You guys tired of me yet?

FINALLY ordering my Truetrac ($$ in the bank, just looking for the best deal, so far Summit has it...wish I was getting it from Clay, but I gotta save $$ when I can)...I decided to let a local drivetrain shop do the install, they can do it quicker and time isn't a friend of mine anyway. So...here is the question...

I am basically rebuilding my rear diff while getting the carrier installed, and the shop that is doing it gave me a good fair price, I have the option of putting in 4:10 gears instead of my 3:55 that I currently have. Since I am supplying all the parts the installer/shop doesn't care what I put back in. (no difference in price, the only difference I am looking at is the cost of the actual Ring and Pinion)

So just how much real world gain would I get with the 4:10? I expect a severe fuel mileage drop but believe I would get more initial pull off the line or be able to get heavier loads moving more easily with the 4:10.

I haven't struggled to pull anything with the 3:55 and don't intend to be towing through the Rockies or anything. So far anything I have pulled through the mountains of NC haven't even began to be a challenge.

So is it worth the fuel cost, and actual gear cost?

Opinions please.

BTW I doubt anyone cares but got my BF Goodrich AT KO2 tires this week, waiting to mount them same day truetrac goes in...

 

Well, I'm still new to alot of this, but I have some experience with go-fast gasoline. I have a spreadsheet I built when choosing gears for my Mustang. I went to the truck and measured ground to center of hub and calculated my rolling circumference from that. That's rough so the math may be a bit off, but here's how it shakes out.

With 3.55's

<table border="0" cellpadding="0" cellspacing="0" width="416"> <tbody><tr style="height:13.5pt" height="18"> <td class="xl65" style="height:13.5pt;width:32pt" height="18" width="43">Gear</td> <td class="xl66" style="border-left:none;width:50pt" width="66">Ratio ("g")</td> <td class="xl66" style="border-left:none;width:50pt" width="67">RMP ("e")</td> <td class="xl66" style="border-left:none;width:47pt" width="62">Axle ("a")</td> <td class="xl66" style="border-left:none;width:81pt" width="108">Wheel RPM ("w")</td> <td class="xl67" style="border-left:none;width:53pt" width="70">Speed ('s")</td> </tr> <tr style="height:18.75pt" height="25"> <td class="xl68" style="height:18.75pt" height="25">1st</td> <td class="xl69" style="border-left:none" align="right">2.72</td> <td class="xl77" style="border-left:none" align="right">2130</td> <td class="xl69" style="border-left:none" align="right">3.55</td> <td class="xl69" style="border-left:none" align="right">220.55</td> <td class="xl70" style="border-left:none" align="right">20.0</td> </tr> <tr style="height:18.0pt" height="24"> <td class="xl71" style="height:18.0pt;border-top:none" height="24">2nd</td> <td class="xl72" style="border-top:none;border-left:none" align="right">1.53</td> <td class="xl78" style="border-top:none;border-left:none" align="right">2695</td> <td class="xl69" style="border-left:none" align="right">3.55</td> <td class="xl72" style="border-top:none;border-left:none" align="right">496.24</td> <td class="xl73" style="border-top:none;border-left:none" align="right">45.0</td> </tr> <tr style="height:18.0pt" height="24"> <td class="xl71" style="height:18.0pt;border-top:none" height="24">3rd</td> <td class="xl72" style="border-top:none;border-left:none" align="right">1.00</td> <td class="xl78" style="border-top:none;border-left:none" align="right">2349</td> <td class="xl69" style="border-left:none" align="right">3.55</td> <td class="xl72" style="border-top:none;border-left:none" align="right">661.65</td> <td class="xl73" style="border-top:none;border-left:none" align="right">60.0</td> </tr> <tr style="height:18.75pt" height="25"> <td class="xl74" style="height:18.75pt;border-top:none" height="25">O/D</td> <td class="xl75" style="border-top:none;border-left:none" align="right">0.71</td> <td class="xl79" style="border-top:none;border-left:none" align="right">2085</td> <td class="xl75" style="border-top:none;border-left:none" align="right">3.55</td> <td class="xl75" style="border-top:none;border-left:none" align="right">827.07</td> <td class="xl76" style="border-top:none;border-left:none" align="right">75.0</td> </tr> </tbody></table>
With 4.10's

