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What's the likely cause of clutch judder with no slipping at all ?. Is it still likely to be primary gear seal even though there's no slip to indicate oil contamination ?. Just wondering if there's any other reason other than contamination.

Engine steady is a possibility

There is no physical engine movement when it judders, no play in the tie rod.

Has car been standing for a while .. our cars get treated too well these days under covers in a garage etc. .. maybe worth to give it some stick out Driving & see if there is improvement before you strip out clutch for inspection

Not really, been using it all summer. There is a drip of oil on the split pin but it's been like that for a long time. I do presume the judder is oil but thought it would slip as well. Job for the winter then.

It could be that the clutch plate is not sliding properly on the primary gear. I would take the flywheel off and check that and the backplate.

The clutch will need to come out anyway, just wasn't sure if there could be any other mechanical issues with rhe crankshaft or primary gear causing it. I have learned to cope with it by not slipping it too much taking up the drive but I'd rather fix it than let it get any worse.

I had a drip of oil on the jingle pin recently and expected the primary gear oil seal to be leaking but found the seal was ok and the oil was coming via the primary gear bush, onto the flywheel and onto one side of the clutch plate. No slip or shudder though.

imack wrote: ↑Sat Oct 31, 2020 11:35 am I had a drip of oil on the jingle pin recently and expected the primary gear oil seal to be leaking but found the seal was ok and the oil was coming via the primary gear bush, onto the flywheel and onto one side of the clutch plate. No slip or shudder though.

Is it an engine out job to replace the bush?.

111Robin wrote: ↑Sat Oct 31, 2020 12:02 pm

imack wrote: ↑Sat Oct 31, 2020 11:35 am I had a drip of oil on the jingle pin recently and expected the primary gear oil seal to be leaking but found the seal was ok and the oil was coming via the primary gear bush, onto the flywheel and onto one side of the clutch plate. No slip or shudder though.

Is it an engine out job to replace the bush?.

No, but the flywheel put up a fight to get off.

imack wrote: ↑Sat Oct 31, 2020 11:35 am I had a drip of oil on the jingle pin recently and expected the primary gear oil seal to be leaking but found the seal was ok and the oil was coming via the primary gear bush, onto the flywheel and onto one side of the clutch plate. No slip or shudder though.

Just out of interest, how 'baggy' was the primary gear bush?
I've had the same experience of expecting the clutch oil seal to indicate a leak, but nothing obvious when dismantled, leading to the conclusion that oil has tracked along the crankshaft tail.
Lots of threads on various forums debating how crankcase pressure might be a factor in this.

Adding a breather to the clutch case does seem to be a good idea.

Rich997 wrote: ↑Sat Oct 31, 2020 10:14 pm

imack wrote: ↑Sat Oct 31, 2020 11:35 am I had a drip of oil on the jingle pin recently and expected the primary gear oil seal to be leaking but found the seal was ok and the oil was coming via the primary gear bush, onto the flywheel and onto one side of the clutch plate. No slip or shudder though.

Just out of interest, how 'baggy' was the primary gear bush?
I've had the same experience of expecting the clutch oil seal to indicate a leak, but nothing obvious when dismantled, leading to the conclusion that oil has tracked along the crankshaft tail.
Lots of threads on various forums debating how crankcase pressure might be a factor in this.

Adding a breather to the clutch case does seem to be a good idea.

I'm running minispares sc drop gears with the floating bush. I had previously increase the clearances slightly on the bushes due to reading various issues with the current bushes being of an unsuitable material and potentially seizing to the crank, I obviously opened them up a little too much.
Mines a fairly recently built 1380 with 3 crankcase breathers open to atmospher so I don't think crankcase pressure was the issue

imack wrote: ↑Sun Nov 01, 2020 7:29 am

Rich997 wrote: ↑Sat Oct 31, 2020 10:14 pm

imack wrote: ↑Sat Oct 31, 2020 11:35 am I had a drip of oil on the jingle pin recently and expected the primary gear oil seal to be leaking but found the seal was ok and the oil was coming via the primary gear bush, onto the flywheel and onto one side of the clutch plate. No slip or shudder though.

Just out of interest, how 'baggy' was the primary gear bush?
I've had the same experience of expecting the clutch oil seal to indicate a leak, but nothing obvious when dismantled, leading to the conclusion that oil has tracked along the crankshaft tail.
Lots of threads on various forums debating how crankcase pressure might be a factor in this.

Adding a breather to the clutch case does seem to be a good idea.

