Dynamax 5 28SS Gear Ratio

V7Sport73 · 01-19-2022, 12:55 PM

I noticed that Dynamax orders the Ram 5500 chassis with the 4.89 gears or 4.88 as listed. I have owned 12 of the Ram Cummins powered trucks. I don't think the 28SS needs 4:89 gears. The stock 4.44 gears should be more than enough. With a 10,000-pound hitch weight it would give the RV GCWR of 29,500. It would be hard for me to believe you could exceed the capabilities of the truck with the stock 4.44 gears. I can see this on larger models but on the 28SS? I'm thinking with the 4.89 gears you would be close to 2,700 RPM's at 75 mph?

CyberShanks · 01-19-2022, 02:23 PM

My 2010 Ram w/ 6.7 Cummins is running 3.73 gears and a G56 manual with heavy clutch disks. I've been 23k combined with it and went over rockies without leaving 6th gear. It may be slightly tuned though.

Jim

V7Sport73 · 01-19-2022, 02:46 PM

We use the Ram trucks for dump trailers and roll-off containers. We haul the containers to the landfill. There you must weigh in and out again when leaving. 26,000 pounds GCW is easily pulled with 4.10 gears on our 3500 Ram trucks. Our 5500 Rams have the 4.44 gears and it's overkill. Even if you exceed the weight rating of 10,000 on the Dynamax 5 28SS hitch, which in my opinion 10K is more than enough for just about any trailer or boat, it would still pull the load just fine with 4.44 gears. So why the 4.89 gears?

1HasBeen · 01-19-2022, 09:06 PM

What are we talking about 200-300 RPM difference?

Desert Boat · 01-19-2022, 11:09 PM

Now you got me curious how to check the final gear ratio. The only call out on my RAM window sticker (2019 chassis for 28ss 2WD) relating to axle ratio is:

Quote:

Max Tow Package (Increases Axle Ratio)

Where do I dig around in documentation or on the vehicle to find this?

Quote:

Originally Posted by V7Sport73

I can see this on larger models but on the 28SS?

It would be illuminating to see if Dynamax is interested in different axle configurations within the Isata 5 line since the usual thought is minimizing configuration differences helps ease production in many ways.

V7Sport73 · 01-20-2022, 07:59 AM

You can run the VIN through the one of the many VIN decoder websites.

V7Sport73 · 01-20-2022, 08:02 AM

Quote:

Originally Posted by 1HasBeen

What are we talking about 200-300 RPM difference?

On a Diesel, 300 RPM is a lot. At 70 MPH with 4.44 gears you are running the engine well above it's sweet spot 1800 to 2100 RPM. With the 4.89?

V7Sport73 · 01-20-2022, 08:06 AM

Quote:

Originally Posted by Desert Boat

Now you got me curious how to check the final gear ratio. The only call out on my RAM window sticker (2019 chassis for 28ss 2WD) relating to axle ratio is:

Where do I dig around in documentation or on the vehicle to find this?

It would be illuminating to see if Dynamax is interested in different axle configurations within the Isata 5 line since the usual thought is minimizing configuration differences helps ease production in many ways.

You can run the VIN through the one of the many VIN decoder websites. If you have the max tow package then the gears are 4.89

1HasBeen · 01-20-2022, 08:54 AM

Quote:

Originally Posted by V7Sport73

On a Diesel, 300 RPM is a lot. At 70 MPH with 4.44 gears you are running the engine well above it's sweet spot 1800 to 2100 RPM. With the 4.89?

I am well aware, and have owned and driven diesels for a long time. I ordered my dually with 4.10s, because I pull at 65, so it puts me basically right there. It's a balancing act, I get it.

V7Sport73 · 01-20-2022, 06:45 PM

Here is one example. This is a run today with my Ram 2021 3500. With a 4.10 gears it handles 26,000 pounds no problem. With our 5500 Ram trucks and the 4.44 gears, you can't even tell the trailer is back there. I tried to get a shot of the scale on the way in but the photo didn't show the weight. The 15,600 is when the truck and trailer is empty. I estimate the trailers we pull are around 6,500 empty. As far as I'm concerned the Ram Chassis are some of the best out there. However, I really question the need for 4.89 gear sets. I pull an ATC 32' toy hauler 5th wheel as well. It weighs about 14,000 loaded. The ATC's have the aerodynamics of a huge brick. You may as well pull a parachute all day. I get 9 mpg pulling the ATC. I average about 11.5 pulling the trailer shown in the photo. Perhaps Dynamax puts 4.89 gears in the RV because of aerodynamics? So those of you that have the Dynamax 5, what RPM are you running at 70 MPH? Any idea's on average MPG in the Dynamax 5?

