I recently installed my headers along with 2 1/4 duals with magna flow super 44's, I also recently put a posi and 3:42 gears, Didn't notice any humm. The last installs have been a TCI saturday night special torque converter along with a set of vista cruiser rear coils in the back of my 76 cutlass supreme, I have noticed a humm at around 60-70 mph, no noise prior to 60mph and after 70 mph it goes away. Is my drive train too high?? Too much pressure on my rear end with it sitting up so high ? Or could it be the exhaust drone I have read in other posts, I have about 1000 miles on the exhaust, and about 300 miles on the torque converter and rear springs. The hummm seemed to start after the converter and rear spring change.
Anyone have any suggestions as to what this could be or has anyone experienced this?
Thanks Eric

 

Just a wild guess, could the springs changed the driveshaft angle?

 

Try putting your stock springs back in and go for a drive , just a thought .

 

Thanks guys I was thinking the same, however I wanted some advice from you guys. I threw the old springs in the metal bin and they are now gone. The ones I took out were original and the rear fenders were beginning to rub on the tire, So I suppose I will have to go with stock springs and lift the rear up another way. It looked good sitting up about 4" off the 245 60's but I guess the driveline won't handle it being up that high.
Cheers Eric

 

I was really hoping it was just louder exhaust drone with it being up so high.

 

I don't think it's springs, it may be harmonics, it maybe the rear end. There are times when a noise appears at a specific speed and then disappears. Your going to have to do some more troubleshooting to isolate it. Also make sure none of your exhaust is coming in contact with any part of the vehicle.

 

Hey, I just tossed the driveshaft angle idea for a possible. The angle maybe ok, let someone else chime in on that. I know there is a way to check it but others can explain better. It may have put more strain on old u-joints. I'm just guessing, get some other opinions before dropping cash.

 

It could be the gears. Does it go away when you break or coast ? Does it do it while you drive ? I installed a used gear set on my dads car and it howls a little while coasting but while driving it does nothing. I can live with that since the drive side does all the work and it was a used set. I think you would have to put a lot of strain for the springs to cause it. By any chance did you install the rubber isolators that go from the spring to spring pocket. You may have raised the car but the drivehshaft slips in and out of the trans so I can't imagine the 4 inches of rake doing that but I have never had a rake like that so I can only make an educated guess. Kinda like lifted trucks we did a 6 inch lift on the fiances blazer and we had slip shafts made. All you hear from that truck is noise from themud bogger tires and exhaust

 

My bet is on gear noise in the rear end. It's not too hard to set up a rear end to hum. Heck, my '87 442 with its never-opened factory 3.73 rear hums.

 

X2 on the rear end. I noticed the hum on mine when 3.42 and posi got put in. It's been like that for 3-4 years. I am used to it now.

 

I had a shaft seal leak.Lost enough rear oil to cause a humming. Luckily I didn't hurt anything..Replaced gear oil and additive,good to go.And it also did it at higher speeds.It's a 3.73 posi.

 

Eric my exhaust is ok nothing hitting anywhere, I did have to get it tweaked after the springs went in. @ copper, I'm hoping it isn't the rear gears, the posi and gears etc were purchased new from Monzaz and installed correctly. The hum seems to be around 60mph - 70mph accelerating, I don't notice anything below that or over 70mph. the humm seems to be less if I let off the accelerator and back into it. @ black gold ,70 Cutty , I will bring it in and have the rear end oil changed and see if it is a problem, I understand that after a few miles this should be checked out. My U-joints were ok when the rear was done I don't notice any shacking or wobble as a u-joint normally feels but I will have them checked out as well. I won't get to it for a few weeks but I will check back when I get the time to take the car in .
Thanks Guys
Cheers Eric.

 

Thanks for your input, any ideas are good ideas. Opinions are always good prior to dropping cash. I appreciate them all . Put-r-ther !!!
Cheers!!

 

If you get back into it and it makes noise and you let off and it goes away sounds like gears. At this point I doubt the gears will show significant wear. It comes down to the set up. it could be .004 of a difference for all you know. Some gear sets are noisy from what I have read. From looking at it I doubt your mechanic will see anything he will have to check the set up and re adjust if the drive side is noisy .

 

Thanks copper, I will have to look into the rear gears I just never noticed it before, I had the torque converter, and the rear springs done at the same time, so I figured the exhaust was louder because its up much higher. As soon as I get time I will get the rear checked out .
Thanks