Transmission Service? keep old fluid or put new..

[calsdad]

I'm not a millennial but don't blame them for this nonsense, this is straight old bomber mechanic crap.

the saying goes if you have a ton of miles on a tranny, say 200k. just leave it alone, don't disturb the fluid. it might start to slip. I doubt there's any truth to it but no one has ever said to reuse the fluid, that's just silly, especially when a normal auto only drains a few qt with a filter change. the rest is left in the converter and tranny itself. but this isn't a normally tranny. he has a Allison made hybrid tranny, it doesn't have a converter and will drain most of it out. the pump. he's changing is eternal.

I have a 96 4l60 with 320k on it, I have a vacuum oil collection at work, I use it to suck out the fluid out of the dip stick tube every few oil changes and top back off from fresh because it's free for me. tranny has never given me issues and it had over 220k when I got it like 12 years ago.

The claims that I've seen in regards to putting in new fluid - is that putting in new fluid - with fresh detergents and so forth - might break up deposits in the transmission and cause crap to circulate and cause problems. I suppose if a transmission is REALLY old - that might have some validity. But transmission fluid does degrade over time - so changing it at 100k or so - and keeping up with it avoids all of that crap in the first place IMHO. So change it and then keep up with it and don't let it go too long.

 

[BG1988]

Put in new. And flush ALL of it. Back in late August 2019 I put in a new deep pan on my 2010 Yukon XL 2500 (6L90 transmission). When I did that - I also changed the filter and flushed all of the fluid. Use quality Dexron fluid of whatever the correct type is. I don't recall reading anywhere that the synthetic stuff is really worth it. The biggest hassle was draining the fluid from the original pan - which had no drain plug. I ended up buying a Mityvac MITMV7300 evacuators. First I used that for getting as much fluid as I could out of the pan before dropping it. Then - and this was actually more useful thing I did with the Mityvac - I used to drain the old fluid into - by using the Mityvac I could set it up off to the side so I could see it from the driver seat. I setup a hose coming from the transmission cooler line - over to the Mityvac - and then filled up the pan. Turn the truck on for a few seconds - and flush some fluid into the Mityvac. Check the fluid level - and add more. Turn it on again and flush some more fluid - rinse and repeat until you start seeing clean fluid draining into the Mityvac. That way you get ALL of the fluid out of the transmission and replace it with clean new fluid.

Heard a bunch of people saying "you're going to blow up the transmission!!" blah blah blah. Well over 2 years and 20,000 miles or so later - the transmission is doing just fine thank you very much.

You're going to need a few gallons to do the flush / new fluid install the way I describe above ( I think I used up 6 gallons) - but you will get ALL of the fluid out including the fluid that is in the convertor.

Oh yeah - and look around for where to get rid of the old fluid. My local Autozone doesn't take it. I had to get rid of my old fluid at the town hazardous fluid collection day.

the pan capacity is 12qt 66% of the total amount

everything is working great now NO more shuttering at 1-2 gears 10-13mph...

my assumption was correct that it was the transmission pump causing it...
also the transmission is not slipping with the A/C on (engine just revved instead of moving) like it did before NOW i can enjoy an ICE cold 36 degree cabin when it's 110F outside it's like a walk in fridge.. sooo cold it makes my eyes water..

i just gotta replace the HIGH VOLTAGE power supply 3,000$ for a lithium battery Nexcell LiFePO4 lithium drop in replacements for the tahoe

 

[gooffeyguy]

$3,000 is just a drop in the bucket with all the money saved on fuel from the mpg you get on that thing

 

[BG1988]

$3,000 is just a drop in the bucket with all the money saved on fuel from the mpg you get on that thing

i'm guessing with the HIGHER capacity battery i can get 3-4 miles in EV mode even if it's the standard 1-2 miles that would be a huge gain over the 200 feet it can go on EV

My record is 8 miles on EV mode (8 mile down hill slope at 29mph) with A/C on full blast (to take up some of the regen slack so it did not overcharge the battery)

 

[wjburken]

the pan capacity is 12qt 66% of the total amount

everything is working great now NO more shuttering at 1-2 gears 10-13mph...

my assumption was correct that it was the transmission pump causing it...
also the transmission is not slipping with the A/C on (engine just revved instead of moving) like it did before NOW i can enjoy an ICE cold 36 degree cabin when it's 110F outside it's like a walk in fridge.. sooo cold it makes my eyes water..

