Moon Shot: Clyde the K2EC at 200,000 miles

CadillacLuke24 · September 15, 2021

On May 19th, 2021, 5 years, 2 months, and 15 days after getting Clyde in Missoula, MT with 27 miles on the odometer, I hit this milestone.

CadillacLuke24 · September 15, 2021

In the spirit of my 100k update, I figured I'd add one for 200k

My experience with the K2XX platform over the past couple years.

Drivetrain: No axle seal leaks or bearing concerns. Radiator was replaced at 140k due to a weeping leak caused by an exuberant thermostat that opened too quickly. No issues since then. 4WD system operates very well and has no issues. Due to cost effectiveness, the rear differential fluid was changed to AMSOIL 75W90 at 193k. Fuel mileage improved noticeably (1 mpg/tank), and the gains seem to have held, so I will continue with it. The easy pack is so nice for fluid changes too.

Transmission: The 8 Speed (M5U) gave me some trouble for the balance of this period. Nothing affecting operability of the vehicle, but the problems found were obnoxious. The issues started at 116k, in June of 19, when I towed a 96 Cadillac Sedan DeVille Concours from Newbury Park CA to Casper WY. Speed limit followed for most of the trip was 55 mph, with a boost to 65 mph from Rawlins WY to Casper WY. The symptoms that developed included a harsh 1-2 shift at all times, with deteriorating shift performance as time wore on. The 1-2 shift was the primary concern, with other shifts being relatively well behaved. Initially I attempted to remedy the situation with a drain and refill at 148k. No dice.

A relearn was performed at 158k with no benefit. A drain and refill occurred again at 162k, again with no improvement in symptoms. A drain and fill occurred again at 173k, along with a new transmission temperature sensor harness (this includes the plugs for the solenoids). Shifting performance very briefly improved, but returned to baseline at 174k and deteriorated after another relearn at 175k. Shifting started to improve at 178k following the thermostat delete, where I reversed the internals of the trans cooler thermostat. However, the shifting would deteriorate at high temperatures (170 and up).

At 180k the transmission wiring (trans temp sensor, speed sensor wiring, and jumper to the body harness) were all replaced, and another drain and fill were completed. Again, performance briefly improved, though a relearn shortly after the repair negated any progress on shift quality. After discussion with my parts guy Tim at the local Chevy dealer, we surmised the heat related nature of shift deterioration was electrically related, and the only part left to replace was the valve body, as the solenoids are integrated.

CadillacLuke24 · September 15, 2021

SO, at 181,524 miles, the valve body for the transmission was replaced, a drain and fill was performed, and a new valve body learn was performed at White's Chevy in Casper. The Chevy FSM says the new valve body has to be learned to the TCM for proper function. That was an adventure, as I do all my own work. Once I replaced all the related parts, I coasted back out of my driveway, and managed to coast downhill 75% of the way to the dealer, seeking to avoid causing any issues. The last 25% of the way was covered at 3 mph in 1st gear.

The valve body resolved all shifting issues. Harsh 1-2 shift is gone, even on start up, all shifts are exceptional, up or down, manual mode works perfectly, and any lingering issues have vanished. Trans delete remains and Mobil LV HP blue label continues as the fluid of choice. I echo sentiments on this forum that GM's pursuit of fuel economy has created performance and longevity concerns.

The L86 6.2L V8 is as reliable as the sunrise. No catch can, no aftermarket air box, no tunes, all stock, and just barely broken in. Performance has not changed, fuel economy is very much alive and well, and Blackstone Reports continue to shine. I can not recommend this engine enough, and strongly encourage anyone looking at a K2 to consider it. Oil changes continue at every 5k miles with Quaker State 0W-20 (not high mileage, as it's not Dexos, and I have enough to last through 300k) and the Purolator BOSS filter.

Brakes were overhauled from the factory parts at 150k due to wear indicator noise. OEM Chevy parts were used, with the thinking that since the rear rotors needed replaced (excessive park brake wear from a sticky left cable), I would service the entire system with new parts. Park Brake system now functions perfectly, and the cause of the sticky cable (some idiot getting carried away with undercoating ) has been resolved. Fluid exchanges continue every 45k miles, and no issues are currently present. LR Bleeder screw was replaced due to same idiot rounding the bolt off.

lucas287 · September 15, 2021

Awesome update. Thanks for your thoroughness.

9 minutes ago, CadillacLuke24 said:

we surmised the heat related nature of shift deterioration was electrically related

In regards to the above - are you saying it shifts completely fine if the trans doesn't get too hot and THEN the shift quality degrades? For example it drives great until it's above 170* and then it gets rough?

