Drivetrain knocking - advice please

Post by **GeorgeHurst** » Fri Oct 16, 2009 8:44 pm

Hi,

Of late a very definite knocking has developed toward the rear of my car, it is speed related (i.e. the frequency of the knock increases as the speed does) and exists at ALL speeds from just taking the hand brake off and rolling, to crawling in traffic to driving fast.

There is also a squeak/squeal which is speed related, though this fades when the brakes are applied so I assume it is something to do with the drums / shoes. The drivetrain also 'snatches' quite often when changing gear which leads me to think the knocking is created by a a worn diff, or perhaps prop shaft.

I'd be grateful for any advice on how to proceed in diagnosing the issue, I figure these are the problems, but I don't know how to actually check if you know what I mean... I don't think I could tell the difference between a good diff and a bad diff.

Any thoughts anyone?

Thanks,
George

Post by **mike.perry** » Fri Oct 16, 2009 8:59 pm

Rear propshaft bolts loose?
Check for backlash in diff/propshaft assembly.
Leading edge of rear brake shoes needs chamfering?

Post by **bmcecosse** » Fri Oct 16, 2009 9:52 pm

Does very much sound like prop-shaft problem. Check the bolts for tightness - and check the spiders by 'lifting' the shaft. I would do this checking URGENTLY! You don't want the prop shaft falling off! If it's ok - then you need to look hard at the diff - especially the input shaft - the retaining nut may be loose. Squeaks and squeals are likely to be brake related - drums off for a good clear out !

Post by **PSL184** » Fri Oct 16, 2009 10:22 pm

I think with your recent post re "axle tramp" you need to get under and check everything out asap. A loose of worn prop would give similar noises and issues and they are deadly if they let go at speed.....

Post by **GeorgeHurst** » Fri Oct 16, 2009 11:44 pm

Thanks for the replies. I will get under the car tomorrow asap and have a look at the prop shaft and 'report back'.
PSL, quite right, having driven from London to the Westcountry two days ago I have come to the conclusion that this all needs doing asap as it really is definitely not right! Alas time to raid the overdraft I fear

Post by **bmcecosse** » Fri Oct 16, 2009 11:51 pm

It may just need bolts tightening! Think positive.

Post by **GeorgeHurst** » Sat Oct 17, 2009 2:24 pm

Just dived under the car and inspected the prop shaft.

The bolts securing the rear of the prop shaft to the diff are all tight as can be, the universal joint however has a lot of play in it on one axis, the sound of it when moving it is the same as the knocking sound. The front universal joint is also has a degree of play in it but not much.

I therefore am going to replace both universal joints and see how it sounds and if it still snatches, and if not solved will get stuck into the diff.

For those that saw my axle tramp post and the 5 or 7 leaf spring debate, I have found on inspection that I infact already have 7 leaves on both sides! So will replace with these this time.

Thanks for the advice
Cheers,
george

Post by **PSL184** » Sat Oct 17, 2009 2:35 pm

Even the slightest play in the UJ's will give vibration and knocking so well found and I would imagine you will se a huge improvement once changed.

Post by **bmcecosse** » Sat Oct 17, 2009 3:33 pm

May b easier to pick-up a secondhand prop shaft -and then fix the joints in yours when you time!

Post by **GeorgeHurst** » Sat Oct 17, 2009 4:38 pm

oh dear, is it a nightmare job changing the joints?! It didn't look too bad from looking in the Workshop manual.

ESM sell second hand prop shafts for £25, so assuming these come with the UJs fitted and in good order I may go for that

Just adjusted my rear brakes to try and stop the squeal but it persists, one drum needs replacing as I ran out of adjustment before the drum locked... the shoes have at least 3mm left so I surmise that the drum is worn. There's a fair amount of brake dust in there, would that create the squeal?

Post by **PSL184** » Sat Oct 17, 2009 4:57 pm

GeorgeHurst wrote:would that create the squeal?

Yes, definately.....

GeorgeHurst wrote:one drum needs replacing as I ran out of adjustment before the drum locked

Check you have the correct size adjusters - They are different between 7" and 8" brakes and not incommon for them to be mixed up.... If not then yes, new drums needed but only about £15.00 a pair.

Post by **bmcecosse** » Sat Oct 17, 2009 5:05 pm

But - you can put a thin spacer strip behind the shoe - at the non-adjust end. This evens out the wear - presenting the shoe more squarely to the drum. If the little 'spacer' is folded round the bracket it can't come out and is perfectly safe. Unless the drums are badly scored - I would stick with them!

Post by **MarkyB** » Sat Oct 17, 2009 5:06 pm

is it a nightmare job changing the joints?

It ranges from being a piece of cake, to an absolute pain where you start wondering if the cups have been welded in.
So, depends on your luck and the history of the car.

Post by **bmcecosse** » Sat Oct 17, 2009 5:10 pm

You should get a prop shaft for much less than that! Ask in 'Wanted'! Then - you can take your time fixing your own shaft - do it at your own pace.

Post by **mike.perry** » Sat Oct 17, 2009 8:29 pm

Swap the drums over before you rush out and buy new ones.

Post by **GeorgeHurst** » Sun Oct 18, 2009 1:51 pm

cool, thanks for the thoughts.
whats the best way to remove brake dust? I don't want to be scraping away at the drums/shoes and damaging them, or using a detergent that might leave everything slippery. Compressed air?

Post by **PSL184** » Sun Oct 18, 2009 1:52 pm

Just rub over the shoes and drums with sandpaper then brush off the dust but becareful not to inhale any dust incase it still contains asbestos.

Post by **GeorgeHurst** » Sun Oct 18, 2009 2:03 pm

cheers PSL

Post by **GeorgeHurst** » Sun Oct 18, 2009 11:57 pm

@PSL - where can you get drums for £15.00 a pair?! The cheapest I can find from the usual suppliers is 14.95 each for 7"

Will check the adjusting cam first, but should I need new drums I would very much like to find a pair for £15!

Post by **PSL184** » Mon Oct 19, 2009 8:08 am

GeorgeHurst wrote:@PSL - where can you get drums for £15.00 a pair?!

My local motor factors with a trade card - See if you have an A1 Motor Store nearby and blag the trade card - some have also managed this trick at Halfords.