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'97 Seville STS
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Discussion Starter #1
Topic: Transmission fluid service at 100K.

Vehicle: 1997 Seville STS.

Background:
  • Purchased at 87K (trade-in from previous owner).
  • Currently 108K.
  • Chilton manual suggests a “transmission service” at 100K.
  • Dealer has some records of previous service history, but there are no records of any transmission service.
  • Dealer recommends transmission flush & filter change.
Observation of Transmission Operation:
  1. When shifting from D to R, there is a slight delay (~1 second). There is no significant delay when shifting from P to R.
  2. If the car is going 30 mph or more, and the pedal is floored such that there are two immediate downshifts, there is a significant delay between the first and second downshift, and afterwards there is a significant jerk. If the car is driven such that it undergoes successive single downshifts, each downshift is fairly smooth. All up-shifts seem smooth.
(I do not know if what I’ve described above is pathological or normal.)​

Goals: I am under the impression that this vehicle has a good chance of lasting a long time from here. (E.g. headgaskets replaced with timeserts at 75K, along with plugs & wires, among other things). I would like to maintain what I perceive as its very high performance for a $5000 used car. If it is advisable to do something with the transmission fluid as preventative maintenance at ~100K -- when the goal for the car is several tens of thousands more miles, maybe even 200K -- I would like to do that. I’m looking to make a reasonable approach towards maximizing both performance and longevity, in the context of an urban daily driver.

Other Threads on Forum: I’ve read other threads on the forum involving transmission service, and there are two problems:
  1. Many of the threads involve engines other than the Northstar, and I’m uncertain which aspects of such threads apply to the transmission on my ’97 STS.
  2. Many of the threads appear to be discussions among experts regarding the nuances involved in achieving the utmost of performance, and the discussions are beyond my current level of understanding and probably also need.
Request for Help on This Post:I’m wondering if some kind forum members could distill the issues with transmission service down to the basic, agreed-upon aspects that are advisable under circumstances such as mine (i.e. reasonable efforts towards “city” performance & longevity).

Some Specific Questions:
  • Based on the above observations of transmission performance, is it likely that the transmission fluid & filters have degraded to a degree that is causing significant adverse affects on performance?
  • If so, would it help to somehow “service” the transmission in order to improve performance and the chances of long-life? Or would any type of service be more likely to increase the chances of future demise?
  • Among any services that may have a good chance of being beneficial, can any be done by a novice willing to follow instructions (me)?
  • I’m interested in the possibility of cleaning filters & magnet, detaching the drain line to the cooling fins by the radiator, and then filling the reservoir while the car is idling and draining fluid out the detached cooling line. Would this be manageable and worthwhile? (If so, can anyone elaborate on “dropping the pan”, “pulling the plugs” and “cleaning the various filters”; such descriptions are a bit vague for a beginner; any pics or more detailed test available?)
Thanks is advance for any responses,

Wx.
 

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  • Based on the above observations of transmission performance, is it likely that the transmission fluid & filters have degraded to a degree that is causing significant adverse affects on performance?
Yes.


  • If so, would it help to somehow “service” the transmission in order to improve performance and the chances of long-life? Or would any type of service be more likely to increase the chances of future demise?
I'm not familar enough with these trannies to give a detailed response. However I do know that the computer will adjust shift timing and firmness based on inputs. For example when I spray nitrous my 01 eldo adapts to shift timing and firmness. It'll take 3-4 good WOT shifts to bring the shift point and firmness back to factory parameters. Even spraying a 100shot! Even at easy driving part throttle operation I'm pretty sure the car is adjusting pressures of the clutch packs to accomidate the wear and tear.


  • Among any services that may have a good chance of being beneficial, can any be done by a novice willing to follow instructions (me)?
If it's a $5k car.. just do it yourself. Here is what I'd suggest. Drop the pan, replace the filter, and re-install. Then top off with how ever many quarts of fluid it takes. (look up in owners manual). Drive it for 1000 miles then again drop the pan and drain. (not changing the filter). Re-fill and then repeat up around 150k miles.

This is not hard to do. If you can change your own oil.. you can do this too.

And btw, I'd personally never do a "power flush" from a service company/dealer on a high milage car with tranny fluid that's never been changed. Any deposits that *may* have built up really ought to be disolved with fresh fluid vs being broke loose with fluid pressure / velocity.

  • I’m interested in the possibility of cleaning filters & magnet, detaching the drain line to the cooling fins by the radiator, and then filling the reservoir while the car is idling and draining fluid out the detached cooling line. Would this be manageable and worthwhile? (If so, can anyone elaborate on “dropping the pan”, “pulling the plugs” and “cleaning the various filters”; such descriptions are a bit vague for a beginner; any pics or more detailed test available?)?
Don't mess with doing it that way. It's true that "dropping the pan" won't change but about 1/2 the fluid. Just change it that way twice and you'll be fine up to 150k or so. A beginner with good intentions is likely to just make trouble for himself if trying to change the fluid that way.

