High mileage Fluid Change?

[Sdp1234]

i’ve had my 2004 Yukon Denali 6.0 all wheel drive since March. It has 170k with limited records available There have been a few things to take care of along the way. I’ve had it long enough that it feels like mine now, if you know what I mean. How often would you change the oil? Would you rely one the electronic oil change reminder? I’ve been using a synthetic blend. Should I be using full synthetic? Should I change fluid in the Transmission, Transfer Case Or Differentials?


In the past I’ve left these things alone but I’d like this to last for more driving or to sell when I upgrade.

Thanks

 

[wjburken]

i’ve had my 2004 Yukon Denali 6.0 all wheel drive since March. It has 170k with limited records available There have been a few things to take care of along the way. I’ve had it long enough that it feels like mine now, if you know what I mean. How often would you change the oil? Would you rely one the electronic oil change reminder? I’ve been using a synthetic blend. Should I be using full synthetic? Should I change fluid in the Transmission, Transfer Case Or Differentials?


In the past I’ve left these things alone but I’d like this to last for more driving or to sell when I upgrade.

Thanks

I would get fresh fluids in your vehicle. If you don’t know the history, assume they did nothing since 80% of people don’t get things changed regularly.

As for oil change intervals, if you poke around here you will find folks that change every 3K, some go 5K, and then some others go 8K-9K or longer. Personally, 4K-5K works for me based on how my vehicles are driven. A number of folks here send off oil samples to get them evaluated to see what’s in the oil, how much it’s degraded, etc. so that’s something to consider. I don’t personally pay much attention to the dash reading for oil life.

A synthetics blend or full synthetic should be fine.

 

[SNKETR]

I agree with Wade. I would change all fluids including brake/coolant/power steering. Most should have been replaced anywhere from 100k-150k. I prefer to run synthetic and just change every 5k miles.

 

[Tonyrodz]

I agree with Wade. I would change all fluids including brake/coolant/power steering. Most should have been replaced anywhere from 100k-150k. I prefer to run synthetic and just change every 5k miles.

Don't forget fluid in the diffs. With no real service history, I wouldn't do a trans flush. Better just to do a fluid swap--dropping trans pan and replace the filter. Check the magnet while you're in there too.

 

[ivin74]

Don't forget fluid in the diffs. With no real service history, I wouldn't do a trans flush. Better just to do a fluid swap--dropping trans pan and replace the filter. Check the magnet while you're in there too.

I dropped the pan changed the oil then flush out the remaining bad oil at 174k miles and have had no issues since. It runs like a champ.

 

[OR VietVet]

What Wade and others said. I got my 2002 Tahoe with approx 145k on it. I want to know when all fluids were done so I recently changed everything. I did the differentials, transfer case, transmission, brake fluid and I use full synthetic with an AC Delco filter and change every 5k miles. The coolant I know was done about 1.5 years ago because the water pump went bad and I installed all new coolant. Get a base where you know for sure the time and mileage intervals.

 

[Wylie_Tahoe]

Ima dino-oil type of guy. Run conventional in everything except my 2.5L 5 cyl Dub. My previous 02 Trailblazer I drove from cradle to grave and put 280K on it all using conventional oil. She was running strong when she had a fatal encounter with a concrete highway divider last year. A lot of that was towing, as well as round town and highway. I never followed the DIC oil %. I typically changed between 3K-4K, which was always between 60% to 75% oil life left. The look of the oil said it was time to change, screw the GM life monitor.

My "new to me" 03 Tahoe 5.3 flex has nearly 300K, but ive only owned it long enough to change the oil once. Will likely stick to the 4K mile mark, depending on season and usage. Using conventional. Right now, im running the recommended weight. I seem to have some oil consumption, which im beginning to monitor. May change weights next oil change.

All other fluids have been changed, except a full coolant flush, full break flush and front diff change. On the list.

Some people are comfortable going long on oil changes. Personally, ive never seen an engine blow because the oil was changed too often.

 

[OR VietVet]

Some people are comfortable going long on oil changes. Personally, I've never seen an engine blow because the oil was changed too often.

Hell, 1/4 mile alcohol and top fuel drag cars change their oil after every race.

 

[SnowDrifter]

I use full synthetic in everything I can get my hands on. But I also live in a climate, and have driving conditions that warrant it. My rig sees a bit of everything. From lots of short trips, to towing a 5 to 7k pound trailer across a couple mountain passes. So take my maintenance with a grain of salt

I do my oil with full syn every 2 to 2.5k. I was going 3k or a bit over but found that I started to get some varnish from short trips that longer drives weren't alleviating. Shortened it up and varnish went away. I also use a larger filter and use one with good flow rates and synthetic media. I'd rather run cheap oil on a good filter than the other way around if I had to cut a corner somewhere

I do Diffs and tcase every 50k. Use the blue gm fluid in the transfer case. And 75w140 in the Diffs with a slight overfill to compensate for less drainage

I drain and fill the trans pan kind if when I feel like it. Anywhere from a couple times a year to one a year. Just when I arbitrarily decide I want the fluid a bit cleaner.

