A minor lecture on doing things correctly... pt 1

(Mitchell Andrus) #1

A notable ‘jutter’ (British term) was encountered from dead stop. At some point in the recent past a mechanic seriously shorted my PO on a clutch replacement job.

The photo of the flywheel tells a lot as does the throw out bearing (carbon block). The surface of the flywheel is worn approximately .013" and is like a potato chip. The clutch plate shows so little wear its almost good enough to re-install, a complete mis-match in the amount of wear.

#1. A new plate was obviously installed onto a worn flywheel.
#2. The fork (clutch slave cylinder) return spring is missing as is it’s small fitting (ear) leading to full-time contact with the pressure plate, or, the block wasn’t swapped out at all.

I’m posting this as a reminder to owners who don’t know how to specify the work they will have done, or those who seek the save a few bucks. Have the job done correctly. Specify the parts to be replaced and the work that is to be done.

This is a shame (although the adjusted purchase price more than compensates for a whole lot of new parts going in on the might-as-well-while-the-engine’s-out plan).

(Ben E) #2

When I was a teenager, my friend’s dad owned an automotive machine shop. One weekend, we pulled a junkyard flywheel out of 5.0 Mustang, and it looked to be in really good condition.

I would venture to say that MOST people might have used it as-is, but since surfacing it would cost us exactly $0, we took it to his dad’s shop, and ground it flat/smooth.

The results were absolutely astonishing. The flywheel had a high-spot that you could have stubbed your toe on!! Ever since then, whenever someone posts that they are doing a clutch job, I comment “you’re surfacing your flywheel, right?”

You wouldn’t believe how many times that comment has been scoffed at…including right here on J-L.

(Geo Hahn 1969 Series 2 OTS) #3

On mine (and possibly on all) there is an inspection hole that gives you a good look at the TOB. I put a dab of paint on it so I can easily see any wear over time:

You don’t even need an endoscope, just a flashlight and a camera will do. I check it anytime I’m working in the neighborhood.

(David Langley) #4


I see that yours is a 67, which means that it may have a hydrostatic clutch slave cylinder which has no return spring. They were first fitted at engine number 7E4607. If yours is a higher engine number, then it will have the hydrostatic clutch slave cylinder. They didn’t always work so well, and resulted in premature throwout bearing wear, so the design reverted to the original setup.


PS: I’m a Brit. Are you sure you don’t mean “judder”?

(Ben E) #5

I’m a Brit too, and I’ve never heard of a ‘jutter’ either.

(Robin O'Connor) #6

Auto correct???

(PhilW) #7

On the old J-L site, I have a photo of a T.O. bearing that not only had the carbon worn away, but half the metal was gone, too. The customer said that he was having trouble shifting and it might need adjusting.


(Paul Wigton) #8

I had one of those, too, from a customer car: similar to the vented front brake rotor, off of a Ford van, where one friction surface was worn into the cooling vanes…!!!

(Mitchell Andrus) #9

Jutter… judder. It’s all Greek to me.

I did take a picture through the inspection hole. The perished TOB wasn’t a surprise. That paint mark is a great idea.

Here’s a video from University Motors discussing TOBs and how they work, how to take care of them and why we don’t have ball bearing TOBs. Fast forward to 4:10 for a look at some extreme examples that have come out of MGs:

Throw out bearing video.

(Mitchell Andrus) #10

It could also be that the PO kept his clutch depressed at red lights, an incredible NO-NO for cars with carbon TOBs. Keep the foot off the clutch unless you’re shifting.

(Mark Gordon) #11

Interesting video, Mitchell. Now I understand why Jags have a carbon TO bearing and not a roller. Next logical question, considering that I would expect a roller bearing on a clutch designed for one should last longer than a carbon TO, why don’t all clutches us a roller bearing design? Is there an advantage to the carbon vs. roller?

(Ben E) #12

While you would never find a carbon TO bearing in a modern car, a good quality one should last 100,000 miles or more, with sympathetic treatment from the driver, as already mentioned.

A roller bearing must remain concentric at all times with the flywheel and pressure plate, and therefore requires a slightly more complex actuation system. I would argue that OEM’s like Jag and MG felt the carbon bearings were simply “good enough”, and made the design simpler, so they went with it. It is worth noting that a vehicle a “crude” as a 50’s Land Rover was already using roller TO bearings…and roller camshaft lifters for that matter!

In the MG world, there was a rash of carbon TO bearing failures about 10-15 years ago. These bearings were obviously made in Chindia by a supplier who didn’t appreciate their function, and they were failing in a matter of 500-5,000 miles. This really gave rise to all these aftermarket roller bearings that some MGB guys swear by these days.

The thing about installing a roller bearing in an MGB is that it can’t possibly work as designed, because it moves in an arc. It’s therefore destined to do some goofy combination of skidding and spinning, but if you try to explain that to these guys, you’re wasting your energy. There are a handful of guys who’ve managed to achieve some decent mileage (20-30k) with them, and that’s all the proof they need.

What usually comes out of the MG discussions is that the guys who have been “successful” with roller bearings have also usually installed elaborate mechanisms to pull the roller bearing away from the pressure plate when not it use. I would argue that with a decent quality carbon bearing, 20-30k would be absolutely nothing to brag about, and you wouldn’t need the retractor mechanism in the first place…again, a waste of energy.

(Paul Wigton) #13

‘49 thru ‘58 VWs used slate…:wink:

(Mitchell Andrus) #14

Model A Fords used rollers, so that isn’t new. The trans REQUIRES a pilot shaft upon which the roller slides in order to keep it concentric to the pressure plate’s contact plate.

A roller TOB:


(David Langley) #15

XK’s Unlimited used to sell a conversion kit for a roller-bearing-based clutch release bearing for the XK engine/clutch. They don’t any more. From what I recall, it was expensive, and had some issues. Seemed like a solution looking for a problem…

(Benny) #16

Exactly what I was looking for. A way to check the the release bearing. Since I have the hydrostatic clutch slave cylinder which I don’t think I abuse the clutch.
The painted dot is your carbon area is that correct? And move that tab away to view it?

(Benny) #17

I don’t ever recall seeing Jaguar bulletins that claim they don’t work well. What I did hear was that mechanics didn’t know about servicing the hydrostatic cylinder and therefore screwed it up resulting in premature wear, So Jaguar reverted back to the outside spring set up.Unless you don’t put a lot of mileage on I wouldn’t worry about it. The video on the MG is very informative.

(Mitchell Andrus) #18

John Swift is considered something of a celebrity in MG-land. He tours the major shows now doing seminars and ‘roll-by’ repairs with a crowd watching, semi-retired. His videos are worth watching no matter the Brit-car you own as many parts and pieces are nearly identical, made by the same suppliers.

(David Langley) #19


I imagine that you are correct that the hydrostatic slave cylinders worked fine when correctly installed. When I said that they “didn’t always work well” I am reflecting the fact that customers experienced problems with them - maybe, as you said, because they were incorrectly installed. The lesson for us today is that if you have a hydrostatic slave cylinder be sure to check that it is installed in accordance with the instructions on page E.S.x.2 of the Service Manual, and not in accordance with the instructions for non-hydrostatic slaves described on page E.7. It’s ironic that Jaguar developed the hydrostatic slave cylinder to eliminate the requirement for periodic adjustment, and that incorrect adjustment of the hydrostatic slaves resulted in them being obsoleted…


(Geo Hahn 1969 Series 2 OTS) #20

I added the paint dot - yes, it is on the outer edge of the TOB.

Mine has a second hole further back than the hole with the metal tab that swings away.

I do not know if all bell housings have that hole.