Trans flushing? Who's a fan?

[ChallengerHK]

I had my oil changed the other day (nowhere to work on the car at home), and the tech wanted to sell me a trans flush. I have issues with this, but I wanted to get some other opinions.

I've had this done twice. Both times:

• It was hellaciously expensive
• The trans was operating fine when I went in
• It was within the manufactuer's spec for fluid replacement
• I had trans trouble almost immediately after the flush, once within days, once within hours 

My opinion is that the flush process kicks up sediment that will otherwise stay where it's at. OTOH, I realize that simply dropping the pan and draining the fluid leaves the old fluid in the converter.

What do you guys think?

[Chryco Psycho]

I religiously do oil & filter service on the vans I use for business , never flushed one though

[Cuda Cody]

We've had work vans flushed before and sometime they start shifting weird after.  I just drain, replace the filter and top off with new trans fluid now.  Never had any problems doing that way and I use synthetic fluid too.  We easily get 250,000 to 300,000 on the trans.   

[1 Wild R/T]

Definitely not a fan of flushing trans....Back in the early 90's I was shop foreman at a dealership that was considering buying flushing equipment, they had a salesman come out & demo the unit...  I gave my input which didn't mean much cause profit wins out over common sense every time at dealerships.....  They choose to flush the service managers personal vehicle.... Normally he drove a demo but brought in his personal car for free work.... The salesman did his demo, all the techs had to waste time watching... When the salesman left he left the demo unit so we could try it out.... Service writers looked like vultures circling customers looking to sell their new trans flush option.... Two days later the service mangers car came in on a hook... Trans had gotten smoked, debris in the valve body had stuck the 2-3 shuttle valve & it was dragging the intermediate clutch pack while the direct clutch pack was applied....
The salesman was back to get his machine the same day....

[RUNCHARGER]

Drain and filter for me. If you tear up a trans or convertor then you need to flush the lines and cooler when doing the rebuild.

[ChallengerHK]

Good info, and I think it supports my opinion pretty well. No flush for me 

[Bullitt-]

I've done my own "flush" twice.. the first time was on the '73, next was a 98 Dakota.. I dropped the pan & replaced filter then disconnected the output line from the radiator & attached a rubber hose to go into a bucket. Had a funnel & plenty of fluid on hand. Started the car & put in gear to run the pump & kept pouring in tranny fluid till it ran clean.  Cost me a extra gallon of fluid I suppose but I felt better afterwards... Don't know if it made a bit of difference to the transmissions 

[Jay Bee]

Thanks for bringing this up HK as my daily driver is nearing its mileage for transmission service. Pan drop, filter change and fluid top up for me now also.

[RUNCHARGER]

Wild Rt, I`m still laughing, thanks for that!

[Oldschool]

Two ways to look at it I suppose. We do both here at the shop. $199.95 for a full synthetic trans flush. There used to be issues with flushes because the flushing machine used it's own pump. This pump was designed to get the job done faster than using the transmissions own pump. This faster rate and pressure did stir up sediment and cause problems in higher mileage transmissions. Nowdays the flushing machines just hook into the cooling lines and use the trans pump which pumps the pressure and velocity as it always has - thus no sediment kicked up. That way, you replace ALL the fluid. It is slower and takes more time, but so far I have never seen a flush cause any issues. Ideally you would do a flush and then change the filter. That way you have a new filter and all new fluid.  0.02....

[71GranCoupe]

I was strapped for time and my truck needed an oil change and went in to get it done for like $39.99. Service guy comes back and says the truck looks to be in real good condition, but showed me the color of the trans oil. It was pale and he recommended a flush and would give me the oil change for free, so thought why not. Drove it the next two days like 1200 miles, no problems at all, but now the above comments may have me reconsider. 

[Burdar]

Nowdays the flushing machines just hook into the cooling lines and use the trans pump which pumps the pressure and velocity as it always has - thus no sediment kicked up.

If the flush isn't getting rid of the sediment in the system, what good is the flush?  I thought that was the whole point? 

[dougdel]

easy gimmick for lube shops, why change the fluid if you don't change to filter.  I can see flush and fill on brake fluid and power steering fluid, but stirring up the trans case and the potential of pushing metal shavings through the system, to me its a no no 

[Bills Auto Works]

  Definitely not a fan of a tranny flush for all the reasons posted previously...Unless of course you are talking about flushing this tranny! LOL

[Oldschool]

Nowdays the flushing machines just hook into the cooling lines and use the trans pump which pumps the pressure and velocity as it always has - thus no sediment kicked up.

If the flush isn't getting rid of the sediment in the system, what good is the flush?  I thought that was the whole point? 

The sediment I am referring to is pretty much settled in the and isn't going anywhere. No need to move it around, thus the trans pump is used. If you do a fluid/filter change, you would clean the sediment out of the pan. The big deal to the flush is the ability to replace ALL of the fluid: transmission, transmission cooler, transmission cooler lines, torque converter. A fluid and filter change only replaces what is in the trans pan. A fluid/filter deal only exchanges 1/4-1/3 of the total volume of fluid - a lot of used/dirty fluid is left in the system...