Trans oil

I have 70k should I drain & fill the transmission fluid? The car shifts and acts fine and I think the previous owner did it in 2012. I read I should not change the filter and don't want to create a problem is this true?

carguy8888 wrote:

I have 70k should I drain & fill the transmission fluid? The car shifts and acts fine and I think the previous owner did it in 2012. I read I should not change the filter and don't want to create a problem is this true?

I bought my Riv with almost 86,000 miles on it in 2004. I have been changing the ATF and filter every 20,000 miles since then. The car has almost 200,000 on the original transmission and shifts mint. I say change it. I have been using Valvoline Dex 6. I use it in my 1970 GS as well.

Thank you, change the filter as well?

carguy8888 wrote:

Thank you, change the filter as well?

Yes.

Once again, appreciate all your great advice.

I would make sure you get an AC Delco filter with an AC Delco seal for the filter. I got a Wix and the seal was garbage. Had to call around to several GM dealers before I found one with a seal in stock. I was in the middle of the job and it was a PITA. The Delco seal fit perfectly once i got it.

I think I got the Wix, good info.

the owner's manuals and shop manuals have long advised that the transmission
oil be renewed every 30k.

there is anticdotal chatter on the internet suggesting that renewing the fluid will
kill a way-past-due transmission.

the theory is that the sludge and loose metal particles somehow hold the transmission together.
that's hard to believe.
it cannot be good for a transmission to operate with worn-out-fluid and a dirty filter.

whenever i remove the pan from a transmisssion, i drill a .25 hole and install a drain plug.
when that is unscrewed, the riviera will drain approx 5 quarts if left overnight.

dextron 6 is backward compatable but the cost is excessive at $8 per quart.
advance auto has reqular sales for castrol dextron VI at half price.

Thank you great info.

Once you change fluid to Dex VI you'll wonder why you did not do it sooner.

BTW, *Never* change back from VI to III.

I always wonder - who the hell invented the word "Dexron"? Because literally everybody says "Dextron", it's just natural to pronounce this word with "t". Being more or less educated person, I pronounce it "Dexron", but every time I feel like I'm abusing my intelligence or some fundamental law of nature )

I think Ford calls it Mercon.

DeepFrozen wrote:

I always wonder - who the hell invented the word "Dexron"? Because literally everybody says "Dextron", it's just natural to pronounce this word with "t". Being more or less educated person, I pronounce it "Dexron", but every time I feel like I'm abusing my intelligence or some fundamental law of nature )

Umm... no. Your experience with "Dextron" is almost certainly either a regional (people in general around your area) or social (people you want to or have to be around) epenthesis. Dexron's been around in one form or another since 1967.

Hmm. Never thought about it. You're right, maybe it is natural to some foreigners to pronounce Dexron with "t". It is to me )

Lmck3 wrote:

the owner's manuals and shop manuals have long advised that the transmission
oil be renewed every 30k.

there is anticdotal chatter on the internet suggesting that renewing the fluid will
kill a way-past-due transmission.

the theory is that the sludge and loose metal particles somehow hold the transmission together.
that's hard to believe.
it cannot be good for a transmission to operate with worn-out-fluid and a dirty filter.

whenever i remove the pan from a transmisssion, i drill a .25 hole and install a drain plug.
when that is unscrewed, the riviera will drain approx 5 quarts if left overnight.

dextron 6 is backward compatable but the cost is excessive at $8 per quart.
advance auto has reqular sales for castrol dextron VI at half price.

Lance you are correct in that it seems counter intuitive that changing/flushing the fluid on an older trans could cause failure of the trans.

If your just dropping the pan and replacing the filter and the 6 quarts of fluid that you removed then you shouldn't have any trans issues on an older trans that you don't have the history on. Or even a vehicle that you purchased new and have been doing the pan drop and filter change on a periodic basis.

The problems happen when you buy a used vehicle with miles on it and you don't know the service history. Or you find the fluid to be dark and possibly smelling bad. Then you if you have a proper flush done, the type of flush where a machine is hooked up to the transmission fluid lines and fresh fluid is sent into the trans under pressure and the old fluid expended into the machines recovery tank.

I have seen and experienced vehicles with about 60K miles on the clock, with dark fluid and after being flushed exhibit various issues. i.e., shifting irregularities, shuddering,  and other issues that render the vehicle unable to drive. Ultimately leading to a tear down and rebuild.

As an example, when I bought my 98 Riv it had around 70K miles on it. Fluid was slightly dark but didn't have the burnt odor so I thought it was safe for a machine flush.
Well, I was wrong.
After the machine flush and a new filter installed it would feel like the front wheels were hopping off the ground when I tried to accelerate into traffic from a stopped position.
Shifted OK once up to speed but the shuddering and wheel hopping felt catastrophic. It was bad.

I ended up having to have the trans rebuild for about $1600.00 plus the cost of new mounts and brake lines while the trans was out.
The explanation from the rebuilder, a GM tech friend of mine, was that there is a varnish buildup in the various ports where shuttle valves and check balls operate. Once the varnish is removed during the power flush then the clearances between the bores in the aluminum valve body and diameter of the shuttle valves/spools increases causing fluid leakage between the two and wreaks havoc on the proper operation of the trans.
During rebuild, rather than replacing the valve body with a new one he used an aftermarket steel sleeve to install into the bore(s) after boring the hole(s) out and installing a new spool valve, thus preventing any fluid leakage internally. Also re-seating the areas for the various check balls.

These parts were not available through GM but only the aftermarket. As a GM Tech he was not supposed to use any aftermarket parts but he did as long as the vehicle wasn't under warranty and or it was for a friend.

I bought my Riviera with 86,000 miles on it. Fluid looked good, but I changed it anyway. Just dropped the pan, R&R the filter and refilled. I have continued to do that every 20,000 miles. My Riv now has almost 200,000 miles on the original transmission which continues to shift flawlessly. My last 3 changes have been with Valvoline Dex 6.

LARRY70GS wrote:

I bought my Riviera with 86,000 miles on it.  Fluid looked good, but I changed it anyway.  Just dropped the pan, R&R the filter and refilled.  I have continued to do that every 20,000 miles.  My Riv now has almost 200,000 miles on the original transmission which continues to shift flawlessly.  My last 3 changes have been with Valvoline Dex 6.

Hey Larry,
The key to your success was to just drop the pan and the 5 to 6 quarts that come out with it and the filter replacement.
Plus the fact that you've been repeating the process every 20K miles or so.

This is the best way to keep a used trans in good shape and not have a failure.

I made the mistake of power flushing mine even though I knew it could/would cause problems.

Rick

Rickw wrote:

LARRY70GS wrote:

I bought my Riviera with 86,000 miles on it.  Fluid looked good, but I changed it anyway.  Just dropped the pan, R&R the filter and refilled.  I have continued to do that every 20,000 miles.  My Riv now has almost 200,000 miles on the original transmission which continues to shift flawlessly.  My last 3 changes have been with Valvoline Dex 6.

Hey Larry,
The key to your success was to just drop the pan and the 5 to 6 quarts that come out with it and the filter replacement.
Plus the fact that you've been repeating the process every 20K miles or so.

This is the best way to keep a used trans in good shape and not have a failure.

I made the mistake of power flushing mine even though I knew it could/would cause problems.

Rick

I agree Rick, not the first time I have heard that about flushing a used transmission.