9th Gear on 2017 V-6's? - Page 2 - 2014+ Jeep Cherokee Forums
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post #11 of 38 (permalink) Old 05-19-2017, 09:49 AM
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If I recall the difference between tow and non tow is 3mph, no more.

When ZF made this transmission, their goal was to sell one - and only one - model of it to as many car manufacturers as possible, with the promise of customizing through programming to adapt to vehicule weight, power and cater to AWD as well as FWD variations for transverse applications.
In other words, one transmission with one set of gears for everybody, then let the *client* program them to their specs. ZF had a promo campaign that attracted a lot of attention for this tranny, with its small size, light weight, 9 gears (well...) and AWD capability.

And then we have the V6 Cherokee : as it is now, it's power band doesn't allow highway cruising below 1500 RPM (give or take), so 9th gear is functionally useless considering the fixed gear ratio.
The I4 has a higher final gearing ratio and can chug along at lower RPMs, so 9th is doable below 75mph on flat ground. Same deal for export models with a diesel : more low end torque means 9th can be used more.

If we really wanted to make 9th happen in 3.2L Cherokees, we'd either need to have a shorter final drive ratio, or hope for a Pentastar improvement on low end torque. With a shorter final drive though, overall mpgs would likely hurt...

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post #12 of 38 (permalink) Old 05-19-2017, 10:00 AM
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My 2015 2.4 hits it pretty reg doing 70-75 on flat highway. But any deviation in road it drops down to 8th


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post #13 of 38 (permalink) Old 05-19-2017, 10:14 AM
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Originally Posted by Mark_ View Post
If I recall the difference between tow and non tow is 3mph, no more.

When ZF made this transmission, their goal was to sell one - and only one - model of it to as many car manufacturers as possible, with the promise of customizing through programming to adapt to vehicule weight, power and cater to AWD as well as FWD variations for transverse applications.
In other words, one transmission with one set of gears for everybody, then let the *client* program them to their specs. ZF had a promo campaign that attracted a lot of attention for this tranny, with its small size, light weight, 9 gears (well...) and AWD capability.

And then we have the V6 Cherokee : as it is now, it's power band doesn't allow highway cruising below 1500 RPM (give or take), so 9th gear is functionally useless considering the fixed gear ratio.
The I4 has a higher final gearing ratio and can chug along at lower RPMs, so 9th is doable below 75mph on flat ground. Same deal for export models with a diesel : more low end torque means 9th can be used more.

If we really wanted to make 9th happen in 3.2L Cherokees, we'd either need to have a shorter final drive ratio, or hope for a Pentastar improvement on low end torque. With a shorter final drive though, overall mpgs would likely hurt...
I would like to see the 4:10 in the V6, and much more low end power. The 56:1 low range and 4:10's is really what all Trailhawks should have. As far as MPG, I believe it would stay the same or go slightly up as the motor wouldn't have to work as hard (load) as it does with the higher gear ratios. The 3.2 does pretty good power wise if you're over 3500RPM but even at that the Hyundai theta2 2.0 turbo has more torque at 2000RPM than our 3.2 does at 4000RPM..... Some low rpm power would be nice.
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post #14 of 38 (permalink) Old 05-19-2017, 11:08 AM
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I would like to see the 4:10 in the V6, and much more low end power. The 56:1 low range and 4:10's is really what all Trailhawks should have. As far as MPG, I believe it would stay the same or go slightly up as the motor wouldn't have to work as hard (load) as it does with the higher gear ratios. The 3.2 does pretty good power wise if you're over 3500RPM but even at that the Hyundai theta2 2.0 turbo has more torque at 2000RPM than our 3.2 does at 4000RPM..... Some low rpm power would be nice.
I hear you.

