Diff switch from 3.55 to 4.10

[Marcus2000monster]

5 hours ago, wagntagn said:

At 1600 rpm I’m cruising 55 mph I climb the hills no problem when I cancel od it will rev roughly 2200 if I floor it it will gain speed but egt’s climbs to 1200 just keeping an eye on egt’s,I’m at setting 5 on my Smarty where should I be set + timing or not??

Marcus are in Canada?

Close. 2 hrs from the border in polson Montana 

[wagntagn]

Why did you switch to 3.55?Do you have to do some shimming when doing the switch or just switch gears?

[Marcus2000monster]

1 hour ago, wagntagn said:

Why did you switch to 3.55?Do you have to do some shimming when doing the switch or just switch gears?

All I did was pop ring and pinion out and reinstall the 3:54 set. It was very easy. Some trucks require shimming but mine didn’t. For a quieter ride, better mpg, higher speed.

Edited July 8, 2019 by Marcus2000monster

[Evan]

I really like my 3.55s I wouldn't change to 4.10 even if I had lots of money to throw away.

 

No clue on what smarty settings. If stock injectors I wouldn't think youd see much heat from any settings.

 

How much boost does it make. If its o ly in 22-24 psi range then turn buckling the waste gate closed would probly knock your egts done 1-200deg and might even make the but dyno register more power.

 

I wouldnt go in a gear change with out proper shims and tools to make sure the gear lash is correct.

Ring and pinion sets cost way to much to screw up and have to do more than ounce. But the job is very doable for the diy seller that is willing to take the time to learn how to do it right and then do it.  I wouldn't even replace 3.55 set with a new 3.55 set with out going through all the same steps same as 3.55 -4.10 swap.

 

 

Edited July 9, 2019 by Evan

[Ironforger]

Ironic,

 

Pretty sure my 02 HO 6 speed NV5600 truck has 4:10's and I'd like to switch to 3:55's

 

But before I do I'd like to find someone local who is running an NV5600 with 3:55's just to test drive and compare with my truck.

 

Btw, here are my current RMP's & corresponding highway speeds.

 

5th gear:

35 mph  1600 rpm

45 mph  2000 rpm

55 mph  2500 rpm

65 mph  3000 rpm

 

6th gear:

60 mph  2000 rpm

66 mph  2150 rpm

80 mph  2600 rpm 

 

 

[Mopar1973Man]

Even though I'm a 5 speed at 0.75:1 in top gear vs. your 6 speed at 0.73:1. 245's tires and 3.55 gears. Final ratio 3.69:1 to the ground.

 

5th Gear (0.75)

66 MPH = 2,000 RPM

80 MPH = 2,500 RPM

 

4th Gear (1:1 Direct)

45 MPH ~ 1,900 RPM

[dripley]

In 6th gear I am turning 2000 rpm at 70 mph and IIRC in 5th gear I am turning 2000 rpm at 60 mph. This is on 265 75 16's. Tire size will make a difference.

 

It would appear yours is 4:10 gears. Look at the sticker on your glove box door and it should be printed there. At least that would tell you it came with.

Edited July 14, 2019 by dripley

[Mopar1973Man]

11 minutes ago, dripley said:

This is on 265 75 16's. Tire size will make a difference.

 

Yup, you on a 31.6 inch tire and I'm running 30.5 inch tire. 1.1 inch difference. 0.14 difference in final ratio.

13 minutes ago, dripley said:

It would appear yours is 4:10 gears

 

That exactly what he asking is if those RPM's he posted are 4.10 gear and he's wanting to find out what 3.55 gears will do. Being that both NV4500 and NV5600 have the same top two gears the transmission is not going to make a difference. 

 

[dripley]

I guess I should have stated that I have 3:55 gears. And as @Mopar1973Man states the 5 and 6 speed tranny's top 2 gears are almost identical. You can see that tire size makes a difference. I dont pay to much attention the the mph and rpm in my truck unless I am cruising in 5th or 6th. 

[Mopar1973Man]

Info purpose...Gear is displayed and RPM.

 

60 MPH...

 

45 MPH...

 

35 MPH...

 

25 MPH...

 

[Evan]

3.55 35s 47re overdrive. 

Smarty set tire size at 32.75

[Bullet]

2 minutes ago, Evan said:

3.55 35s 47re overdrive. 

Smarty set tire size at 32.75

I'm a bit confused about why you are running 35's and have the speedo set to 32.75".  Your speedo is about 5 mph slow...you are actually going about 77-78 mph.  Mpg hand calculations are negatively affected and a higher risk of getting a speeding ticket.  Only benefit I can think of is a few hundred less miles on the truck at resale...or am I missing some other reason to do that? 

[Evan]

I go off actual measured tire size not sidewall. It's about 1mph off my 2012 caravan that has stock tires.

 

I could care less what resell is not sure odometer is working correctly anyways.

 

I haven't verified speed with GPS but it seems close enough for me. I'd assume all those that plug sidewall size into the smarty are off. In my case that would be off by 2.25" of rubber

[dripley]

If you are running 35's should you not plug that in? Just curious here. Thats the tire diameter and not the sidewall as best I know. I dont how the smarty accounts for it though.

[Bullet]

1 hour ago, Evan said:

I haven't verified speed with GPS but it seems close enough for me.

Once you do verify it with GPS you'll learn at that point that you are 5 mph off.  But to each their own.  I was just trying to find out the reasoning behind it...thought I might have been missing out on some new trick.

[Evan]

I highly doubt I'm off 5. Though I may be off .25-.5" measuring tires.

 

Manufacture will list specs for they're tires. I think mine list at 33.2.

 

Either way it's close enough. Everyone passes me when I run 1800-1900 rpm.

 

I dont think the tacks off

[Bullet]

2 hours ago, Evan said:

Either way it's close enough. Everyone passes me when I run 1800-1900 rpm.

I might be one of them.  I cruise at 2k which puts me at exactly 80 mph on gps and speedo (Smarty corrected) with 33's.  Lot of concrete to cover here in Texas. 

[Mopar1973Man]

From 235/85 R16 (31.7 inch) to 245/75 R16 (30.5 inch) which is a 1.2 inch difference. Now the speed difference is 5 MPH and about 200 RPM different. I'm corrected by @Chris O. CCD Network tool.

[Evan]

Yes so you run listed tire size not actual rubber measured in front off you.

 

Being passed I'm off 1ish wich I figured to be the .25-.5" variance between tires. I bet dropping to 32.5" squashes my 1mph being passed.

 

Man why am I even putting the effort in thinking about this

[Mopar1973Man]

Simple compare you GPS against a Live Data tool If they match then the speed is on. I'm less than 1 MPH off in speed. No thought required just compare two sources of speed and see if they match.