If so, I'd be plumbing in an external cooler before replacing the valve body. Though the latter is actually quite simple. I've done several on auto trans in the past installing shift kits, etc. and it's not hard at all.

From a tuning perspective, the 8L90 can be dialed in quite nicely with some small changes so if I were you I would consider that also. Surprisingly the trans responds most noticeably to changes on the engine side. Once that's dialed in (since it's all torque-based) the stock trans tuning is actually pretty damn good (minus the awful torque converter lockup schedule).

Anyways - just rambling and maybe you'll find something helpful

lucas287 · September 15, 2021

4 minutes ago, CadillacLuke24 said:

The L86 6.2L V8 is as reliable as the sunrise. No catch can, no aftermarket air box, no tunes, all stock, and just barely broken in. Performance has not changed, fuel economy is very much alive and well, and Blackstone Reports continue to shine. I can not recommend this engine enough, and strongly encourage anyone looking at a K2 to consider it. Oil changes continue at every 5k miles with Quaker State 0W-20 (not high mileage, as it's not Dexos, and I have enough to last through 300k) and the Purolator BOSS filter.

Awesome feedback for a guy about to hit 100k on his L86

STRONGLY emphasize this engine over the L83 5.3 if at all possible. They're hard to find - but seriously worth it. It's actually quite bizarre how well this engine performs and get's pretty much identical fuel mileage as a 5.3.

lucas287 · September 15, 2021

7 minutes ago, CadillacLuke24 said:

The L86 6.2L V8 is as reliable as the sunrise.

Considering the 14 and 15 models have persistent valve spring issues (upgraded in 2016) I'm pleasantly surprised that you've been trouble free.

CadillacLuke24 · September 15, 2021

Wheels and tires are doing well. I've come to accept aluminum wheels show rock damage a little more due to the nature of aluminum. New RD4 wheels and Michelin Defender 275/55/20s went on at 140k miles. Same wheels are still on, and have weathered fairly well. I dinged one dropping my lug socket on it, but it's very minor and I'm sick of spending money on minor issues . The Michelins have worn well, with my first set getting 81k miles. The second set lasted from 140k to 207k, due primarily to my bad habit of running pressures a tad high. They grip well, handle snow very well, and stand up to lead foot use very well. Highly recommend.

Frame had developed surface rust in spots, and I have been touching it up with spray cans of the frame wax used by GM. Works well, sticks very well, and the frame looks much better for it. I deleted the frame end caps in the wheel wells cause they liked to trap dirt. One area of concern is the crossmember that goes above the fuel tank. It trapped dirt between the tank and the crossmember, so make sure to clean it out periodically. I found the mess during suspension service.

Suspension received a full overhaul at 206k. Rear suspension overhaul included new leaf springs, ubolts, spacers, shackles, and shocks. Shocks do not last 200k. Ride was a little stiff in the rear, but upon inspection they were thoroughly worn out. I am happy with how well the Ranchos did, so OEM Ranchos were installed, along with all OEM Chevy parts for all parts replaced. The front suspension received new UCAs, LCAs, Swaybar links, Swaybar bushings, and strut assemblies. The front Ranchos seemed to fare better, though they were overdue too. New OEM Chevy parts were used for all parts replaced, including new Rancho struts.

Edited September 15, 2021 by CadillacLuke24

CadillacLuke24 · September 15, 2021

10 minutes ago, lucas287 said:

Awesome update. Thanks for your thoroughness.

In regards to the above - are you saying it shifts completely fine if the trans doesn't get too hot and THEN the shift quality degrades? For example it drives great until it's above 170* and then it gets rough?

If so, I'd be plumbing in an external cooler before replacing the valve body. Though the latter is actually quite simple. I've done several on auto trans in the past installing shift kits, etc. and it's not hard at all.

From a tuning perspective, the 8L90 can be dialed in quite nicely with some small changes so if I were you I would consider that also. Surprisingly the trans responds most noticeably to changes on the engine side. Once that's dialed in (since it's all torque-based) the stock trans tuning is actually pretty damn good (minus the awful torque converter lockup schedule).

Anyways - just rambling and maybe you'll find something helpful

Shifting would gradually deteriorate as the trans warmed up. I say above 170 because one night after replacing the wiring harnesses I sat and idled until the gauge read 171. Once I proceeded to go driving the symptoms had glaringly worsened.

I have Z82 trailering provisions, so part of that is a transmission cooler that occupies a fairly large section of the AC condenser. GM thought it would be good to install a thermostat, if you will, that bypasses the cooler until 192, at which point it opens. Since I've modified it to constantly stay open, the trans consistently runs 120s- 140s in the summer, and 90s to 120s in the winter. The hottest I've seen to date is 185....in Las Vegas in early July, with temps of 110s outside.

