2004 C70 Cleaner Additive Before Trans Flush?

[landl4u2]

Recently purchased and fluid level was 1-1/2 qt over full blowing out and under-body was soaked. 2nd to 3rd shift was bumpy. After siphon of excess it shifts better... but not perfect. Am thinking someone didn't have an abundance of knowledge working on it. Fluid looks a little dark and would like to do a flush.

Appreciate thoughts as to adding some type of cleaner before flush.

[precopster]

There are treatments for transmissions to help them shift better however haven't heard of flushing fluids for transmissions. Because of the fact that you'll not be able to fully recover any fluids you pour in to a AW55-50SN transmission due to dilution I would stay away from any flushing fluids.

When you drain that transmission you only recover around 3.5 quarts. The capacity is 7.2 litres. To get 95% of the old fluid out you need to drain and fill 4 times due to the dilution factor.

[jimmy57]

ATF has great detergents but not aggressive like flush chemicals.
Do what Mike said and do drain n fills on the next 4 oil changes. You will effectively do a flush but with little risk of shocking the transmission.
Flushing a high mile trans carries a risk of dissolving build up that is making an age hardened rubber seal still seal. You dissolve the buildup instantly before the additives in fluid can soften the seals and the transmission will slip or fail to engage some gears. Drain and fill gets at the problem slowly but effectively.

[landl4u2]

Great responses and information... I thank you for them.

[landl4u2]

Do you think using the flush via trans fluid hose that attaches to radiator method would be more efficient, better than, same as, or less efficient than drain and flush 4 times? I don't know what brand and type fluid is in there now but wouldn't there be a question as to whether the new 3309 would be compatible with who-know-what? Thanks

[scot850]

If you have a 5 speed auto, chances are it is 3309 fluid. But check the handbook, or with the dealer. Some of the guys on here may be able to chime in on this.

I think the point made about just doing the drain and flush over a few oil changes is a good suggestion on an older tranny that you may not know when it was last (ever) done. Perhaps a couple of drain and flushes, followed by the full flush using the cooler line may be a safer way to go without shocking the seals and potentially blowing a seal.

Neil.

[oragex]

Do you think using the flush via trans fluid hose that attaches to radiator method would be more efficient, better than, same as, or less efficient than drain and flush 4 times? I don't know what brand and type fluid is in there now but wouldn't there be a question as to whether the new 3309 would be compatible with who-know-what? Thanks

Yes, it's more efficient as you are sure in the end all the fluid was flushed, and especially, I think it's a lot less work because you are doing it only once. It is recommended to replace the clip and the o-rings at the line. However, if this is the first fluid change in the history of the vehicle, like all others said, 3-4 drains at a few weeks interval is the safest choice. And, at the end, a software update with the 'new fluid' setting is needed.

[landl4u2]

Seems like good info and advise. Will start with a couple of drain (3 qts) and replace then full flush in about 4-6 months.
Thanks