6.4l 8 speed towing review
I'm in the market to replace our eco diesel. Its exceeded expectations as a tow vehicle,but after the AEM, its not the same truck. I know a tune will solve the problem but I have personal issues with ...
Forum Discussion
What mtofell said, except that the 66/68re gear ratios are not even ideal for a diesel, pulling heavy. They're more preferable for a diesel lightly loaded, but look at the ratios side by side on the recent years' crop of 6 speeds.
The 6R140 and Aisin are geared deeper across the board until high gear, which is better for towing, regardless of the power plant in front of it.
The 66/68re and Allison are geared similarly at higher ratios which is less power to the ground apples to apples speed and rpm.
Speaking for the diesels, GM kept 3.73 as the highest rear gear (and only) available, whereas the Cummins was paired with only 3.42s for years. Part of the reason similar power yielded a faster truck in the Duramax (and the V8 revs quicker than the inline 6). And why the powerstroke could pull the 3.31s and 3.55s? seemingly so well compared to say 68re Cummins with 3.42s.
For a 6 speed behind a Hemi (or any gasser), I'd want Aisin or 6R140 type gearing over the 66/68/Allison gears.
Now look at the gear ratios of the 8HP70 and 8HP75 that have been backing Mopar V8s for the last several years. They're stump pullers down low and smaller splits in the mid range compared to the others.
The new GM/Ford JV 10 speed gets off the line not quite as deep as the 8HPs but has slightly narrower splits mid range and, IMO, looks to have at least 1 too many gears in the overdrive range.
Haven't found the 10 speed Allison ranges yet.
While some doubt the benefits from 6 to 8 speeds (and I may somewhat if comparing to the 6R140 or Aisin 69), in general, both big gassers and diesels can make better use of the 8 speed like the 8HPs than the 5 and 6 speed variants they had or have currently (particularly the 66/68s and the Allis).
10 speeds IMO has reached the point of diminishing returns, especially in gassers.
The 6R140 and Aisin are geared deeper across the board until high gear, which is better for towing, regardless of the power plant in front of it.
The 66/68re and Allison are geared similarly at higher ratios which is less power to the ground apples to apples speed and rpm.
Speaking for the diesels, GM kept 3.73 as the highest rear gear (and only) available, whereas the Cummins was paired with only 3.42s for years. Part of the reason similar power yielded a faster truck in the Duramax (and the V8 revs quicker than the inline 6). And why the powerstroke could pull the 3.31s and 3.55s? seemingly so well compared to say 68re Cummins with 3.42s.
For a 6 speed behind a Hemi (or any gasser), I'd want Aisin or 6R140 type gearing over the 66/68/Allison gears.
Now look at the gear ratios of the 8HP70 and 8HP75 that have been backing Mopar V8s for the last several years. They're stump pullers down low and smaller splits in the mid range compared to the others.
The new GM/Ford JV 10 speed gets off the line not quite as deep as the 8HPs but has slightly narrower splits mid range and, IMO, looks to have at least 1 too many gears in the overdrive range.
Haven't found the 10 speed Allison ranges yet.
While some doubt the benefits from 6 to 8 speeds (and I may somewhat if comparing to the 6R140 or Aisin 69), in general, both big gassers and diesels can make better use of the 8 speed like the 8HPs than the 5 and 6 speed variants they had or have currently (particularly the 66/68s and the Allis).
10 speeds IMO has reached the point of diminishing returns, especially in gassers.
