I just got my newly bought Longchamp engine to run, so I now discovered issues with my C6.
I've changed the oil on the C6. I did it by unplugging a hose to the radiator, and with engine running the oil came out. This is the first time I've changed autotrans oil like this, so I'm not sure how much more oil I actually got out than the usual oilpan-off method. I also changed the oil filter which is an external spin-on filter. I then added 4-5 quarts, and that's about right on the oilstick (idling in Park).
When idling there was no gear, only after 1500rpm for almost a minute there suddenly was Reverse gear, the tires squealed, good thing I was sitting in the car with my foot on the brake...
Stopped engine, spent a few hours fixing something else, started engine, no gear again. In my previous experience (GM cars) this means too little oil and 4-5 quarts sounds too little, depending on how much I got out of course. But the stick showed oil level 1" above where it should be. However, I added 2 quarts, and now I got gears, after 1-2 seconds. I added another quart.
Status after the 8 quarts added is:
-I have gears
-When moving gear lever to Reverse or Drive the gear comes in quite hard, especially Reverse
-When driving very softly it shifts perfectly into 2nd and 3rd
-When accelerating at half throttle, I get no 2nd gear until I release the throttle, same with 2nd to 3rd
-The oil level according to the oil stick is 4 inches(!) above where it should be
Any ideas? I'm tempted to add more oil. There's no foaming of the oil, which on GM cars is a sign to take oil out. I've checked the vacuum from the engine to the transmission, seems fine. And the kick down rod is only actuated when the throttle is a lot more open.
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