So I made it to 100K miles and I just haven't been able to replace my 2009 Tahoe Hybrid, I've Tried a few times, I even bought a few replacement vehicles but they just sit there, the Tahoe is like an old pair of sneakers(sort of like my 62 Bel-Air bubble).
This is the first vehicle that I put all 100K miles on, I've owned many vehicles with over 100K on them but not one I bought new.
So I decided that I may as well reap the benefits of having taken care of the Tahoe for the first 100K and keep it for a bit, I figure I should be able to get 150K-200K out of it without too much trouble.
I know what I've done to it and what my opinions are but I wanted to get everyone's input.
My dealer(Courtesy Chevrolet) has been excellent but in reality I know they service very few Hybrid Tahoe's, I like to discuss the plan of action with the mechanic to make sure were on the same page but I get the feeling that when servicing the Tahoe they are reading a manual online for proper procedure(not that they aren't competent, they just don't have the opportunity to see a lot of Tahoe Hybrids)
What would you do for service and maintenance at 100K? Here are my thoughts & questions,

1. Changing the transmission fluid, proper procedure?(I have read there is 12 quarts and a tube has to be removed to get it all out) what's in there now?(hydraulic fluid?) is there a filter?, is there any better quality fluid I should request?(Courtesy is very accommodating but I'm not 100% certain they have ever performed this service before)

2. Changing the rear diff fluid, proper procedure?(is there a drain plug or is vacuuming acceptable?) what's in there now? is there anything higher quality?(I know what my opinion is)

3. Transfer case- mine is 2WD, so skip for me.

4. Suspension, I've never been thrilled with the suspension on the Hybrid Tahoe, even my young kids comment that it doesn't ride as smoothly as our Escalade or Denali, my assumption is GM dumbed it down for weight savings. My suspension guy has two modes, launch like a dragster or corner like a formula one car, neither of which I want for the Tahoe. anyone have any experience or suggestions?

5. Spark plugs, proper procedure?(standard V8 I assume), what's in there now? any upgrade suggestions?(not snake oil plugs-lol)

Any other suggestions?

I've already replaced the exhaust and intake(my choice, not by necessity), The tires are new Michelins, the 12v battery is an optima, I just can't think of anything else it could need(except for maybe a lock actuator or 4-lol).

 

1) Full Synthetic Dexron 6 or better for trans. There are 2 filters in there. One main one and the other on the auxillary pump. There should be a drain plug and a magnet donut in the pan. No tubes to remove, you don't need to get it all. You probably don't need to go in there.

2) No drain on rear diff. I would take the cover off and inspect the little teeth on the side gear that activates the locker and look for any other signs of trouble. It came with full synthetic so maybe a known brand name purchased at a "big box" auto parts store.

4) if the shocks are still full of oil and working, probably leave them be. My Auto Ride K2500 Suburban needs new fronts. $325 each on-line plus shipping. Ouch!

5) Factory plugs are Irridium AC Delco. The anode/cathode pair are one is flat and wide (ground) the other is a small point. Double platinum I like too. You don't need any more fancy than that. $6 each max is all I would pay. Sale at big box store.

Check the "cheese grater". On the drivers side under the middle row seat, tilt up the seat, carefully pry straight up the plastic and carpet cover over the high volt battery pack.

NOTE: the clips break easy. You are NOT going anywhere near anything that can zap you.

Look in at floor level from drivers side. There is a metal mesh screen on the HV battery cooling air inlet. It is about 1.5 inches tall and maybe 6 inches long. With pet hair, blanket/towell lint etc. fuzz can and will build up slowing air flow. So just like the lint screen on the dryer make sure it is clear.

A HV battery that is too hot will cause all sorts of odd revving and bad performance. A too hot battery will never go into Electric Mode.

 

Thanks Hillbilly, that's pretty much what I was thinking but I wasn't 100% positive.

I don't ever let kids or pets in the Tahoe(we have a minivan for that) and I regularly check the vents for the HV battery, the guys at the car wash like to jam the mats over them.

Do you know at what temperature the HV battery would be "too hot"?

Being in Arizona the interior of my Black Tahoe regularly climbs to 150-160 degrees when parked in the sun and can even climb to 110-120 even when parked in the garage.

I have noticed that in the heat of the summer it takes a looooong time after starting to go into auto-stop or electric mode(sometimes up to 20-30 minutes). Now that we are cooling off(85-90 degrees), I have noticed the Tahoe goes into EV and auto-stop almost immediately after starting. My assumption is the HV battery likes temperatures >100 and it's probably like a giant heat sink that takes a long time to cool to the core.

 

congrats on reaching 100k miles. you are not far behind. I have a little more than you. did all the works, fluids at 100k miles by dealer of course.

 

Too hot for this type of Ni Mh battery chemistry is 116 to 120 F range. That is not hot enough to damage the battery chemistry. It is hot enough for the hybrid system to stop using the HV battery and vehicle performance to change. When the battery cells rise to just over 110F, the hybrid will begin to limit usage to avoid more heating. By 120F ( battery tmp ), the total vehicle performance may be unpleasant. You can adjust your AC and force cool a battery if you want to see if that is an issue. See below.

