2025-11-23 Kelly Flats

This was the last trail ride of the season for Kelly Flats, a Larimer County 4-Wheel Drive Club run to close the trail. The plan was to get everyone past the trailhead gate, lock it behind us, and make sure nobody was on the trail before locking the gate at the other end.

We met at the King Soopers in north Fort Collins around 8:30 AM and left around 9:00 AM. Lee and I decided to take our 1997 Jeep Wrangler (TJ series) on this one. Michelle briefed the group on the plan for the day, and Lee and I took the lead in our TJ to the trailhead, stopping briefly at Century Park along the way. There were 19 vehicles in the convoy at that point. At the trailhead, we met up with four more vehicles, bringing us to 23 total. We aired down and headed up the trail to the split between Heart Attack Hill and Aneurysm Hill. About half the group went one way and the other half went the other way. We led the group up Heart Attack Hill, while others checked spurs along the way to ensure nobody else was out there before we closed the gates.

As we went up Heart Attack Hill, I tried to engage the lockers and discovered something was wrong. Both lockers were not working. My suspicion is that the wiring harness behind the dash came loose, but it might be something as simple as a fuse. Either way, I did not have lockers available for the rest of the day.

We stopped briefly where the two routes reconnected but moved on before the other group caught up with us. They caught up sometime later as we headed toward the chutes. At the chutes, Lee and I were still at the front. Lee got out to film me going through. I was a little hesitant to run the chutes without lockers as an option, but I decided to go ahead. We had just run the chutes recently in our JL, and I wanted to try a different line at the beginning, putting my left front tire high on the rock wall. I was having trouble making that line work, so I backed out and tried the line we had used before.

On the second attempt, I was losing traction, slid back, and then caught traction again. In that moment, I overpowered the rear end and snapped the pinion at the differential, between the rear driveshaft and the axle housing. At the time I thought I had broken the driveshaft, but the failure turned out to be at the pinion. I suspect not having the differentials locked contributed, since all the available power may have been going to the rear — with front tires elevated — and primarily to the rear passenger side tire instead of being spread more evenly. My understanding is that snapping the pinion off flush at the housing is not common, but it is a known failure point when things line up just wrong and the axle sees a big shock load. I’ll need to confirm details once the differential is opened up.

(Update: see follow up notes on New 5.38 axles for TJ after pinion break.)

I climbed under the TJ and removed the driveshaft with Luke’s help. It was still connected to the transfer case by four 13 mm bolts, and the other end had separated at the pinion. The TJ was in a sketchy position on some rocks and was not obviously stable, so for added safety we ran the TJ’s winch uphill through the chutes to anchor it while I worked underneath.

With the driveshaft out, I hoped the rear wheels would spin freely, but something was causing noticeable resistance in the drivetrain. That meant I was not going to get through in “front-wheel-only mode,” so we used a combination of winches, straps, a recovery ring, and tow ropes to get the Jeep out. Luke assisted with the winch controls and spotting. Nick used his TJ as an anchor point and helped tow us, eventually getting our TJ out of the chutes. Many others provided help, mechanical advice, and encouragement along the way. For what it is worth, several other vehicles made it through the chutes without any damage that I am aware of after we got out of the way — but I felt bad holding every one up while we sorted out our issues!

Because of the resistance in the rear axle, Nick flat-towed us through much of the trail, especially on the loose uphill sections, while I added a little power through the front axle where it helped.

At one point, we stopped in a thickly wooded section to unhook the tow rope. Through the trees, I heard a woman yelling. At first she was hard to understand, but as she came closer, she said we were on private property. We were on the designated trail within the road easement and not off-route or causing any issues. I told her we were just stopped for a moment and would be moving along. She continued to yell as we unhooked the tow rope, and then we headed out. It was unusual timing that, at the exact place and moment we stopped, someone appeared out of the woods to yell at us, so I mostly found the whole thing odd and a little entertaining. You never know what you are going to run into out there.

By the end of the trail, the rear axle had loosened up a bit, so we switched from 4L to 4H, still only driving the front axle, and continued a couple more miles to the Sevenmile Creek trailhead where there is trailer parking. Dan had trailered in Ben’s rig and offered to trailer us back instead, which meant Ben would drive back rather than being trailered. We took Dan up on the offer. Dan retrieved their trailer from the Kelly Flats trailhead, and they trailered our TJ home from the Sevenmile trailhead. That gave us some time to ride with Dan, talk on the way home, and get to know him better.

Overall, it was a beautiful day on Kelly Flats, especially for this time of year. I did not pay close attention to the exact temperature, but I started the day in a sweater and ended up in a t-shirt with the windows down for most of the ride. I think we had almost as many guests on this trip as club members. Hopefully, seeing a rear axle failure on the trail was not too discouraging, and instead highlighted what a great group we have and why it is so valuable to run these trails with a group.

I am personally very thankful to everyone who helped Lee and me get off the trail and home safely. In particular, I appreciate Luke for the mechanical help and winch operation, Nick for the help pulling us through the chutes and up the trail, Dan for trailering us all the way home, the trip planners for organizing and leading the day, and everyone else who jumped in with ideas, labor, and good humor.

In spite of the mechanical issues, it was a great day with some unexpected memories. As for our TJ, I am going to let things sit for a bit and weigh options. I plan to pull the rear differential cover and inspect everything more closely. From there, we will decide what we want to do. We had the TJ before we bought our newer Jeep and 4Runner, so we were already thinking about its future. Whatever we decide, having the newer Jeep and the 4Runner means we will not miss a beat going out on rides.

We will most likely skip the December ride, but that is due to a trip we are planning to the Saint George area, where we will take the 4Runner out at least once. Right now, we are leaning toward running Toquerville Falls.

Update

I ended up replacing both front and rear axles with a pair that had some upgrades, including 5.38 gearing. I posted the details of the axle swap and a bunch of other things I did while I had the Jeep torn apart in my garage here: 1997 TJ Axle Swap Log.