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If you look at the specs, 0W40 does thin out a little more at temp than 5W or 15W. It definitely didn’t help, but I don’t think 5W or 15W would have necessarily prevented the failure. I think the main things factors were the wastegate and lack of oil cooler.

Back for an overdue update. Around 18k miles after the swap, the motor developed a bad rod knock. I do not know the exact cause, but know a few things that I believe might have compounded together to make a bad situation: broken wastegate wired shut, 0W40 oil to aid in cold temp starting, 3.55 gears putting cruising RPM too low, and no oil cooler. The knock developed after a long hard 3hr drive on a hilly section of interstate. I was able to find a FREE replacement motor. Guy I had met years ago getting out of MB diesel stuff, was happy to see it go to a good home. I did a dingleball re-ring and regasket and had the crank and flywheel balanced together. I also changed the turbo to a TD04 from early 2000s WRX - extremely common and easy to find replacement parts for. Result: very smooth running motor. As far as longevity goes: Functioning wastegate 5W40 in the winter, 15W40 summer, no more 0W40 3.55s changed out to 4.10s Turbo motor oil filter housing with oil cooler ports and large -10 oil cooler added Oil pressure stays noticeably higher at operating temp, boost will peak at 10psi and settle to 8 (was running 15psi at time of failure), cruising rpm is now 2500rpm at 60mph rather than 2200. After reading this thread: https://comancheclub.com/topic/65867-16-gallon-vs-23-gallon/ I modified the factory tank by closing off the factory 16gal vent and adding own as high up as possible to fit the maximum amount of fuel. I welded closed the tank vents as they are not needed with diesel fuel. It netted me a solid 8-10 gallons more at each fillup which took my range from ~350 miles to ~600. I extended the sending unit arm and it took a few tries to get the angle right but this was a cheap mod that was well worth the time invested. Drove like this for a long time. Many squeaks, rattles, and other annoyances developed. It was also just generally loud and after 30k+ miles, it was wearing on me a little. In August, the proportioning valve failed during an emergency stop and I parked it while I finished my buggy. In October I pulled it into my shop and tore the interior out and sound insulated everything as best I could. I reassembled everything with added supports, isolating washers, etc to reduce vibration and rattling. I also added hydraulic motor mounts. The result was a huge improvement in in-cab noise, however the intake was still loud and idle vibration was a bit extreme, especially when cold. A few weeks later, we had a streak of cold weather where temps during the day didn't rise above 15°. It left me stranded at work and my wife had to come get me. I replaced all the glowplugs and that helped - but cold starting even at 25° was still difficult - and this had always been a reliable cold starter without a block heater even down into the teens. I adjusted the valves and replaced the timing chain, this resulted in a much smoother idle but starting still lacked. I ended up replacing the starter and that finally did it - it now cranks quickly and fires right up. I also built a new air intake using a Fleetguard equipment type filter. It required moving the battery, but well worth it. It fits nicely, is a high quality filter, significantly cut down on noise, and was able to be plumbed to pull cool air from the grill. Around 38k miles on it now and May of this year will be 3 years since getting this thing on the road and I believe this is as good as it's going to get. It starts right up, idles smooth, is easy to drive, easily maintains speed with traffic, carries 8ft lumber and many other things with ease, and goes 2 weeks between fillups. I couldn't be happier with it and have no further changes or upgrades planned. I were doing it again, I would probably look closer an an ALH TDI. It wouldn't have the same bare bones all mechanical charm as the Mercedes, but would probably move it down the road a little easier, consume even less fuel, and generally provide a little more comfortable driving experience. No regrets, though. As it sits today:

I was just thinking the other day how it had been a long time since I updated this. Was not expecting to see it on the first page in this subforum! 38k miles and coming up on 3 years of daily driving. There have been some bumps in the road, a few things have changed, but I think the current iteration will be the final one. I am really happy with it right now. I'll put together an update tomorrow...

Are you local to CT? I owe you some beer.

I can’t believe the timing of this thread! I’ve been researching extending the range in my Mercedes diesel swapped LWB with the 16 gal tank. I may have to put some thought into how to trim that tube. I am guessing the only difference between the 16 and 23.5 gal sending units is the length of the float... I don’t suppose anyone has a 16 and 23.5 gal sending unit to compare?

Gave it some thought and decided I put too many miles on this thing to not have snow tires. Mounted four of these this weekend along with the Powertrax Pro Grip helical gear LSD. Can’t wait for some snow!! The NH Oil undercoating seems to be doing well. Probably apply it in the wheel wells a couple more times this winter.

I used about twice the mount of oil they recommended. Filled rails, rocker panels, fender wells, and up inside the bed (where it looks like it’s already started [emoji3525]). I like the oil because it never hardens and seeps into areas a normal coating can’t get. I definitely plan to make sure I wash it after every storm.

I get it, but I don’t own anything to preserve it, I own things to use them. I’m no newb to snow, but I think LSD and weight with decent tires will work pretty well [emoji3]

10k miles on the swap on this thing today. Ready to keep racking up the miles. Underside got a heavy coating of NH Oil. Need to grab some sand bags to toss in the bed before it snows.

Bump. Anyone?

