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Discussion Starter · #1 ·
In case you missed it the WK2 Trackhawk has been officially announced for a 4th quarter 2017 release-basically at the beginning of MY 2018.

http://www.motortrend.com/cars/jeep...9ea0204d30111b2f6438e&utm_medium=&utm_source=

Also mentioned in the article is that it will feature the ZF 8HP95 transmission, which is a 2nd gen ZF 8HP transmission. The Hellcat autos already feature a modified 8HP90, which in stock form is good to 664 lb-ft. From what I have seen the 8HP95 is not any stronger than the 8HP90 as the 8HP75 is compared to its 1st gen brother, the 8HP70 (8HP75 is good to 553 lb-ft input compared to 516 on the 8HP70); however the 2nd gen 8HPs have a wider range, are supposedly 3% more efficient and smoother.

The 1st gen 8HPs were introduced by ZF in 2008, the 2nd gens in 2014. The 2nd gens have a wider ratio spread of 7.81:1 compared to 7.03:1 for the first gen 8HPs; looking at the ratios (rounded to the nearest hundredth):

__________1st gen___2nd gen
1st:--------4.71:1-----5.00:1
2nd:--------3.14:1-----3.20:1
3rd:--------
2.11:1-----2.14:1
4th:--------
1.67:1-----1.72:1
5th:--------
1.29:1-----1.31:1---^Underdrives
6th:--------1.00:1-----1.00:1---Direct drive
7th:--------
0.84:1-----0.82:1---Overdrive
8th:--------
0.67:1-----0.64:1---2nd Overdrive
Reverse:---
3.30:1-----3.46:1

So not only do you get a slightly taller 8th gear for more efficient cruising (taller than the GM 8L90 8th gear of 0.65:1), but an even lower 5.00:1 1st gear, while keeping similar even spacing throughout.

That means that a Ram with an 8HP75 and 3.21s would be like having a 3.41 rear end on a Ram with an 8HP70; or an 8HP75 with 3.92s would be like an 8HP70 Ram with an outrageously low 4.16:1 rear end gear.

Or, to get the same first gear final drive ratio that I have with an 8HP75 you'd have to have a 3.02:1 differential; or 3.69:1 to equal a 3.92 geared truck.

To put it all together, now that Chrysler is using the 2nd gen 8HPs in one of their vehicles I think it is safe to expect them to appear in the 5th generation Rams, and perhaps the 2018 4th gens-though that may be a bit of a stretch. The spread in these transmissions will have a super low stump pulling 1st gear and an even wider range than the current 8 speeds-and even the GM 8 speed (the 8L90) and somewhat surprisingly the GM/Ford 10 speed. Check out their ratios:

__________10 speed___8L90
1st:--------4.70:1------4.56:1
2nd:--------2.99:1-----2.97:1
3rd:--------
2.15:1-----2.08:1
4th:--------
1.80:1-----1.69:1
5th:--------
1.52:1-----1.27:1
6th:--------1.28:1-----1.00:1
7th:--------
1.00:1-----0.85:1
8th:--------
0.85:1-----0.65:1
9th:--------
0.69:1-----------
10th:-------
0.64:1-----------
Reverse:---
4.87:1-----3.82:1

So stacking up the competition, the current 8HP70 already has a lower 1st gear than both the 8L90 (7.02 spread) and Ford/GM 10 speed (7.34:1 spread), and the 8HP75 has a similar top gear to the 10 speed and slightly taller one than the 8L90. Both competitors do have an advantage of a lower reverse gear and input capacity (8L90 can take 738 lb-ft, the 10 speed is 650 lb ft), but the capacity of all 4 transmissions mentioned in this post far exceeds the output of any 1/2 ton truck engine and an 8HP90 will match the 8L90 and would be easy to implement for Ram.

Looking at it subjectively, with all the hoopla about the 10 speed I expected it to have a wider spread. It is barely any greater than the 8HP70 that Ram has been using for 4 years and it seems that the two extras will just make it hunt more. There was an interview with one of the design leads at ZF a couple years back where he was asked how many gears he thought transmissions would get to in consumer vehicles. He replied that once you get past 8 or 9 you get to a point of diminishing returns, and this certainly suggests he was right.
 
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2014 345ci 8hp70 44-44 3.92 Truetrac NX Express Comp Greene Racing
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Thanks for sharing, I also feel a 7 speed tranny is optimal for fuel economy and performance in a standard non hauling commuter outside of the autobahn. Any larger towing vehicles can benefit from the high ratio extra first gear to provide less stress on the initial torque transfer.
 

