Looking to tow 8000 lb trailer with a Hemi

mileshuff wrote:

AH64ID wrote:
Where did you think redline was? 35 in 3rd is roughly 1400 rpms, which isn't working that hard. 2nd Prime would have been around 2100 and 1st at 35 is only 4200

I'd say your gearing is vastly different than my 2004 Durango or your figures are way off. As for heat, not sure where you live but towing up steep mountain grades in 100-110F heat isn't so easy at times. Some TV's certainly do better than others with heat. Most here add aux tranny and/or engine coolers. The Durango ran hot, my 2500 diesel towing 11,000lbs runs cool.

Those are calculated based on the Dodge transmission used in the 2004 Durango Hemi and the 3.55's in your sig. I also used OEM tire size. Not sure what to tell you, but unless you had a different trans or tiny tiny tires those numbers are correct. It sounds like you were not aware of the gear you where using.

Dodge 545RFE (the only 5 speed used on a 2004 Durango)

1st 3.00:1
2nd 1.76:1
2ndP 1.50:1
3rd 1.00:1
4th 0.75:1
5th 0.67:1

Gear Ratio 3.55:1

Standard Tire size 245/70R17 684 rev/mile

Using those numbers it is easy to calculate rpms based on a locked torque converter. An unlocked torque converter will increase rpms by a few hundred.

Lets then look at the peak torque rating of 4200 rpms.

1st 35 mph
2nd 62 mph
2ndP 69 mph
3rd 104 mph
4th 138 mph
5th 155 mph

Even if you had 3.92's you wouldn't be anywhere near redline at 35 in 1st gear as it would be 4750 plus the torque converter slippage.

So how far off are they? Do the math yourself and see that you where not in 3rd gear and probably not even in 2P if you thought a downshift would send you thru redline.

Yes ambient temp makes a big difference on the cooling system, but so does running with a torque converter unlocked.

The HD trucks of the same year with the Hemi did have a larger cooling system but only 15% larger.

How many rpms where you turning at 35?