TonyG111

Finally got my first corvette and transmission issue on my way home from dealer. Its a 04 base automatic transmission with 66k miles. Around town no issues but if I get on the highway for 15 to 30 min and then come to a stop I get a really hard slam from 1st to 2nd gear. Now if I restart the car the issue is gone. The only code i get is transmission slipping P0894. Any help or advice would be greatly appreciated.

Missileboy

Fluid level? Fluid color? That would be my first thing I would look at. You could have low fluid and that hard shift could be the symptom of low fluid. There could be other issues as well but I would start there. And if it is low, then I would go back to that dealer and give them some "advice" and ask for a transmission service to make sure all is well.

I have a 02/A4 and the only time I ever felt that (hard shift from 1st to 2nd) is when I had the rear end swapped out to a 3.42 from the 2.73 stocker. I waited 2 months to have the ECU re-programmed since I was sending my car to be boosted and dyno tuned already scheduled. While I could drive the car if I went more than ~half throttle, the shifting was hard (like you describe) and I got the same code, but mine was due to the different physical rear gear ratio versus what was programmed so the speed tables were out of whack and I knew/expected that until I got the re-programming done.

TonyG111

Fluid looks great, level was perfect. As far as the dealer, they told me if they knew there was a problem they would not have sold it. "Good luck". So im on my own. The glove box option codes says it has the performance option 3.15 gears. I do remember when I under there checking the level that something was written on the diff cover in white maker. You maybe right. Gonna check it soon as i get off work.

TonyG111

3478 written on the diff cover. Means nothing to me.

oktx

I wouldn't give up that fast. I would become a pain in their *** if it showed up on the ride home. To me they either didn't do a test drive or didn't disclose it. Good Luck!

Supercharged111

It sounds to me like you may have a torque converter lockup issue. That'll throw the slippage code, and ramp up line pressure and cause that harsh 1-2 shift. Of course there's other stuff that can too, but that particular issue comes with both of your observations.

TonyG111

What's got me confused is the part where while I'm at a red light I cycle the car off and on and she runs great again.

Supercharged111

I wouldn't read too much into that.

fun_n_sun

you probably already know that you need to check the oil with the car running and the tranny oil temp around 105 degrees right? If it was checked with the engine off then it is not properly filled. Specifically I think you check between 86 and 122 F. Add if necessary at that time until it just drips out. Then replace the plug and your done.

TonyG111

yes, did it running and at temp with the car on jack stands and level.

grinder11

It may, or may not indicate your filter is plugged. However, given that you have an issue, and it improves somewhat if you shut it down, and gets better when you restart it, crap blocking the filter may drop away while the engine is off. Then, after restarting, it takes awhile before it plugs again. I'd stop driving it immediately!!! Drain the pan and remove it. There's supposed to be a strong magnet in the pan. If you don't see it, but there is a large clump of metallic fragments in one part of the pan, it's there. This usually means the Torque Converter Clutch has puked. The 4L60E is a decent trans, but it is the grandson of the 700R4. I had a 700R4 in an '85 IROC. The TCC clutch puked in that. It took out the entire transmission. It didn't want to shift from 1st to second, even at part throttle. Finally, at maybe 1/6th throttle at around 4,500rpm, it shifted. The rear tires really chirped as the car banged 2nd, and tried to fishtail!! A pan inspection should tell the tale.......

norcalace

Have you had the car tuned? I had a email ECS tune after headers and axle back install and it did the same as yours. Seems the tune was commanding full line pressure to the converter lockup when driving at highway speeds but didnt reduce it at slower speed so when I came to my first stop I got the hard 1-2 shift. Sent the ECM back and they reprogrammed it. Worked fine after that. Before the fix while driving on the highway I would pull codes and clear the fault. When I came to my forst stop the 1-2 shift was normal. Hope this helps.