The higher pitch is me blipping the throttle. When coasting it's quite and on acceleration where the engine is actually pushing i.e. going down hill faster than gravity, it has this whine. The last transmission flush had an inch of shavings on the magnetic drian plug. I have a 4 speed 260z and a unknown welded diff. Plans to swap out to spare open diff. and swap in a 5 speed 240sx transmission. Any info on that swap would be helpful to have!!! PS 75mph is actually 60mph

"Whining baby" is not a title that makes people want to look.

Here is a good writeup on the "71C" swap.  There used to be another one by Nigel on Motortopia.com but it's gone now.  @Nigel

http://zhome.com/ZCMnL/tech/240SX5spd/transmission.htm

 

It's still there. The link may have changed. I'm not sure if that site is even maintained anymore though.

https://www.motortopia.com/members/Nigel/mediapress/240sx-transmission-swap-14041/

 

I get a high-pitched whistle from the transmission at high RPM when I'm banging the gears.  It sounds like some sort of extra boost, but it's probably just something wearing out.

Thanks I'll have to look at this stuff in depth when I start to put the car together. Rn I'm going to try and pin point the sound on a lift and see from there.

You might look into Redline MT-90 gear lube.

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