Change transmission fluid or not?

And I "KNOW!!!!!!!" walking down the street can get you hit by a city bus.

DS

Say, John, have you ever -- ever in your life -- given advice on something that did not lie within the field in which you work to pay your bills?

Yes, of course you have. So now's the part where you shut in the direction of "up".

DS

Then one of two things happened:

1) The transmission was already dead to the point that the pump couldn't pick up fluid once air got in the line (would you want to continue driving something like that?) 2) The shop screwed up the filter installation and got a rebuild job out of your friend.

New fluid doesn't damage transmissions. PERIOD.

Rick Bla> I've seen it happen. A guy I know took his truck (old Ramcharger 727) to

I've heard that, and I don't buy it. The filter catches the shed clutch material, which is why its so important to keep it clean. If it starts restricting oil pressure, its guaranteed that the clutches will slip. ESPECIALLY in Chrysler transmissions and others that use dacron filters instead of just fine mesh like some automatics use.

The clutches are stacks of disks, alternating between disks that have friction material on both sides, and disks that are bare metal. The friction disks have splines on their inner circumferencs so they can slide lengthwise on a splined drum but must rotate with the drum, and the metal plates have tangs around their outer circumference so that they are driven by a shell that they ride within. A piston in the end of the drum-inside-a-shell pushes the stack of plates together to squeeze them hard enough that the shell drives the steel plates, the steel plates drive the friction plates, and the friction plates turn the splined drum. The piston travel is limited such that if you stripped ALL the friction material off, it wouldn't be able to squeeze the plates together all the way. There HAS to be friction material present, or the clutch wont work whether the fluid is clean or not.. Do you seriously believe that a clutch made that way would somehow work in dirty fluid but not in clean fluid? Forget it.

How do you know it wasn't simply coincidence and it was going to die at that time anyway? And a normal fluid change only changes about half the fluid anyway so there would still be lots of old fluid and debris still in there. And, the new fluid wouldn't get circulated through all of the clutches instantly anyway, so the tranny wouldn't fail when it was first put in gear if it was the new fluid. It would slowly fail as the fluid was circulated.

Next attempt...

Matt

Yes, this is obvious.

, just a guy whose seen a thing or three. What was explained

Anything that reduces future wear will extend the life of the transmission. If not changing the oil doesn't extend the life, then why ever change oil in any transmission? Or engine for that matter. Just drive it on the original oil until it dies.

Matt

Naw, you haven't. You've heard what a "guy you know" said a transmission mechanic told him. Not the same at all.

DS

Actually Dan ol' boy, I was there. Anyway, I was just relating an experience I've had whether you believe it or not I care not.

You're right it was an old transmission on it's last legs for sure. The point is it was working before the fluid change and not after. Draw your own conclusions. The shop in question was not a transmission shop, though they are capable mechanics and did not (to my knowledge screw up the filter install. Which is not difficult anyway).

Isn't it amazing that you know all about the original posters transmission EVEN THOUGH he didn't even post WHAT KIND IT IS!?!?!?!?!!!

Sheesh!

The original poster almost certainly does not have a A604 4 speed Ultradrive computer controlled transmission from 1992 with 100,000 miles on it!!! The people all posting the need for frequent fluid changes are right on the mark if it was a 4 speed Ultradrive. But if it's the 3 speed I can well believe that it has gone 100,000 miles on the original fluid.

However, if it is the 3 speed then is has transmission bands that wear and need adjustment. To do this means dropping the pan and losing the fluid so he has to do a fluid change anyway. Band adjustment is recommended by Chrysler in these transmissions long before 100,000 miles.

John you don't sound like you own either the Chrysler 3 speed or the 4 speed transmission, so kindly shut the hell up. You don't know what your talking about.

A 4 speed Ultradrive from 1992 that is original was shipped with a trans computer with incorrect programming that make it wear out prematurely. So if it is really a

4 speed that by some miracle is still going after no service whatsover, it's about shot. If you don't believe me refer to the Chrysler transmission shop publication which detail the TSBs that discusses this.

If the OP has a 3 speed he needs to get it serviced pronto. If he has a 4 speed then he might as well save his money - the trans is walking dead right now, and it going to take a crap within the next 20,000 miles and need to be rebuilt. A fluid change now on it would be a waste of money, it should have had a new trans computer installed a decade ago.

Ted

Ever disassembled a valve body? It's full of the fine powder residue of worn clucthes/bands; passes right through the filter.

Nice theory but I've disassembled many a trans where the friction discs are worn metal-to-metal and the trans still worked just fine. As long as the rubber piston seals will still hold pressure, there IS sufficient piston travel to apply the worn clutch discs. John

Indubitably, but I try to have some knowledge on the subject; you should try the same philosophy.

Upper U.S. John

Thank You Matt. I think that should be the final posting in this thread. This could go on forever. Ladies and gentlemen of the jury, the information is on the table.

Doesn't matter whether it is a high miler or not. I'm an engineer, licensed in NYS. You can look me up on the NYS professional registry.

Matt

A couple, but it has been a long time ago. Yes, they had a film of very fine residue, but the residue was so fine you couldn't even say it was particulate in nature. Looked like a thin film coating and it wiped off easily.

I'd be very surprised if it worked just fine if they are all worn metal-to-metal, assuming they weren't metal friction disks to begin with. A disc or two in the pack won't make night or day difference, although under heavy torque you'd be susceptible to slippage. I'm fairly familiar with multi-plate clutches from both motorcycles I've owned an maintained over the years and also heavy equipment I worked on in my prior life (JD dozers mainly). While they are very robust and will take a lot of abuse, they are also very well engineered to work with certain oils and certain friction from the friction material. If the friction material is completely gone, your coefficient of friction is going to be quite different and slippage is almost guaranteed under any significant amount of torque. The proverbial little old lady who drives at 25% throttle or less might not have a problem, but the transmission certainly wouldn't work as it was designed to work (full torque range, shift characeristics, etc.).

As I said, the last car automatic I had apart was long ago (late 70s), so I don't know the precise details of the newer trannies, but the clutches in motorcycles and other equipment have a wide range of designs. I had a 100cc motorcycle where the friction plates were entirely made of a composite material, including the tabs that engaged the clutch basket. The biggest failure mode here were the tabs shearing. My current motorcycle, a 1200cc touring bike, has all metal plates with friction material on the metal plates that engage the basket. Many heavy duty clutches use bronze as the friction material, so these cluthes can't "wear down to metal" as they are metal to metal contact by design. So it may be possible you have seen a transmission that had all metal components to begin with and thus it would work just fine with metal-to-metal contact.

Matt

Finally. Now was that *really* so hard?

DS