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Discussion Starter · #3 ·
Thanks for sharing, I also feel a 7 speed tranny is optimal for fuel economy and performance in a standard non hauling commuter outside of the autobahn. Any larger towing vehicles can benefit from the high ratio extra first gear to provide less stress on the initial torque transfer.
:smileup:

The 8 speeds we have now have the same top gear that the old 5 and 6 speed had, but have more even spacing and lower 1st gears. The 5/6 speed had a 3.00:1 1st gear, both 1st and second in the 8 speed are lower.
 

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Discussion Starter · #5 ·
Will they put an 8 speed in the 2500's, do you know?
Thanks!
Not sure, HDs don't have fuel economy requirements so probably not, to save money. There was a rumor in a Motor Trend article about the PW a while ago saying it was not durable enough but there was no substantiation to it
 

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Discussion Starter · #9 ·
What would be REALLY nice is the ability to skip shifts by a user configurable settings tables.
Would this not be possible from a custom tune? Most MFGs don't like to give the user too much leeway to mess with trans programming, which is understandable since they offer a warranty

I hope they have the 2-1-gear bump under control now. more important than 0.1mpg saving.
Does your do it? Mine doesn't and its a very early hemi 8 speed
 

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Yes it does. with AC off very strong, with AC on, barely, which makes me believe, because the rpm with AC is slight higher, that it has something to do with the idle rpm's.
 

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Fantastic Post Thunderhorse :smileup:

Thanks for taking the time to share :rep:
 

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The 8HP70 transmission, also called the "TorqueFlite 8". ( it was called that because everyone at one time wanted the TorqueFlite 727 )

The 8HP70 transmission has 40 different “control maps” to change shift patterns based on operating conditions

You may have noticed that when your teenage son has the vehicle for a Friday or Saturday night, not only is the seat position & fuel tank level changed, it also shifts more harshly than when you last drove it.
The transmission changed the shift map to accommodate the different type of driving.

Think about connecting up your laptop & changing shift patterns the next time a Ford Lightning or Chevy Cyclone pulls up next to you at a light :)
 

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In case you missed it the WK2 Trackhawk has been officially announced for a 4th quarter 2017 release-basically at the beginning of MY 2018.

http://www.motortrend.com/cars/jeep...9ea0204d30111b2f6438e&utm_medium=&utm_source=

Also mentioned in the article is that it will feature the ZF 8HP95 transmission, which is a 2nd gen ZF 8HP transmission. The Hellcat autos already feature a modified 8HP90, which in stock form is good to 664 lb-ft. From what I have seen the 8HP95 is not any stronger than the 8HP90 as the 8HP75 is compared to its 1st gen brother, the 8HP70 (8HP75 is good to 553 lb-ft input compared to 516 on the 8HP70); however the 2nd gen 8HPs have a wider range, are supposedly 3% more efficient and smoother.

The 1st gen 8HPs were introduced by ZF in 2008, the 2nd gens in 2014. The 2nd gens have a wider ratio spread of 7.81:1 compared to 7.03:1 for the first gen 8HPs; looking at the ratios (rounded to the nearest hundredth):

__________1st gen___2nd gen
1st:--------4.71:1-----5.00:1
2nd:--------3.14:1-----3.20:1
3rd:--------
2.11:1-----2.14:1
4th:--------
1.67:1-----1.72:1
5th:--------
1.29:1-----1.31:1---^Underdrives
6th:--------1.00:1-----1.00:1---Direct drive
7th:--------
0.84:1-----0.82:1---Overdrive
8th:--------
0.67:1-----0.64:1---2nd Overdrive
Reverse:---
3.30:1-----3.46:1

So not only do you get a slightly taller 8th gear for more efficient cruising (taller than the GM 8L90 8th gear of 0.65:1), but an even lower 5.00:1 1st gear, while keeping similar even spacing throughout.

That means that a Ram with an 8HP75 and 3.21s would be like having a 3.41 rear end on a Ram with an 8HP70; or an 8HP75 with 3.92s would be like an 8HP70 Ram with an outrageously low 4.16:1 rear end gear.

Or, to get the same first gear final drive ratio that I have with an 8HP75 you'd have to have a 3.02:1 differential; or 3.69:1 to equal a 3.92 geared truck.

