atari_st

After reading several post about TBF, I find is time to measure my TB play. I bought a dial indicator at Costco this weekend and plan to do it soon. Here is my question: I know to pry the crank forward...measure it and pry the crank back and measure it. The difference...well I hope its in spec. Once I am done measuring, do I just leave the crank in the forward or aft position or do I somehow try to move it back to the middle? Do you remeasure to be sure your in the middle? All the post talk about moving it forward and back to measure but never mention what position they tighten everything back up at.

Thanks

borland

You might want to pick up one of these:

http://www.harborfreight.com/cpi/cta...temnumber=5645

Its arm works nicely at holding he dial gage (without the magentic stand), while being bolted to the bottom of the clutch housing bottom surface.

You'll find that the crank wants to rest against the thrust bearing, either in the forward or rear position, so its somewhat difficult to get the crank centered at the mid-point. In fact having the dial gage installed allows you to observe this percularity, as well as showing the mid-point.

I moved the crank to the mid-point before reseting the pinch bolt. However since the flex plate allows for some mis-alignment, it probably makes no difference in bearing wear while the engine is running with oil pressure at the thrust bearing.

borland
90' S4, Slate Metallic

SharkSkin

It would seem that the problem occurs when the crank is pushed forward. Mayb tighten the pinch bolt with the crank set to the rear?

H2

I might get the courage someday to buy an auto 928. I'm interested in how I can check thrust bearing play, easily in a PPI. Hoping you can come up with something easier than I've seen thus far...that is both easy to do and works.

Harvey

fabric

Wouldn't it be best to give the motor a few manual cranks, and let it settle into it's natural position? That's the procedure recommended here when simply releasing the pre-load.

SharkSkin

Fabric, you're probably right... just thinking out loud....

Bill Ball

Garth has some hard-to-describe technique using straps for assuring the crank is staying at both ends of the endplay. I had a hard time visualizing his setup. I have just levered the crank forward, levering at the center so as not to distort the flywheel (if you could) set the dial, levered back till it clunks and looked at the maximum reading. Never gave it too much thought, but it would be worth making sure we are doing this correctly. Garth seems concerned that the accessory belts pull the crank back towards center. Suppose you could temporarily slacken the tension.

FeedNfrenZ

Jeff, I assume that you have recently read my post about TB checking. My car DID settle back into a more forward position than I was able to pry it to. I think it was due to the belts (Timing, A/C, power steering and Alt.) I wouldn't suggest undoing or loosening these belts. Just have someone read the dial while your holdng the flywheel torqued to each end of travel.

Garth S

The typical amount the flex plate releases rearwards when first done is ~3 +/- 0.5mm: the spec range of crank end float one is trying to conserve is 0.1 to 0.4mm.
The ratio of the two is, say, a nominal 15:1. The flex plate does precisely that ... 'flex', and quite easily in both directions. Then as long as any large forward static preload is released from the flexplate, it matters little if the crank is moved 0.05mm to 0.10mm to 'center' it within its float range prior to reclamping via the pinch bolt. The important thing is to prevent the long term reoccurrence of a slipping spline on the prop shaft - so that the ~3mm preload does not creep back into play.
In theory, centering is a good idea: in practice, I've concluded that it's not worth the effort - and next to impossible to assure the result if attempted. As Borland said, quote " However since the flex plate allows for some mis-alignment, it probably makes no difference in bearing wear while the engine is running with oil pressure at the thrust bearing." Agreed ....

BTW, the strap thing Bill noted ... a web strap was secured to the top crossbar and dropped down over the front pulley to under the car. Pulling back on the strap when under the bellhousing will give the crank rearward position ... then, pushing the flexplate/flywheel forward allows the crank float range to be measured - no prybars

Bill Ball

OK, Garth, I get the setup. I'll try it this weekend.