So the truck came with a set of Rickson wheels 19.5" and a set of tires that were less than a year old.  I liked the old forged-in-America wheels so I decided ot keep them on the truck.

 

I have never had one of these trucks befoer this one so I have no comparative baseline on how it "should" run and drive.  In LA these trucks are like hen's teeth and I have not found anyone near me that knows much abou them at all.  My local dodge dealer is a waste of real estate and every time I've gone there they turn up their nose at my old truck and try to sell me a new truck :-)  I couldn't even get a radiotor cap from that palce.

 

After studdying this issue of tire size, on this website, more closely I decided to take a closer look at my set up as believe there is a fly in the ointment.

 

Now for the more-fun-with-math part.

 

So according to Mopar1973Man the goal is to have a Final Drive Ratio that is between 3.55 & 3.73

 

My truck started its life with a final drive ration of 3.55 (Dana 80 in the rear and Data 60 in the front)

 

Stock tire size was 235/85-R16

Current tire size is  203 245/70-R19.5

 

So I have a lift of about .85"

https://tiresize.com/comparison/

 

 

 

Upon running the calculation I now have a paultry effective final drive ratio of 3.41, so far so bad.

https://tiresize.com/gear-ratio-calculator/

 

 

Now the question is to should I lower the water or raise the bridge?

 

I could keep the wheels and change the gearing in the Axels or I can get a set of wheels and tires.

 

Either solution will cost about the same in the greater LA Area.

 

So let's say I decided to go the regearing route.

 

I believe Dana offers 3.73 and 4.1 gearing.

 

The question is this, if I went the re-gearing route which would be preferable (either 3.73 or 4.1) and why?

 

Also I have the NV5600 at (0.73:1) and I'm not exactly sure how to add that into my math here or that's even relevant.

 

Thanks @Mopar1973Man for this article this is super helpful in trying to sort this all out.

 

Edited October 13, 20204 yr by leety

11 minutes ago, leety said:

the carrier has to be changed for that leap to happen

Is that for the front or rear?  This isn't really my wheelhouse, but have looked at these enough to know there are questions I would ask an expert before I dismissed it as impossible!  I THINK you may be in luck - maybe not.  Yukon makes "thick gear" 4.11 gears to fit - I believe - the same carrier as your 3.55s.  They also make "thin gear" 3.73s to fit the 4.10 and up carrier.

Here's a link:
https://www.randysworldwide.com/product/yg-d80-411t/
Now, if you buy these and Randy sends me a 4.5% commission, don't come calling me with any complaints 

 

44 minutes ago, LorenS said:

Is that for the front or rear?  This isn't really my wheelhouse, but have looked at these enough to know there are questions I would ask an expert before I dismissed it as impossible!  I THINK you may be in luck - maybe not.  Yukon makes "thick gear" 4.11 gears to fit - I believe - the same carrier as your 3.55s.  They also make "thin gear" 3.73s to fit the 4.10 and up carrier.

Here's a link:
https://www.randysworldwide.com/product/yg-d80-411t/
Now, if you buy these and Randy sends me a 4.5% commission, don't come calling me with any complaints 

 

It’s all about Hoopers Rear Ends.  They’ve been in the greater LA area since 1976.  That’s the place to go.

 @leetyJust gonna take a shot at this, I'll let @LorenS do the math. If you would eventually swap to a 3:73 gear and when it's time for tires step down from the 240/70/19.5 to a 225/70/19.5 you would loose a bit over an inch in height which may make those gears work even better for you.

 Biggest drawback to the big wheels is the rotating mass. I don't know what that tire combo weighs compared to a stock wheel/tire but I would guess they would be heavier. They do look good though. Just my $.02

More-fun-with-math, humm, Loren, gonna need some help here...

 

But, I think the difference between 3.55 and 3.73 gears is about 5% or about 100 rpm or about 3.5 mph @70. $1500 for a 5% bump in performance?

 

The oem power of the HO is 245/505...add 5%...that gives a new rating of 257/530. My guess is the butt dyno wont feel it.

 

The Edge EZ adds 65/180...so now the oem power jumps up to 310/685, you will feel that

 

The EZ also claims a mileage increase of 1-2 mpg.

 

When your 245's wear out you can drop to 225's that is about 3.5%

 

How many miles per year do you drive the truck? Unless you are running a huge tire, like 37's" a gear change is the last thing I would do, then 4.10's make sense. 

 

If it ain't broke don't fix it. Now, with that said....65/180 additional power increase will make a fun ride out of that 3500 truck!

I’m with @NIsaacs Changing gears is a lot of money for not much result, but it is your money. 

One possible problem with a tuner is California emissions, unless it has a CARB certificate (Gale Banks may have one?). Gears surely wouldn't come in to play.