Thank you for the recommendations though! I appreciate it! Starting to consider shifting. I agree, the 8L90E is actually pretty good.

CadillacLuke24 · September 15, 2021

12 minutes ago, lucas287 said:

Awesome feedback for a guy about to hit 100k on his L86

STRONGLY emphasize this engine over the L83 5.3 if at all possible. They're hard to find - but seriously worth it. It's actually quite bizarre how well this engine performs and get's pretty much identical fuel mileage as a 5.3.

Glad to hear it! The L86 is legendary! Glad you like yours too...it really is weird (but great) that it runs so well with no real fuel economy hit.

Me too...no valve spring issues whatsoever. He's a LATE 15 build though, so I think I may have got a lot of updates that came down the line in 16.

lucas287 · September 15, 2021

1 minute ago, CadillacLuke24 said:

I have Z82 trailering provisions, so part of that is a transmission cooler that occupies a fairly large section of the AC condenser. GM thought it would be good to install a thermostat, if you will, that bypasses the cooler until 192, at which point it opens. Since I've modified it to constantly stay open, the trans consistently runs 120s- 140s in the summer, and 90s to 120s in the winter. The hottest I've seen to date is 185....in Las Vegas in early July, with temps of 110s outside.

Thank you for the recommendations though! I appreciate it! Starting to consider shifting. I agree, the 8L90E is actually pretty good.

I wonder If I have that RPO code too. I'll check it out. I've heard from many VERY knowledgeable people that the 8L90 is a straight-up stud mechanically. I mean a beast. When GM built the C7 Z06 they changed almost everything in the engine to handle the boost but didn't changed a single thing in the 8L90. That's sweet right there.

lucas287 · September 15, 2021

2 minutes ago, CadillacLuke24 said:

Me too...no valve spring issues whatsoever. He's a LATE 15 build though, so I think I may have got a lot of updates that came down the line in 16.

If you ever pop a valve cover - the '16 updates include blue valve springs. That could give you some peace.

CadillacLuke24 · September 15, 2021

Thanks man! Will do! Yeah build date is 9/19/15, I wonder.

Yeah Z82 gets you the trans cooler, 7/4 pin connecter in the bumper, the 12k hitch, and other goodies. If you have the L86 odds are you have a pretty sick rig in terms of options, so I bet you might

That is very impressive! I don't doubt it, it runs very well. They just give it some equally studly electronics!

CadillacLuke24 · September 15, 2021

Exhaust: I had swapped various front pipes and tried entire new systems to eliminate the obnoxious howl above 4k on the Chevy Borla system, with no luck. For some reason I decided one last go with a Chevy Borla I sourced from Findlay Chevy in Las Vegas. For whatever reason that did the trick! New system and tips and it sounds like it should! Quiet at cruise and LOUD at WOT. VERY happy! It even has a nice bark at cold start. I surmise the old muffler has some internal issue causing the howl. Perhaps it's time to get out the old boroscope.

Bodywork: No issues. There's be a few accidents, and half the battle is finding a competent shop. I've solved that problem, and I've been driving more cautiously, which have both paid dividends. No rust concerns in the wheel wells, inside the box, under the cab, inside the fenders, etc. There's surface rust on some of the bumper mounts and trailer hitch, as well as inside the left rocker panel, but those are being remedied with petroleum based undercoating.

Paint is doing ok. Multiple rock chips are present, but they can be touched up easy enough.

Glass is fairing well, no issues, and the current windshield is weathering well.

Interior continues to wear well. Plastic panels don't respond well to abuse from service technicians, but they hold up very well in daily use, and even the occasional bump from a Fitbit, tool bag, or set of keys in the door panel pockets. Leather has some stress wrinkles from high traffic areas but no cracks, and the colors hold fast well. Cushioning and heating/cooling modules were replaced in the driver's seat for comfort concerns at 195k miles, but no other issues have arisen. Multiple interior panels have been replaced due to the aforementioned abuse.

CadillacLuke24 · September 15, 2021

Exterior plastics tend to show wear, especially from rocks. I am referring to the black air dam, aerospats in front of the rear wheels, and obviously the mud flaps. Wear improves when some goon learns patience and doesn't follow winter traffic too close. I prefer sand to salt for sure, this is just a side effect of that.

Infotainment continues to work very well, and it adapted seamlessly to my Iphone 11 I got in March of 20. Prior to that it worked well with my Microsoft Lumia. I have kept up with map updates and they serve me very well. Additionally, the SiriusXM Travel Link is extremely helpful in aiding me to navigate around troublesome weather.