Done. Glad it’s behind me. Undercoating oil coming up soon.

Don’t look too close, this is not a SEMA build. New carpet and rear window next. Heavy dose of NH Oil undercoating under the whole truck. Then, keep racking up the miles.

Full gauge cluster swapped in and working. Tach run off alternator using Dakota Digital conversion box thingy. Floor patch, carpet, rear window in the coming weeks. Couple healthy layers of undercoating oil and keep on driving. Over 7,000 miles on it to date.

Thanks guys! My intention was to try to make it look like it came there from the factory, makes me happy to hear an objective opinion that it looks that way. Lot of zip tied stuff I plan to clean up. 6hr round trip this weekend and could not be happier. Has motivated me to give it that last 10% of love it needs to drive like new. Ordered some new shocks, rebuild steering gear, add some sound deadening.

Turbo installed. Drives much better. Averaging 29mpg on my commute.

Nope, no AC. Never had it. Seats and console done. I adapted to MJ boot to the auto shift cover but found the boot is too stiff where it’s located and makes shifting difficult. Bought a leather boot on eBay. Also bought a blank for the t case shifter hole.

About 1200 miles so far, averaging 28.5 mpg. Really needs a turbo with the 3.55s... soon enough. Grabbing seats and console from a 99 2dr XJ this weekend.

I am pretty much committed to keeping manual steering. I have what I believe is a 20:1 or 5 turns lock to lock box. Looking for a 24:1 or 6.25 turn lock to lock box. Hoping someone has one laying around after a power steering conversion.

In CT, anything 25 years and older requires only VIN verification if it was registered out of state. No safety inspection on anything. I got the VIN verified and transferred the reg from the Mercedes to the truck. The title from TN didn’t even mention fuel type. I know, we have it easy. Don’t have much else going for us in this state :)

Drove to work today!

5th looked perfect. I put two small tack welds between the snap ring and 5th gear so it can’t come off. Bushing and seal replaced. The slip yoke has some wear too, but it is much tighter now and drives noticeably smoother. May replace the slip yoke at some point. I was having vibration issues from the diesel swap and had no headliner so it was really hard to tell if the issue was isolated to 5th while being shaken in an echo chamber. Got a headliner in and vibration issue sorted and it became more clear that the issue was not isolated to 5th gear.

Very close to DD status. Before doing a complete configuration change on the motor mounts, I decided to try stock Jeep mounts. They didn’t change much, but... I found the motor side bracket was touching the unibody side bracket and took significant force to pry apart. Pulled bracket, sliced in half, bolted each half back up, tack welded in neutral position... BAM! Vibration that’s about 15% over what it was in the donor car. That made a huge difference in driveability. Slip yoke bushing a seal are shot, tomorrow’s job. Stereo working with 4 new speakers Sweet headliner (fatigue mat, idea stolen from ComancheClub) Lots of misc interior assembly LED instrument lights H4 conversion Needs tires balanced Have bolts to replace door pins No dome lights Rebuild manual steering box w fresh grease 3.55s and .85 OD are useless. 3.73 would put me identical to where I was rpm/speed wise in the Mercedes. I think that’s going to need to happen, even with a turbo.

Are you saying you had a sort of rhythmic rumbling that was due to a bad output slip yoke bushing?

Guessing a lot of you are on the "All Things Comanche" FB group where I already posted this, but figured I'd post here too... 86 2wd I just swapped a 4cyl Mercedes diesel in. I did not drive the truck at all before the swap, but I suspect this issue is unrelated. Rumbling only present in 5th gear, fades in and out roughly ounce or twice a second. I had initially suspected tire balance, but I believe I have isolated it to 5th gear specifically, regardless of road speed. I see lots of talk about c clips falling off and either causing partial engagement of gears that damages teeth or a complete loss of 5th gear. As I kept reading, I came across a couple people saying earlier AX5s used a crimp style lock nut to hold 5th. Can't get a whole lot earlier than 86 so my question is... is it likely that my transmission has the nut rather than clip? Are the 5th gear issues mostly isolated to the later AX5s with the c clips? I suppose its possible the gears are damaged, but seems less likely to me on a stock 4cyl 2wd truck if they never became only partially engaged. I found my slip yoke wobbling more than what seems acceptable to me with a leaking seal, so I ordered a bushing and seal and plan to pull the rear extension housing to replace both of those parts. I will inspect 5th at that point.

Test drive tonight!!! Cooling system isn’t doing much. Only idiot light that never came on but hot radiator top and cold lower hose. Will pull thermostat tomorrow and run again. Needs alignment, will do that tomorrow. Once those things are done, it’s ready to put some miles on. Powermaster starter cranks like a champ. Super happy with it. Mounts pictured significantly reduced vibration but I don’t see them lasting long. I think I’m going to adapt the stock Mercedes mounts. 5spd is smooth and fun but 3.55s aren’t going to cut it. 3.73s in 5th would put me identical to where I was with the Mercedes in 4th, will have to give some thought to those or 4.10 especially with a whirly boi in its future. It’s loud. No headliner and muffler doesn’t muffler as much as I’d hoped. Going to be fun turning this into a comfortable DD over the coming months.