Rethinking Dex VI

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daves87rs

daves87rs

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Maybe it's just me, maybe not...


I've noticed that there seems to be some issues here with using Dex VI in some older GM cars. One was one this board, and two more popped up around me. One was an 02 Cavalier, and other a 00 Impy. Both made the switch, and both had odd (shifting) issues. An issue with the older 4 speeds, perhaps?


I was considering dex VI for my old 4speed Cav (04), though this trans dates pretty far back. Though I would really like to stick to a synthetic myself. M1 always seems to be a good choice, or I can get Wolf's Head full syn ATF for a pretty good price.


Your toughts?
 
I have an 01 blazer that has run on mostly M1 ATF its entire life except one run on reg dex3. At 160K miles i went to napa and dropped 70 dollars on a case of dex6. Since the change to dex 6 i have noticed very sluggish shifts. I dont want to really say slipping but im not sure. Also during acceleration it started to feel like some of the power was not getting to the ground. Well at 192K i checked the transmission fluid to find it brown. Usually at 50K changes it looks brand new and i usually feel foolish for replacing it. Well i have flushed it out two times now with ST dex 3 and it is shifting noticeably better and does not have that sluggish feel. Maybe its not related to dex6 as it is supposed to be completely backwards compatible and a very good fluid. Ill let you know in 20 or 30 K miles. If the blazer is thriving on the dex3 then the answer is obvious or if is not, then maybe the dex 6 is off the hook. It might just feel better because all the fluid is fresh and new, maybe it will get burnt up in a short time indicating another problem. I too have seen this a few times where people have changed out the dex 6 and got many more miles out of a seemly "going bad" tranny. If i were you and your not above doing reasonable tranny changes, i would just stick with dex3 and not risk it. Im a great fan of synthetics but i will definitely think twice about dumping dex 6 into my old trannys.
 
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Hmm....catch with this car is that it does a decent amount of city driving too...I'd notice that in a heartbeat. Granted, the Dex in the Cobalt (dex VI) was pretty toasted @ 35k....
 
Im so glad I found this thread... now I KNOW Im not crazy.

Replaced the trans fluid & filter on our 2005 Saturn L300 (4T45E trans, 3.0L DOHC V6) with Dex 6 a month ago. Car mileage = 88,000. The first day it shifted like a dream. After that, We're getting weird shifts. It will shift, then after a second or two, actually "roll" into gear. Kinda like a flare up between gears.

This has only been happening between 1-2 gear, I keep telling myself its always done that (it hasnt - we bought the car new with 9 miles on the odometer in 2005!).

Its definitely the Dex 6.
 
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My experience with dex-6 has been indifferent to positive. I have a 95 Buick park avenue with 170k and the 4T60E trans. I first did a pan drop at around 133-35k and used Vavoline Max-life trans fluid. Didn't notice any difference in operation. Did another pan drop around 159k with dex-6 my trans still seems to shift the same way. Car still shifts smooth and doesn't show any sign of failure. Fluid looks the same. Car has always had a slightly harder 2nd-3rd gear shift that seems to smooth out as the trans warms up or sometimes it just smooth from the start.

I do mostly city driving and have did wide open throttles 30 seconds after I start the car. I try to drive conservatively because the car does have 170k and it's the original trans but I'm pretty young and have a somewhat lead foot but I can't afford a new transmisson and hope this will last to atleast 200k.

So I guess in my opinion dex-6 doesn't seem to be anything special but I used it becuase It specs are twice as good as Dex-3. I will say that the Vavoline Max-life trans fluid seems to be a very good fluid. I had barley and clutch material in my trans pan when I did the 159k pan drop.
 
Search for my thread praising Dex-VI, and search for my threads not praising Dex-VI a few months later when my Buick started shifting harshly with it after 10k miles. Switched to a Valvoline ATF, and it's all better.
 
Guy I work with put the Dex VI in his Sunfire, and had all kinds of issues. I told him to use Mercon V and it worked great for him.
 
Maybe my trans is vaccum modulated as far as the shifting is concerned maybe it effects the shifting in transmission that PCS valves controls the shifting maybe its more sensitive to the fluid. I'll have around 20k on the fluid in about another year. I'll probably do a pan drop if it feels like the trans is getting sloppy. But I tried for the life of me to tell if there was a difference in shifting when I changed the trans fluid the first time with Vavoline Max-life and the second time with super-tech dex-6. I really couldn't.

