pertains to 3rd gens though so disregard what i have said lol.

The guys name is Mike and his common forum name is hemi_loredo03. Not sure if he is a member here but is active on a few others.
I think his PB is 12.29 @ 110 on a 125 shot
 
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