Transmission Flush, panacea or poison?

[Grif]

Had my VX in the tranny shop recently, and he fixed me up good, runs great, smoother than it ever has. However in our discussions he stated he is not a fan of doing a "flush" on a transmission with an unknown service history.

His reasoning is that if the tranny has been neglected for so long that doing a flush and fill with all new fluid will break up any tarnishing that has built up over the years, loosening things up and causing more problems. His take on it was that a full fluid replace introduces so much new detergent into the system that it can make things worse.

He stated that he has seen it so many times on our sealed systems that he does not recommend it unless it has been known to be done at regular service intervals. He stated that doing a full drain and fill on a transmission of unknown internal condition is likely to DECREASE its working lifetime and often require a re-build or replacement sooner than otherwise. The service interval for our transmission (drain and replace fluid and filter(s)) as I recall is at approx 55K miles. Mine has just over 110k. I have no record of the PO having the trans serviced at all tho the records are spotty.

Furthermore, he stated that the whole concept of a "backflush" which I interpret as flushing out the fluid and debris via reversing its flow for a short period is a complete falsehood. He stated that the valves in the txmission are not designed to allow a backward flow (seems logical to me!) and that the mechanics who say they will perform a backflow are selling snake oil. Yes, they can push it back thru a bit, but never thru the entire system. And again his concern is by backflushing even a bit you would just be re-introducing particulates right back where they came from which would accelerate wear.

That is his position on the subject, I look forward to comments.

As for the mechanic himself, he lives, eats and breathes transmissions. Its all he does. He has worked on Troopers and Rodeos extensively and more than one VX. And if indeed his advice was correct he just lost money. For if he had flushed it out like I asked which would in his mind precipitate a sooner than later overhaul, then he just shot himself in the foot profit wise.

As it was he just checked for leaks, topped off the fluid which was really low for some odd reason, (there were no leaks). And sent me on my way for 10 bucks. I tipped him a 20 spot since we sat and chatted so long taking up his valuable in-shop time.

What say you all?

[VX KAT]

Wow, does sound honest....that's so refreshing...but oh too rare! I gotta believe when a mechanic is talking you out of work (and i.e. his money/profit) he's just gotta be honest.

Did he give any thoughts about doing 2 complete flushes within a pretty short period...wouldn't that catch a lot of the particulate matter that will be loosened by the detergents?

[Grif]

Did he give any thoughts about doing 2 complete flushes within a pretty short period...wouldn't that catch a lot of the particulate matter that will be loosened by the detergents?

I did not ask that, and though your suggestion sounds valid my impression was he was concerned the new fluid would have stronger concentrations of detergents and would break up any "varnishing" (ok we are getting into high temperature polymer science here) that has accumulated on the valves and gearing thus loosening the up tolerances inside causing even more problems in the near future.

Good question tho, and I'll ask him. Thanks!

To clarify, the particulates are not the only concern. Its the buildup of layers of varnish (very long string hydrocarbons formed under extreme temps) on the internal components. Once those layers are removed, everything would chatter around more.

[VXR]

I did a lot if research on this and decided not to do a flush (for some of the reasons you stated) but I did do a drain, refill and filter @ 30k with Mobil 1 ATF because I thought it may stand up to the heat better.

[VX KAT]

Sounds like a "flush" is different than a "drain & refill"...can somebody explain the difference to me? I had my tranny fluid changed at about 68k...I know he changed the filter and refilled it with Royal Purple Max ATF synth I picked up, then I had it done again about 2 months later. Is this considered a flush or drain/refill?

[Marlin]

For what its worth, I had a flush done on mine at the Isuzu dealership, tranny failed 3K miles later. Only took them 45 min to do the flush, and the truck was cold when they gave it back. That means they didn't follow the procedure, which says upon filling, it has to be running, and you shift through the gears and refill as you go along. Lesson learned, too bad the dealership closed up not long after Zu bailed on us.

[Grif]

Sounds like a "flush" is different than a "drain & refill"...can somebody explain the difference to me?

For the purposes of my original post I was using the terms pretty interchangeably, however some may consider the "backflush" procedure a flush as opposed to a drain and refill. The txmission guy didn't like either idea due to the issues described.

[VX1032]

nothing wrong with doing a drain and refill when there is no previous maintenace history. It won't hurt the tranny. The flush is better, but if you don't know the history don't do it. I flush mine but I have been doing that since I got it at 29K. It has been flushed 3 times and only havs 54k on it now, a little excessive, but I know the history.

