Help me fix an annoying driveline rattle

[Sigurd]

I bought an '87 GN about three weeks ago, 114K.

Engine and trans are stock.

At about 1600 rpm in drive I get a loud rattle/vibration that seems to be coming up through the floor. It only happens about 1600 rpm though, any higher or lower than that it goes away, and performance doesn't seem to be affected by it. It's just annoying the hell out of me.

Any ideas as to what could be causing it? something in the trans? driveshaft? something else?

Thanks for the help

Nathan D Brown

CPL USMC 1/6
Jacksonville, NC

 

[mybuick]

while driving and when it happens keep it at 1600 rpm and put the trans in nutral and keep it at 1600 and see what happens.

 

[1985BuickGN]

I would check the trans and motor mounts, chances are if they're still stock, they are shot. Also check your drive shaft, including the u-joints and make sure it's a fairly straight line between the differental and the transmission. If the mounts are bad, I would strongly recommend going with the HR Parts N Stuff mounts (motor and trans) real nice pieces. Even if they aren't bad it would be a good thing to do if you plan on upgrading the engine at all. HTH.

Paul B.

 

[QuickWrench]

Depending on the exhaust that's on your car, it could be the mufflers. Many of the commonly-used mufflers on these cars drone pretty badly around 1,800 RPM.

 

[salvageV6]

I second the exhaust system idea.

Muffer, pipe, or cat. on the floorboards.

Very annoying.

 

[captrob]

Check the exhaust...

My "Y" pipe was pressed against the floorboards and the harmonics would drive me nuts. Dropped the mufflers one hole on the hangers and problem solved. Fast and quiet.
Just another place to look, CaptRob