But here is a pic of vavoline max-life trans fluid after 20k miles (159k), mostly city driving 6-10 mile trips. I would recommend this fluid for the dex-3 route. Hardly any band/clutch wear and the magnet is clean. The first pan drop at 133k was thick with gray paste at the bottom and I couldn't see the trans stamp. That was what I was expecting again and was very surprised.

0912091431.jpg


On another note it hard to get the car to go past 4k rpm on the interstate at full throttle when it drops to 3rd gear . Wondering if this is a 3800 thing. I know it makes it peak torque at 4000 rpm and max hp at 5200 rpm. Even when in cruise control it will usually accelerate at a 3k rpm pace if set at 70mph and 4k rpm pace if set at 80mph. Not worried just wondering if other people with 3800 experience the same thing. It starts to feel like its loosing power at 4-4.5k rpm anyway and 2.5-3k rpm seems to be the sweet spot for nice acceleration in everyday driving from my experience.
 
I posted above about how my blazer did not seem to like the dex 6. At the same time i did a pan drop and refill with the same valvoline full syn dex6 on my 99 suburban. At that time i did a complete tune up on the suburban along with a throttle position sensor and the 2nd to 3rd shift, which used to be very harsh at time, had smoothed out to a nice firm shift. Im not sure if it was the dex 6 or the tune up, but something helped it out. I cant speak for the long term effects of the dex6 in there though because we dont have 10k on it since it did that. We drive it very little as it has been in and out of service for all kinds of reasons but as of now the fluid looks good.

Could it be that some clutches are set tighter or looser even in the same transmissions so if you have one a little on the looser side maybe they dont like the new stuff whereas if it was on the tighter side maybe it wont harm it at all. Just a thought, i dont know much about transmissions so i might be in left field somewhere.
 
My Malibu doesnt seem to like Valvoline Dex VI very well either. I'll probably drain out a couple quarts and put in M1 or Maxlife.
 
My '01 Lumina did not like Dex VI. I swapped in the Dex VI very soon after it came out... sounded like the best thing since sliced bread. Shortly thereafter I started noticing that the 1-2 shift at full throttle (or close) wasn't just soft... it would do this sickening slip & grab thing. Other shifts were fine, no problems otherwise- only the 1-2 shift during hard acceleration.

This car doesn't get driven hard very often, so this wasn't a big issue... I left the Dex VI in there for maybe 20k miles. Maybe a year ago I did a complete flush with Transynd (Allison Synthetic DexIII). The full throttle 1-2 shift was immediately improved. It's still softer than I'd like- but none of that slip & grab behavior that it showed with Dex VI. So no more Dex VI for me- at least in my 4T65e transmission.

My '94 Corsica (4T60e trans) ran just fine on Dex VI, though. Couldn't tell any difference between running it with Dex III, Dex VI, or Transynd.
 
I think it's an issue with the electronics in the 4T65, which is electronically controlled and actuated instead of vacuum actuated. The common thread I'm noticing about the cars in this thread complaining is most of them are H or W bodies with the 4T65 transmission. These transmissions, especially until a 2003 redesign, are known for having issues with their electronic controls. It appears that Dex-VI doesn't play nicely with these units, and that other alternatives are in order.
 
Originally Posted By: SteveSRT8
No fluid fixes a worn/damaged trans.

Shift flare is a well known sign of problems to come.


Maybe i missed it but what is shift flare?
 
Originally Posted By: SteveSRT8
No fluid fixes a worn/damaged trans.

Shift flare is a well known sign of problems to come.


True enough. But when a transmission experiences shift flare with Dex VI... but shifts normally with the Dex III that it was designed for- then I'd tend to think the Dex VI is the cause.
 
On a car I dealt with (2002 Malibu) the 1-2 shift was normal until replacing the Dex III with Dex VI which made it very soft. I wouldn't say it was "flaring" between gears, but it was very sluggish.

It appears to have settled down after ~3500 miles but it's not very confidence-inspiring.
 
DexVI is a joke on older vehicles, it all looks fine the minute you put it in, in a few thousand miles it comes out like water. My tranny slipped so much I am concerned what damage I have done to something I have pampered all along...
 
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