45 minutes ago, LorenS said:

One possible problem with a tuner is California emissions, unless it has a CARB certificate (Gale Banks may have one?). Gears surely wouldn't come in to play.

 

Appears to be legal.

 

https://edgeproducts.com/shop/2001-2002-dodge-24-v-ez-5-9l

1 hour ago, NIsaacs said:

 

Appears to be legal.

 

https://edgeproducts.com/shop/2001-2002-dodge-24-v-ez-5-9l

The edge is definitely legal.  The truck had an old on on it when I got it but it was contributing to al full-time coal plume so I deleted it.  Most of the plume is gone.  That wasn’t the only contributor.

 

I have a BHAF which is not legal.  For that I keep an original air box handy so I can swap it in every 2 years for smog.  A girls gota do what a girls gota do.

2 hours ago, LorenS said:

One possible problem with a tuner is California emissions, unless it has a CARB certificate (Gale Banks may have one?). Gears surely wouldn't come in to play.

That’s not difficult to get around.

 

Tuners are easy enough to temporarily remove every 2 years for smog.

 

I do that with my BHAF

My dad had an Edge EZ on his 01' dually with 6/speed and loved it, even tipping the scales at 35k pounds on a trip to the dump.  He drove slow (65 MPH usually) and would regularly get well over 20 MPG, hand calculated.  I think his record round-trip to our cabin +100 miles away was upper 20's.  It was cool, almost foggy weather.  Enough the air felt saturated, but the pavement was dry.  He didn't run any gauges, though, so who knows what EGTs would get to be when he refused to downshift and just rode the torque curve all the way down...  Otherwise stock truck besides coolers on the tranny.

Could go with a quad and tune out smoke. Still way cheaper than gears 

27 minutes ago, Royal Squire said:

Could go with a quad and tune out smoke. Still way cheaper than gears 

The quad is something on my short list of considerations.  It'll do everything the Edge EZ does and much much more.  The quad is not legal in CA but smog happens every 2 years so I just have to swap out a couple items to pass smog.  Not biggy.

 

I wanted to get as much smoke gone as I could with the orriginal equiptment.  I don't like to solve problems with a bandaid, I'd rather get at the phisical root of the problem and then introduce the the quad on to take it beyond the limitations of the hardware. By correting the issues with the OEM bits first I have gotten most of the smoke to go away.  I think my final drive ratio is the last bit of OEM adjustment I need to consider.  I believe I have covered all the other contributers to my coal plum at this point.

10 hours ago, leety said:

I have a BHAF which is not legal.

On 10/12/2020 at 8:12 PM, Royal Squire said:

You should probably make sure gears haven’t been changed previously 

So armed with the beautiful math of @Mopar1973Man and @LorenS coupled with the best question on the post I attempted to take this picture. Yes it’s blurry but this my actual realty in terms of speed per rpm.  So is it possible that a gear change happened by a PO?

 

How can I figure this out?

 

Pretty sure you're still at 3.55.

https://www.rocky-road.com/calculator.html

It's not mobile friendly! Very small.

 

Remember, the MMR is to get us in the vicinity of 66 to 70 MPH at 2,000 RPM. If you had 3.73s, you'd be at 2,000 RPM @ 68 MPH.

Edited October 15, 20204 yr by LorenS

Just pull the cover and count the teeth. Divide the drive gear into the driven. I believe ratio is stamped on ring gear also. 

57 minutes ago, LorenS said:

Pretty sure you're still at 3.55.

https://www.rocky-road.com/calculator.html

It's not mobile friendly! Very small.

 

Remember, the MMR is to get us in the vicinity of 66 to 70 MPH at 2,000 RPM. If you had 3.73s, you'd be at 2,000 RPM @ 68 MPH.

Thanks that's an awsome calculator!!!!

3.73 would be just about right for most people with slide in camper or tow a lot. For me its all the steep mountain roads. 

9 hours ago, Royal Squire said:

Divide the drive gear into the driven

Hard to see the pinion, isn't it?  I've never seen the insides of a DANA 80.

1 hour ago, Mopar1973Man said:

3.73 would be just about right for most people with slide in camper or tow a lot. For me its all the steep mountain roads. 

Yep it’s very steep twisty mountain roads for me.  And a bit of towing.

Assuming that you were in 6th gear (.73:1).

 

Axle ratio = [(engine rpm) (tire diameter in inches)] / [(mph) (336) (transmission gear ratio)]

 

 

? = [(1825 rpm) (33.4")] / [(70 mph) (336) (.73)]

answer = 3.55 rear axle gear ratio

 

 

If you pull the diff cover you will find that Dana gears are marked on the ring gear like this.  At the top you will see 43X13, that is 43 teeth on the ring gear and 13 teeth on the pinion.  43/13=3.5384 or 3.54 gear ratio.

 

 

 

Edited October 15, 20204 yr by Joe_Pool
To add information