<table border="0" cellpadding="0" cellspacing="0" width="416"> <tbody><tr style="height:13.5pt" height="18"> <td class="xl65" style="height:13.5pt;width:32pt" height="18" width="43">Gear</td> <td class="xl66" style="border-left:none;width:50pt" width="66">Ratio ("g")</td> <td class="xl66" style="border-left:none;width:50pt" width="67">RMP ("e")</td> <td class="xl66" style="border-left:none;width:47pt" width="62">Axle ("a")</td> <td class="xl66" style="border-left:none;width:81pt" width="108">Wheel RPM ("w")</td> <td class="xl67" style="border-left:none;width:53pt" width="70">Speed ('s")</td> </tr> <tr style="height:18.75pt" height="25"> <td class="xl68" style="height:18.75pt" height="25">1st</td> <td class="xl69" style="border-left:none" align="right">2.72</td> <td class="xl77" style="border-left:none" align="right">2460</td> <td class="xl69" style="border-left:none" align="right">4.10</td> <td class="xl69" style="border-left:none" align="right">220.55</td> <td class="xl70" style="border-left:none" align="right">20.0</td> </tr> <tr style="height:18.0pt" height="24"> <td class="xl71" style="height:18.0pt;border-top:none" height="24">2nd</td> <td class="xl72" style="border-top:none;border-left:none" align="right">1.53</td> <td class="xl78" style="border-top:none;border-left:none" align="right">3113</td> <td class="xl69" style="border-left:none" align="right">4.10</td> <td class="xl72" style="border-top:none;border-left:none" align="right">496.24</td> <td class="xl73" style="border-top:none;border-left:none" align="right">45.0</td> </tr> <tr style="height:18.0pt" height="24"> <td class="xl71" style="height:18.0pt;border-top:none" height="24">3rd</td> <td class="xl72" style="border-top:none;border-left:none" align="right">1.00</td> <td class="xl78" style="border-top:none;border-left:none" align="right">2713</td> <td class="xl69" style="border-left:none" align="right">4.10</td> <td class="xl72" style="border-top:none;border-left:none" align="right">661.65</td> <td class="xl73" style="border-top:none;border-left:none" align="right">60.0</td> </tr> <tr style="height:18.75pt" height="25"> <td class="xl74" style="height:18.75pt;border-top:none" height="25">O/D</td> <td class="xl75" style="border-top:none;border-left:none" align="right">0.71</td> <td class="xl79" style="border-top:none;border-left:none" align="right">2408</td> <td class="xl75" style="border-top:none;border-left:none" align="right">4.10</td> <td class="xl75" style="border-top:none;border-left:none" align="right">827.07</td> <td class="xl76" style="border-top:none;border-left:none" align="right">75.0</td> </tr> </tbody></table>
Being a spread sheet, I can play with speeds and RPM and tell you where you should end up. What I can't really tell you is the real work difference in pulling power, but most of that comes from getting the RPM's up anyway. I will say going from 3.27 to 3.73 in my 03 GT made a huge difference in acceleration.
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I decided to attach the spread sheet for you guys to play with if you want. The yellow down at the bottom needs to be correct to your vehicle. Currently has gear ratios for a E4OD and tire size 265/75 16. The blue are numbers you can play with, to see what speeds and RPM's correlate.

I changed a few things to make it more flexible, so if any numbers seem outta whack, let me know. I didn't double check all my formulas after moving stuff around.

 

That is a handy little formula. Thanks.