With a flush you disconnect the trans line to the cooler, and hook it up to a michine that pushes the fluid under pressure through the entire system. AT that point you can see the change in tranny fluid in the machine as the fluid changes color from the black that it is to the red of the new fluid. Typically the flush takes a tad more fluid than the specs for the trans due to the overlap in fluid.

A drain and refill, is just that. You drain the fluid out of the trans and then refill it. All the fluid is not taken out because of the fluid in the lines and residual in the tranny. Since there is no pressure, the risk of taking anything out that has been varnished on is limited and you should not get the chunks floating around in the valve body.

You need to change the fluid on our trannys due to the breakdown of the fluid, escpcially with the heat our trannys can generate, and heat kills.

If the flush isn't done every 30K, I would never do one, drain and refills are fine.

[Diogenes]

Good thread guys! I just had my tranny flushed and had them drop the pan to inspect for metal..

Question I should ask.. Isn't it generally expected to find very fine particles of metal in the bottom of the pan due to normal wear and tear?

I'm still questioning the credibility of the shop that did my service, since I'm new to the Boise area. The mechanic claims that the amount of metal flakes I had in my pan was excessive. But then again, he had also told me that the ATF levels were good before he dropped the pan and that the fluid looked good. The residue he showed me after dropping the pan was pretty damn black. So I'm wondering if he showed me particles from someone else's transmission.. ;0) I wasn't present for the inspection. However, had the Tranny refilled about 4K miles ago and there were no signs of metal.

My gut tells me they were far too ready to get me to invest in a complete rebuild, even though I'm not detecting any physical signs of slippage. And given the amounts of money involved, as well as proclivity for false sensor readings, I'm a bit dubious of many transmission mechanics recommending repairs that are not necessary.

I'm still under the belief that I was generating a false positive on my P1870 code. So I'm wondering how quickly that code will pop up again after the flush/replacement.

Still trying to find out if transmissions from Troopers or Rodeos/passports are interchangeable with VXs..

Dio

[Marlin]

Still trying to find out if transmissions from Troopers or Rodeos/passports are interchangeable with VXs..

Dio

Yes, my 4l30E came out of a Trooper. If you are going to spend the money, you should get the 4l60E, direct bolt in, and a much stronger tranny. Wish the insurance company would have okayed that for me, they said they wouldn't pay a dime if I did, even if I offered to pay the difference. Now that company went tits up, and I am waiting on the court date for the lawsuit. BOOOOOOOO!!!

If you aren't getting slippage, I would do nothing, what is the worst that could happen, you have to get the tranny rebuilt? I paid 900ish for mine, shipped, with a 3 year warranty.

[etlsport]

i agree with your mechanic.. at my shop we won't do a trans exchange on anything over 100k without documented service history or a waiver. i did my trans at 50k, 75k and 95k, with a few top offs in between

[VX1032]

You will always have metal in the bottom of the pan, how much, well, that is the question. The debris is what the flush gets out better than the drain and fill, limiting the build up.

The isuzu autos are mostly interchangeable. Their are a few not 4l30's on the 02 or 04 rodeos and axioms, I forget the year break, but the rest of the 2nd gen autos are 4l30's.

I think there is a computer issue with switching to a 4l60, but not positive about that. If it was a direct swap, a lot more people would be running them.

[Diogenes]

Thanks guys!! Yeah.. I took a bit of a road trip this afternoon and no problem with any slippage. Actually seemed to shift better, but could just be my imagination.. ;0)

Now I gotta figure out why I can't move the shifter from 3rd into 2nd or 1st. I suspect the button on the shifter isn't engaging, since it's not required for a shift from D to 3rd (according to the manual), but is required for shifting into 2nd or 1st.

Btw, I find it interesting that both of the tranny shops I talked to about substituting a non-Vehicross tranny told me that because the shaft was shorter, it would require major modification to bolt one on to a VX.

Are all Tranny mechanics morally challenged??... ;0)

Dio

[nfpgasmask]

I don't know about this "flush", but if you open your tranny and burnt chocolate comes out and you decide NOT to change the fluid/filter at that point, regardless of history, I think you are making a mistake.

Bad fluid is bad fluid.

Bart

[CowboyErik]

I did two tranny drains/flushs/fills within a short inverval; didn't see the filter catching anything; 99k, then 104k; changed filters of course, and used compressed air to blowout fluid from the intercooler, I took down both pans of course, and only used new gaskets the first time, reused gaskets 2nd time; my only mistake was not using a factory replacement drain plug, the autozone plug drips slightly if if the car sits a few days, not if I run it, because; I'm at 119.9k now and going to service all fluids again. LOVE MY VX!