21C - Towing with Jeep Cherokee 3.6L V6

[JeffreyG]

Originally Posted by Micheal K

I have to admit I felt the same about the new Cherokee as it seemed to have strayed far from the legendary XJ. But I’ve watched videos of them being taken on some pretty difficult trails and it looks quite capable when equipped with the low range transfer case and locking rear differential. The main shortcomings are the same as for most vehicles like it with independent suspensions - relatively limited clearance and articulation.

We're straying far from towing here, but the KL has a typical front drive based "AWD" type powertrain that is not nearly as good off-road as a typical "4WD" system.

In "4WD" a typical system locks the front and rear axles together so that they must turn the same speed. In practice this means that if only one axle has traction, that axle gets 100% of the torque. If you mate 4WD with lockers, then all four wheels must turn the same speed. In practice that means only one wheel with traction can get 100% of the torque as the other three slip.

The KL is a front wheel drive vehicle with the ability to send torque to the rear axle. This system under normal conditions sends all available torque to the front wheels while monitoring the speed of the front and rear axles. If the system detects that the front axle is moving more quickly than the rear axle then the system will send power through the power transfer unit to the rear axle until the speeds are the same.

This latter system is a lot harder to use on a really difficult trail. Also heavy use in loose conditions (like sand dunes) can overheat the transfer case and wear it out.

I like this author's writing for laypersons on drive systems. Article one talks about the Bronco Sport off-road, which has the same type of system as the KL:
https://jalopnik.com/multiple-ford-b...s-t-1846450499

Perhaps better, here is an explainer of just about every 4WD/AWD system:
https://jalopnik.com/how-all-wheel-d...ech-1846233533

[Micheal K]

Originally Posted by JeffreyG

We're straying far from towing here, but the KL has a typical front drive based "AWD" type powertrain that is not nearly as good off-road as a typical "4WD" system.

In "4WD" a typical system locks the front and rear axles together so that they must turn the same speed. In practice this means that if only one axle has traction, that axle gets 100% of the torque. If you mate 4WD with lockers, then all four wheels must turn the same speed. In practice that means only one wheel with traction can get 100% of the torque as the other three slip.

The KL is a front wheel drive vehicle with the ability to send torque to the rear axle. This system under normal conditions sends all available torque to the front wheels while monitoring the speed of the front and rear axles. If the system detects that the front axle is moving more quickly than the rear axle then the system will send power through the power transfer unit to the rear axle until the speeds are the same.

This latter system is a lot harder to use on a really difficult trail. Also heavy use in loose conditions (like sand dunes) can overheat the transfer case and wear it out.

I like this author's writing for laypersons on drive systems. Article one talks about the Bronco Sport off-road, which has the same type of system as the KL:
https://jalopnik.com/multiple-ford-b...s-t-1846450499

Perhaps better, here is an explainer of just about every 4WD/AWD system:
https://jalopnik.com/how-all-wheel-d...ech-1846233533

I don't own a Cherokee so I may be wrong but I'm almost certain I read that the low range of the KL Cherokee locks up the front and rear axles. I'll have to see if I can find where I read that...

As far as I know, there is no other vehicle in its class that has an available low range and locking rear differential so they are not all created equal.

Edit - here's a link to 2019 press kit, under the Jeep Active Drive II system it says "The 4-Low mode locks the front and rear driveshafts for low-speed power or towing."

https://media.stellantisnorthamerica...=18872&mid=898

[Micheal K]

Originally Posted by JeffreyG

...
Perhaps better, here is an explainer of just about every 4WD/AWD system:
https://jalopnik.com/how-all-wheel-d...ech-1846233533

Thanks for this link, it's probably the most comprehensive coverage of the topic I've seen.

Back when I owned a Jeep YJ, at some point I decided the open rear differential wasn't cutting it and decided to upgrade - initially I was going to go with an ARB air locker but was concerned that the rear axle (Dana 35) wouldn't be strong enough, so I started looking into options to strengthen it or a complete axle swap. Luckily before I went down that road I learned about torsen differentials and decided to install a detroit truetrac instead. It worked really well to improve traction both on and off road and I found I didn't need to engage 4WD nearly as often.

[JeffreyG]

Originally Posted by Micheal K

I don't own a Cherokee so I may be wrong but I'm almost certain I read that the low range of the KL Cherokee locks up the front and rear axles. I'll have to see if I can find where I read that...

As far as I know, there is no other vehicle in its class that has an available low range and locking rear differential so they are not all created equal.