Now to convince myself that I actually need to go to the 4:10 gears.

I know a few people on here swear by the 4:10 gear ratio for our trucks, and some of them are virtually pulling a "train" across the country. A cattle trailer, hay trailer and occasionally pulling a trailer with my MF245 is about the most weight I will find behind my truck.

Decisions...they are tough when you only have so much $$ to spend and the holidays are right around the corner.

If anyone is looking for a master installation kit for a Sterling 10.25 I found one on Amazon for a $188 bucks shipped (Motive gear kit with Timken bearings). Saw a few more on eBay for a little less, but I didn't trust those sellers. Don't want some cheapo junk in the rear end.

 

I have 4.10's and I don't tow heavy loads much and my personal preference would be to stay with the 3.55's in order to get a little bit better fuel mileage. I think it all depends on your personal preference, do you want to accelerate a little bit quicker or do you want to get a little bit better fuel economy. If it were my truck I think I'd stay with the 3.55's.

Bob

 

And not just the fuel economy. But dropping 350-400 rpm at cruising speed, and the wear on the motor, EGT's, and noise associated with that. The transmission is also turning faster at that point also. Not sure what implications that has? My .02, if the 3.55's pull what you need, stay there.

 

I have 4.10s and the only thing I don't like are speeds over 55 mph. It's great I can really get going well with my 26ft TT. Mileage doesn't seem too bad, empty I average 16.5 to 17.5 and my truck is completely stock. Haven't had the TT on the interstate but towing it on back roads and state highways I am around 12.5 to 14 mpg. I think when the time comes to do my Dana 60 swap I will buy 3.73s for the front and rear axle. Will lower those highway rpms but not sacrifice all of the get up and go.

 

I "feel" like 3.73's would be a great in between. that spread sheet will let you play with that idea.

 

With mods the 3.55 feel nice

 

I love my 4.10s.

I've never driven a truck with 3.55s, but then again I don't drive my truck for a daily driver or for MPGs.

I use it to tow things and for that I wouldn't trade the 4.10s for anything.

 

When the Mule had 4.10 and was a company truck it felt really strong, but after we switched to 3.55 all the power was gone, after I acquired her and started the mods it felt strong, I guess it stays in its power band more and mpgs went up

 

I have both. In that last 60k the 4:10s average around hand calculated 17-17.5 mpg with a ZF at 70 mph on 285/75/16s. If its a DD just put 3:55s in it. If you plan to tow, the 3.55s will be painful. If you are re-gearing why not run 3.73s?

I wish I had a gear vendor OD unit behind the ZF when highway driving unloaded...and that's the only time.

 

Thanks for the replies everyone. Seems like its basically on how often I tow, which I will some but my truck is also my farm truck, work truck, daily driver, pretty much anything I need vehicle.

A coworker made the statement to me "If you can't pull it with that truck, you don't need different gears, you need a bigger truck..." Kinda made sense to me..

If it were just a vehicle for the farm and pulling I think I would definitely go with the 4:10, but since I use it all the time, I mean all the time...I think I might stick with the 3:55, they haven't let me down pulling anything yet...

As for why I didn't bring the 3.73 gear ratio up, it just didn't seem to me as though it would gain all that much vs the 3.55, if I were to change it would be for a big difference, or no need to change at all. Truck performs plenty well off the line and gets reasonably fuel mileage for 3/4 ton truck. Probably working in my favor is that its a 2wd regular cab and thus doesn't weigh as much as the ccb 4wd. So just in weight reduction alone off the line acceleration is plenty good enough for me, and the power is there when I need to pull something behind me.

 

Seems like a logical conclusion from here.... Enjoy the tru-trac. I thought I was going to be sick when I discovered that I had and open diff. WHAT!??

 

You got it bud. The whole 3.55 or 4.10 thing comes down to personal preference and what you do with your truck......plain and simple. I think with what have described, you have made the right decision to stay with the 3.55s.