My 95 C4 lost suddenly it's third and fourth gear. It shifts normal in the first two gears, but there is no performance in the third. The car has run only 20.000 miles so I don't expect a mechanical defect.
I received an H72 error in modul 4, but it seems to be an older DTC. 72 means the Vehicle speed sensor (VSS) has a problem, but the linked cruisecontrol works, I've tested this.
Oil is enough and the color seems to be alright, even it smells a bit burned, but my workshop told me it smells only "old". Nevertheless they want to rebuild the gear box because of a mechanical defect. I think this is a bit to early to state this with this H72 DTC, but they don't know how to solve this problem. What can I do?

there are full scale electronic tests that can be performed on the transmission, but I am not well versed enough to tell you exactly how they will help.

I am afraid the transmission is dead... from what I have read on the 4L60E, when it does something like this, it is DOA.

I will ask a friend... maybe he can post an answer for you... he knows a lot more about this than I do.

I hate to be the bearer of bad news, but I must. The 700r4 and the electronic versions have a weak 3-4 clutch pack. The typical way that they die of old age is exactly what happened to you. When you rebuild it, use a shop that will work with you. The aftermarket has stepped up to the plate and offers many h/d upgrade kits specificly for the 3-4 clutch pack. Some shops will only build them per the gm shop manual though. Because the fluid smells burnt, and the symptoms are typical of the failure I described, I am somewhat confident I am correct. You can have the car scanned in case the problem is solenoid related. The scanner can tell the input shaft vs output shaft rpm (to monitor slippage of the clutches and the torque converter). Get some opinions before writing a $2000 check though. Good luck!

Pete said what I thought he was going to say, but I don't have the experience he does to say it.

The man knows these transmissions... sorry for the bad news.

I agree with Pete too. My 700r4 went out a couple years ago. I fought the notion of paying someone to rebuild it or do it myself and learn. I bought the technical video, some manuals and studied them. I finally decided to tear into it, but some Hi-Po parts in including a Trans-go shift kit, and it has been running great ever since.

I hope you get it worked out. If you take it somewhere, take to someone you can trust or atleast get a second opinion. When they hear Corvette most shops will think big $$$$ right off the bat!