Edit - here's a link to 2019 press kit, under the Jeep Active Drive II system it says "The 4-Low mode locks the front and rear driveshafts for low-speed power or towing."

https://media.stellantisnorthamerica...=18872&mid=898

I believe the KL has a Power Transfer Unit for the front/rear axle split, so it is not locked and can actively manage the torque split F/R from 100%:0% up to the torque capacity of the PTU. It's the system I first described.

The KL does have a rear locking axle (available) and apparently (as you found) also a front locking axle (available). So it it a pretty solid off-road vehicle actually, for what it is. It's not a Wrangler, but still.......

Back on the towing topic, I was also surprised to see the Cherokee can be specified with GCWR of 5500 lbs and will typically weight 3960 to 4250 curb. That's actually a reasonable cargo capacity.

[bborzell]

Picked up our 21C last month during the BC and Washington floods. 2014 Jeep GC with factory tow, sway control on receiver and 8 speed good for rated 6,200 lbs tow capacity.

I brought along a Blue Ox SwayPro WDH, but since we picked up the camper in a driving rain on Thanksgiving Day, I passed on installing the hitch. Following the pickup, we headed south on I-5 and then hung a right to the Oregon coast.

During the trip home to northern California, we encountered driving rain, winds gusting to 50 mph, big rigs passing in both directions and a lot of hills after we headed inland at Newport. Never felt a need to install the WDH. Not to say it wouldn't have been a good thing as a preventative safety measure, just that I felt no clear need to put it on.

Satisfaction with a tow vehicle that isn’t being tasked with pulled beyond it’s weight capacity quickly becomes a matter of personal preference. In our case, the Jeep did fine. It pulled strongly enough to maintain decent pace up hills and the combination of engine braking and attentive use of paddle shifters for downshifts made long and steep descents no big deal.

That said, I sold it last week and replaced it with a RAM 1500 Laramie 4x4. Not because I felt that the Jeep couldn't serve our towing needs, but because after 109,000 miles, the electronics were giving up at a growingly persistent rate. In fact, I profited with one of the last lifetime warranties that Chrysler offered just on electronic sensor failures this past year.

[Micheal K]

Originally Posted by JeffreyG

I believe the KL has a Power Transfer Unit for the front/rear axle split, so it is not locked and can actively manage the torque split F/R from 100%:0% up to the torque capacity of the PTU. It's the system I first described.

The KL does have a rear locking axle (available) and apparently (as you found) also a front locking axle (available). So it it a pretty solid off-road vehicle actually, for what it is. It's not a Wrangler, but still.......

Back on the towing topic, I was also surprised to see the Cherokee can be specified with GCWR of 5500 lbs and will typically weight 3960 to 4250 curb. That's actually a reasonable cargo capacity.

Well I know you're way more knowledgeable than me on this stuff and high range does operate as you describe but I still think low range is different. I decided to check the 2019 Cherokee owner's manual (I know, apparently I have too much time on my hands) Anyhow it says this about 4WD Low:

4WD LOW is intended for loose, slippery road surfaces only. Driving in 4WD LOW on dry, hard-surfaced roads may cause increased tire wear and damage to driveline components.

This reads about the same as every part-time 4WD I've ever owned. Doesn't prove it's 100% locked, but seems consistent with the claim in the press info.

Regarding a front locker, I didn't know that was an option, maybe someone else mentioned it?

[Brian B-P]

Originally Posted by John in Santa Cruz

When did the Cherokee become FWD ?!? I'm mostly familiar with the 'classic' Cherokee XJ, and they were certainly RWD centric with manual transfer cases, 2H, N, 4H, 4L.... googles...eeew, 2014+ Cherokees (KL) are based on a Fiat car platform. oh well.

The XJ was followed by the Liberty, then the next Liberty after that, which were two more generations of Cherokee - they were only called "Liberty" in North America. The Fiat Compact Wide platform was used starting with that KL generation; like all of the Cherokees since the XJ, they are unibodies. The mechanical differences with the KL are a transverse powertrain (instead of longitudinal) and an independent rear suspension; potentially that means a weaker transmission, but the earlier Cherokees were as much "cars" as this new platform.

[Mike G]

Originally Posted by Micheal K

As far as I know, there is no other vehicle in its class that has an available low range and locking rear differential so they are not all created equal.

I believe my 2008 Lexus GX470 has these features. I've never used the electronic locker, but I've had it in low range a couple of times. Is it in the same class as what you're discussing? I'm not certain, but maybe. Actually, the GX is probably closer to the Grand Cherokee, now that I think about it.

