I've only seen one in person and it had 3.92 gears. Almost all of the 08's that I have seen have 3.92's as well. Especially with the 20' wheels and tires. 275/60r20's that are about 33" tall.

 

I think its with the 09s dodge started introducing the lower gear ratios, to help boost the EPA mileage.

 

they don't need 3.92 or 3.73 gears when you couple them to a 6 spd tranny.....the really low gear offsets the difference

 

3.92's have been in Dodge axles forever and a coon's age. Probably longer than I even know. Dodge only has a 5 speed right now, and I don't know the gears on it but I'd say it's first gear isn't even as low as the 3.06 in the GM 700R4, 4L60(and E), 4L80E(I'm not sure of it's first gear ratio, but it's at least as low as the 4L60E).

 

The 09 Rams come with the option of 3.21:1, 3.55:1 and 3.92:1 axle ratios, the Ram RT has 4.10s however. From what I've seen on the forum most of the 09s on dealer lots have 3.21s or 3.55s with 20" Wheels and like it was said almost 33" tall tires.

Gear ratios of the Ram's transmission are
1st 3.00:1
2nd 1.67:1
2nd Prime 1.50:1
3rd 1.00:1
4th 0.75:1
5th 0.67:1

1st gear isn't that bad, but the huge 2nd gear drops the engine way below the peak torque RPM, really hurting acceleration. Couple that with 3.21s and those 20" wheels, acceleration will not be that great. It has two second gears, one for normal acceleration from a stop, and 2nd prime for passing.

So gearing is very important to how the truck will accelerate, ford seems to have done good with the 6 speed in the new 09 F-150

 

Agreed.

Let's not forget the 545RFE in the Ram is essentially an ancient 4spd with a taller overdrive programmed in. The 2nd gear is so tall that no steep final drive ratio will fix the gap from 1st to 2nd.

Keep in mind the 2nd gear ratio is even taller in a kickdown situation. So if you're at a speed in the Ram where it's too tall for 1st, say - 35 mph, you'll end up in a super tall 2nd and totally bog. This is an area where I think Ford is clearly ahead, now, if only we can put a 390hp engine in there that gets reasonable fuel efficiency...

 

Well the 545RFE is essentially the 45RFE which was introduced in 1999. So it is not THAT old, but dated none the less. Motor trend commented on the 09 Rams 2nd gear drop with the Ram R/T. I did the math one night and worked out that the at the estimated shift point of ~5600 RPM it will dump the engine to about 3200 RPM on 1-2 shift.

The 5.4 with the new 6 speed does appear to have better fuel efficiency then the old 4 speed. But like its been said many times before, trucks will not really get any better fuel efficiency until they get much more aerodynamic.

 

Now, just imagine how bad a kickdown would be, with the 1.50 kickdown 2nd gear (3.0 first gear).

If you're at a speed where it'll be 5000 rpm in first, most dodge transmissions would choose 2nd because of the conservative programming. In this case, you'll be dropped all the way down to 2500 rpm, where the truck falls flat on its face.

The worst thing is, with the Getrag deal having just gone bad, I don't see where Dodge will find a better transmission any time soon. The 68RE on the Cummins is out of the question - too costly and heavy.

 

[quote=RoyJ;6695783]Now, just imagine how bad a kickdown would be, with the 1.50 kickdown 2nd gear (3.0 first gear).

If you're at a speed where it'll be 5000 rpm in first, most dodge transmissions would choose 2nd because of the conservative programming. In this case, you'll be dropped all the way down to 2500 rpm, where the truck falls flat on its face.

The 68RFE 1st - 2nd gear spacing is not much better
1st 3.23:1
2nd 1.83:1
3rd 1.41:1
4th 1.00:1
5th 0.81:1
6th 0.62:1

Of course behind the cummins at full throttle, a shift at 3000 RPM (peak HP) would dump it right at 1800-2000 or so, right into the sweet spot in the rev range

I really honestly would have expect chrysler to have modified the gear spacing on the 545RFE. Look up 2008 Chrysler Town & Country -- Acceleration 0 - 90 mph on youtube. The first 3 gears upto 60 MPH keep the engine right between 5100-6000 RPM, then the gears get steeper after that to keep mileage up.

 

It doesn't bad at all, not even towing 7500lbs. It is much better than the 4R70W that Ford used!!! There is plenty of torque @ 3000rpm.