Drumming sound

[Danz3]

I searched extensively and found a couple suggestions but am not sure they will address my current issue. Over the winter I replaced the rear transmission seals and guibo. During installation I was sure to verify driveshaft, output flange alignment etc. I even made an alignment tool to verify driveshaft alignment. The differential was loosened and moved rearward as suggested. The sound is like the sound you get when opening the windows of a modern car when the air reverberates in the cabin. There is no odd vibrations or metallic sounds. It occurs at 25-30 mph weather in gear or coasting down hill. One observation is that it seems to improve with time. After a long drive it is much better. My thought is that it may be exhaust related. The rubber hanger at the rear is worn out so I needed to add a rubber spacer to take up the slop, new part ordered. I did find a short post about the transmission exhaust hanger and binding but haven’t checked that yet. Any thoughts appreciated.

[Stevenc22]

Take your exhaust and shake it hard up down left right. If it hits anything then there is too much slop.

 

Use some zip ties to temporarily limit its movement and then take it for another drive and see if sounds does away.

[Danz3]

Thanks for the quick response. I did that first. Shook exhaust and did take out slop by tightening the worn rubber hanger with some rubber. I will verify again just to be sure.

[BarrettN]

If you're not opposed to spending some money on a tool that you'll only use infrequently - but make you instant best friends with anyone with the odd sound they can't track down, take a look at a Steelman ChassisEar - https://www.amazon.com/STEELMAN-06600-ChassisEAR-Electronic-Squeak/dp/B000IHIAES?ref_=bl_dp_s_web_3043628011 I have one, in total others have used it more than I have, but it sure is handy when you want to track down a hard to locate noise. They make a really neat unit with wireless pickups, but I already have mine and the wireless unit is even more expensive.

[tech71]

Possible its not related to the driveshaft and work you did. How are your tires?

[Mike G]

Exhaust tip properly spaced from the body/bumper?

[Danz3]

Possible its not related to the driveshaft and work you did. How are your tires?

I believe the tires are fine. Relatively new but worth a look.

[Danz3]

Exhaust tip properly spaced from the body/bumper?

I will check tonight when I check the exhaust system to be sure.

[Simeon]

Did you have the exhaust down pipe off the car when doing the guibo work? When reinstalling did you tighten the flanges at each end before fitting and adjusting the transmission hanger?  If you tighten that bracket before securing the rear downpipe flange it can tension the down pipe and cause drumming. 

[Danz3]

Did you have the exhaust down pipe off the car when doing the guibo work? When reinstalling did you tighten the flanges at each end before fitting and adjusting the transmission hanger?  If you tighten that bracket before securing the rear downpipe flange it can tension the down pipe and cause drumming. 

I did have the down pipe off. I just got done loosening the transmission hanger and re tightening. It didn’t seem to move but who knows. I’ll let you know.

[TobyB]

If it's a really GOOD drumming sound, 

look underneath again- this guy might be down there.

 

he's a bit of a prankster.

 

t

[Mike Self]

I had a vibration/drumming on my '73 some years ago between 55 and 60 mph that drove me crazy (enough to keep the car 41 years).  Turned out to be a rear tranny mount that had turned to black goo.  Replaced it with the much beefier E21 mount (or you can use one from a Bavaria) and the drumming ceased.

 

mike

[Simeon]

10 hours ago, TobyB said:

If it's a really GOOD drumming sound, 

look underneath again- this guy might be down there.

 

he's a bit of a prankster.

 

t

 

Love Keith. 

[Danz3]

Finally got a chance to drive the car after loosening the exhaust connections and transmission bracket and replacing the muffler hangers. Sound is gone. Not sure what causes the sound but it’s gone.