Transmission is whining Options

[adolimpio]

My understanding of my recent barn find is that the transmission was rebuilt and was never driven after.

It does run great and shifts nicely, but there is a steady whine which appears to come from the transmission when cruising. At 55, while applying just enough gas to maintain speed, the whine is very annoying. It does it in all gears, the pitch increases with speed, and is quiet when coasting.

Two extra transmissions came with the car, one looking like it was a donor, and the other looks untouched. I cracked the untouched one and examined things and the ring and sychros all looked pretty good, so I swapped it in. Magically, no whine, but grinds when shifting into 1st.

So I cracked the one that whines and found that the pinion and ring gears are mismatched. One is marked 617 and the other 240. I opened the donor and found that they were also mismatched, but I now had gears from 4 sets, there were no two that matched.

So I pulled the transmission that ran quiet and its gears matched. So I swapped the gear stack between the quiet one and the whiny one, and now had a transmission with all good synchros and rings, and matching pinion and ring gears. I was very proud of myself to have identified this issue and found a resolution.

So I installed my new creation and it ran great, shifts beautifully, and still whines!

By the way, all new transmission oil installed using Red Line 75W90.

Any thoughts would be greatly appreciated!

[wndsrfr]

It's the Ring/Pinion matchup that creates that whine. I'm no expert, but have heard that Porsche assembled the transmissions and ran them on a test stand and selected the intermediate plate gasket thickness that minimized the noise from the R/P. Since you've had yours apart and did a mix/match you may have gotten the R/P off of it's sweet spot....
I'm sure some better qualified folks here can chime in....where's Dr. Evil when we need him??