Thumping sound

[williamv]

Hello to the people reading this post. Being new to the alfa world everyday i get in the car I'm always listening and smelling for new things, getting to know the car. Well the sound of the day happens when going from neutral to first during that first take off i feel a thumping sound, well like 5 or 6 very quick and one right after another, it almost like if i feel it under the seat it seems. It only happens at that moment, usually when fully stop at a red light for example. Any clues on what this sound might be?

[spiderserie4]

sounds like the flex coupling (Giubo) between gearbox and propellor shaft.
Get under the car and inspect it, if it is torn/cracked, replace it now before it completely fails on you. Mark the propshaft before removing so the whole stays in balance.
for photos etc, see:
http://www.alfabb.com/bb/forums/spid...ad-spider.html

[mcola]

Also check the exhaust. Grab it at various locations and try and bounce it from side to side and up and down, looking for any spots where any part of the exhaust might be hitting the under carriage. I believe the most likely place where there can be contact is the rear muffler as it snakes between the spare tire and gas tank.

Also check the driveshaft center support. Not sure what amount of clearance or play is acceptable, but if the shaft can bounce too much within the support, the same sound is supposidly possible there too.

I have the same issue with my car, and the guibo and center support appear fine. But I did recently notice my center muffler rubber bumper is broken, which means the center exhaust area is free hanging, and the system can likely bounce under initial engine torque off the line. I too only get it from a stop, if I accelerate moderately hard.

Good luck.

[Alfastruns]

U joints

[Stan Murray]

It could easily be your transmission mount... Before you go to the trouble to replace it, you can cut some 2inch pieces of fuel line and stick it into the voids in the transmission mount. If your noise stops then it's the mount that needs replacing.

[alberbat]

I agree with "MCOLA", I rebuilt many parts of my driveline before finding the ehaust issue, so based on my limited experience I would try that first. But all of the suggestions are valid problem areas.

Good luck.

[VeloceDuetto]

I've got the very same issue in my '84 Veloce; a series of loud 'thumps' under the seat when I'm starting off from a dead stop. I just replaced all of the rubber exhaust hangers, so, based upon reading these posts, I'm guessing I also have a U-joint or flex coupling problem. Thanks very much for including the repair link.

Thanks,

David

[Gubi]

It's usually a weak center support bushing causing the driveshaft to thump off something. But even with a new bushing it'll thump sometimes on a hard takeoff.

I just turn up the radio.

[williamv]

Thank you for all the responses. So I looked under the car and the part you guys suggested seem to be fine, so I'm going to keep looking around for anything that may look wrong under there.

[williamv]

I also found another odd well atleast to me it is, so I will leave it to you experts. In both sides in the front of the car i notice what seems to be a bracket with a bolt hanging at the end, but it looks to have been cut, Is this normal? is it suppost to look like this and what is the bolt at the end for?

[alberbat]

I'm not sure about the pictures but I think that is the "stop" for the steering. There should be one on each side that limits the wheel/tire from hitting body work.

[bianchi1]

yes , steering stops.

[Forzaguy]

Found this flex joint on ebay, new. Have no info on the flex joint itself or the seller, just thought someone might want to look into it.

ALFA SPIDER 2000 1750 DRIVE SHAFT FLEX JOINT | eBay

[mcola]

I've very briefly checked my exhaust a few times, and the first time I found nothing. The second time I found the broken center muffler rubber hanger and still didn't see how that area of the exhaust could slop side to side enough to cause the sound (never replaced the hanger). Today with another Alfisti under the car (doing other work), saw scuff marks on the underbody right above the front edge of the center muffler. This means that area of the exhaust can bounce upwards about 2" when not properly stabilized. Not saying this is your problem but something for you and others with the same problem to consider. I guess its as they say... third times a charm. Cross my fingers this gets rid of my thump thump!

[pabeaver]

There's a bushing inside the front of the driveshaft that centers it. If this is worn, you get thumps. The rubber donut can be quite worn, but if the bushing is good, no thumps. And as others said, the center support would be the next choice.

Thanks.