750k mile preventative service recommendations?

Synthetic oils modern diffs are to be changed every 500,000 miles.
Rolling in new main (lower) bearings was required with the older mechanical engines, modern electronic engines can go well into the million mile plus range and never need them as long as you’ve done regular oil changes.
38-45 psi oil pressure was normal on mine at highway speed depending on how new the oil was and how hot outside it was.
The early DD15’s had problems with the oil pickup tube seals getting brittle and sucking air causing a loss of oil pressure. I think by 2014-16 they had it solved, but if you’re looking to spend a few bucks that would be a good place to start. Your local Freightliner service centre would have a better idea if that’s still an issue.
If you happen to catch your oil pressure being erratic, oil pickup tube seals would be the first thing to check, if they go you can lose the rod and main bearings and the crankshaft.

 

drive another 50k miles and if you have original injectors replace them. Also replace injector cups o rings. replace the fuel pump and air compressor's unloader valve. If you have money replace air compressor..

 

I have a very different opinion on all of it. While all the advice is good. Sometimes it can cause problems. Sounds like it’s running fine. I wouldn’t let anyone touch the engine, till there’s a problem. Blow 1 injector, then change them all. They can easily last 1 mil or more. Mpg’s are good. Leave it alone. An overhead in the future, with a good inspection of the valve train at most. Synthetic rear oil unless it’s burnt, can go 750 easy, warranted to 750. Rear axle seals and bearings, unless ones leaking, rears are getting hot, or has wheel end play. I’d leave them alone. I’d at least wait till it’s time for brake shoes. Then new seals, and a bearing inspection, if you want to avoid a possible leaking seal later. Definately front wheel bearing inspection and new seal with brake job. Be sure they’re done/torqued correctly, by a good Mechanic, or you’ll have a problem, Wouldn’t hurt to change trans oil now. It’s thinner than differential oil. and not very expensive. Fairly easy DIY. Especially since Trans warranty is 500k. 13 spd only 350k. Change it and inspect/clean cooler fins. Change rear oil too, eventually. no big hurry , if it looks good. The things I’d be looking at inspecting now are air bags on axles and cab for dry rot, and leaking at the base. Plastic bases are known for leaking. A soapy spray bottle helps.
Motor mounts and cab mounts for deterioration. Clutch linkage for worn/sloppy parts. All spring bushings, torque bar bushings, on axles and cab. king pin bushings, front end parts for play, including steering shaft u joint, both ends, at box and in cab. Inspect, only change if somethings bad. Change power steering filter, and fluid if it looks burnt. Crawl underneath and inspect air lines for chafing. Wires for chafing, u joints/carrier bearing for play. Change air dryer filter before winter, if needed, at least every 2-3 yrs max. or just change the whole dryer, $$$ for peace of mind. At your mileage, you can count on soon needing the fan clutch rebuilt, I’d wait till it’s leaking, slipping, wobbling, or clutch material looks thin, or has pieces missing. Water pump if it’s original won’t last much longer. I’d get one ASAP , along with a good radiator flush (2-3x with water) Or once with water, then flush with Cleaner from dealership, then 2x with water. Last time with distilled water,( if using hard water for flush) new coolant filter if equipped, use a pre charged self releasing additive type. new pre charged coolant, ( Final Charge is good) and of course thermostats. Then monitor the DCAs in coolant at oil changes, adding any if needed. New hoses, at least every 5 yrs. max. Sooner is better. Change coolant filter annually if equipped. If not, just keep a good eye on it, testing with test strips, adding additives if needed. Not sure about your engine, but if it’s prone to oil pump seals going bad, I’d have them replaced ASAP. While I agree a lot more could be done. The list is endless. I would do the most important things, that really aren’t that expensive. Reason being, you may suddenly need a clutch, trans, power divider, emission repair, etc. Major costs. Part of successfully running an older Truck is knowing it well. Planning repairs, hopefully catching things before they break. Having money available for the possible unexpected major repair. Doing it right, will pay off in lower total operating costs. Trying to make an old Truck brand new again can cost more than a new one. Simple things like cleaning battery connections once a year, keeping old belts and hoses in case of emergency, an extra front hub oil cap and gasket. Air lines repair couplings for emergencies, all can save you time and money if in a jam. All inexpensive things. Save your money for the major repairs, or for your next Truck, if you beat the odds.

 

I hate fixing trucks on roads. It much better to fix it at home and drive headache free... After driving and fixing cascadias i already know when what can go bad )))

 

You forgot to mention Injector cup o-rings...at 450k-500k they go bad.

 

There’s a lot of things that can go bad. Literally any mechanical part at any time. My Truck has 2.4mil miles. Original parts include whole front end, both rears. power steering pump and accessory drive. They will get replaced eventually, at my convenience. Only recently replaced radiator, bull gear, during an inframe. Radiator was 21 yrs old. Its had 2 inframes, 3 transmissions, first 2 were abused, each only lasted 500k, Current reman trans has over 1.3 mil miles. Drive shaft U joints have been replaced once, by Me, at 1.8 million miles. Probably go through it again in a few yrs. when I replace the trans. Proper maintenance and inspection, knowing the Truck. That’s the key. I usually buy parts needed, having them onboard, changing them when I have time. Preferably at home. Meanwhile I have the part, and won’t hesitate to change it on the road if needed. It all adds up to avoiding shop time, and high repair bills. Most important is knowing it’s done right. Whether it’s your work, or a Shops work. Too many hands into any old Vehicle causes problems. The OP could go to 5 different Shops, and get 5 different opinions on what he should replace right now. Based on problems they see. Good info to consider, but may not apply to his Truck. Most failures can be traced back to neglect or abuse. Just because clutches are often replaced around 700, power dividers and rears rebuilt at 800k, doesn't mean they can’t last much longer. Often they’ve been abused. My original clutch lasted 950k, not bad, considering it was probably abused. Second clutch was a Local reman, cost half the price of a new Eaton. Changed clutch only, reused flywheel, throwout, fork bushings. Money was tight. I didn’t expect much. Yet it lasted 1.2 mil miles. I recently replaced it myself, along with resealing the rear structure, rear main seal, new flywheel and clutch kit. A job I wouldn’t recommend doing yourself. But I wanted it done right, without spending a lot of money. It will last Me 10 yrs or more. As much as I wanted to swap the 1 mil+ mile reman trans, while it was out, I didn’t. It may last another 500k, maybe more. If it goes bad, I’ll replace it, or have a shop replace trans only. Clutch won’t get touched. It was a hard decision, since Labor is $900 to swap a Trans. $900 can go towards something else now, that’s definitely needed. Simply because you never know when a surprise costly repair can occur. Best you can do, is know the Truck, pick your preventative repairs best you can. Works for Me. The things I mentioned are things often overlooked. Things I’d never had to deal with. Things that usually aren’t a problem till 800k or more. I’m truly amazed at how long something’s can last. Never had a Truck with over 1 mil miles, before this one. I replaced my compressor at 1.5 mil. along with the fuel pump. Just because. The new compressor (not rebuilt), same identical brand, pushes more oil than the original. Always has. It’s due to be replaced again, at only 700k. You never know. I know Guys who rebuild rears at 750k just because. That’s crazy. The warranty is 750k. They’ll easily last twice as long. Unless abused. Never let the wheels spin, and only lock them in, if needed to avoid spinning wheels in a steep dock or pot hole. Change fluid at 1 mil. unless it’s burnt. If it’s burnt, there’s a problem anyway. Then go deeper. Replacing perfectly good parts is a waste of time and money. Might as well apply it to a new Truck. Avoiding the cost and aggravation trying to make an old Truck new again.