To flush or not??

[dodger1]

Heard pros and cons regarding machine- flushing of auto trans. I understand the principle - get the max amount of fluid out in the minimum time with no mess. Some say however this will still leave residue behind, possibly disturb enough debris to cause issues even after fresh fluid is added. I spoke to a local one-man shop about this. His procedure is to drop and clean the pan after emptying the old fluid, change filter, then re-circulate the old fluid back through the trans and the machine's own large-capacity filter system until it appears clean in the sight glass. Only then is new fluid exchanged for old. I still have questions though - as in what happens to the old fluid still in the converter, for instance? Be interested in your thoughts.

[John Kunkel]

Fluid is constantly flowing through the converter so the fluid in there will eventually be replenished also.

[dodger1]

Where do these machines connect to the trans? One of the cooler lines?

[nhdriver]

What worries me about this procedure is will they use the correct fluid ? Late model Chrysler vehicles need type 4 fluid & a lot of places try to give you universal fluid with an additive. Maybe if a Chrysler or Dodge dealer does it, you will get the correct fluid. I would not let anyone do it unless I was assured that the correct fluid was being used.

[dodger1]

OK, did some more Googling. Seems some equipment connects at a cooler line (return?), other machines require the pan and filter to be dropped and I guess an adapter is used to hook it to the filtered fluid return ports. I see what you're saying, JK; the engine is run to use the trans pump to circulate. I also came across another opinion to the whole flushing idea - why not just drop the pan and filter yourself, clean and re-install, dump some new fluid in, and divert the cooler return line to a bucket. run the engine and keep adding fresh fluid until the return line flows clean oil. Wasting some ATF but saving the shop cost (est $125 in my case)
i think in my case I'll opt for the flush if the shop uses the internal pickup method. Cause it's getting cold and snowy here now. nhdriver, you bet I'll be sure that ATF4 is used!!

[John Kunkel]

Another DIY option is to disconnect the pressure line to the cooler and run the engine in Neutral to pump the old fluid into a bucket, as one quart of fluid is pumped into the bucket pour a fresh quart down the dipstick tube....repeat until the original capacity (about 11 quarts) has been cycled through.

This isn't as thorough as a flush but it's cheaper.

[chirorod]

ATF is a fantastic cleaner. So I'm not sure that a flush is really necessary. Just changing what's in the pan can make a huge difference. They stopped putting drain plugs in the torque convertors a long time ago, which opened the door for the expensive flush.

[c318cuin]

I used a boat oil change pump on my 05 PT GT (Bougth it for my Mercruiser engine in my boat with no oil plug in the pan).

http://www.westmarine.com/webapp/wcs...classNum=10440

Emptied the pan out no mess! Made the whole process easy.

I've never let one of those flush machines near my car. Watched the techs hook them up wrong, blow hoses, and drenched the car (not mine) with tranny fluid. So its drain and change the filter for me. Not the 100% best way but has worked for me.

[Duster_340]

In my opinion do not do a flush. Drop the pan and get most of it anyway. The risk is getting metal shavings from someone else's damaged tranny in your good tranny, spelling doom for your transmission.
Better just to drop the pan and do more frequent changes.

[rodsvolare]

My concern with the "flush" method is that if they just disconnect lines and flush and refill with new fluid, don't you still have a dirty filter??? Don't like that idea.

[John Kunkel]

There are two types of transmission flushing machines, the first type hooks to the cooler lines but the second more efficient type hooks to the pump inlet after the pan and filter have been removed.

[LDS3500]

Drop the pan change filter and add new fluid i never flush don't trust it as mentioned in prior threads.

[cudabob496]

use synthetic tranny fluid

[J-BODY]

Overhauled my 48RE and used it 10k. Dropped the pan to inspect, verified bands were ok, changed the filter..... been flushed every 30k since then. 80k on it now. Dropped the pan on it last week to replace the solenoids as fluid was leaking up through the connector. Looks like new in there, but put a new filter on since I was in there anyways. Old high mile trans you don't know the history on? Flushing can cause some issues there.

[dodger1]

Originally Posted by cudabob496

use synthetic tranny fluid

Not sure if that's acceptable replacement for ATF-4 (Chrysler spec for 99-04 frontdrivers) but the shop (SMR Trans) where I bought the overhaul kit for my 999 was very emphatic about NOT using synthetic in that trans. Dexron II or Mercon equiv. only.
Edit: I see that ATF+4 is in fact a Chrysler licenced and developed synthetic fluid. (source: Allpar)

[cudabob496]

Originally Posted by dodger1

Not sure if that's acceptable replacement for ATF-4 (Chrysler spec for 99-04 frontdrivers) but the shop (SMR Trans) where I bought the overhaul kit for my 999 was very emphatic about NOT using synthetic in that trans. Dexron II or Mercon equiv. only.
Edit: I see that ATF+4 is in fact a Chrysler licenced and developed synthetic fluid. (source: Allpar)

no problems in 10 years, and the tranny has 40,000 hard miles on it.
Be interesting to hear why not synthetic. Have it in my engine, tranny, and rearend,and its good for at least 20 rwhp!

[dodger1]

Originally Posted by cudabob496

no problems in 10 years, and the tranny has 40,000 hard miles on it.
Be interesting to hear why not synthetic. Have it in my engine, tranny, and rearend,and its good for at least 20 rwhp!

Good question. I didn't argue the point, since it was my 1st Torqueflite overhaul. The SMR site is : http://smrtrans.tripod.com/smrtransm...tro/index.html Want to run it by them?

[John Kunkel]

Not all synthetic fluids have the same friction characteristics, applied clutches/bands will slip sooner with the "slipperier" fluids.

[dodger1]

Originally Posted by John Kunkel

Not all synthetic fluids have the same friction characteristics, applied clutches/bands will slip sooner with the "slipperier" fluids.

Might SMR's Kevlar bands and clutches "like" conventional ATF better than synthetic, then? (I recall your prev. comment to me that Kevlar was not your personal choice of friction material)

[aarracer]

My Protrans does not use synthetic either.