First gear "judder"

[TimK]

I got rubber mounts. The poly bushes from British Car Specialists. The bushes are for both ends of the tie back.

 

[andrewss]

Gearbox off centre... check and tighten each bolt or clutch pate misaligned.. again check bolts that retain the clutch plate.. faulty slave cylinder cheapest and simplest thing to change..

You may also want to check on the 'play' in the rear axle. Over time there is wear which will also cause a juddering sensation only heard in first gear engagement..

 

[trotti]

Why take the risk.. just change the clutch plate and be done with it..

So - I thought the judder had subsided, but I've learned over time that it was just a variable judder. Sometimes more pronounced than others, but always there. It got the point where I seldom if ever drive the car to avoid the issue and take the MGA anytime I take out a two-seater. This is sad because I love the Healey.

I've finally taken andrewss advice and I have the transmission out and the clutch pulled. Some interesting observations. The clutch system looks nearly new. There are two key issues and I wanted the group's help in making sure I do the right thing.

1. Loose clutch mounting screw - one of the six mounting screws for the clutch was barely more than hand tight. At first, I just assumed that this was the PO's error and that I'd solved my judder problem. But, I also noticed that the screw that was loose was a couple of millimeters shorter than the other five screws (see in the picture, the screw furthest to the right). From Moss I can see that there are two different screws. This car originally had the BN6 engine when the PO rebuilt it, but it was later replaced with a BJ7 engine. The two different engines call for different bolts and I think one of the old ones was used.

I think this may be the source of my judder - the unbalanced torque on the pressure plate allowed the clutch to sit unevenly and created the shake. I'm hoping I get some knowing nods confirming I've diagnosed the issue.

2. The other issue I saw is the marring on the pressure plate that is shown in the picture below. There are identical grooves cut into the face and it appears as if the plate was scratching against the bell housing near the cover plate where the clutch fork enters the housing. See the second picture and you'll notice the scratched area.

Should I grind away some material where it's making contact? I think this may be due to the 10 inch clutch of the BJ7 and the housing meant for a 9 or 9.5 inch. Should I--can I--replace with a 9 inch that would have come in the BN6 originally to avoid this problem?

I took some other photos so that I could show the condition of the parts and context. The flywheel is smooth and there was no grease/slime. The pressure plate surface was also smooth with no grooves. The clutch disk is a bit "shiny" but there is plenty of friction material. The release bearing looks almost new. The last photo is of the monster - I wrangled this out of the car solo; that is something I'll never do again. Thanks in advance! I very much appreciate the help.

 

[British_Recovery]

The earlier bell housing on your gearbox was binding the pressure plate of the 10" clutch. It was forced to rotate as seen in the worn bits on the bell housing and the pressure plate. Hard to believe it could even turn over. To go to the smaller clutches, the flywheel would have to be changed also. A simpler option is to find a side shift 3000 bell housing and put it on your gearbox. Make sure that the throw out (release) bearing is the correct one for the clutch used. Use the correct bolts for the flywheel used, and have the correct face of the disc against the flywheel.
Bob

 

[trotti]

Thanks British_Recovery - the grooves in the pressure plate are quite shallow but I think the best method would be to keep the current flywheel and find the appropriate bell.

I need a 3000 bell designed for the larger, 10 inch clutch and sideshift. Anyone have a spare lying around!?!

 

[Patrick67BJ8]

I recall that the BJ8 clutches are the ones to have because they handle more power. Also a lot less effort to operate the pedal is a plus too.

 

[Keoke]

Thanks British_Recovery - the grooves in the pressure plate are quite shallow but I think the best method would be to keep the current flywheel and find the appropriate bell.

I need a 3000 bell designed for the larger, 10 inch clutch and sideshift. Anyone have a spare lying around!?!

If you keep this flywheel it needs to be resurfaced by a knowledgeable machinist.

 

[steveg]

A few years ago I switched to the BJ8 flywheel and diaphragm clutch with my Toyota trans. Pedal pressure is much lighter.

Suggest getting the BJ8 pressure plate and disc and either having your flywheel pinned for that or getting a used BJ8 flywheel from BCS or Healey Surgeons. This will likely require a different release bearing. From my notes: the old 10" clutch was 3" thick and the BJ8 clutch is 2-1/8" thick.

Tom's Import Toys does flywheel lightening - they may be able to drill the different pin placement for the BJ8 pressure plate.

PS - flywheel lightening gives a performance boost off the line.

 

[EV2239]

I didn't notice much more power from a lightened flywheel on my BJ7 engine, so I didn't lighten the one on my BJ8 engine, but on both engines is a BJ8 clutch attached to and balanced with the flywheel. This is absolutely essential or the engine will vibrate. The earlier flywheel needs drilling to suit the later clutch, but it does give a lighter pedal pressure and is more pleasant to use.

 

[steveg]

I didn't notice much more power from a lightened flywheel on my BJ7 engine, so I didn't lighten the one on my BJ8 engine, but on both engines is a BJ8 clutch attached to and balanced with the flywheel. This is absolutely essential or the engine will vibrate. The earlier flywheel needs drilling to suit the later clutch, but it does give a lighter pedal pressure and is more pleasant to use.

Thank you for clarifying that re the lightened flywheel. I was passing along heresay.

 

[TimK]

I replaced my clutch disk and pressure plate and now have a minor but annoying vibration at about 2000 rpm. I had a major vibration when I reinstalled the flywheel 90 degrees off. I was unaware of the need to have the number 1 stamped in the flywheel at top dead center. After learning of this requirement (on this forum), I removed the transmission after looking at the photos I had taken before and after and noticed the change in flywheel location. After correcting the flywheel location, the vibration was much less noticeable, but I recommend anyone replacing the clutch/pressure plate to have it balanced with the flywheel.

 

[trotti]

I replaced my clutch disk and pressure plate and now have a minor but annoying vibration at about 2000 rpm. I had a major vibration when I reinstalled the flywheel 90 degrees off. I was unaware of the need to have the number 1 stamped in the flywheel at top dead center. After learning of this requirement (on this forum), I removed the transmission after looking at the photos I had taken before and after and noticed the change in flywheel location. After correcting the flywheel location, the vibration was much less noticeable, but I recommend anyone replacing the clutch/pressure plate to have it balanced with the flywheel.

Thanks for the info on the location of the flywheel and I'll definitely take the whole thing in and have balanced together. I'm lucky to live less than 10 minutes from a shop that specializes in clutches specifically - I'll have everything mated and balanced and, now that I know there's a position marker on the flywheel, correctly aligned as well!

 

[trotti]

All is well with the world. Finally got the car buttoned up and back together. First and reverse judder have been completely eliminated. The culprit was either one or a combination of: imbalanced pressure plate due to one bolt that was loose and too short; and glazed over clutch disc. All the rubber mounts were in good shape and alignment appears to have been good.

Took it out for a short drive with the tunnel off to observe all the parts and verify all was good (read: I lacked confidence in a complete fix and didn't want to pull out the interior all over again).

Thanks all who contributed and got me back on the road. Next project: tackle the carbs!