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MG MGB Technical - Changing the Clutch

Hi Guys,

The car is a 1974 C/B roadster with overdrive. Recently I have sometimes been having a hard job selecting first (or indeed any) gear after sitting stationary with the clutch up; even more recently I have noticed a distinctly unhealthy feeling in the clutch pedal, a sort of grinding resistance on both clutching and declutching. My take on this is that the release bearing very close to failing.

My question is thus: Is replacing the clutch assembly a job which I can hope to achieve on my own in a weekend (or preferably a day)? Also what specialist tools am I likely to need for the job?

Thanks,

_
(_arl,
Carl Kambites

First check the actuator rod, they wear down at the point of contact in the slave cylinder, and where the pin joins to the clutch release arm, the hole goes oval, and can be unseen. A clutch change can be done in a day, but it needs an engine hoist and probably experience of doing it once or twice, so first check how far the release arm is moving.


Tatty ( Non-member since 2003 )
Tatty

Changing the clutch is relatively easy if:

You have the facilities to pull the engine

You have a GOOD set of tools

You have a clutch alignment tool (should be available cheaply from wherever you buy your clutch)

A manual

All the extra bits such as exhaust manifold gaskets that should not be re=used

Replace the clutch dixc, pressure plate and throw-out bearing at the same time.

For a first timer, allow a day to pull it out and a day to reassemble everything.

Good luck....Rob
R. L Carleen

Carl
The first bit of advice is to obtain a copy of the Haynes manual…or BL workshop manual.
If you are a confident mechanic then you should be able to undertake the work in a long day. There several areas that may cause you small difficulties…but nothing that will cause you any real headaches. Things like removing the starter motor; Realigning the clutch with the spines on the gearbox; ensure that you support the bonnet as high as possible, I would not recommend removing it. Remove all the fixtures including the gill. A swinging engine can damage it..As I found out once!
Tools; you will need a clutch alignment too and an engine hoist. Plus the usual assortment of spanners and screwdrivers.
I am sure there will be others who can supply tips for you.
Cecil Kimber

To malign the splines on the gearbox I use a large wrench on the front dog nut and turn the engine over until the splines line up - it's quicker and easier than any other technique I know of.
dominic clancy

While you have the motor out, it may be time to consider taking care of any nagging problems such as bad synchros, oil seals, etc. that aren't usually easy to get to. Also, it is my experience that the QH clutches are pretty shady. Had 2 of them go with under 10K on one, 3K on the second. Bought Borg & Beck, and no problems in 40K since.
Mike Lord

Carl. In addition to the above, the flywheel really should be removed and professionally re-surfaced when replacing a clutch. This will require that you purchase a new loc-tab set for the flywheel to crankshaft bolts. These bolts have a 3/4" head. The head is rather shallow. If you look at your socket, it has a tapered lead in so it fits more easily on the bolt head. With the crankshaft/flywheel bolts, this results in much of the bolt head being in contact with this tapered area which results in the socket slipping off and deforming the bolt head. Removing most of the tapered area will result in a better contact between socket and bolt heads. I use a lathe because I have one. Others use a grinder or a belt sander. If using one of the later, use a dish of cold water to keep from overheating the socket.

If the rear main seal is leaking, it is a good time to replace it and inspect the sealing surface on the crankshaft for grooving. This requires removal of the rear engine plate and a new rear engine plate gasket and a new rear oil seal. I replace these parts whenever I change out a clutch.

Clutches. Borg and Beck is now made by Phoenix. I have purchased several over the last year as "clutch kits" (clutch plate, pressure plate, throwout bearing and throwout bearing retaining clips). All the parts are contained in a single box and are poorly packed. About 50% of the throwout bearings have been received in chipped condition and the pressure plate has a preservative oil on it. Often, the cluch plate (also called a driven plate) has been incontact with the pressure plate and has oil contamination. Clean the clutch plate throughly with a good brake cleaner and wipe as much oil off the pressure plate as you can. Then, use a solvent on the part of the pressure plate that comes in contact with the clutch plate.

One last area that needs to be inspected is the pilot bushing or spigot bushing. This goes into the rear of the crankshaft and the nose of the transmission imput shaft/first motion shaft goes into the center hole. This should be throughly cleaned and inspected. If it is loose or if the inner hole shows signs of wear, replace the spigot bushing. Information on how to remove and replace one is contained in the archives. Les
Les Bengtson

Unfortunately I have a very narrow time window for getting this job complete as I don't have my own garage. Thus I have to drive the car to my parents' house, do any work that needs doing and drive back in one weekend.

I should have a garage of my own within 6 months (~4000 miles I suppose). Judging by the symptoms that I have described will it last that long? If not how much should I be looking at to get a garage to perform the replacement (+ refacing the flywheel, replacing seals, etc, etc)?
Carl Kambites

Carl,

As you may have gathered from the responses, this is one job that, like many others on a 29 year old car, the "might as wells" will get you. There are lots of little things that you might as well do while you have the engine out, such as the rear main oil seal, but if you're not experiencing any oil leaks or other problems, you could just replace the clutch.

And yes, if you have the equipment and tools, it can be done in a day. It may be a long day, depending on your working conditions and experience. A professional shop would probably do it in four hours; certainly no more than six, barring unforeseen problems.

The only special tools you will need are an engine hoist, and a torque wrench. An engine tilt bracket is extremely helpful, by allowing you to tilt the engine as it is removed and replaced, to clear the chassis crossmember.
Paul Noble

Before you pull the engine, make sure the clutch master cylinder and slave cylinder are up to par and you have good movement at the actuating rod. If you can get someone to push the clutch and get under the car and check to make sure it is working correctly. The hydralic system is something that can be fixed without a garage and should be checked first.
John A

John. An excellent point and one that all of us forgot to mention. The clutch hydraulic system ages along with the clutch system and, frequently, will go out after a new clutch is installed. All of the slave cylinders are the same. Easy to rebuild as long as the bore is not too pitted. The flex line from the slave cylinder to the hard line is a bear to replace except when the engine is out. There are two types of clutch master cylinder, requiring two different rebuild kits. The one having the "dot in circle" marking is the most common and I have only seen one of the clutch MCs not having this marking. I suspect it was for the older Mark I cars. However, the car I pulled it out of was an 80, so it may have been the last model used or it may have been a replacement over the years. Perhaps someone else knows? In any event, a new flex line, a slave cylinder rebuild kit and kits for both styles of MC would be a good thing to have on hand. If time does not allow you to rebuild the MC and slave cylinders, simply replace the flex line and hope the system will last until you get your own garage. Fairly simple to rebuild either and does not require a garage if the weather is not too bad outside. Les
Les Bengtson

This thread was discussed between 14/04/2003 and 15/04/2003

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.