Anyone here get RPM drop? - Crankwalk

[DSM Storm]

A local DSMer has just installed 3 motors in his talon, those 3 motors all crankwalked, he and a few others noticed it was walking not by the car stalling but by the RPM's dropping whenever the clutch was pushed in, there were 1 7 bolt, 3 6-bolts and now my stock 6 bolt developed the same, unfortunatly ive already begun to pull it apart but im going to measure crank play tomorrow, I can actually push on my crankshaft and see my crankshaft move from side to side never mind the fact that i can hear it clunk when i do so, does anyone here have thier motor drop RPM? This is very important, there are alot of people that are having this problem on thier stock 6 and 7 bolt engines, any feedback is appriciated, if anyone could measure the play that would be even better. Symptoms are pretty obvious, you push in the clutch, RPM's drop usually between 30-60rpm's and when you let off the pedal it goes back up, the tone of the engine is noticable, it is hard to tell on the factory tach so I used the digital feature on my AFC to see so.

TIA

P.S. The point to this post is to get feedback from the general masses.

[Edited by DSM Storm on 07-23-2001 at 05:45 PM]

[Viprklr]

Mine dropped a hair. I wasn't sure what caused that though. I just wrote it off to the fact that the battery was out of the car for about 2 months.
My endplay was .021 by the feeler gauge

[Le Talon]

Mine drops a bit too, but at least, it doesn't "seem" to move when pushing the crank pulley with a pry bar. In fact, it looks very tight. BTW, my thrust bearing was way out of specs when I replaced the bearings this spring. I'll check for endplay during the winter...

The joys of owning a 2G!

[DSM Storm]

You have crankwalk. Limit is .010, what does the battery have to do with the crankshaft walking?

[Edited by DSM Storm on 07-25-2001 at 12:43 PM]

[ShapeGSX]

As far as I am concerned, Leon got it right when he coined the phrase "The Dreaded RPM Drop" or TDRD.

I put a 6-bolt engine into my 97 because of crankwalk.

When I put it in, I didn't measure the thrust play. Nor did I set the thrust bearing. 150mi later, I noticed that the RPMs were dropping by 30 every time I pushed in the clutch.

You have to measure this RPM drop with an AFC ro some other digital tach. A datalogger doesn't have enough resolution. The stock tach won't show it.

So I removed the oil pan and bearing caps and I put in a new thrust bearing. The old bearing was worn on the block half. This means that the cap half was pushed farther towards the timing belt side.

At this point, I had heard about setting the thrust by prying the crank to one side. So I pried it to one side and then the other, and then tightened the cap.

1000mi later, I was getting TDRD. 30RPM again. Damnit!

At this point, Charlie Vlachos pointed me at a page:
http://www.atra-gears.com/crankshaft/

So I filed a channel into a new bearing to give direct oil flow to the thrust face. I removed the old bearing. It was worn, but not as bad as the previous one. I put in the new bearing, following the directions for thrust bearing alignment on that page. When I did that, I found that my thrust was not even across the entire thrust face, checked with a feeler gauge. The reason was that I was prying on one side of the crank instead of the center.

So I tried it again. I pried the crank all the way over to the flywheel side of the engine. I then had my wife pump the clutch a few times (2600). Then I had her hold it down while I tightened down the cap. SUCCESS! The thrust was even. The thrust play was measured with a feeler and a dial indicator, and they both matched.

4000mi and one shootout later, there is no DRD. I'm crossing my fingers. My thrust play with this new bearing was RIGHT on the edge at 0.0065 to 0.007".

If your engine is not in the car, I suggest prying against the crankshaft at the direct center of the crank on the flywheel side while someone tightens down the bearing caps.

In the car, I suggest using a heavy duty clutch to align it.

And I'd look into the alignment dowels that CRCO has started offering.

[Viprklr]

I know I have crankwalk. The bearing is already on order. I only brought up the battery cause it was disconnected forever from the car and I figured the RPM drop was due to the computer relearning everything.

[Schneidr80]

Is there any other reason that the rpm's would drop? According to the PMS computer, my RPM drops from 800 to 720 when the clutch is pushed. I don't experience the clutch not coming up on the left hand turns though. The car is a 96 X.

Matt

[DSM Storm]

I measured crank end play today, .007 and the feeler gauge fit snug! I had RPM drop, check out these pics:

http://people.ne.mediaone.net/override/thrust/1.jpg
http://people.ne.mediaone.net/override/thrust/2.jpg
http://people.ne.mediaone.net/override/thrust/3.jpg
http://people.ne.mediaone.net/override/thrust/4.jpg
http://people.ne.mediaone.net/override/thrust/5.jpg
http://people.ne.mediaone.net/override/thrust/6.jpg

[Schneidr80]

What do those pics tell me?

Matt

[Peter 92TSI]

Originally posted by Schneidr80
What do those pics tell me?

Matt


How worn out the bearings are. ;)

[DSM Storm]

They show you worn thrust bearings with no crankwalk.

[Stephen]

who wants to come put a new thrust bearing in my car, Ill pay you$$$$$$$$$$!

[supraklr]

i am not really understanding what you guys mean by the rpm dropping how do i conduct this test?

[PJpankratz]

just push the clutch in when you are in the driveway
and see if the rpm's drop (do it when it is warmed up)

[PJpankratz]

to set the crank endplay (thrust bearing) what you want to do is yes tighten the main caps down except the thrust bearing one. push the crank forward by jamming a flat head screwdriver against a counter weight and a main cap. not the thrust bearing cap. then tighten the thrust bearing cap down and check your crank end play. if for some reason it is more that .010 or tighter than .003 than redo everything and jamm the crank towards the back.

[ShapeGSX]

Originally posted by PJpankratz
to set the crank endplay (thrust bearing) what you want to do is yes tighten the main caps down except the thrust bearing one. push the crank forward by jamming a flat head screwdriver against a counter weight and a main cap. not the thrust bearing cap. then tighten the thrust bearing cap down and check your crank end play. if for some reason it is more that .010 or tighter than .003 than redo everything and jamm the crank towards the back.

I'm more careful than that. I did that with one set of bearings, and I was replacing the thrust bearing 1000mi later.

Search this forum and the regular tech forum for posts by me on crankwalk. I have posted tons of info on this.

The basis for my fear is that prying on the crank on one side (on a counterweight) leads to an unven thrust because of uneven pressure on the thrust bearing. It is better to pry on the center of the crank. You have to check the crank endplay with both a feeler gauge and a dial indicator. Make sure that they match! And make sure that the thrust play is even across the entire thrust face using a feeler gauge. If not, do it again.