The good ol' clutch shudder

[AB7]

I know this is an old topic, but anyone from here with NB8B fixed their clutch shudder problem. I mean its annoying sometimes but its not that 'annoying' enough for me justify upgarding the clutch...not right now anyway.

[Woo]

It's not the clutch that is at fault
The cause of the problem is excessive crankshaft endfloat. It affects about a third of the 1.8 lt motors. Not specific to any build date or VIN (NA & NB !!!!) as batches of blocks are cast periodically. However, it does manifest itself more with the 6 spd (hence NB8A/B/C).

The only surefire fix is to re-thrust bearing the crank.

Not cheap .... or easy

A new clutch will relieve the problem till it beds in, then it's back to shuddering again.

Oh and btw, the thrusts are non-std so will cost $138 to have made ++ fitting.

Sorry,

Wòó

[StanTheMan]

It's not the clutch that is at fault
The cause of the problem is excessive crankshaft endfloat. It affects about a third of the 1.8 lt motors. Not specific to any build date or VIN (NA & NB !!!!) as batches of blocks are cast periodically. However, it does manifest itself more with the 6 spd (hence NB8A/B/C).

The only surefire fix is to re-thrust bearing the crank.

Not cheap .... or easy

A new clutch will relieve the problem till it beds in, then it's back to shuddering again.

Oh and btw, the thrusts are non-std so will cost $138 to have made ++ fitting.

Sorry,

Wòó

First time I've heard that.

[Woo]

Mazda ignored it as it was easier/cheaper to refit a clutch kit till the cars were out of warranty (source: Mazda service/spare parts chieftan).
Motor builders have known about it for some time and the empirical research I've done fully supports their findings. 10 out of 33 have excessive end float and 8 of those with endfloat have clutch shudder.

Owners in the states have mentioned it previously so I thought I'd run with it, and investigate, as the new motor I have has 8 thou greater end float and signs of the shudder. My original motor was from the 2/3 that were fine and never shuddered in it's 70kklm life.

I too was very suprised

Wòó

[AB7]

Mazda ignored it as it was easier/cheaper to refit a clutch kit till the cars were out of warranty (source: Mazda service/spare parts chieftan).
Motor builders have known about it for some time and the empirical research I've done fully supports their findings. 10 out of 33 have excessive end float and 8 of those with endfloat have clutch shudder.

Owners in the states have mentioned it previously so I thought I'd run with it, and investigate, as the new motor I have has 8 thou greater end float and signs of the shudder. My original motor was from the 2/3 that were fine and never shuddered in it's 70kklm life.

I too was very suprised

Wòó

Thanks for sharing that with us, Woo.
I never heard that either...but do you think it will damage the engine in the long run?

[Woo]

In the short term, probably no damage. But longterm (insert six figure klm here) the crank float will skew the conrods causing axial wear to the cylinders relative to crank. By this stage the motors will be showing a marked decrease in oil pressure due to increased bigend bearing wear and we will eventually see quite a few of these throwing rods or siezing pistons.

Probably the best thing to do is to maintain the oil quality and quantity and avoid shuddering the clutch as the oscillations of the crank are what is actually doing the damage.
Maybe Mazda wasn't far off just replacing the clutches to bandaid the problem because when you do the math on how many motors actually are afflicted ..... the mind boggles

Wòó

[jules]

F*** me. Are you sure of this.
This is really major news if true.

I mean, it would rank as high as the short nose crank flaw, as far as severity.


Jules

[Woo]

F*** me. Are you sure of this.

Unfortunately, yes Jules

Considering that it only affects about a 1/3 of 1.8's and then to various degrees (between 4 and 20 thou endfloat) I'm not sure it's as big as the shortnose saga, but its still a significant number that will prematurely fail.

The hard part is diagnosing if your motor is one that has this problem and what to do about it. It's not real easy to measure endfloat (accurately) when it's in the car and rebuilding bottom ends isn't cheap (~$500 + labour).

Standard endfloat is 4 thou.

Wòó

[JBT]

Is this the alleged cause of intermittent clutch shudder too?

[Woo]

Nah JBT thats just your fat feet

It could well be the cause of intermittent shudder, mechanically it depends on whether the crank starts oscillating back and forth causing the clutch to engage disengage rapidly. This would definately depend on ones driving style for it to happen all the time or only intermittantly.

Geez its not good being the messenger .....

Wòó

[Benny]

That's really interesting.
My SP has had a degree of shudder since I got it, although it got worse around the 30,000K mark, and now, it only rears its ugly head every now and again when it's cold.
When the engine/gearbox warms up, it goes away completely.
I have also noticed that if it is shuddering, but using more throttle and more clutch slip, it alleviates it.
If the clutch shudder problem is end-float of the crank, why does it go away when the car is warmed up?

[AJ]

not trying to shoot the theory down in flames, but wouldn't excessive end float in engines that have been spanked on a regular basis see more of them blowing to bits???.....20 thou end float in a crank at 6500 rpm would chuck a leg out of bed REAL quick.....i haven't heard of any 1.8's going bang??....just asking as there was a batch of 253 holden V8's back in the LX Torana days that had the same problem (excessive end float that is)......i don't recall them having clutch shudder tho, just going bang for no reason

[Woo]

If the clutch shudder problem is end-float of the crank, why does it go away when the car is warmed up?

Just spoke with a top-notch engine builder and he believes that there should be enough clearance in the conrods to accomodate the movement so ignore what I said about the bigend wear (partially). It will only be the very high milers that will have problems. Actually the motors will probably need rebuilding for other reasons (rings, valves etc) before they suffer failure from the bigends.

Having said that, he also believes that the vibrations will shorten the motors life. To overcome it, exactly as you suggested Benny, he said just give it a bit of welly when it would normally shudder.

In answer to your question Benny, when the motor is cold the clearances are greatest. As the motor warms up the clearance on the crank reduces to 2 thou (from 4 thou standard/cold).

Sounds like it's not nessasarily terminal, but something to think about when rebuilding.

Wòó

[Woo]

i haven't heard of any 1.8's going bang??....

Haven't you been listening to me again AJ

I've had one go bang (rod through the block, sump, steering rack, aircon pump, block) and have heard of a few (3) others that have gone to the great boat harbour in the sky.

The variation in clearances is significant, maybe only 10% (guess) of the 30% that exhibit the excess endfloat are really really excessive. Just trying to put it into perspective.

Oh and btw some of the Toranas and Prems did have clutch shudder caused by the endfloat, I remember it well

Wòó

[AJ]

Haven't you been listening to me again AJ

*scrolls back up* oooooooh, there's more typing stuff back there ........seriously tho, clutch shudder seems to be fairly common, but going bang isn't so much

Oh and btw some of the Toranas and Prems did have clutch shudder caused by the endfloat, I remember it well

Wòó

yeah???.........i can go one better, one 253 premier i drove had TORQUE CONVERTER shudder