As far as general ability to turn wrenches.. um. Might want to go to the library or book store, (or internet) and look up generic how to's.

Changing the air filter, oil, and tranny fluid on these caddys is not hard to do. Just need to carefully support the car on stands so you can safely get undernieth and wrench.

Regards, Rich
 

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This has been covered many times.

Do NOT flush it.

A fluid change is recommended and fairly easy. There is an upper sump that must be drained also. The plug is hidden behind a filter screen.

There are filter screens that only need cleaning. They are not fiber filters.

The pan gasket is reusable but at 10 yrs old I'd get a new one.

There may be detailed instructions in Tech tips.
 

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White Diamond 2001 STS
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Technically, the fluid in these transmissions is "fill for life". If you are having issues with it, though, changing it (and NOT flushing it) would be reasonable.

My '97 SLS still has it's original fluid (160k miles), currently living in AZ with my brother. Runs like a dream.
 

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Technically, the fluid in these transmissions is "fill for life".
That's a pipe dream of the late 90s from the OEMs.

Fluid degrades with debris and heat. Even if the filter is capable of high milage.. it doesn't change the basics of degradation.

I'd suggest that everybody change thier own fliud at 50k intervals. You get to see first hand the debris in the pan, the smell of the fluid, and just what the actual condition is.

Rich
 

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1997 ETC
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I just wanted to add my 2 cents and say that I'm in agreement with the "do not flush" an older transmission. I have a 97 with 90K miles and spoke with two reputable transmission repair shops. Both agreed that a flush, which replaces ALL the fluid, is a bit questionable with the northstar system. They have seen problems created by doing it. I asked if it was their car would they, and they said no. All this and they could have charged me $100 or so to do it.

They implied that if I was flushing it every few years it would not be a problem, but waiting 10 years presents too much risk.

Regards
Pete R
 

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Discussion Starter #8
OK fellas thanks for your responses.

I think I'm going to follow the procedure outlined by wydopnthrtl and zonie77.

A few more questions though:
  1. Can anyone recommend a good online source that desribes how to drop the pan, remove the various plugs and clean the filters? (Pics would be good.)
  2. Should I mix new Dextron VI with the original Dextron III using the procedure described by wydopnthrtl?
  3. It seems like it's some sort off "shock" to the system if the transmission fluid is changed too significantly after 10 years (e.g. all fluid changed or a flush). Why is that?
  4. Just out of curiosity, would it be possible to get the transmission "back in shape" over time, so that it becomes ammenable to more thorough maintenance?
  5. What is the technical name/numbers for the transmission in a '97 STS?
 

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2 - I would'nt mix. Just use what ever the owners manual calls for.

3 - Flushing 100% at once using pressure can *possibly* do two things. It may.. or may not... a) It can dislodge debris. That debris can be realively large and get into spaces that it ought not (tightly fitting machined surfaces). b) Also, all new fliud is much more able to disolve debris. If the tranny clutch pacs are on thier last legs.. removing that debris will only shorten what little life is left. The exact same thing can be true for brake fluid btw.

4 - Mechanical parts wear out. And as I posted earlier, the computer adjusts for this. For example the time it takes for the motor to decelerate during a shift is know by the computer via the crank position sensor. We engineers in motown have a good understanding of wear / power curves and have got ya covered up to about the 150k mile range. ;)

Don't over think this on a 5k car. Just "drop the pan", change the filter, re-bolt the pan (new gasket), and fill. It's really very easy to do as long as you can get undernieth the car.

Sounds to me like you really need someone close who can walk you through it once.

Rich
 

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White Diamond '03 DHS (with DTS floor shift)
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I would use the new Dexron VI.
Just remove the perimeter bolts and drop the pan. There is a side case drain inside under the side cover. If I remember correctly it is near the screen and under the wire harness. Be sure to remove it and drain the side cover. There is a picture posted somewhere if you do a search you may find it.

The trans is a 4T80E.
 

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That's a pipe dream of the late 90s from the OEMs.

Fluid degrades with debris and heat. Even if the filter is capable of high milage.. it doesn't change the basics of degradation.
Wow. The engineers are dead wrong then. And my experience is a miracle!

Fluid does degrade with debris and heat, things modern transmission fluids don't typically see. There's no fuel blow-by. There's no other source of contamination. Operating properly, the transmission should always operate well within the temperature parameters of the fluid. If the fluid DOES overheat, the car knows it and tells you to change it.

We always lecture new folks to follow the oil life monitor for the engine oil. I always fail to see why we have a second standard for transmission fluid.

