What are your views on transmission power flushing. Can it help? My new Vette has 101,000 miles. Just got it and am thinking of getting a flush. It seems to shift pretty good, but not like my 88 roadster.

Any recommendations, yea or nay??? :eek:

 

By the way, the new (old) Vette is a 1993 40th, LT1, thanks for any info gang...

 

I had bad luck with the reverse flush. About 4-6 weeks after having it done my transmission cratered. The mechanic who rebuilt it for me said GMs should never be flushed. Just drop the pan, change filter and refill. If your worried about getting more of the fluid changed, just drop the pan and change the filter again after a couple of weeks.

The explanation from the mechanic was that the cleaning agents in the pressure flush tend to wreak havoc in a higher mileage transmission, breaking lose friction material and other stuff on the disks. Apparently, for Fords it's a good to pressure flush, but not such a good idea for GMs because of the difference in design.

 

what he said. if you want to replace all of the transmission fluid, just disconnect one of the transmission cooler lines that runs into the radiator and let it all pump out. i wouldnt do the pressure flush on a 100k mile transmission.

 

I have heard some horror stories (essentially just like above) about Powerflushing transmissions from forum members. I would just do pan and filter changes.

 

I guess you can call me LUCKY!! :blueangel:

I had mine power flushed @ 70K miles and the 700R4 is still running strong, knock on wood. :smash: Shortly after that I found this forum and heard the horror stories about power flushing. I recently serviced my trans in my van and just drained the fluid and changed the filter. I was taking no chances w/ the power flush b/c those darn Dodge trannys SUCK!! :yesnod:

-John

 

These are the first comments I've seen on the possible harm of a transmission flush. I'll have to keep tuned. I may be wrong, but I don't think that there is a lot of power in a power flush. Not more than the internal transmission pressures, is it? I had mine done (two doses a one time to eliminate water in the fluid) two years ago. After 15-20,000 miles and 300 or so quarter mile passes, no problems. As I see it, the advantage is that ALL the fluid gets chenged. The disadvantage is that the filter does NOT.


[Modified by CFI-EFI, 12:20 PM 11/27/2001]

 

There is just one other thing you have to concider. Most of the oil change places have yo-yo's as employees. If Mr. Yo-Yo decided to connect the power flusher the opposite direction you will have problems. I caught a Mr. Yo-Yo trying to connect the coolant flusher to my Vette the wrong way. He even argued with the manager saying WE were wrong! :rolleyes: That incident was the last b/c I have done most of my own work since.

-John

 

The good thing is I know the folks that run the service center. No Yo Yo's will touch the Vette. I had not heard about problems on 700R4 and flushing. All good stuff to know. I may just have the tranny pulled and serviced, and a shift kit put in. Thanks everyone for the help... :yesnod:

 

I think it's most dependant on the condition of the tranny before the flush. Does the fluid smell burnt? If so leave it alone and run it til it fails.

The theory is this: in a high mileage used hard tranny, clutch material is held in suspension and helps the clutchpacks clamp. In a situation where thos clutchpacks have a lot of material removed, and you replace the fluid with new fluid (and new detergents) the tranny loses the friction modifying abilities of the old fluid...the detergent breaks down the varnish in the galleries and you end up with one or two possible end results: clutches that won't grab or a tranny that won't shift as teh pistons in the valvebody don't move smoothly.

I'm my PERSONAL experience:

I purchased the sled with 78000 miles on it. The tranny was in an unknown state. I raced and ran the bejeezus out of it and at 85000 miles, it occurred to me to smell the fluid. :U Man was it burnt.

I asked the vettenet about serviceing it and a lot of the lore was: leave it alone (for the reasons above).

About this time, it started leaking out of the filler tube seal. I let it do that, refilling as necessary, until the fluid no longer looked and smelled burnt, then fixed the seal.

When I decised to take some of my Dot.Com earnings and pay off the car, (by now at about 112,000 miles) I also took out enough to rebuild the tranny. (Then the market tanked. WOO HOO! Free Corvette! :D )

The results of the rebuild? The 2/3 clutchpack was pretty burnt. The 1/4 clutchpacks looked pristene beautiful. The tranny probably had another 10,000 miles of life left. (it _was_ starting to get lazy on 3-4 upshifts, but nothing out of spec.)