One big potential problem I see with 4.10 final drive on 3.2L KLs is first gear : it's already very short as it is now, we'd likely need to drive around in Snow mode (no 1st gear). But for off-roading, no problem going shorter, that's for sure.
Which brings up another interesting problem : TH vs the other trims with a 3.2L. The TH offers more resistance to the wind and is heavier, so in theory it would do better on gas mileage with an even shorter final drive ratio when we consider how difficult it is to get them to stay in 8th gear on the highway (for many-many TH drivers). And a shorter final drive would mean even more power over rocks, on tough climbs, etc... But for city/highway cruising in Limiteds/Overlands/Latitudes/Sports, a shorter final drive would be costly.
Now if the ZF9 could be offered with different gearing options, perhaps FCA could find sweet spots for all trims/engines. But they can't...
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post #15 of 38 (permalink) Old 05-19-2017, 11:29 AM
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Originally Posted by Mark_ View Post
.... Now if the ZF9 could be offered with different gearing options, perhaps FCA could find sweet spots for all trims/engines. But they can't...
Wondered about that too, but with 4 planetary gearsets and 6 shift elements, and with the gearsets nested to save space, not sure if the math would allow it. Way beyond me.
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post #16 of 38 (permalink) Old 05-19-2017, 11:35 AM
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These Transmissions are made in Germany. I don't think they have a problem getting up to 9th gear speed legally. That is the problem. Not designed with US highway laws in mind.
Sorry to burst your bubble, but these transmissions are built, under license of ZF (located in Germany), in Kokomo, Indiana. The transmissions are programmed for our Cherokees, for driving conditions in the US. Chrysler has a huge presence and Campus in Kokomo. All transmissions are built in Kokomo. I see the semis on the Interstate all the time full of transmissions going to Toledo or Detroit. If you remember, Chrysler delayed the sale of the new Cherokee for months. All the ones that were built sat in Toledo until they got the programming correct. Once the engineers got it right (or so they thought!), all Cherokees were re-programmed and test driven and then were unleashed to the public.

Honda builds their version of the 9-speed in South Carolina, for the Acuras and whatever other models it is found in.

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post #17 of 38 (permalink) Old 05-19-2017, 11:56 AM
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Originally Posted by Mark_ View Post
I hear you.

One big potential problem I see with 4.10 final drive on 3.2L KLs is first gear : it's already very short as it is now, we'd likely need to drive around in Snow mode (no 1st gear). But for off-roading, no problem going shorter, that's for sure.
Which brings up another interesting problem : TH vs the other trims with a 3.2L. The TH offers more resistance to the wind and is heavier, so in theory it would do better on gas mileage with an even shorter final drive ratio when we consider how difficult it is to get them to stay in 8th gear on the highway (for many-many TH drivers). And a shorter final drive would mean even more power over rocks, on tough climbs, etc... But for city/highway cruising in Limiteds/Overlands/Latitudes/Sports, a shorter final drive would be costly.
Now if the ZF9 could be offered with different gearing options, perhaps FCA could find sweet spots for all trims/engines. But they can't...
I'm curious if the transmission and rear PTU from a 2.4L would work as replacements in the 3.2L. The 4:10 final drive would be nice with my 245/75R17's!
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post #18 of 38 (permalink) Old 05-19-2017, 11:59 AM
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Originally Posted by dhh3 View Post
Sorry to burst your bubble, but these transmissions are built, under license of ZF (located in Germany), in Kokomo, Indiana. The transmissions are programmed for our Cherokees, for driving conditions in the US. Chrysler has a huge presence and Campus in Kokomo. All transmissions are built in Kokomo. I see the semis on the Interstate all the time full of transmissions going to Toledo or Detroit. If you remember, Chrysler delayed the sale of the new Cherokee for months. All the ones that were built sat in Toledo until they got the programming correct. Once the engineers got it right (or so they thought!), all Cherokees were re-programmed and test driven and then were unleashed to the public.

Honda builds their version of the 9-speed in South Carolina, for the Acuras and whatever other models it is found in.
I was politely corrected for recently saying the FCA tranny plant was in Indianapolis... I'm a Canuck, and I Googled the plant and it said 100 miles from Indianapolis, so... well... 100 miles for me is a short distance so I said Indianapolis. I love the 500, been watchihg it on TV since I was a kid lol.

Anyway (sorry about that, heheh). Yeah, the ZF9 is a German transmission, genetically and legally, but FCA are building theirs under licence in their own plant (near Indianapolis LOL), but it is a ZF9 clone.

The other ZF9s are built in South Carolina (Gray Court, 105 miles from Charlotte so I'll say Charlotte ! ). The Gray Court plant is huge, and it is an official ZF plant. Last time I checked, Honda/Acura and Land Rover were buyers
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post #19 of 38 (permalink) Old 05-19-2017, 12:02 PM
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Originally Posted by edge600 View Post
I'm curious if the transmission and rear PTU from a 2.4L would work as replacements in the 3.2L. The 4:10 final drive would be nice with my 245/75R17's!
The PTU is bolted to the transaxle up front. Maybe someday in the future modified gear sets will be sold for the AD1/AD2/ADL. But the sets would have to be swapped in both the front and rear differentials.

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post #20 of 38 (permalink) Old 05-19-2017, 12:24 PM
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The PTU is bolted to the transaxle up front. Maybe someday in the future modified gear sets will be sold for the AD1/AD2/ADL. But the sets would have to be swapped in both the front and rear differentials.
So no need to swap transmissions just the front and rear PTU's? That gives me more hope about it's possibly.
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