Ur-Turn: Saturation Dive Into The ZF 9-Speed

A TTAC reader is an engineer with a major powertrain company, and offered his extremely detailed analysis of the ZF 9-speed. Consider this an AP level course in powertrain engineering.

Before we dive right in to the 9-speed gearbox, let’s take a quick refresher on the basics of gears. The simplest gear set consists of 2 parallel gears mounted on 2 parallel shafts. Shown in Fig. is a gear set with a 20 tooth drive gear on the right and a 30 tooth driven gear on the left. For this gear set the speed of the driven gear is 1.5 times lower than the drive gear, and assuming no frictional losses anywhere, the torque on the driven gear is 1.5 times higher. This gear set has a ratio of 1.5:1. This type of a gear set is usually not favorable for packaging since it requires 2 parallel shafts, and there are largest separating forces that push the 2 gears apart which means that the bearings supporting the shafts have significant radial loads on them, in addition to an axial load if the gears are helical.

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Review: 2014 Jeep Cherokee Limited V6 4×4 (With Video)

The folks at Jeep have known for some time that high volume on-road models have to be part of the mix to keep low volume off-road models viable. From the 1946 Willys Station Wagon and the original Wagoneer, to the Grand Cherokee and the Compass, Jeep has been on a steady march towards the word no Wrangler owner wants to hear: “crossover”. Their plan is to replace the off-road capable Liberty and compete with the RAV4, CR-V and 20 other small crossovers with one vehicle: the 2014 Cherokee.

With two ambitious (and contradictory) missions and unconventional looks, the Cherokee has turned into one of the most polarizing cars in recent memory. It is therefore no surprise the Cherokee has been getting mixed reviews. USA Today called it “unstoppable fun” while Consumer Reports called it “half baked” with a “choppy ride and clumsy handling.” Our own Derek Kreindler came away disappointed with its on-road performance at the launch event, though he had praise for the Cherokee’s off-road capabilities. What should we make of the glowing reviews, and the equally loud dissenting voices?

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The Wobble Comes To An End As Consumer Reports Echoes TTACs Criticisms Of The Jeep Cherokee

In late 2013, TTAC was invited to review the Jeep Cherokee. As the journalist assigned to cover the launch, I gave what I felt was a nuanced but critical assessment of the vehicle: that it delivered with respect to its off-road prowess, but left a lot to be desired in other areas, namely the on-road driving experience and overall packaging.

TTAC was alone in its criticisms, with other outlets heaping praise on the Cherokee for attributes that I felt were lacking. A backlash from readers, Mopar fans and other entities ensued, and we were left looking like a fringe element of anti-Cherokee cranks, despite what we as an organization felt was a fair and nuanced, if – ahem – slightly colorful review of the car. It turns out that in the end, we weren’t alone.

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ZF's 9-Speed 9HP Transmission Puts Dog Clutches On The Leash

In a week we will post our first full review of the all-new and all-controversial 2014 Jeep Cherokee. The new Jeep isn’t just raising eyebrows for the love-it or hate-it styling. Or the resurrection of the Cherokee badge. Or the constant delays in production. Or the transverse mounted engine. Or the lack of solid axles. None of that laundry list seems to cause as much discussion around the automotive water cooler than ZF’s 9HP 9-speed transmission. Click past the jump for a deep dive into the tranny with more speeds than my bicycle. If you don’t want to explore transmissions in detail, don’t click. You have been warned.

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Chart Of The Day: Here's What The Jeep Cherokee Is Up Against In 2014

With the first month of 2014 sales nearly wrapped up, we’ll soon get our first look at how the Jeep Cherokee has fared, following the initial shipment of delayed units. Much has been made of the Cherokee selling 10,000 units in November and 15,000 units in December: it was a great storyline for Chrysler to promote in the run-up to NAIAS, and one for the hometown media (in both Detroit and Toledo) to rally around. Left out of the cheerleading was the fact that these figures accounted for the 25,000 units reportedly sent to dealers in one fell swoop. Can you say “pent up demand”?

But even if the Cherokee continued to sell at that pace – say, 15,000 units per month as an optimistic projection, where would that place it in the larger picture of the small crossover segment?

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Powertrain Chief In Charge Of Cherokee Launch Leaves Chrysler

Mircea Gradu, who had headed Chrysler’s transmission, powertrain and driveline engineering since 2011, left the company to pursue other interests, according to a company statement released last week. Part of Gradu’s responsibilities were the development and launch of the new Jeep Cherokee’s innovative all wheel drive system that can allow the rear axle to freewheel to save fuel. That launch was delayed when 25,000 assembled Cherokees were held back from dealers while engineers recalibrated the software that controls the powertrain and then tested the vehicles. The same basic drivetrain components are planned to be used in a number of other Chrysler group vehicles, starting with the all new 2015 Chrysler 200 introduced last week at the Detroit auto show.