I know your vehicle has extraordinary capabilities, but when most vehicles only 30° to 35° temperature drop across their A/C coil, for you to get a 74°F drop, that’s is simply amazing.

 

[BG1988]

I know your vehicle has extraordinary capabilities, but when most vehicles only 30° to 35° temperature drop across their A/C coil, for you to get a 74°F drop, that’s is simply amazing.

350vDC A/C industrial grade> mechanical


it starts getting cold quickly too with in 15 seconds or so
it uses 4awg wire with lug terminals

i think it's about 2.5 to 3kw A/C so powerful there is nothing about it in the user manual lol....

 

[calsdad]

the pan capacity is 12qt 66% of the total amount

everything is working great now NO more shuttering at 1-2 gears 10-13mph...

my assumption was correct that it was the transmission pump causing it...
also the transmission is not slipping with the A/C on (engine just revved instead of moving) like it did before NOW i can enjoy an ICE cold 36 degree cabin when it's 110F outside it's like a walk in fridge.. sooo cold it makes my eyes water..

i just gotta replace the HIGH VOLTAGE power supply 3,000$ for a lithium battery Nexcell LiFePO4 lithium drop in replacements for the tahoe

Go to Youtube and check out the "DIY Solar Power with Will Prowse". He does a bunch of in-depth evaluations about lithium batteries for solar systems. I think in a lot of cases - they're the same batteries used for EV vehicles. You might find there's a cheaper alternative that could be used other than the "factory" solution.

 

[BG1988]

Go to Youtube and check out the "DIY Solar Power with Will Prowse". He does a bunch of in-depth evaluations about lithium batteries for solar systems. I think in a lot of cases - they're the same batteries used for EV vehicles. You might find there's a cheaper alternative that could be used other than the "factory" solution.

well the cells are an "exact fit" and designed with being used as a drop in upgrade/replacement for nickel metal hydride battery

 

[jmil1974]

The claims that I've seen in regards to putting in new fluid - is that putting in new fluid - with fresh detergents and so forth - might break up deposits in the transmission and cause crap to circulate and cause problems. I suppose if a transmission is REALLY old - that might have some validity. But transmission fluid does degrade over time - so changing it at 100k or so - and keeping up with it avoids all of that crap in the first place IMHO. So change it and then keep up with it and don't let it go too long.

Saw this 1000s of times in my service advisor days. On high mile and/or hard use vehicles, it can get to a point where the varnish is actually holding some things together. On high mile trannies, you have a decision to make. If you flush it and it was a bad decision, you will know within a couple hundred miles - slipping/chattering starts. You killed it but it was on borrowed time anyway. This is kind of rare but does happen regularly and really is only rare because so few people actually do trans flushes. If you make it though the first 500-100o miles, you just extended the life of the trans. Flushing the tranny is something I do every 40-60k, depending on cooling and how hard I am driving it. 30k is the aftermarket recommendation but is overkill IMO unless driving it commercially/genuine severe duty. My old burbs 4L60e was slipping, did just a service not a flush and slipping stopped and it's STILL going. Cleaning the injectors/TB/intake and replacing fluids are the best things you can do if you plan to drive the wheels off a modern vehicle.

 

[calsdad]

Saw this 1000s of times in my service advisor days. On high mile and/or hard use vehicles, it can get to a point where the varnish is actually holding some things together. On high mile trannies, you have a decision to make. If you flush it and it was a bad decision, you will know within a couple hundred miles - slipping/chattering starts. You killed it but it was on borrowed time anyway. This is kind of rare but does happen regularly and really is only rare because so few people actually do trans flushes. If you make it though the first 500-100o miles, you just extended the life of the trans. Flushing the tranny is something I do every 40-60k, depending on cooling and how hard I am driving it. 30k is the aftermarket recommendation but is overkill IMO unless driving it commercially/genuine severe duty. My old burbs 4L60e was slipping, did just a service not a flush and slipping stopped and it's STILL going. Cleaning the injectors/TB/intake and replacing fluids are the best things you can do if you plan to drive the wheels off a modern vehicle.

Great response!!. I think I said this in a previous post - but at this point I've gone just under two years and 10-15000 miles - and I'm sensing there are any issues with the transmission. Now that I've got a method to relatively painlessly flush all of the trans fluid - I will let it go maybe 50k - and do it again. Hopefull that helps the trans live a nice long life.