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MG MGB Technical - How tight?

I've got a '78 MGB GT and just lately i've been getting a creaking from the rear when pulling away...

I'm now trying to find the cause, so i put the handbrake on and tried pulling away whilst someone was looking under the car and the diff moves downwards and 'creaks' so i've checked how tight the 5 bolts are either side that bolts the diff to the springs and they can all be turned quite easily with a spanner? i expected these to be very tight?

Could these not being tight enough be causing movement on the diff? resulting in a creaking noise?

any ideas welcome, as its starting to annoy me now! i've put lubricant on all the bushes and rubbers i can see, anti roll bar bushes etc. it only happens when pulling away.....and no other time.

Gavin J

Anyone? sorry need to get it all sorted by monday to get to work :(
Gavin J

Gavin, The Bentley manual does not give a torque setting for the spring hanger bolts, but gives 55 to 60 lb. ft. for the rear shock absorber bolts which should be a rough guide. They need to be tight enough to prevent movement. Somewhere there are tables on standard torque wrench settings for various thread types and bolt sizes which might also help.
Hope the creaking ceases, Greg
Greg Taplin

Hi Gavin

There are rubber pads on either side of the springs, and there will always be a 'bit' of movement because of this.

The U bolts do need to be tight, and as Greg says there is no figure given in the manuals, but getting to 55 lb.ft may be a bit optomistic.

As a guide, do them up as tight as you can comfortably can turn them with a ring spanner about 200mm long - I know this is a bit vauge, but it is the best that I can think of.

The centre bolt will tighten and come up solid. I forget the bolt size off hand, but 55 may be a bit too much.

cheers
ian F
Ian Fraser

Thanks for the replies, so if i tighten them up as much as i can by hand with a spanner that should do be ok and not cause any damamge by going to tight? as i've not got a torque wrench but i might pop out and buy one this afternoon.

Cheers
Gavin
Gavin J

Gavin; I think Chris mentioned 20-25 lb ft in some previous posts.

Clifton
Clifton Gordon

gavin, if you break one of the U-bolts by overtightening it, chances are good that it really needed to be replaced anyway. Maybe replace the nuts with the locking type to prevent further problems.
Jeff Schlemmer

Well i have tightened them up, all the bolts turned at least 2-3 full turns so they were all fairly loose.

They are locking type nuts aswell, seems as though the garage that fitted the diff didn't tighten them up properly and they also missed a bolt out of one of the rear anti roll bar clamps...

Just took it for a drive though and the creak has gone! and there is less movement on the diff.
Thanks for all the replies.

Gavin J

Gavin, it's really hard to tighten the U bolts without squeezing the rubber pads out completely. I've experimented with mine and found that somewhere between 20-25 ft pounds should stop the axle from moving. 55lbs is way too much.
Andy
Andy Preston

Andy. My experience is similar to yours. Tighten until the rubber/poly bushings just begin to deform and leave it at that. Just did this job a few weeks ago and that seems to work the best. Les
Les Bengtson

20-25 ft lbs is correct Gavin and will stop the creaking
Iain MacKintosh

This thread was discussed between 16/04/2005 and 18/04/2005

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