I stand by what the owner's manual recommends, and what my experience has told me.
 

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Wow. The engineers are dead wrong then. And my experience is a miracle!

Fluid does degrade with debris and heat, things modern transmission fluids don't typically see. There's no fuel blow-by. There's no other source of contamination. Operating properly, the transmission should always operate well within the temperature parameters of the fluid. If the fluid DOES overheat, the car knows it and tells you to change it.

We always lecture new folks to follow the oil life monitor for the engine oil. I always fail to see why we have a second standard for transmission fluid.

I stand by what the owner's manual recommends, and what my experience has told me.
WOW! Arrogance on top of ignorance. You sir really really ought to back away from the keyboard and go into the garage for a few years before coming back. And for it's worth... **I am an OEM automotive engineer in Motown** Have over 12years of drivetrain experience too. And.. I was a gear head rebuilding my own engines and transmissions before I even started this dicipline.

btw.. "fuel blow-by" ?? You do know this thread is about transmissions don't you?

Rich :bigroll:
 

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WOW! Arrogance on top of ignorance.
There are enough insults on this board already, let's not add to them please.

And for it's worth... **I am an OEM automotive engineer in Motown** Have over 12years of drivetrain experience too. And.. I was a gear head rebuilding my own engines and transmissions before I even started this dicipline.
Well, then, riddle us this...why does almost every modern (including those from the 1990s) owners manual recommend that transmission fluid is good for the life of the transmission, except if the vehicle is driven under the severe service cycle? It says so in my 1997 Cadillac owner's manual, it says so in my 2001 Cadillac owner's manual, it says so in my 2003 Dodge owner's manual, it says so in my 2007 Chrysler owner's manual, etc, etc, etc.

btw.. "fuel blow-by" ?? You do know this thread is about transmissions don't you?
Uh, yes, that's why I mentioned it. Fuel blow-by is one of the main sources of contamination for engine oil, something a transmission fluid never sees. All you said was that fluid degrades with heat and debris. I agreed with you, and suggested that those factors are largely missing from modern transmissions. Your reply was to insult me and call me arrogant, and go on to spout out how much experience you have.

Let's keep the discussion technical. If you'd care, I'd love to hear your technical discussion on how hot modern transmissions run, how much that degrades the fluid, and where the source of debris is that degrades it, and the length of time that process takes...

Edit: let me clarify something I said earlier, which might be the source of your contention... When I said that the "engineers are wrong", I meant in the context of putting the "good for the life of the vehicle" in the owner's manual if that's really not valid. Are you engineers not consulted when the manual is written? I just fail to understand a big (and important) difference between what an engineer says and what the owner's manual says.
 

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If a pressure flush messes up the transmission though you just take it back to the garage and demand they fix it at no cost as they did damage.
 

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Discussion Starter #16
OK well I'm changing the fluid right now.

I came in to look here because now that I've dropped the pan, I can't find that darn side plug people talk about.

The trans fluid looks pretty bad to me. Near brown.

Otherwise I'm surprised how clean it is in there -- except for a lot of fine metal grit that I've cleaned from the pan. The magnet was so full of it that I thought the magnet had ridges untill I cleaned it.

My present synopsis: clean in there, yes, but fluid does seem degraded.
 

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White Diamond '03 DHS (with DTS floor shift)
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The trans fluid looks pretty bad to me. Near brown.
Not good.

The magnet was so full of it that I thought the magnet had ridges untill I cleaned it.
Normal.

I can't find that darn side plug people talk about.
It is close to or between the screens as I recall. I remember that I had to move the wire harness over to get at it.
 

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Discussion Starter #19
Success!

Thanks to many of you for your helpful posts. :worship:

Inside the transmission it was surprisingly clean, but as I said above, the transmission fluid was brown. The shade of brown was darker than new motor oil going in for an oil change, but not as dark as old oil coming out. (And of course not as viscous as motor oil either). I'm assumming the browness was due to oxidation.

I ended up replacing the two pan filters & the pan gasket (ACDelco kit from dealer,$45.00), and draining what poeple call the "side" plug (it's vertically orietated though).

Then I refilled with Dextron VI -- because that was the only Dextron available where I bought it (dealer) -- and then I "purged" the system: I disconected the metal return conduit at the top, driver's-side of the radiator, and replaced it with a threaded lead connected to a hose going to a bucket; then with the vehicel running I poored Dex VI in the trans resevior until the fluid from the radiator turned from brown to red.

In retrospect none of this is really that hard, but I feel compelled to write a post of this for beginners like me (we'll see if I follow through), because having not done this once before, everything above can be pretty vague.

As for results, I really think the hard double down-shift I described in the initial post was ameliorated by purging the old fluid with new.
 
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