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re-gear time coming soon.

Discussion in 'Differential & Driveline' started by SirRobyn0, Sep 23, 2020.

  1. SirRobyn0

    SirRobyn0 Full Access Member

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    Truck Year:
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    Engine Size:
    350
    My truck is a 1984 C20, with the semi-float 14B. It is verified as currently geared a 3.41.

    I have an 18 foot open trailer that is often grossing around 5-6K. I live in a hilly area, with two mountain passes to the east of me and one to the south. I tow over two of them on occasion. The truck has the 350 with 700R4 and before you ask, yes I have a huge cooler and trans temp gauge. The 350 is pretty much stock, and is a healthy.

    I've about made my mind up to re-gear to a 4.56. I know that's a pretty big change, but not to long ago I had a motorhome the 727 in it and a 4.56 rear end. I had that thing for 10 years and on a three speed that low rear end did limit it to about 60 - 65max. but with the over drive in the truck I figure I should be able keep up with the 70 MPH speed limit, not when towing and loaded of course, but when empty. While I would welcome comments on that it is not my main question.

    Honestly I really like to go to the full floater, but that's not in the cards right now. It's to much time and money, both in getting the used unit and rebuilding it before install. Right now either this weekend or next I'm going to do some work on the fuel system and add a second tank since this truck only came with one, obviously that costs money.

    So the solution I've come to is to re-gear the existing rear end. This is where I could really use the help. Most of you probably already know that I'm mechanic, but all though my carrier, I've either either had a guy at the shop, or another shop nearby with a guy that did this sort of work. Look I change, axles, axle bearings, seals, carrier stuff, about the only thing I currently send out is actual ring and pinion work. So if any of you guys would be interested in schooling me, or encouraging or discouraging me from tackling this I'd appreciate the input. Thanks.
     
  2. bucket

    bucket Super Moderator Staff Member

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    Go for it! There's lots and lots of articles in magazines and online too. And probably youtube videos as well. Imho, inexperienced people can do the job just fine, it might just take a lot longer than someone who has done a bunch of them.
     
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  3. SirRobyn0

    SirRobyn0 Full Access Member

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    Oh I'm pretty sure I can do it with a little guidance, I reason that I can do all sorts of other stuff on cars. I did think about youtube, right after I posted my message. So I guess I would say this, I'm going to head over to see what is on the youtube academy, if anyone would like to suggest any tips for this particular axle, I'd like to hear it.
     
  4. Grit dog

    Grit dog Full Access Member

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    There’s a semi floater 4.56 axle for sale in Wenatchee. $200. probably take $150 and a 6er of Oly. Sounds like the easy button to me.
    And a half dozen other 14 bolt full floaters for sale by folks who apparently don’t know how to figure a gear ratio...lol. But good chance of finding one with lower gears.
    Wish your truck was 4wd. I’d trade you for a set of 4.10s!

    Otherwise, I’m sure you can set up a ring n pinion since your profession is auto mechanic. Go for it!
     
  5. SirRobyn0

    SirRobyn0 Full Access Member

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    Oh I'm sure I can do it to, but always like to get thoughts from those that have done the job before. Ya, like I said I would really to go full floater, but I just cant spend the money to buy the unit and rebuild it before install right now. i think 4.56 would be best for me, I'd settle for 4.10 if need be.

    The only thing I don't like about used is not knowing how much I'd have to put into it. But then again, I'd have my existing unit, for parts if needed. I'll think about the one you pointed out.

    Sometimes I wish my truck was 4wd to, but most of the time it isn't an issue. The biggest thing is occassionally on the farm in the winter I'll get it stuck, but the jeep which is 4wd will pull it right out.
     
  6. SirRobyn0

    SirRobyn0 Full Access Member

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    Ok so I spent a little time on the youtube academy and I think I'm good to go and will give the re-gear a shot after I'm through with the fuel system stuff.
     
  7. Swearbody

    Swearbody Supporting Member Supporting Member

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    Its not a 14b but its a lot of good info....A lot. I think the procedure is the same for 12b,14bsf,gm/aam 9.5 etc
     
  8. JoeR Jr

    JoeR Jr Full Access Member

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    I'm kinda in the same boat as you. I've been a tech all my life, and have only built maybe a half dozen diffs. You'll be OK. Worst thing that might happen is that it would howl a bit.
    Also, so you know, I dropped a set of 4.88s in my C10 last year, just for giggles. It was a total hoot! If I didn't drive so much highway stuff I would have left them in there. It launched like a drag truck. I've got a 4L80E, so it wasn't impossible to drive on the highway, it just wasn't economical. So, you'll be fine with 4.56s, especially if you tow a lot.
    Have fun,
    Joe
     
  9. SirRobyn0

    SirRobyn0 Full Access Member

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    That's not one of the videos that I've already watched, so I'll watch it tonight after work. Thanks for pointing it out.

    I appreciate that. I've done the calculations and I thought the 4.56 would be ok, but it is good to hear what you have said. So just to add to that a bit, my commute is mostly free flowing country roads with varying hills, and speed limits between 40 - 55mph. Then about 2 miles on 65mph freeway and a few miles of backed up city traffic to the shop I manage. I do not think that the lower gears will hurt my mileage on my commute, heck with the hills I expect it will stay the same, maybe improve the MPGs a tiny bit. We will see. My other thing, is my bird farm. I have to do feed runs every few weeks, one run is to the south a little over 100 miles each way. I come back with the trailer weighing somewhere around 5 - 6K gross, and doing the hills and then the pass currently sucks and is pretty hard on the truck with the high gearing. The run up north is similar, but there are no mountain passes, just hills.

    What will suck about the re-gear is on my feed runs when I'm empty the truck will do mid-teens for gas mileage and I know I will kiss that goodbye, but it's a comprise that I need to make.
     
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