first post...need help:)

[Scarboy]

hey guys thanks for all the great info. ive learned tons form this site. I have an 86 GN with most of the common mods and a few extra goodies. I have a million questions but ill start with this one... If i have a passenger over 150lbs in the car with me (even worse when they are in the back seat) there is a rumbley thud,thud,thud noise when i corner. coming from the middle to rear of the car. the more weight the worse it gets. ive been under there plenty but i cant see any problems.....any ideas?

 

[87_we4]

Exhaust hitting driveshaft, or floor board. Mine hits the floor board and makes the thud

 

[asto-t]

Do you have a posi rear? I take a guess and say maybe the rear axle`s gm additive is missing? I dont have the additive in my car and it chatters around corners? Not sure about weight in the car cause I never had anybody in the back seat.

 

[Scarboy]

no posi...which i plan on changing in the near future. i just used 75w90 castrol synth in the rear. no additive. ill check the exhuast and drive shaft. thanks guys

 

[TurboGee]

Welcome to the world of knowledge.
I would also check your driveshaft "U" joints for looseness in your weight loaded condition.
Safety first, level ground, remember to block your wheels, release the pressure (torque) on the driveshaft. There is more detail but I think you get the ideal (the motor is not running).

 

[Scarboy]

U joints eh? ... Thanks gee I'll definently check that out. Thanks

 

[gunslinger]

How big are the rear tires?
Mine will rub the frame and the outer wheel well with added weight, or when cornering hard.

 

[RIFF RAFF]

Yeep

exhaust hitting driveshaft, or floor board. Mine hits the floor board and makes the thud

mine too .. Changed it twice. Still bangs on the floor and pisses me off went from hooker to pypes still the same. Put people in the car it hits the floor and rubs the driveshaft .put the old hooker set up on my w-30 no problem no rub no thud and its a g-body ..

 

[GNRick]

Mine did the same with people in the car. Every time I hit a bump. Finally figured it out. Previous owner installed these rubber blocks on the frame to keep the car from squating when launching at the track. I don't think it happened around turns though.

 

[RIFF RAFF]

I think

mine did the same with people in the car. Every time i hit a bump. Finally figured it out. Previous owner installed these rubber blocks on the frame to keep the car from squating when launching at the track. I don't think it happened around turns though.

mine has to do with the aftermerket downpipe & test pipe and electric cutout .im tweeking it now .with a pipe bender . Hope it works out .. Or im going for three ..

 

[mongoose87]

its was my springs

My 87 did the same thing and it was the stock spring.

 

[Scarboy]

How big are the rear tires?
Mine will rub the frame and the outer wheel well with added weight, or when cornering hard.

rear tires are just 245/60r15....pretty sure they dont rub. thanks for all the replies guys. Lots of stuff for me to look in to...