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wagntagn

Diff switch from 3.55 to 4.10

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So I'm planning on buying a fifthwheel roughly 10,000 lbs I have 35" tires on my truck I would like to keep those for pulling probably best is the switch to 4.10?What's best do the complete axle or just do the gears?I'm running a Fass ddrp with fuel lines 3/8" from tank,installed a bhaf breather,4" exhaust and a smarty s03,turbo is the hy 35,my tranny is the 47re rebuilt triple disc.

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2 hours ago, wagntagn said:

So I'm planning on buying a fifthwheel roughly 10,000 lbs I have 35" tires on my truck I would like to keep those for pulling probably best is the switch to 4.10?What's best do the complete axle or just do the gears?I'm running a Fass ddrp with fuel lines 3/8" from tank,installed a bhaf breather,4" exhaust and a smarty s03,turbo is the hy 35,my tranny is the 47re rebuilt triple disc.

sounds like my truck and changed differentials from another truck I got that was crashed. put the rear end in directly but the front was damaged and had the gears switched out to my front differential. I think it is a small change but so hard to do an exact study. I pull about 12k total 5th wheel does ok with a exhaust brake rv275 edge ez hx35w turbo. Been on a 4000 mile trip and all was well, a bit sluggish going to the sierras up some very steep grades.

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The last person I know that had axle gears swapped out from 3.55 to 4.10 it's rather expensive. Local gent in McCall ID did his for a sum total of $4,000 for both front and rear axles. This was fresh and brand new gears, bearings, and pinion seal. He's running 4.10 gears now with 37" tires and loves how his truck runs now. 

 

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Probably cheaper to find used ones instead of switching gear,this is probably the best to start with then maybe the injectors,turbo upgrade?

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I'd be looking for an axle swap.  Be a lot cheaper if you do it yourself.

 

6 hours ago, Ed ke6bnl said:

Been on a 4000 mile trip and all was well, a bit sluggish going to the sierras up some very steep grades.

I pull my 5th wheel up those grades, Sherwin and Conway,  two to three times a year.  I just lock out over drive, lock up the torque convertor, set the cruise control to 50-55, and let the truck do it thing. 

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Posted (edited)
8 minutes ago, IBMobile said:

I'd be looking for an axle swap.  Be a lot cheaper if you do it yourself.

m

I pull my 5th wheel up those grades, Sherwin and Conway,  two to three times a year.  I just lock out over drive, lock up the torque convertor, set the cruise control to 50-55, and let the truck do it thing. 

sounds good I am about 10 mph slower than you, I do have 35 in tires though, may be the factor.  will be headed up there in Sept. for a month.

Edited by Ed ke6bnl

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Personally I do the axle swap, cheaper easier and you can always keep your old axles in case you want to change back. Unless you're pretty confident in doing gear swap yourself then maybe that's the route to go. 

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12 hours ago, Ed ke6bnl said:

will be headed up there in Sept. for a month.

Going back there last week of July with the grandkids and for 10 days starting October 2.

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I think I would rather spend money on a stocker over s369 compound turbo setup ($2800ish) and 7x.010 injectors ($400-500ish) and headstuds ($435ish) and keep my 3.55's.  Truck will spool fast with much more air and be a torque monster with much more power...and more bulletproofed and no more egt issues.  Sounds like your transmission is already up to the task.

 

The extra power (500ish hp) will help out towing tremendously.  If you ever need a little more gear just hit the O/D OFF button and lock up your T/C.  4.10's will rev much higher at 70-75mph without a trailer even with 35's...around 2000-2200.  Right now you are around 1600-1750 at those speeds.  That's gonna reduce your mpg's a bit more. 

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Might not work good. We just had this conversation on EGT's thread. 

 

Even though I went to 245's (30" tires) and rev to 2,500 RPM at 80 MPH but still taking 19.58 MPG. Then at 66 MPH I'm at 2,000 RPM exactly and still twisting out 21 to 22 MPG with EGT's at about 550*F. The best part is EGT's never rise above 750*F empty truck even at 80 MPH.

 

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I tow on 3.55s anywhere from 5k to 20. 99% of my towing is stop and go city traffic the other 1% is freeway and mtn rds.

My truck does very well. I'm also on 35s.

 

I have priced parts to rebuild my dana 80 with 410s

 Had my pinion nut back off this allowed my gears lash to walk in and out.

 

With me doing the work myself I'd still be in the dana a small fortune. I haven't priced the dana 70 or hybrid 70 but I cant imagine they're much cheaper. 

 

If you find a rear 410 axle then consider swapping 410 gears into the front.. dana60 has tons of aftermarket support tons of used parts used axles. The ballpoint dana 60 in our trucks isnt very desirable so often times the offroad guys dont want an arm and a leg for them.

 

If you tow daily I think a gear swap might be worthwhile. If you tow on slow mtn roads with speed limits under 65, 

 

If you tow freeway with 80mph speed limits I say no to lower gears

3.55s put me right in the power on overdrive at 70-75mph

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So the front diff is a 60 and the rear a 70?The gears are probably different?On the weekend I'll try towing my buddy's fifthwheel 11K I'll give it a shot with my 35" I have all gauges set up if any issues with high tranny temp or high egt's I'll switch to my winter tires 33" and see the difference I'll give you the results next week

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You'll be fine towing that, lock out overdrive and let er rip.

 

The D60 and D70 definitely have different gear sets. I have 3.54 diffs as well, and 35" tires. I'd love to swap in 4.10's, I just can't justify the price. The only way I'll do it is if I can find a couple whole axles ready to swap in for dirt cheap.

