Thunk/Clunk from rear

[Mephisto]

Hi Guys,

I've got an 83 320i, and sometimes, not always, when I'm starting in 1st, there is a loud thunk from the rear of the car. It feels like its coming from the left rear, but from the drivers seat I could be mistaken. I have checked wheel bearings by grabbing the tire at 6 and 12, and at 3 and 9 when its jacked up and there isn't any play. So I'm thinking it might be a ujoint in the propshaft?

My questions to you guys is:

a) What test can I do to see if it actually is the propshaft?
b) is it possible to replace the ujoint in the shaft? I read somewhere that BMW made it so you have to replace the entire shaft instead of just the ujoint.

Of course, if there is something else I should check too?

Thanks!

David

[E21noob]

You can change the joints (the crosses) on the shaft indepedantly. Not a DIY job though. Well guess that depends, one type is pressed in another is held in with circlips. I guess the latter you could do yourself.

That said, I have been told that a worn prop shaft joint would "sing" not thunk..

[Mephisto]

Thanks for the reply, my drive shaft doesn't sing, and it's smooth when I'm driving, so perhaps it's something else?

I'm planning on putting the car on a lift and taking a close look in about a week, and just want some ideas of what to check and look for!

Thanks!

[A.P.V.]

http://bmwfans.info/parts-catalog/E21/E ... e_carrier/

I think that number 6 your problem is. Is it the right side or left side where the klung comes from? This sound is mostly when you release your clutch or when you start or stop ad once to accelerate.

[Jeroen]

If its a real loud clunk that is a likely cause indeed. There are more common clunks but these aren't as loud, like movement in the exhaust system, diff hanger rubber, rear shock top mounts. Time for a check round. The suspension bushes pointed out by APV are dramatically expensive these days, BMW just more than quadrupled their price. Be careful with cheap imitations with much softer rubber. Alternative? Remove, burn out the rubber and replace with poly urethane. Saves loads of money!

[E21noob]

I've just replaced mine with polyurethane ones.

Despite the cost, If I was to start over, I would probably get these instead of the whole burning thing:

http://www.iemotorsport.com/bmw/E21-sus ... ameMT.html

[Mephisto]

Thanks for the replies! I think the clunk is coming from the left rear, not the right. But it is definitely an audible and physical clunk, you can hear it and feel it. It happens mostly when I am letting out the clutch when I'm starting off in 1st gear. But sometimes after I slow down and then accelerate after braking fairly hard.

[E21noob]

Let us know how it goes and what you find out about the mounts!

Also lookomg forward to you getting a thread started so we can see your e21

[Mephisto]

Let us know how it goes and what you find out about the mounts!

Also lookomg forward to you getting a thread started so we can see your e21

For Sure! I will get a thread started in the next couple days to show you my car and let you know what I'm planning on doing with it!

[Jeroen]

BTW thanks for the IE link. I was off considerably cheaper but this is easier haha. Their comment is spot on "Given the decline in quality (and sharp increase in pricing) we've seen in the oem rear subframe mounts in the past year..."

[Thegs]

If the sound appears under load my best guess is for the drive line. I think I would check number 1 and 7 first (on the lower diagram).

[Grewham]

I have the same prob, its a subframe bush for sure