[Rossue]

Originally Posted by bborzell

Satisfaction with a tow vehicle that isn’t being tasked with pulled beyond it’s weight capacity quickly becomes a matter of personal preference. In our case, the Jeep did fine.
That said, I sold it last week and replaced it with a RAM 1500 Laramie 4x4. Not because I felt that the Jeep couldn't serve our towing needs, but because after 109,000 miles, the electronics were giving up at a growingly persistent rate.

At this point in life "fine" isn't acceptable when towing a 10K# combo. My 2013 Yukon SLT was better than fine, and at 107,000 miles was still great-zero issues, yet I figured what the hey, and replaced it with a 2019 Expedition. Wow, was that an upgrade. I bet you feel the same way about the RAM 1500 too.

[John in Santa Cruz]

Originally Posted by Brian B-P

...the earlier Cherokees were as much "cars" as this new platform.

cars with leaf spring and live axles, which are MUCH sturdier and more suitable for towing than any sort of IRS setup with all its moving parts under the load of pulling the trailer.

[Brian B-P]

Originally Posted by John in Santa Cruz

cars with leaf spring and live axles, which are MUCH sturdier and more suitable for towing than any sort of IRS setup with all its moving parts under the load of pulling the trailer.

Typical little cars that you wouldn't use to tow a little red wagon were built with leaf springs and live beam axles. On the other hand, a military HMMWV has fully independent suspension, and has no problem carrying or towing tons. Leaf springs and live rear axles are used in pickups because they're the cheapest form of driven axle, and they're traditionally considered good enough, not because they're better than anything else.

Someone should probably tell the US Marines that they should stop towing 110,000 pound loads with their MKR15 all-independent-suspension trucks and stop towing 80,000 pounds with their MK31 all-independent-suspension trucks.

It's all about the components being properly designed and constructed for the intended loads, not whether or not the suspension is independent.

[John in Santa Cruz]

Originally Posted by Brian B-P

Typical little cars that you wouldn't use to tow a little red wagon were built with leaf springs and live beam axles. On the other hand, a military HMMWV has fully independent suspension, and has no problem carrying or towing tons. Leaf springs and live rear axles are used in pickups because they're the cheapest form of driven axle, and they're good enough, not because they're better than anything else.

Someone should probably tell the US Marines that they should stop towing 110,000 pound loads with their MKR15 all-independent-suspension trucks.

Well, if your FiatJeep has MKR15 grade suspension, more power to it.

but on an IRS RWD passenger vehicle with the typical 5-way multilink setup, instead of the 4 leaf shackle bushings, and 2 panhard rod bushings, you've got something like 20 precision bushings which were engineered to be just barely adequate, your half shafts have 2 expensive CV joints each, etc etc. using this to tow will greatly accelerate the wear on all that.

btw, those older cars with live axle rear ends were actually pretty decent towing platforms, if you beefed up the springs sufficiently.

[Brian B-P]

Originally Posted by John in Santa Cruz

Well, if your FiatJeep has MKR15 grade suspension, more power to it.

but on an IRS RWD passenger vehicle with the typical 5-way multilink setup, instead of the 4 leaf shackle bushings, and 2 panhard rod bushings, you've got something like 20 precision bushings which were engineered to be just barely adequate, your half shafts have 2 expensive CV joints each, etc etc. using this to tow will greatly accelerate the wear on all that.

btw, those older cars with live axle rear ends were actually pretty decent towing platforms, if you beefed up the springs sufficiently.

A Cherokee has suspension which is suitable for its load. A Grand Cherokee has a different and stronger suspension, suitable for a greater load. Ford Expeditions and Chevrolet Suburbans have two more different designs, even stronger for their even higher rated loads. The military trucks are just much larger examples for much greater loads, to illustrate that you can go as big and capable as you need.

I don't think that a Datsun 1200 was a decent towing platform for more load than you could comfortably move by hand, no matter how stiff you made the springs. Sure, a full-sized sedan could be decent, because its suspension was sized for the load... if you see the theme.

Towing won't kill CV joints - they're generally life-of-the-vehicle things that only die if the boot is damaged and dirt gets in.

[John in Santa Cruz]

my last FWD car, bought new, went through a set of CV joints about every 100k miles, so I was halfway through the 2nd replacement set when I sold it at 250,000 miles. now, I drove the pants off that little car, a 1989 VW Jetta GLI, lots of high RPM double clutching on mountain roads... both replacements were genuine VAG parts.

I do hope we get better mileage out of the 8 CVs on our 2016 Mercedes 4matic, but I don't drive that car like the wanker I was 30 years ago...