I'm running minispares sc drop gears with the floating bush. I had previously increase the clearances slightly on the bushes due to reading various issues with the current bushes being of an unsuitable material and potentially seizing to the crank, I obviously opened them up a little too much.
Mines a fairly recently built 1380 with 3 crankcase breathers open to atmospher so I don't think crankcase pressure was the issue

Thanks for sharing the background.
Ive read about issues with the floating bush, Keith Calver has a few good articles about how problems can occur (heat).

I like the idea of a floating bush and would try it if they were available for 850/997/998 primary gears. Sourcing new front bushes for the small primary gear isnt easy, then its also a challenge to fit them.

Regarding crankcase pressure being the root cause for oil passing by the clutch oil seal, I see why this is improbable, but also there is clearly merit in having a breather on the clutch case (or BMC wouldnt have added one).

Rich997 wrote: ↑Sun Nov 01, 2020 1:22 pm I like the idea of a floating bush and would try it if they were available for 850/997/998 primary gears. Sourcing new front bushes for the small primary gear isnt easy, then its also a challenge to fit them.

They are available to size a 1275 primary gear down to small bore size - https://www.minispares.com/product/Clas ... o%20search

Strangely after a long run today the judder has all but disappeared. I'll try again tomorrow, seems to be worst when cold. I've cleaned the oil from the bottom of the housing and will monitor for drips appearing. No doubt it's wishful thinking but you never know. I was about to start tearing it down today as well.

minibitz wrote: ↑Sun Nov 01, 2020 9:45 pm

Rich997 wrote: ↑Sun Nov 01, 2020 1:22 pm I like the idea of a floating bush and would try it if they were available for 850/997/998 primary gears. Sourcing new front bushes for the small primary gear isnt easy, then its also a challenge to fit them.

They are available to size a 1275 primary gear down to small bore size - https://www.minispares.com/product/Clas ... o%20search

Thanks for pointing them out, I generally find Minispares special bits to be very good.

I recently had a clutch judder problem with a new engine build in a 1275 GT ADO16. I had fitted a new Mini Spares (C-22G1053) Primary Gear with floating bush. I had used the standard shim washer and had over 1.5 thou clearance I recall. When I pulled out the unit and removed the flywheel all looked fine and oil free. I subsequently found that the rear mounting on the remote was shot.

I put the engine back in and fitted all new mounting and happy days, clutch judder gone.

Those Mini Spares primary gears with the floating bush look to be a good answer for 1275cc engines

Alan

I'll post up some photos tomorrow however, I have to express some considerable caution with the floating bushes and also the current offerings on the Rear (Top Hat) Bushes.

Both of these were borne out of ignorance and laziness. Both of these EAT Crankshafts and in the case of floating bushes, the Primary Gear too. The Ignorance being that the correct fitting instructions for the proper bushes were somewhat obscure and not easily found (in the UK at least) so some considerable frustration has been experienced in the past trying to successfully fit them. The Laziness part is a lack of need to machine the Front Bush when a floating Bush is used, however, considering that the Rear Bush still needs machining it's rather pointless.

At all times that the crank is spinning, these floating bushes too will also be turning withing the Primary Gear, only serving to further heat the bush and wear the crank. Of course, the spinning does speed up when the clutch is disengaged, but even when engaged, it is spinning, something the proper bush doesn't do.

If you'd like to run with these and not have these issues, there is a solution though and that is to periodically remove the Primary Gear and re-grease the bushes - fuck that for a joke.

BMC went down this road and examined & tested all many of methods of 'bushing' the Primary Gears when it seemed that wet bushes weren't the way to go, some of what they did try were bushes of the same material that's being used in these 'new age' bushes. Despite being considerably more expensive and also more expensive to fit, they settled on Deva for the Rear Bush (that runs dry) and a semi-wet Front Bush.

Contestant No. 1 - Floating Bush - done around 6 000 Miles, Road Car




Contestant No. 2 - Floating Bush - done around 5 000 Miles, Road Car




Last Contestant - the latest offerings of the Rear Bush, made in Silicon Bronze - done around 7 500 miles, Road Car




I've seen and had many many more bought to me.

Every single one of these types of bushes fitted that I know of, has sooner or later failed and buggered the crank in the process. It's not a question of it but when.

After having had a few of these let go, I approached a Bearing Design Engineer to seek professional advice, they came back saying that grease would be the best lubricant, but agreed that would only 'last' a short time before being washed out, but all the same, they did say it wasn't remotely a material they would recommend for this application, for one thing, it's way too hard (and that's evidenced in the damage they do).

Beware.

Thanks Chris for that great information, very interesting for sure. I've to split a engine this week with a floating bush primary gear that has only done about 3k miles. Will now look into this area and more than likely change back to the standard primary gear

Will post up what I find later this week.

Alan