Desert Boat · 01-21-2022, 09:15 AM

Quote:

Originally Posted by V7Sport73

I get 9 mpg pulling the ATC. I average about 11.5 pulling the trailer shown in the photo. Perhaps Dynamax puts 4.89 gears in the RV because of aerodynamics? So those of you that have the Dynamax 5, what RPM are you running at 70 MPH? Any idea's on average MPG in the Dynamax 5?

14000 miles in last year, 10.6 average towing JLU Rubicon, by spreadsheet (not the dash gauge, which can be off by up to 1.5 MPG either high or low), usually cruise around 68. Will check RPMs today.

Quote:

Originally Posted by V7Sport73

You can run the VIN through the one of the many VIN decoder websites. If you have the max tow package then the gears are 4.89

No joy, either don’t recognize the VIN, return just basics (6.7 diesel, GVWR, and a few other generalities), or want $.

milkman55 · 01-21-2022, 10:25 AM

Try this lookup tool. Worked for my VIN.

https://windowstickerlookup.com/

V7Sport73 · 01-21-2022, 10:44 AM

Quote:

Originally Posted by Desert Boat

14000 miles in last year, 10.6 average towing JLU Rubicon, by spreadsheet (not the dash gauge, which can be off by up to 1.5 MPG either high or low), usually cruise around 68. Will check RPMs today.

That's pretty good mileage. Much better than the 8 MPG I see often with my ATC 5th wheel.

V7Sport73 · 01-21-2022, 11:03 AM

Quote:

Originally Posted by milkman55

Try this lookup tool. Worked for my VIN.

https://windowstickerlookup.com/

Thanks! That is a great link!

mjbenedict · 01-21-2022, 03:37 PM

I average between 8-12 mpg at 70mph depending on wind direction, towing my Ram1500 limited loaded with kayaks, bikes, etc. I think the gear ratio is perfect given there are few times it needs to downshift and I don't have to work it on the hills. A couple things to remember:

The max tow package changes the gearing
The transmission is different than what comes on 3500
Dynamax orders these rigs so they can build to order when the orders come in

I don't know if the AISIN transmission comes with different gearing, it could.
Dynamax doesn't know how many orders for each different rig they will get in the future so one rig fits all is better for them and us. They could put your smaller rig on backorder and allow me to jump line if they have the larger rig chassis available. I'm not sure anyone would like that, except for the ones getting pushed ahead.

1HasBeen · 01-21-2022, 04:28 PM

Other than, potentially, the programming, the AS69RC in the 3500 pickups is the same as what is in the 4500/5500.

Desert Boat · 01-21-2022, 06:45 PM

Quote:

Originally Posted by milkman55

Try this lookup tool. Worked for my VIN.

Quote:

Originally Posted by Desert Boat

Now you got me curious how to check the final gear ratio. The only call out on my RAM window sticker (2019 chassis for 28ss 2WD) relating to axle ratio is:

Max tow package (increases axle ratio)

Where do I dig around in documentation or on the vehicle to find this?

As previously posted, I have the window sticker. It doesn’t list the axle ratio. And the one you posted doesn’t either, just has the same statement about max tow.

Desert Boat · 01-21-2022, 06:52 PM

Quote:

Originally Posted by V7Sport73

So those of you that have the Dynamax 5, what RPM are you running at 70 MPH? Any idea's on average MPG in the Dynamax 5?

on our 2wd 28ss:

60 MPH is 2000 RPM

70 MPH is 2300 RPM

milkman55 · 01-21-2022, 07:01 PM

Quote:

Originally Posted by Desert Boat

As previously posted, I have the window sticker. It doesn’t list the axle ratio. And the one you posted doesn’t either, just has the same statement about max tow.

FCA shows it on their data sheet, page 5

Axle Ratios: 5500 — 4.44 (DMK)
— 4.89 (packaged with Max Tow Package

https://www.fcausfleet.com/content/d...ChassisCab.pdf

Desert Boat · 01-21-2022, 10:34 PM

Quote:

Originally Posted by milkman55

FCA shows it on their data sheet, page 5

Axle Ratios: 5500 — 4.44 (DMK)
— 4.89 (packaged with Max Tow Package

https://www.fcausfleet.com/content/d...ChassisCab.pdf

That is a useful link. I had found a shorter version of this, but not the detailed one. And now we know max tow includes a 12” axle along with the 4.89 gear.

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