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Yes fronts a dana 60

 

Dana 60 and 70 share the same cover.  Wich is cool because theres some sweet dana 60 covers out there. But that may be where there similarities stop.

 

There is also a dana 70 hybrid hybrid with what I'm not sure 80?. I haven't researched it much because I have a dan80.

Regardless the 70 70/hybrid and dana 80 are plenty stout for any tire combo and whatever weight we want to put on our trucks. 

 

I like cruising at 1800-1900is rpm on freeway 3.55s 35s 47re are perfect. Can run cool towing 20k. And not slow down on the rolling hills. It does sound like a airplane. Hitting 30psi with cruise set on the rollers. Though I'd rather not tow that heavy if I can help it, most the time I can.

We just bought a 20,000lb machine my old man has towed it a few times with the 6.7 you can bet I'm not gona put it behind my 47re. Machine and trailer 26500.  No thank you

We have a big truck for that. 

 

I bet you find that 3.55s will work just fine

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Posted (edited)

Like most highway not interstates are 55 to 65 MPH out here. 55 MPH is 1,800 RPM roughly then 66 MPH is perfect 2,000 RPM. Even though my 80 MPH is 2,500 RPM still beating 19.5 MPG roughly. If I set for 60 MPH it turn out 21 MPG or very close. Depends on weather, traffic, road construction.

 

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Edited by Mopar1973Man
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Evan with those 35” and 3.55 gears do you have mods on your truck like injectors,programmer, turbo?

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6 hours ago, Evan said:

There is also a dana 70 hybrid hybrid with what I'm not sure 80?. I haven't researched it much because I have a dan80.

Mine has Dana M80 I believe it's 80 in the pumpkin and 70 on hubs. 

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I have 100horse I injectors stock turbo and smarty doing whatever it does.

I also ran for a long time with just injectors. 

 

With 35s and 47re 3.55s it appears I can match Mike's manual transmissions rpm by touching the little button on the end of the shift hand and grabbing 3rd gear. Might actually be slightly less rpm. I can run 65 pulling grades at 2000-2200. I cant remember exactly. Under 2500 that's for sure. I dont like winding it passed 2000 but do on acasion if I have to downshift on a grade. Wich is semi often on mtn rds like mike says. 3rd gears is perfect to go 55-65

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What setting are you on the Smarty?Is your Tranny a 4 speed my truck if I push the button on the end of the stick which takes OD off I’m pretty sure I’m in 4th gear 

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If you have an auto, it's a 3 speed plus overdrive, OD is your 4th gear. If you lock out overdrive, you are in 3rd gear, torque converter locked. If you lock out OD, you'll feel the 1-2 shift, 2-3, and then torque converter clutch lockup.

 

With OD on, some earlier trucks shift 1-2, 2-3, 3-4, then lockup. My truck usually will go 1-2, 2-3, lockup, 3-4... Except for the odd time it decides to drive along 4th unlocked at the perfect speed and light throttle. 

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At 65mph 3rd gear locked I'm at 2400rpm.

 

Being able run 3rd to 65 makes the range between 3rd and fourth gear very usable and adjustable between roads and driving conditions.

 

I'd imagine small tires and 4.10s st times may feel like a one speed tranny.

 

The more we talk about this the less I'd want 4.10 and small tires.

 

I did get my 65mph reading with 285x70x17s wich I just mounted wich are slightly shorter than my 285x75x17s

Picked up a second set of aluminum geniii wheels with kinda decent cooper sst pro tires on them.  

 

I wonder if mike can make it to Ontario without shifting gears. Lol kidding. He does run on the river and mtn rds where  speed is often reduced

 

Normally run smarty on 6 or 7. Though right now its on 8

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21 minutes ago, Evan said:

At 65mph 3rd gear locked I'm at 2400rpm.

Nope ratio is wrong. 66 MPH in top gear (5th at 0.75:1)  I'm twisting 2,000 RPM perfect. Difference is I'm doing better than 20 MPG which I doubt your getting with 35-inch tires. 

 

22 hours ago, Evan said:

With 35s and 47re 3.55s it appears I can match Mike's manual transmissions rpm

Nope. Not in top gear you not. I'm pretty sure not in MPG either. 

 

65 MPH is ~1980 RPM in 5th gear making roughly 20-22 MPG.

55 MPH is ~1760 RPM in 5th gear making roughly 23-25 MPG.

 

 

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I never said I'm getting 20. I have got better then 20 but not while packing 2k om the truck.

I'm getting 17-18 depending on conditions of each tank checked. Towing alittle mostly empty but always 9400lbs.

 

3rd gear is perfect for slow rd towing 65 and under. I definitely cant fo 80 in 3rd. 

 

I'm sure my ratios of my mpg is off but there is no deciding that it's working very well for me. 

I wouldnt doubt your numbers are off to. I'm sure I could get in your truck and like how it's set up just fine. Only thing I wouldnt like is spinning so many Rs om the freeway . Well that and shifting gear. I love getting out of our big truck and just pushing the pedal down in my pickup.

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9 hours ago, Evan said:

3rd gear is perfect for slow rd towing 65 and under. I definitely cant fo 80 in 3rd. 

I used to be able to tow at 55 MPH in 4th (1:1 direct). No longer with the change of tire by 1 inch. All done in top gear now. 

 

So I've gotta ask what is your MPG logs looking like? 

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