trans fluid-flush it or change it.

Dealership charges $200 to simply flush trans fluid-no filter change. Other shops say just flushing is the same as changing your motor oil without changing the filter. It does seem in the case of your tansmision that once you crack open the pan you risk developing leaks. The dealership mentioned that the filter is just a metal screen and flushing the fluid is fine. If this is the case, is it better to go to a Terrible-Herbst and have them do it for a hell of a lot cheaper? I have a 2001 Rodeo.

I haven't figured out why but a lot of people with later model Rodeos strongly recommend that you never flush the transmission. Somehow it can cause problems eventually leading to transmission failure.

But, you are right, transmission pans can be difficult to re-seal because fluid keeps on dripping down onto the sealing surface. I'm not sure what the solution is here.

If you're over 40k miles and you've never flushed it before do NOT start flushing it now....the problem is, once that atf fluid gets dirty and you flush the fluid thru the transmission, you risk loosening up crud and relodging it somewhere else which can cause major failure.

Not only that, but if you're over 60k miles especially with no previous atf fluid swaps, and you do a flush, a complete new amount of ATF can actually cause more harm then good. Sometimes the older fluid can be holding the tranny together.

I WOULD definitely find some place to drop the pan, change the filter, it IS very important on this transmission, and replace 5-6qts of fluid.

FWIW Here is an excerpt from an article I found on the web awhile back that discusses the myths and truths of flushing a transmission. The link where the excerpt came from follows the article.


The myths of the Deadly Trans Flush:
This is one subject that leaves a lot of people in mistrust, doubt, wrongful information and a bitter feeling when mentioned. First of all let me clarify what a transmission flush REALLY does since it is very commonly misunderstood. A transmission fluid flush machine does nothing more than hook up in line with your transmission cooler. One line hooks up to the supply coming from the trans and the other line hooks back up to the return side, which is in series with the cooler. This IN NO WAY flushes the inside of the transmission! All it does is take the old fluid from the transmission side out and replace what goes back in with fresh new fluid. There is no magic wand that crawls inside the transmission and pressure washes anything to disturb particles and gunk buildup. The transmission fluid flush machine has a bladder inside that transfers existing pressure that comes out of the transmission, roughly 10-40 psi, and passes it along to the opposite side of the bladder containing new fluid to properly displace the same amount that came out. NOW with that said here are some problems. I have seen many times where a shop did a flush and NEVER checked the trans fluid before OR after the flush! I have found cars up to 4 quarts low on fluid because of this neglect and leaving the customer stranded with a burned up transmission. It is more of a user or operater problem than the machines fault, its just putting back in what came out.... or is supposed to. During transmission fluid flushes there is also an additive that commonly is added before the flush to help clean the inside of the trans and can be harsh if the transmission has been very neglected over its life. After a transmission ages, and the fluid ages respectively, things chemically change inside the trans as far as friction materials and the adhesives on them. If you never change your trans fluid and it has very high mileage on it or is severly burnt then NEVER expect a flush to magically cure problems or expect new fresh fluid with strong detergents not to cause problems. It is a shock to the transmission to remove all of the old well past due fluid with all new fluid and the new fluid with its fresh strong detergents can break down the friction materials and adhesives that bond them to the clutch plates. On a vehicle with higher mileage and an unknown past it is always much safer to drop the pan and change the fluid and filter, that way you are giving the fluid a chance to slowly adapt, new with old and not be such a chemical shock to everything. Again checking the fluid level is a MUST! Neglect is the biggest problem with transmissions and making sure the fluid level is full and periodically serviced is the best you can do for it. Another problem is that new transmission fluid has friction modifiers in it and tend to keep shifts smooth. A lot of times if you change trans fluid that is old and burnt with new fluid it will feel like it is shifting softer, that is because the fluid is doing its job again. Fortunately on computer controlled transmission this can be troublesome since the pcm controls shift timing and now has to play catchup to firm up shifts because it has been softening them up over time. Not a common occurance but again neglect will only lead to worst case scenarios. I have nothing wrong with flush machines IF used properly and not used on a trans that is just plain worn out, again it is not a solution fix all, it is maintenance pure and simple and if neglected too long then only time will tell longevity of the trans. I hope this clears up some of the confusion and mislead information that has been floating around for years. I have NEVER seen a flush machine cause a failure, I HAVE seen an operater of a flush machine cause a failure.

Link: http://www.tripleedgeperformance.com/4T65E_Transmission_Info.html

Do as you wish....I've gotten all of my information from a long time Isuzu specialist mechanic who's worked on these tranny's for years. He highly recommends to not flush any GM transmission; he sees more harm then good come out of it.

Like I said, it's not a matter of any type of pressure, it's a matter of literally getting rid of all the old fluid that could be holding the transmission together. Too much new fluid on a tranny that has NOT seen regular ATF fluid swaps (i.e. every 25k miles) is NOT a good thing.

And, fwiw, I've only ever once done ONE flush at 30k miles, all other maintenance has simply been with drain/refills, I now have nearly 200k flawless miles on my transmission.

I flushed mine at 30 and 60 and at 90 and had the pan dropped and the filter replaced.

From here on out will will probably do drain and refills every 10k.

what kind of fluid is needed for a filter change and how much...is mercon 4 the correct fluid?

No, Dextron-III. The 4L30-E is a GM tranny, not Ford.

The 4L30-E tranny holds about 9.1 qt. total, but it is difficult to get it all out of the torque converter unless you disconnect the cooler hoses & let it pump it all out itself.

I added about 5-6 qt. just by draining both pans & replacing the filter. Of course, that leaves the torque converter loaded with the rest of the charge of old fluid.

so i need to remove both pans and put a new gasket on each? I bought a filter from oreillys auto, and it comes with a gasket but i did not get one for the small pan. I think i have one somewhere from when i thought it was leaking, but it turned out to be the accumulator piston. Can the flud swap be done without removing the small pan?

so i need to remove both pans and put a new gasket on each? I bought a filter from oreillys auto, and it comes with a gasket but i did not get one for the small pan. I think i have one somewhere from when i thought it was leaking, but it turned out to be the accumulator piston. Can the flud swap be done without removing the small pan?

Certianly! But you will get about 3/4 of a quart less of the old fluid out than you would if you pull both pans. Plus, when I did mine for the first time (at 95K miles) there was considerably more sludge in the adapter (smaller) pan than in the large main pan. But really, there was not much sludge in either. The gasket for the adapter pan is separate, & does not come with the main filter/gasket set.

Just pulling the main pan & changing the filter + 4-5 qts of fluid will certianly help.

Couple of questions. Is there any benefit to draining the trans fluid and refilling it without changing the filter. Also, I'm confused on where you refill the fluid. I have a container the same as my brake and power steering fluid containers marked ATF right on top of the engine, but it seems I remember seeing a picture of a couple of plugs down below where the refill is done. Sorry about the naivity but I dont want to make any mistakes in refilling.