ABY Crankshaft - End Float - How much is OK ?

[macspring]

1. As per the title, how much end float is acceptable for the crankshaft on a worn ABY engine, and also on a newly rebuilt ABY engine ?


By end float, I mean the movement of the crankshaft forward towards in the direction of the bumper when the clutch is pressed and back to the gearbox when the clutch is released.


2. What causes it, a worn crankshaft or a worn block, or a combination of both?

3. What are the problems that will occur if the end float is outside Audi's tolerances ?

4. Is there a cure for it ? Shimming stuff ?

5. Is it more the case that one has to rebuild the engine ?

6. Or it is that one has to replace the block and / or the crankshaft ?



Sorry of the glut of questions, but just wanted to ask them all in one go.

Thanks for any replies.

[UrS4boy]

Worn thrust washers, items 24:

Wear limit show in pg 30/93 of this AAN workshop manual:

Range New = 0.07 mm to 0.23 mm, MAX = 0.30 (> 0.30 mm = yer F'd)

http://s2-audi.co.uk/workshop/aan/aan.pdf

[UrS4boy]

Wear limit show in pg 30/93 of this AAN workshop manual:

Range New = 0.07 mm to 0.23 mm, MAX = 0.30 (> 0.30 mm = yer F'd)

http://s2-audi.co.uk/workshop/aan/aan.pdf

[macspring]

Thanks Dave,

I presume one has to take the crank out to be able to fit new thrust washers ? (#24).

Rather than be able to fit it in situ.

Do the washers come in different sizes to effectively shim the tolerance to the desired amount ?

[UrS4boy]

Thanks Dave, I presume one has to take the crank out to be able to fit new thrust washers ? (#24). Rather than be able to fit it in situ. Do the washers come in different sizes to effectively shim the tolerance to the desired amount ?

I presume that officially the crank has to come out but practically (as in mechanics' secrets') I am guessing that only the bearing cap for No. 4 has to come off and then there is a trick to get the top halfs of the thrust bearings out and new ones back in).

My friend Kate doesn't seem to know about other sizes. I am guessing that new ones would get you back into tolerance.

I'll check on my home forum.

[macspring]

Thanks very much Dave.

[mcandmar]

Ohh god what have you done now

As above factory specs are .007 - .023mm, maximum wear limit of .025mm as quoted from the 7A Bentley manual. Measure with feeler gauge at the washers, or dial gauge on the end of crank shaft. Its a fairly large range of clearance so if it wore enough to be out of spec something is wrong. Main causes of premature wear, clutch release mechanism without enough free play, or if you drive around with your foot resting on the clutch and sit at every traffic light in gear. I have no idea if auto box's put any loading on them, probably not.

I really dont think you can get the top two washers out without lifting the crank. You may only have to move it a few mm's to tease them out but all the flywheel and oil pump would have to come off first, not really feasible to do in car.

[Wheeljack]

You can pull them with the crank in situ. Only the cap side thrust washers are keyed, so it is just a matter of poking one side of each upper washer and grabbing the other end of it as it rotates around(after pulling cap and lower thrust washers). BTDT. This is of course with the OEM style separate thrust washers. The aftermarket ones that are built into the radial bearing would be quite a bit trickier, but still doable if you rotate the bearing in the direction that doesn't bind with the keyed tab.

[UrS4boy]

Ohh god what have you done now

As above factory specs are .007 - .023mm, maximum wear limit of .025mm as quoted from the 7A Bentley manual.

You are out by a factor of 10 for the AAN (and ABY). I repeat 0.07 mm to 0.23 mm with 0.30 mm max.

And they can be removed in situ (its not fun but it can be done).

[UrS4boy]

I presume that officially the crank has to come out but practically (as in mechanics' secrets') I am guessing that only the bearing cap for No. 4 has to come off and then there is a trick to get the top halfs of the thrust bearings out and new ones back in). My friend Kate doesn't seem to know about other sizes. I am guessing that new ones would get you back into tolerance. I'll check on my home forum.

Here is the thread on my home forum (the answer is yes, it can be done in situ, after you drop the pan and pull Cap No. 4):

http://forums.quattroworld.com/s4s6/msgs/202224.phtml

Good luck.

[mcandmar]

You are out by a factor of 10 for the AAN (and ABY). I repeat 0.07 mm to 0.23 mm with 0.30 mm max.

And they can be removed in situ (its not fun but it can be done).

Always had a problem with reading and writing, should have copied and pasted

[DJones]

As a side note never use the one piece bearing and thrust washer, only ever use what is shown in the picture above I.e. separate main and thrust bearings.

[macspring]

Thanks DJ.