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Panko

Crank end float - causing shudder?

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Hi guys, 

 

so any of you who have followed my thread on my wagon, will know for some time now I've been chasing a bad driveline shudder when taking, when taking off in the car (5 speed manual). so as the clutch is taking up. 

The first thing that seemed to be the culprit was the T5. And sure enough, the extension housing bush was buggered, allowing too much movement in the yoke. I had it checked out by a transmission place, in which they agreed. So I've had another T5 rebuilt, better synchros fitted, and an extension housing bush from a AU V8 T5 (better life span apparently). 
I knew the diff original 2.77 diff (i converted it from auto to manual) wasnt great either, having serviced it before having the T5 replaced, and finding the LSD had been grabbing, or locking, causing some interesting noises. Being the wrong ratio i had planned on replacing it anyway. Again, confirmed by a diff place that the centre needed to be machined, and shimmed. i figured i might as well do the same to a correct ratio diff. So i have done that as well. I had a 2.92 LSD built up, and has made a world of difference. This also eliminated about 75% of the shudder, just by building up a new diff. 

 

Now to my question, that this topic is related to..

Someone suggested to me, that if the crank has too much end float, this could be the cause of the shudder. And considering I have rebuilt and replaced the gearbox and diff, and had the unis done on the tail shaft, its starting to look like a good candidate. 

So the engine has clocked over 330,000km, never been built. It was out of the car once at 180,000km to have all the gaskets replaced etc etc. but never had a rebuild. 

Ive also replaced the rear main a few times, and it has never stopped leaking, could this be a result of the fact the crank has too much end float? 

I have another engine in the pipelines ready to be built up. I would just like to seek people's opinions on whether it is the crank end float causing issues, considering the engine runs near perfect, and still has plenty of torque (considering how low on compression it is :D). 

 

any advice or info would be great. cheers guys. 

 

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Was the flywheel machined/resurfaced properly? Correct endfloat in the box for lay gear and mainshaft?

 

Iv never heard of eccessive crank endfloat causng driveline shudder but it could be casuing it. Only way to find out is to put a dial indicator on the nose of the crank and use a prybar between one of the counter weights and a main cap.

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its not the flywheel. 2 different flywheels, 3 clutches, new box, new diff. same deal. everything has help but not gotten rid of it totally. 

 

Im still planning to start the engine build soon, i just dont want to drop the new donk in and still have issues, 

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At 330,000 the thrust bearing probably has a decent amount of wear. I would say that to be causing a shudder the end float would nearly have to be seen with the naked eye (i.e. No dial indicator required.)

 

You could try loading the car up in first gear (foot brake it) while some watches the harmonic balancer to check for movement. Failing that it can be checked properly when the engine comes out for freshen up.

 

Are the eye and shackle bushes in good condition? Uni joints?

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At 330,000 the thrust bearing probably has a decent amount of wear. I would say that to be causing a shudder the end float would nearly have to be seen with the naked eye (i.e. No dial indicator required.)

You could try loading the car up in first gear (foot brake it) while some watches the harmonic balancer to check for movement. Failing that it can be checked properly when the engine comes out for freshen up.

Are the eye and shackle bushes in good condition? Uni joints?

Well when i had the gearbox done it had a new clutch and thrust bearing put in. Then again when for whatever reason the thrust bearing flogged out. So its only about 7000-10000km old.

 

I did the unis a few years back, when i just started to have an issue. Maybe need doing again.

 

The rear suspension has never been re-bushed as far as im aware.

 

I had footage that i took on my GoPro, setup on the driveway under the car, holding my foot on the brake whilst slowly letting the clutch out, essentially inducing the shudder. On the footage i could see the driveline front to back, vibrating. Tailshaft and gearbox. So it seems to come from either end of that. Ie crank or diff.

 

On a side note, i remember when i had the new diff built, i originally put in the oil the diff place recommended, a fully synthetic 90w120(?). Drove it, and immediately wasnt happy with it. The following day dropped it, put a mineral oil with the correct factory spec (thinner) oil. Plus a Penrite LSD additive, and immediately better. The shudder was near gone and it didnt feel like it was dragging like it did with the thicker oil.

Sadly it did an axle seal and had to back to them to be sorted, in which i know they will have put the thicker oil back in. I havent bothered to change it back yet, would the thicker oil be causing issues?

Considering the reason i had a new built is because apparently what was happening was the LSD centre needed machining, and it was locking and unlocking and getting sticky, which would cause a bit of shudder as it released. Hard to explain without a cone set to demonstrate.

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I meant the thrust bearing inside the engine, not the spigot bearing. The thrust is taken at no.5 main bearing. It may well be worn considering the k's, but to be honest I think you are looking in the right place in the diff centre.

 

Correct LSD fluid is important and I would be using the factory recommended LSD oil. Yes new fangled oils are great, in new fangled modern cars. These old girls weren't designed for it. Use the stuff the factory recommended. Cause it worked for a damn long time when these cars were new. If you have had the LSD machined it is essentially new again so no reason why correct lube won't work.

 

I'd be looking at suspension bushes as well, in particular front eye bushes, as they are the ones that seldom get changed and they could cause the diff to screw and cause all sorts of issues.

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