D3AeighT

Since tranny oil and filter change, no more torque converter "thunking" every now and then at highway speeds as tranny tries to find 4th or 5th ( I guess that would be the proper description ).

PaulW

I tried dropping my tranny out on the highway again the other day, was at perfect conditions for it, it does drop maybe 250 RPM, but that's it, and no thump in the drive train at all!

I think the oil change and filter are so critical to the life of the tranny.

I got the results back from ScotD's oil analysis, nothing looked really bad, as compared to JimR's A6 or A8-GTI's analysis, it actually looked better.....weird, I know. That probably confirms that the dealer did change the oil six months prior.

There has to be some kind of wear component in the tranny that causes some kind of wear. I'm wondering if it:

1. Clogs up the filter and causes too much pressure drop to the hydraulic pump, causing it to cavitate and make the loud noise (I think we know if can do that).

2. Clogs up the hydraulic passagways with foreign material, and maybe that is what is causing the torque converter to drop out. After changing the oil/filter, maybe it clears up with time. Bringing my car to Grattan sure had the tranny going full speed ahead for a while, high temps, plus probably high pressures, maybe it dislodged some material? There are hydraulic passageways all over the tranny.

I'm thinking after the car has 50,000 miles, the tranny needs its oil and filter changed once a year for two years. Maybe at this point whatever is wearing, has completed its wear cycle.

Will have to get those oil analysis' up on audipages.

pw

ryoung

I'm also proud of your son. Please thank him for me for his service.

ttuling

and that we just don't feel it with clean fluid? Aren't torque converter clutches supposed to unlock when coasting for better economy?

I think the real difference is that with old fluid, the torque converter clutch may grab abruptly but with fresh fluid it engages smoothly. The clutch still locks and unlocks at the same time; we just don't feel it with fresh fluid.

Your coasting 250 rpm drop is like what I experience, plus briefly 100 rpm above the cruising rpm before the converter clutch locks again after stepping on the gas. These rpm changes indicate that the torque converter clutch is unlocking and locking whether or not we can feel it.

D3AeighT

So, are you saying if you "can feel the thunk" or "not", it doesn't really matter and the tranny/torque converter is just doing what's it's supposed to do, therefore changing oil/filter is a waste of money and won't do a darn thing for tranny longevity and health.

D3AeighT

Thanks for the thoughts and kind words. Heard from him twice until about 30 days ago, guess it's getting more hellish each day. He's 75 miles South of Bagdad.

ttuling

My transmission fluid's changed every 40-45k miles. I want the thing to last.

I asked the question to try to distinguish between two views, because It can matter when troubleshooting whether something normal is happening badly, or whether something abnormal is happening.

My view:
torque converter drops out when coasting: normal
feeling the drop out because of old fluid's friction charateristics: bad

My (mis?)understanding of Paul's view:
torque converter drops outs when coasting: abnormal & bad

ttuling

I meant to write "torque converter clutch drops out (or disengages)" not "torque converter drops out".