To put it all together, now that Chrysler is using the 2nd gen 8HPs in one of their vehicles I think it is safe to expect them to appear in the 5th generation Rams, and perhaps the 2018 4th gens-though that may be a bit of a stretch. The spread in these transmissions will have a super low stump pulling 1st gear and an even wider range than the current 8 speeds-and even the GM 8 speed (the 8L90) and somewhat surprisingly the GM/Ford 10 speed. Check out their ratios:

__________10 speed___8L90
1st:--------4.70:1------4.56:1
2nd:--------2.99:1-----2.97:1
3rd:--------
2.15:1-----2.08:1
4th:--------
1.80:1-----1.69:1
5th:--------
1.52:1-----1.27:1
6th:--------1.28:1-----1.00:1
7th:--------
1.00:1-----0.85:1
8th:--------
0.85:1-----0.65:1
9th:--------
0.69:1-----------
10th:-------
0.64:1-----------
Reverse:---
4.87:1-----3.82:1

So stacking up the competition, the current 8HP70 already has a lower 1st gear than both the 8L90 (7.02 spread) and Ford/GM 10 speed (7.34:1 spread), and the 8HP75 has a similar top gear to the 10 speed and slightly taller one than the 8L90. Both competitors do have an advantage of a lower reverse gear and input capacity (8L90 can take 738 lb-ft, the 10 speed is 650 lb ft), but the capacity of all 4 transmissions mentioned in this post far exceeds the output of any 1/2 ton truck engine and an 8HP90 will match the 8L90 and would be easy to implement for Ram.

Looking at it subjectively, with all the hoopla about the 10 speed I expected it to have a wider spread. It is barely any greater than the 8HP70 that Ram has been using for 4 years and it seems that the two extras will just make it hunt more. There was an interview with one of the design leads at ZF a couple years back where he was asked how many gears he thought transmissions would get to in consumer vehicles. He replied that once you get past 8 or 9 you get to a point of diminishing returns, and this certainly suggests he was right.
I don't completely agree with the math. Going taller from the '70 to the '75 would make the rearend seem to go down in number with "taller" high gear. In my driving through river hills, it seems the 8 to 7 downshift is too much from a fuel economy standpoint. Now, for people who are just wanting more passing punchdown, the wider spread might seem better. With 8 speeds and such quick shifting I'm sure that I'm not passing in 7 or even maybe 6. What do you think?
 

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Discussion Starter · #16 ·
I don't completely agree with the math. Going taller from the '70 to the '75 would make the rearend seem to go down in number with "taller" high gear. In my driving through river hills, it seems the 8 to 7 downshift is too much from a fuel economy standpoint. Now, for people who are just wanting more passing punchdown, the wider spread might seem better. With 8 speeds and such quick shifting I'm sure that I'm not passing in 7 or even maybe 6. What do you think?
I think there you run into the argument that people have with the 3.21 or 3.92 diff gearing giving better fuel economy. Sure the 3.21 will cause the engine to run at lower RPMs than the 3.92 under similar conditions, but those in hilly areas argue that the 3.92 causes less downshifting which adds another variable.

I do think that since the 2nd gen trannies are more efficient in terms of parasitic loss the difference would be marginal and likely more academic in nature than practical
 

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Sorry for bad syntax. I'm learning to type with 9 fingers. More of my opinion: I also think that the lower 1st gear is aimed at getting more street performance minded people into the fuel efficient 3.21's and when towing in tow/haul mode. When a transmission is designed with (is it 4 or 5 planetary gearsets), they can't just make any combination of steps in gearing ratio. A change to one affects others since only two shift elements are open at any given time. Wada ya think? Don't hesitate to criticize my thinking on this one.
 

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The cafe rating of a model line doesn't just depend on the highest geared model. The "take ratio" of the customer base affects the whole line. Especially in 2017 where there is no ecodiesel. They might be attempting to steer people from the 3.92's or make them more efficient with taller gearing in the trans. Dealers and customers dwell too much on the gearing in the diff. Some dealers (I know of at least 4) will only order 3.92's. FCA might be just trying to get better mileage out of the 3.92's. I don't want to talk about tow ratings. Someone else can jump in and do that.
 

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Discussion Starter · #20 · (Edited)
No, by all means, I am glad this thread is getting more attention; I think the wider range allows a best of both worlds which makes the rear end less important, a paradigm shift for many to be sure.

A taller rear end with a deeper first gear gives the same performance as an older trans where the first gear wasn't as deep so they compensated by adding a deeper gearing in the diff; but has the added benefit of enabling a lower RPM at a given speed which theoretically (and in EPA tests) improves fuel economy. Therefore, whereas the diff gearing used to be a very important consideration I think that in the future it will become less important, and we may even see the elimination of diff gearing options. One transmission and one diff gearing that allow for better economy of scale for the manufacturer and both increased fuel efficiency and torque application in low gears for the consumer.

It is true that with planetary gearsets there is a constraint with regards to what the ratios can be, but I think that the current 8 speeds (not just the ZFs either, the GM 8Ls too) show that they allow for more even spacing between all of the gears; while allowing for that wider range at the same time. There is still some wiggle room.

I am of the philosophy that there is generally balance in the world; the economy works in cycles, and for every benefit there is a disadvantage. I would say that the benefits to these newer transmissions are increased efficiency and range (and consequently more torque), while the disadvantages are the cost and complexity.
 
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