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WHICH REAR END?

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  • m1685m1685 Member Posts: 71
    I just bought a 2000 chevy 3/4 ton with 4:10s in it, and I love them. I have had 3:42s and 3:73s in the past, but the 4:10s are awesome. I had 3:42s in my 95 k1500, but got worse gas mileage than the 4:10s. I had 3:73s in a 97 2-door tahoe, got better gas mileage, but towing is a piece of cake now with the 4:10s. The only drawbacks I have found is that I have to shift quicker, but i can usually skip a gear or two. It is also hard to keep my tires from spinning in the rain. I also plan to upsize tires in the next year. If you can afford the extra couple dollars a week for gas, go with the 4:10s
  • BrutusBrutus Member Posts: 1,113
    I think the V-10 with the 3.73 will get about the same mileage as the 5.4L with the 4.10s, while providing alot more power for pulling the loads you are talking about. If you choose the 5.4L, you will definitely want the 4.10s to pull those weights. Personally, I'd give the V-10 with the 3.73 some serious consideration. Remember that the Superduties are heavy trucks. The 5.4L provides more than adequate power for the lighter trucks, like the F-150s and some of the Ford SUVs, but most people agree it is underpowered for the Superduty, especially if you are going to do any towing.
  • jerobbinsjerobbins Member Posts: 48
    According to the towing specifications on Ford's web site, you will need to have a 4.10 in order to tow 9000 lbs with a 5.4L V8. Going to the V10 with a 3.73 gets you another 2000 lbs towing capacity. It's likely that your gas mileage when towing a trailer of that weight will be better with the V10/3.73 than with the V8/4.10, because the engine won't be working as hard. I'm not sure what the gas mileage empty would be for the two different systems (your Ford dealer should be able to tell you).
  • herbenusherbenus Member Posts: 1
    Don't know mif this is right place for this. But can someone enlighten me a little about posi-trac? Pros and cons?
  • markbuckmarkbuck Member Posts: 1,021
    When you go around a turn, the inner wheel travels a shorter distance than the outer wheel. A differential (differential speed between the tires) allows this to happen.

    Unfortunately, the design of an open differential also sends the most power to the tire with the least traction. If one rear tire is on a frictionless surface, then you are not going anywhere. One trick to become unstuck with an open diff is to apply parking brake, thus allowing some power to go to the tire with some traction.

    Other diff styles balance power in several ways. Start with some of the best:
    Torsen Gleason - internal gears transfer up to 80% of the power to the wheel with the most traction. Formula one cars use this. Maybe not quite as durable for off road vehicles.
    Jeep and Mercedes and some others- Actually apply the brakes to the side that is spinning away.
    Air locker - run around with open diffs, press a button and the rear end locks up solid thru an air actuated valve. Once locked, acts like a sprint car
    Locker - what the nascar cars and trucks run. The tire with the most traction spins at least as fast as the tire with the least traction. Heavy duty, but sometimes annoying clunkiness on the street, esp when used on the front end.
    Lim slip - has a clutch pack that engages the non spinning tire. Kinda like a centrifigal (spelling) clutch on a gocart. Historically, the most common non open diff from the factory.
  • mwatchmwatch Member Posts: 5
    I used to have the formula for calculating RPM's at a given speed based upon tire size, axle ratio, and vehicle speed. I can't find it now. Does anyone know that formula?
  • quadrunner500quadrunner500 Member Posts: 2,721
    1056*MPH*RATIO/circumference (inches)
  • markbuckmarkbuck Member Posts: 1,021
    Is that formula in D (not OD) or 4th of a 5-speed?
  • lvstanglvstang Member Posts: 149
    I always get the highest numerical gear available in any vehicle I order. One or two mpg to me is a small penalty to pay for the added quickness and towing ability. I know that last comment is open to much debate depending on financial considerations. Remember that oversized tires will also effectively bring your ratio down numerically. So those 3.73's might act like 3.42's with big tires. Just what I do and may not be right for everyone.
    See Ya.
  • markbuckmarkbuck Member Posts: 1,021
    Remember pi = 3.14159......
    Diameter x pi = circumference
  • mgdvhmanmgdvhman Member Posts: 4,157
    What you do is right for me!

    I agree...get the highest you can...within' reason...

    - Tim
  • quadrunner500quadrunner500 Member Posts: 2,721
    Put a mark on your tire with a piece of chalk or paint. Then drive it a few feet. Measure the distance between the marks left on the ground.
  • grubbygrubby Member Posts: 10
    Have dually on order, will I be happy with this combo. and PSD engine towing 34 ft Airstream?
    What will my rpm's be at 65?
    thanks
  • rrichfrrichf Member Posts: 211
    I'm not sure why the controversy over the circumference of tires/wheels. But, wouldn't it be easier to go to an independent (a.k.a. Sears, Wards, Pep Boys, etc.) tire dealer and ask to look in the book? Usually they have the figures stated as revolutions per mile by tire/wheel size.

    Rich
  • quadrunner500quadrunner500 Member Posts: 2,721
    I need to know the ratio of the transmission gear you will be towing in. If 6th gear was 0.70 ratio, then about 2210 rpm @ 65 mph.
  • markbuckmarkbuck Member Posts: 1,021
    On goodyear's web site, they list number of rpms per mile for each of their tire sizes. If you want to be that exact.....
  • mozeemozee Member Posts: 12
    I own a 96 auto/cummins 4x4 3.54,I have towed 10000,ball hitch-no problem at all.How often are you towing? If it's more than 50%,and the trailer is tall,and you plan on adding bigger tires,definetly get 4.10's.How many long hills will you have to climb on your route?If you dont have all of these conditions at once I would go 3.54.Your cruise rpm will be lower,fuel mileage better and the motor will still be able to move that weight.The cummins is the ultimate torque motor!And with the 245hp/505ft-lb/6spd you should be able to meet all your road speed needs with 6 gears to choose from.Have you been to the TDR website?They answer this and more in there FAQ section.there at Turbodieselregister.com good luck-and get the 3.54!
  • trambitistrambitis Member Posts: 21
    mozee - thanx for taking the time to respond to my query. Which rear end I'll ultimately choose is still up in the air but your words will certainly enter into my deliberations.
  • coulterccoulterc Member Posts: 21
    I just ordered a Dakota Quad, 4.7 5 speed. I went with the 3.92 rear end for several reasons: 1) Less stress on the rear end, 2) I will be towing 2000 lbs 500 miles round trip 6-8 times a year, 3) Make it easier getting a boat in and out, 4) easier ability to run taller tires and plow a little snow in the future.

    I'm thinking that the gas mileage difference between the 3.55 and 3.92 with the 5 speed stick will be negligible.

    Comments?
  • lmeyer1lmeyer1 Member Posts: 215
    coultrec, my local dealer said that if I order the Quad in 4 wheel drive with the 4.7 and 5 speed I MUST take the 3.92 and limited slip differential. Were you told the same thing?
  • coulterccoulterc Member Posts: 21
    No, I was told nothing of the like. The dealer actually questioned me if I was going to be towing with it, gave me the impression he was going to recommend against it if I said no.

    -Curt
  • meredithmeredith Member Posts: 575
    As a result of 30 or more days of inactivity....

    this topic is being "frozen", it will be archived or deleted in the next 10 days or so.

    Front Porch Philosopher
    SUV, Pickups, & Aftermarket and Accessories Host
This discussion has been closed.