Question about rear axle ratio and transmissions

[TheGoose]

I found a really good deal on a ram 4x4. This is a 4x4 5.7l lone star package. It even has the brake controller.

Like most ram trucks it has the 3.21 gear ratio. My old F150 had the 3.55. It was rated to tow 10,600 from what I recall. From what I can tell the ram is rated for 8500 which is probably good enough for what I need but I would really prefer the max tow option.

This truck has the 8 speed transmission. Is the rear ratio as important with so many more gears in the tranny? When I bought my F150 I assumed the 3.55 would be better on gas but this truck has never avg above 14-16 in mixed driving.

For those who are curious I can get this truck for $33,750 + ttl. This is without any trade in. It's a 2016 model with a good bit of options, more than my xlt ford.

 

[moriboy]

It seems more and more, axle ratios are much higher than they used to be. My new Ram 3500 diesel has 3.42 gears and pulls like a freight train. Ultimately, the transmission gearing will dictate where your rpm's will be when driving down the road. I wouldn't worry too much about the 3.21's with the 8 speed (unless you are towing a lot at max GCVW). If that's the case I might look at something different.

 

[Ford850]

The payload will probably be the limiting factor on a Ram. What do the door stickers list for payload on your old Ford and this new Ram? If they let you test drive it, take it home and take a short drive with a heavy trailer. Compare both old and new trucks on some heavy pulls and at cruise.

 

[TheGoose]

Payload listed at 1400 lbs

 

[TheGoose]

For some reason I thought my 2012 F150 was rated to tow 10,600 but after looking at this chart: https://www.fleet.ford.com/truckbbas/topics/2012/12_FLRVTT_gde.pdf it looks like it's only about 9,500 lbs. I'm not sure on the payload. The Ram I'm looking at is rated a little less at 8,500 lbs. Close enough to the Ford for my interest that it's probably not much of a difference. It's super hard to find the 3.92 axle from my research.

 

[Diamondpilot]

Payload listed at 1400 lbs

That's pretty light by today's standards. Your F150 is around 1750 or so.

Figure 2 guys at 200# each and 2/3 tank of fuel at 200# and you are left with 1000#

A 8000# trailer with 10% tongue weight and you can't put your dog in the bed.

 

[dodge man]

I'm not sure I understand the phyiscs of it, but the higher number rear gear ratio takes a lot of shock out of the drive line, taking off from a stand still being the most important. I'm not sure even with the extra gears in the transmission equals a higher numbered gear in the rear end or not.

 

[tcartwri]

I found a really good deal on a ram 4x4. This is a 4x4 5.7l lone star package. It even has the brake controller.

Like most ram trucks it has the 3.21 gear ratio. My old F150 had the 3.55. It was rated to tow 10,600 from what I recall. From what I can tell the ram is rated for 8500 which is probably good enough for what I need but I would really prefer the max tow option.

This truck has the 8 speed transmission. Is the rear ratio as important with so many more gears in the tranny? When I bought my F150 I assumed the 3.55 would be better on gas but this truck has never avg above 14-16 in mixed driving.

For those who are curious I can get this truck for $33,750 + ttl. This is without any trade in. It's a 2016 model with a good bit of options, more than my xlt ford.

I have owned both the 3.21 and the 3.92. I regret getting the 3.92's in the second truck. There is no difference in the towing performance other than the published numbers. It does however translate into about 1 mpg loss on average.

The first two gears in the 8 speed are very deep. Like a granny low in an old 4 speed. It has NO issues moving a loaded trailer, quickly.

 

[TheGoose]

Getting conflicting information about the dodge. Think maybe the payload is 1500 lbs.

 

[tcartwri]

Getting conflicting information about the dodge. Think maybe the payload is 1500 lbs.

If it's a Lone Star, it will be about 1400 lbs. One other thing to be aware of, is the transfer case. If it has the Auto transfer case, they are not suited for moderate to serious off roading. It needs to sense wheel slip before it engages and if you're already buried you will be sol. It is brilliant in the snow though.