I do my brake fluid and power steering fluid annually. Along with air and cabin filters. Don't need to do the fluids as often as that but an ounce of prevention is worth 1000lbs of cure when running hydroboost

I changed out my coolant to a PHOAT mixture that doesn't attack nylon fittings and while I've not yet changed it, I plan to every 3 years or so. Will decide when as data allows. I check mine with a multimeter to evaluate for electrolosys.

If you want me to name drop specific brands and products I can


149k on it and not a single leak, tick, pop, or knock from anywhere. Not so much as a wet spot

Edit now that I'm on desktop: I also don't use any "high mileage" type fluids. Never believed in 'em because I've not seen anything past anecdotal evidence or been able to find any documented behavior on their effects, particularly around items like seals, regarding their long term use.

 

[SnowDrifter]

I also should add I don't burn any measurable amount of oil. And have yet to observr any blue smoke on startup consistent with valve seals

 

[Sdp1234]

Working first to determine everything I have in the Truck
4L60-E/4L65 4 speed heavy duty A/trans (M32)
NR3 - Transfer Case
Stabilitrac?

What are the differentials?

3.73R(GT4) (from the build sheet)
Can't find the front one on the build sheet.​

How do I tell if they are limited slip (want to use the right gear lube)

Should I use RTV or a gasket on the differentials? (I use RTV on my 2004 wrangler)

 

[Sdp1234]

Don't forget fluid in the diffs. With no real service history, I wouldn't do a trans flush. Better just to do a fluid swap--dropping trans pan and replace the filter.

I'll do the other fluids but I'd rather not mess with the Trans. What would I tell a transmission shop to do. Just tell them to "drop the pan and replace the filter"?

Should I go to my local garage mechanic or a Trans Shop? What is a reasonable charge to do this?

 

[wjburken]

I'll do the other fluids but I'd rather not mess with the Trans. What would I tell a transmission shop to do. Just tell them to "drop the pan and replace the filter"?

Should I go to my local garage mechanic or a Trans Shop? What is a reasonable charge to do this?

I’d call around and talk to a few shops, mechanic and tranny shops, and see what prices are and which ones try and talk you into doing more that just dropping the pan and replacing the fluid.

 

[Wylie_Tahoe]

I'll do the other fluids but I'd rather not mess with the Trans. What would I tell a transmission shop to do. Just tell them to "drop the pan and replace the filter"?

Should I go to my local garage mechanic or a Trans Shop? What is a reasonable charge to do this?

Id have the filter changed since its new to you with little known, then ive a trans flush performed. The flush will cycle all the fluid out. Just dropping the pan leaves 6+ qts of old fluid in there.

 

[treehan77]

I would not do a flush on an unknown high mileage transmission unless you want a new transmission

 

[OR VietVet]

I would not do a flush on an unknown high mileage transmission unless you want a new transmission

That has been said many many times here. It's true every time I hear it. Unless of course you just have money burning a hole in your pocket and you want a new trans. If so, drive it close to home.

 

[Sdp1234]

I get it, no flush. Not questioning, just curious what the benefit is of droping the pan and changing the filter?

Thanks for all the responses.

 

[treehan77]

You get a new filter that you know isn’t clogged, and some fresh fluid. And don’t immediately wreck the transmission

 

[Wylie_Tahoe]

I would not do a flush on an unknown high mileage transmission unless you want a new transmission

Please explain your theory. There is absolutely ZERO harm in the transmission pumping out its old fluid, as fresh fluid is pumped in as the same rate and pressure. In under 2 minutes, you have 12 qrts of fresh fluid in the transmission.

@Sdp1234

As stated earlier, dropping the pan only changes out about HALF the transmission fluid and a new filter. So upon startup, you mix the 6 qrts of fresh fluid with 6 qrts of who knows long long its been in there fluid.

 

[OR VietVet]

Please explain your theory. There is absolutely ZERO harm in the transmission pumping out its old fluid, as fresh fluid is pumped in as the same rate and pressure. In under 2 minutes, you have 12 qrts of fresh fluid in the transmission.

@Sdp1234

As stated earlier, dropping the pan only changes out about HALF the transmission fluid and a new filter. So upon startup, you mix the 6 qrts of fresh fluid with 6 qrts of who knows long long its been in there fluid.

I believe what I have heard many times before is that trans fluid is high with detergents and to replace all fluid could shock the system and help damage the plates. then all that gets clogged in the recent fresh filter and the problems get worse from there. I see no problem with a fluid flush if it is done every 50k miles or so but if is high mileage and don't know if flush has ever been done it is best to skip the flush and just do the filter and add back what is lost when drop pan. I also saw a couple times on here that the 4L60 trans is good for about 160k before likely having to plan on replacement.