Transmission Flush not recommended for 850's

[jblackburn]

I think once you do a couple drain and fills you can graduate to a full out flush. At that point, you don't really even need to drain the pan again, just pull off the radiator hose and flush 12 qts through it. You'll be amazed at how long it pumps out dirty fluid, even after 2 years mine was pretty dirty

If you have a turbo, or do a lot of hill-climbing or demanding driving, I highly reccomend the Mobil-1 fluid. It smells AWFUL if you spill it but it works great.

[volvomileage]

sorry ...i ment drain and fill for mine ...

[IVIUSTANG]

Not an old wives tale. Using synthetic in a high mileage trans that hasn't been serviced will usually deteriorate the seals and clutches

I can't speak for the clutches deteriorating; but modern synthetics will NOT harm seals. This used to be a problem when synthetic was an innovation, but they soon realized that synthetic requires countermeasures to not shrink seals; nearly all of the manufacturers have taken the proper chemical steps.

- Jesse

[shiloh51933]

I got a 96 GLt wit 90 thou on it and I'm doin' drain n' fill with one bottle of Lucas Tranny Treatment and synthetic
tranny fluid since that's what she's always had. I would never flush a tranny unless I definately know her history cause
who knows what you can disturb internally

Engines and transmissions get gunky buildup in them which can be loosened by flushes. This may sound like a good thing, but it's an incredibly bad thing when some of those gunky deposits don't flush out, and they basically move around and clog things up even worse than they were just being left alone in there.

I

[marginal]

I did the drain & fill using (as suggested by a mechanic from Volvo) CASTROL ATF+4.
Now it shifts rough but not much.
Next, I am going to do another drain & fill, but before that, I'll add the Sea Foam Trans - Tune ...

[polskamafia mjl]

Not an old wives tale. Using synthetic in a high mileage trans that hasn't been serviced will usually deteriorate the seals and clutches

I can't speak for the clutches deteriorating; but modern synthetics will NOT harm seals. This used to be a problem when synthetic was an innovation, but they soon realized that synthetic requires countermeasures to not shrink seals; nearly all of the manufacturers have taken the proper chemical steps.

- Jesse

+Infinity

[mdempst_79]

My 97 850 had over 400,000km on the tranny when I did a drain & refill a few times. The fluid was not burnt at all (non-turbo) but you could tell there was quite a bit of metallic content in the fluid. When I drained it and looked at the pan it had a metallic look to the fluid, and it looked like candy-apple paint. Trans is still working fine now 20,000km later. I honestly think this trans will outlast the engine. My V70T-5 tranny went out @ 270,000km (diff broke).

Drain & refill every oil change and your car will last a long time.

Mark

[FastLane]

Well, there are differences. I think Jesse and Mark are right on. OK, not doing the transmission every oil change, but certainly staying on top of it. Transmissions are much better 'sealed' than an engine, and don't have openings and blow by to contaminate them, so they need a lot less service over their lives.

Draining and filling a transmission isn't bad. If your car holds 8 quarts, and you can drain 4, such as my S40, you can get 50% of the fluid out in one drain and fill. I would not think at any time fresh fluid would cause a transmission to fail. Kinda defeats the purpose of changing the oil in the first place... I would be more leary of the process than the fluid.

On my MY00 S40 last fall, with 90k, I drained it, topped it off, drove it until the next weekend and did it again. That got the fluid pretty well cleaned up after a few weekends. And, it had not been done by the last owner, per the silly "sealed for life" crap they were doing ten years ago. In theory, fluid goes from 50% clean to 75%, to 87.5%, 93.8% etc., right now I am at like 93% fresh ATF. I will also do that process once a year, which should more than stay ahead of the oil's deteriation and breaking down /aging processes. Of course it varies on what comes out, but I have a basic script that will calculate it.

I am not sure of the issue about synthetic. My S40 calls for Dexron II/III, its from just before the 3309 cars came out. 30 years ago, there were problems with seals, etc. not reacting well to the synthetics. But back then, the seals relied on components in oils to keep them "wet" and swollen/pliable. In the last 15-20 years, the explosion of synthetics and people understanding their benefits, as well as factory specs, have forced manufacturers to make seals and gaskets capable of handling all types of oils. Even though it specs a synthetic, a lot of people (Dealers!!) will cut corners and still use dino oil.

I am not exactly sure about the varnish issues, whereas cleaning the inside of the trans causes any varnish to break down leading to leaks, catastrophic failures, etc. Were that the case, I would be nervous with Type-F, as it is has a lot more detergent, that might cause problems. I am wondering if some of the afore mentioned issues were from the flushing itself.

I can see issues with power flushing, such as forcing fluid through valves the wrong way, pushing 'dirty' fluid back into bearings, or blowing out filters, seals, etc. But I imagine a lot of the yocals doing flushes are not aware of the consequences of ramming fluids backwards through the valvebodies and bearings, filters, etc. I have taken apart transmissions with 150k plus on them and they looked factory new in terms of the fluid deposits. They had wear, but weren't varnished at all.

Clean fluid would have better additive properties (seal conditioners?), less microscopic crap in it, things like that, but I don't get how it ruins a gear box.

Anyhow, I am enjoying lurking here and decided to post. Looking forward to hearing back.

Mark

[polskamafia mjl]

Welcome to MVS and thanks for posting! I've never taken a tranny apart so I can't give any opinion on that but I do agree with your post.

[FastLane]

Thanks. Well, I am not sure about everything going on here, but it made sense to me.