So: Check your fluid. If it looks like the tranny's been maintained, just do a filter service. If it looks burnt, then drive it til it drops -- then make it better. :cool:

Oh, and don't pay $2200 for a rebuild. Find a Yoda type guy who doesn't care that it says Corvette. I lucked out and found a guy to pull, rebuild and harden and replace for $800. ;)


[Modified by RocketSled, 7:31 PM 11/27/2001]

 

The responces have made perfect sence... My own scenario was this... Bought my 88 coupe ( now sold ) with 23k... Did normal drain, filter and refill at 40K ( a little late ) Next 2 sevices ( 60K & 90K ) I drained, installed filter, then disconnected cooler line at radiator... opened 13 qts of fluid, dumped 6 quarts in... then had wife start car and let tranny pump push fluid out while filling with fluid on hand... I already connected a hose to the cooler line and so it could flow onto a white piece of paper ( supported by a small board and well lit ) ) before draining into a catch pan... You could see the fluid brighten up slightly when the cycle was complete... Just make sure you stay ahead of the pump when filling the trans... if you don't, you may burn the pump, and it will be terminal ! I kept the wife at the ignition to turn off the engine if I felt I was getting behind ( slow flow through tall funnel ) At 104K the trans was working well other than the 3rd gear to overdrive shift which was not as solid as it use to be... I would guessitmate that somewhere in the 120K+ it will need a rebuild... It gave me piece of mind knowing that the trans was flushed as near a 100% as I could do on my own. It beat paying someone $60 to $80 to do it for me...
Good Luck...
Ted
90 ZR-1 # 334
Sun City, CA

 

I agree with rocketsled. This is my expereince with GM Auto transmission, if the tranny fluid hasn't been regulary changed (I believe is the service interval is 30K miles) and the tranny has more than 50k miles don't touch it. My Corvette Tranny was changed at 56K miles for the first time @ 60K I need a full rebuild. You probably don't want to hear about my Syclone's 700R4.

 

Flushing will not remove any friction material from the disks that wasn't already loose. I was at a shop watching them flush a car. The good points of this machine flush are: 1)it changes all the fluid in your trans 2) you don't have to get under the car. The bad points are: 1)the trans filter is not replaced 2)one machine to do all the cusomers cars. Different cars require different types of trans fluid. Even if different fluid is added to the machine(which I doubt), there will still be some left in the plumbing from the last guy. I think that is the reason for people having their trans fail after a flush. :reddevil

 

I had my '87's flushed 2 months ago. I've had no problem at all with it. I've checked the level on the dipstick and it's correct. Mine was done at a local quick oil place called Greased Lightening. I've had work done there on my other cars and I've had no problem. Although, I elected to stay in the bay and watch. They did drop the pan (I know because the guy handed it to me pointing out a couple of dings where the car bottomed out. They replaced the filter (I bent down and watched them replace it-they have one of those drive over pits. They hooked up (I think) two (maybe more) hoses. They said all the fluid is forced out including what's in the torque converter. This took 20 minutes or so. They replaced the gasket(new) and the pan cover. And filled it. He said it called for 16 quarts but actually took 18½ quarts. I found this acceptable since a tranny mechanic once told me when you replace the filter, you will have to put more fluid in than anticipated because the filter will absorb some. As he was filling it he had me turn on the car and sit in it and slowly shift through all the gears. After a minute or so he would stop and check the dip stick. He kept doing this until the level was at full. I checked the level myself when I got home and several times since. It's perfect, right at the full line.
The fluid is a nice clean looking red color. My car had approx. 65,800 on it at the time it was done.

Bob

[Modified by Bob Hovey, 9:08 AM 11/28/2001]


[Modified by Bob Hovey, 9:11 AM 11/28/2001]


[Modified by Bob Hovey, 9:13 AM 11/28/2001]

 

The reason that the transmission slip after fluid changes is the worn out transmission fluid breaks down. The broken down fluid starts to change the chemical compound of the clutches and forms an interdependent bond between the fluid and bands/clutches. When the fluid is changed is clean off the bands and clutches and start to slip because semi mettallic material is different. The cleaning procudure take a little while, so the transmission usually doesn't initially slip. When the transmission is flushed via the line this cleaning is accellerated becuase there is less of the old fluid.