engine and drivetrain 5 speed bad noise

[AustrianVespaGuy]

Ok, I need a little help diagnosing this one. I recently bought a 75er that the previous owner installed a 5 speed in. It works pretty well but needs a fluid change as soon as I find a 17mm allen wrench for the plugs. However, it makes a bad whirring-almost-scraping noise under acceleration in 1st gear, particularly when in a curve. It sounds like gear howl, but louder closer then the gears inside the transmission. I *think* I can almost feel it from the forward transmission tunnel area. I crawled under the car and looked around pretty closely and couldn't find much. Shift tower is very secure, I can barely move the transmission on its mounts, and I felt all around the guibo and while there wasn't much clearance in places, it wasn't right up against anything. I did notice that all of the bolt heads were on the back side of the guibo, not alternated as they should be, could that make a difference? If not, any other thoughts? Again, this only happens in first gear and a tiny bit in second, under acceleration. Sound is like gear howl but somehow closer and more pronounced. Any thoughts appreciated, thanks.

-Carl

[Arizona02]

only on acceleration from the torque load of engine.

[AustrianVespaGuy]

That sounds like a good possibility. If so, is that A.) bad, and B.) correctable?

[ifayeoh]

Does it do it even after driving for a while?

Perhaps the Center bearing for the drive shaft is off a little bit, very possible after a 5speed swap, also maybe the center bearing was not pre-loaded.

i don't think the bolt on the guibo will cause it, but they should be alternating. check the archives for correct orientation.

make your self and alignment tool and check the drive shaft alignment, also in the archives, center bearing from the usual suspects less then 30 i believe.

if it is the engine bearing i would think it would be bad. bottom end rebuild or complete rebuild.