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2015 Chrysler 200 Revealed
The folks at Allpar have discovered an undisguised Chrysler 200 driving around sans camo. Looking like a cross between a Dart and a Chevrolet Impala, the 20…
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Fiat Hoping To Boost Sagging Chinese Sales With Jeep Production

Remember the Fiat Viaggio, the Dodge Dart clone that was supposed to be the brand’s breakthrough product in China? The compact sedan has missed its sales targets by as much as 60 percent, and now Fiat is hoping that local production of the Jeep Cherokee can help fill some of their plant’s capacity and capitalize on China’s insatiable demand for crossovers.

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Nine Speeds Of Grey: What's Really Going On With Cherokee Transmissions?

As the plot thickens in Toledo and un-shipped Cherokees start to pile up in the storage lots, there’s a new conspiracy theory being passed around to explain Chrysler’s problems.

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19,000 Jeep Cherokee Units Built, None Delivered

Jeep Cherokee units keep piling up at the Toledo, Ohio factory, as Chrysler attempts to iron out production issues, but according to Yahoo Autos, none have been delivered yet.

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Editorial: Cherokee Delays Deserve Praise

We live in an era of instant gratification. We want everything, right now, done perfectly, right away. A consequences of that is that delays, even when legitimate, are seen as a sign of incompetence, slow movement and an inability to get things done. In many cases, it’s true. But that doesn’t mean we should pillory Chrysler for delaying production of the Cherokee again.

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Jeep Cherokee Production Delayed Due To "Extended Quality Validation Testing", Workers Temporarily Laid Off At Toledo

Chrysler has decided to delay production of the Jeep Cherokee again as the company seeks to iron out further quality issues with their crucial new product.

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Capsule Review: 2014 Jeep Cherokee

There may not be a more important car launched this year than the Jeep Cherokee. A symbol of the union between Chrysler and Fiat, designed to lead Jeep’s push into the booming global crossover market, a bold new styling direction for the brand – these elements are all inextricably bound with the vehicle itself, with the Cherokee’s success in the marketplace vindicating all three. Predicting how well a vehicle will sell is always a crapshoot. I try to refrain from forming opinions of vehicles before driving them, but I couldn’t help but root for the Cherokee a little. It had sufficiently angered the Internet Product Planning division with its out-there styling, car-based platform and bold claims of off-road superiority. Charmed by the sheer gall of its contradictory mission (a CUV that can hang with true SUVs off-pavement), I wanted it to be a good vehicle on its own and succeed in the marketplace.

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Editorial: Chrysler Dodges Poison Pen Darts By Delaying Jeep Cherokee Launch

Monday night at 5:43 PM, TTAC received this note from Chrysler PR

Due to unforeseen circumstances, the 2014 Jeep Cherokee and Dodge Durango short-lead media drive program – originally scheduled for August 4-14 in Seattle – is being postponed. We deeply regret this late notice and apologize for disrupting your busy summer schedule. We will get back to you as soon as possible regarding information for the media drives of the Cherokee and Durango, which we expect will take place in the first half of September.
For those of you that have already booked your flights to the program, your reservation will automatically be canceled by our travel company, BCD Travel. Should you have questions related to this, please feel free to contact me and/or the individuals noted below:

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The New York Times Consults A Cherokee About The Cherokee

When Jeep introduced the new-for-2014 Cherokee, the cute-ute’s polarizing styling, Eurotrash underpinnings, and front-wheel-drive base configuration immediately sent the autoblogosphere into a violent tizzy. Much of the criticism seemed to be engendered by the use of the name “Cherokee”, which is associated in the name of the average Jeep fan with the time-tested, AMC-era XJ Cherokee. (It should be noted, however, that Jalopnik has already decided the new Cherokee is superior to the old one.) Had Chrysler used the name “Liberty”, which is primarily associated with dorky-looking uranium-dense crapwagons leaking oil in traffic, or “Patriot”, which is primarily associated with the Dodge Caliber, much of the initial agitation might not have happened.

That’s all car-geek inside baseball, however. In the real world, meaning Manhattan, what really matters isn’t crawl ratio or wind noise or durability — it’s identity-based politics. It’s a surprise, then, that the New York Times has taken this long to uncover the critical feature of the new small Jeep: it’s all racist and whatnot.

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  • Dave Has to be Indy 500. Many more leaders and front passes than NASCAR, and Monaco is unwatchable with the inability to pass on that circuit.
  • Jeff How did the discussion get from an article about a 56 billion dollar pay package for Elon Musk to a proposal to charge a per mile tax on EVs in California or paying increase registration on vehicles to make up for lost gas tax revenue? I thought such a discussion would better fit Matt's Gas Wars series.
  • Master Baiter Both people who bought ID.4s will be interested in this post.
  • Urlik Not a single memorable thing happened in the big three races this weekend IMHO.
  • Ajla If Goodyear makes rain tires that allow NASCAR to race in damp conditions at longer ovals (other that at Daytona and Talladega) then I promise to purchase at least four new sets of Goodyear tires in my remaining life.