Now if you live in Arizona and it has been 118F for most of the day and it got down to 110 at night, and the vehicle was outside in the sun, the HV battery may have had time to get to 110F. Nothing wrong just getting close to the hot limits side. There are cold limits too. The extreme cabin temperatures in the 150-160F do not usually get to the battery. The dashboard yes. Door handles? Seat belt buckles? Ouch yes.

The HV battery and the hybrid transmission are big and heavy. The battery is in the cabin low under the seat and cover so temperature transients take almost a whole day to get to it. So if parked in the proper time/temperature conditions, the battery may need to cool a few degrees for full EV mode. Your 110-120 garage schenerio.

If you drove from Phoenix to Laughlin at freeway speeds and AC on to keep you comfortable, the battery was comfortable when you parked it. If you leave it parked a full 24 or more hours, the battery and transmission will be pretty much outside average ambient air temperature. So a 2 day park at 84F will put your transmission in EV ready temperature range right off the bat. The battery will be totally happy and ready for peak charging and discharging operation. The only time delay is getting the engine to run long enough to meet emissions.

So I'm betting that your time delay is time to cool enough to get out of the penalty box. To test that I have the following trick.

Battery Forced Cool Down:

Set front and rear AC as cold as possible. Do NOT use Re-circulation, it reduces the pressure differential across the battery pack by creating a lower cabin pressure. Set the air flow to the floor front and rear. This forces outside air into the cabin and creates a slightly higher cabin pressure. The increased cabin pressure forces more air through the battery. The cold air directed to the floor pools on the floor in front of the horizontal battery air inlets down low. Now if possible drive faster than 55 for about 15 minutes with the above AC settings. Vehicle velocity above 55 mph increses the pressure differential across the battery even more.

This way the mass air flow across the pack is maximized and the air is as cold as possible.

So Arizona or Alaska, a long drive where the driver is comfortable will make the battery comfortable. It will take at least 12 hours from that parked time for the battery to get anywhere near outside temperature and put you back in the penalty box.

 

the battery is placed and cooling is efficient enough that one time I was caught in a traffic standstill in Las Vegas Interstate for three hours where the temp went close to 213 F, not sure if it was tranny or engine but it cycled between auto-stop and ICE idling that it still kept fuel consumption in check. ambient or outside temp was close to 112 F!

 

I have driven my Silverado Hybrid in temps as high as 120 with no ill effects on the battery or auto stop. I believe there is an A/C vent under the drivers seat which directs cooler air to the battery. With higher ambient temps I have seen the truck enter auto stop sooner in the mornings since less warm up is required. Sometime it does not even leave the driveway before it shuts off.

It is important to note that the black plastic cover over the battery pack is purely decorative and it is important to check the vents inlet INSIDE the battery pack under the cover. The vents in the black plastic are not really functional. The Ford Escape has an actual filter for the battery pack which needs to be changed every 10k miles or so (and most dealers skip).

The only temp issues I have had have been coolant temperatures when rock climbing in death valley on a hot day with the A/C on in "D" mode. I should have been in "M" with the A/C off. The temp gauge shot up to near the pin - but no warning lights. I had a similar experience climbing the "Grapevine" on I-5 with a heavy load in high temp (110F). I don't like to see temp gauge move off 210. In both cases there were no actual problems - just unease because of the gauge position. In both cases this is near the extremes for the vehicle.

Interestingly I think my Chevy Volt has had some issues with Temperature while climbing up the Grapevine in hot weather. Twice I have noticed the gasoline engine shut down unexpectedly - even in "mountain mode" and the vehicle switch to 100% battery power for a minute or so. Then the ICE restarts and picks up the load again. I believe the computer says "too hot" and shuts it off and uses the battery until temp cools down again. It has no impact on driveablity, but it is not normal Volt behavior. As far as battery temps go the Volt is bullet proof - since they are liquid cooled.

 

Just for note: I test drove a 2008 Tahoe Hybrid this weekend with 167,000 ( a record possibly?) miles on it. Looks and drove very nice, with great engine power. Only thing I noticed was a slow 2-3 shift, and the engine shut off/battery run from a stop sign did not work until driven about 12 miles. Any concern with any of these two observations?

 

Engine and transmission and HV battery all need to be "in-the-zone" of temperature. Engine coolant > 150F ish. Transmission > 80F battery > 30F ish

 

I changed Transmission fluid and filters(yes, there are two) today and it was shockingly clean, no bits, no metal dust, no slime, still somewhat see through. but man was there a lot of fluid, it was like a waterfall of fluid, about 3 gallons came out. of course I'm going to get the old fluid analyzed but I can't imagine the report will show anything.

Also popped the rear diff cover and changed out the fluid, also, very clean, nothing to report, no bits, no metal dust, no slime, slightly greyish(I wish I knew the original fill color tone for comparison) but nothing alarming.

Barring any unforeseen circumstances I think I should be able to make it to 200K miles without any headaches, The drive train is in excellent condition.