[Brian B-P]

Originally Posted by John in Santa Cruz

my last FWD car, bought new, went through a set of CV joints about every 100k miles, so I was halfway through the 2nd replacement set when I sold it at 250,000 miles. now, I drove the pants off that little car, a 1989 VW Jetta GLI, lots of high RPM double clutching on mountain roads... both replacements were genuine VAG parts.

Yeah, I maintained a Volkswagen once... never again.
Try Toyota, Honda, even Ford - no problem.

Poor component choice and quality can cause problems with any design. Ford Transit vans have a classic leaf-sprung live beam axle... and they still have joint problems, because Ford uses one of those ridiculous flexible disk or "giubo" joints at the transmission output, which doesn't last.

[John in Santa Cruz]

Originally Posted by Brian B-P

Yeah, I maintained a Volkswagen once... never again.
Try Toyota, Honda, even Ford - no problem.

Poor component choice and quality can cause problems with any design. Ford Transit vans have a classic leaf-sprung live beam axle... and they still have joint problems, because Ford uses one of those ridiculous flexible disk or "giubo" joints at the transmission output, which doesn't last.

my various IRS mercedes have all used flex-disks on the main driveshaft, but they have a fixed differential (ok, rubber mounted on a rear subframe thats rubber shock mounted to the body, but it doesn't move significantly with the suspension), I've only had to change out one set of those on a 25 year old 250,000 mile station wagon. It hadn't failed, but it had sufficient cracks in the 25 year old rubber disk to be worrisome.

[SteveDRO]

We towed our 2018 19 with a 2012 JGC for two and a half years. We live at 7,450' in SW Colorado and routinely tow big grades and high passes. The Grand was an excellent vehicle in every respect, except one: when towing up long grades and the temps were above 75F, the coolant temp would approach 235F, at which point the vehicle would go into limp mode (upshift instead of maintain current gear or downshift). Only solution was to pull over and let it cool. Dealer and independent mechanics acknowledged the issue, but were unable to rectify it. As a result we now tow with a 2020 F150 3.5.
The Grand had Factory Tow, Offroad 1 4x4 and a 5 speed tranny. The latter is important, as 2014 and after came with an 8 speed, which increased tow capacity and may have alleviated this issue. We purchased new and it was always well maintained. Hope this helps!

[Brian B-P]

Originally Posted by John in Santa Cruz

my various IRS mercedes have all used flex-disks on the main driveshaft, but they have a fixed differential (ok, rubber mounted on a rear subframe thats rubber shock mounted to the body, but it doesn't move significantly with the suspension), I've only had to change out one set of those on a 25 year old 250,000 mile station wagon. It hadn't failed, but it had sufficient cracks in the 25 year old rubber disk to be worrisome...]

The difference between IRS and the Transit's live beam axle is important - that extra motion kills these things in Transits (and of course component sizing to suit the load is important). Thanks for the illustration.

[John in Santa Cruz]

Originally Posted by Brian B-P

The difference between IRS and the Transit's live beam axle is important - that extra motion kills these things in Transits (and of course component sizing to suit the load is important). Thanks for the illustration.

do those Transits have a driveshaft center bearing with a U joint right behind it, or is it transmission -> flexdisk -> driveshaft -> differential/axle directly ?

older RWD Volvos (from the 60s to the mid 90s, at least) had live axles and the manual transmission versions had a flexdisk, but the driveshaft had a U joint in the middle (and another at the differential/axle), so the front section of the driveshaft stays inline to the transmission output shaft, and only the section between the two U joints changed angles with the rear axle suspension travel. Those flex disks lasted very long time, too, just like my Mercedes.

AH, like this, picture worth 1000 words, the drive shaft assembly for Volvo 240, 740, 940's from the early 80s to the mid 90s..



(transmission is on left, differential on right. top segment is the automatic trans. version, it has 3 U joints, next one down is the manual with the flexdisk, then the center bearing carrier assembly, then at the bottom is the rest of the driveshaft back to the rear axle.

anyways, this is neither here nor there. I drove those Volvos for 20 years, hah. They were actually quite good at towing small trailers, within the limitations of their low performance 4 cylinder engines.

[Brian B-P]

Originally Posted by John in Santa Cruz

do those Transits have a driveshaft center bearing with a U joint right behind it, or is it transmission -> flexdisk -> driveshaft -> differential/axle directly ?

I suspect that it depends on wheelbase, but yes... a two-piece propeller shaft with a steady bearing in the middle would take the angular movement out of the flex disk... which is still not up to the task, the point being that any design (including a live beam axle on leaf springs) can be weak if it isn't built with the adequate components, and conversely any competent design (including various IRS systems) can be strong if it is built properly.