Flexplate wobble!

[hillytim69]

Well I've run into a problem, I've posted a few times on my progress on my 75 Stepside, sm-465 to Th 350 swap. I put in a 383 turbo 350 combo with a new B&M 2000 converter and the Pioneer flexplate that came with my shortblock. I thought when I bolted the flexplate/converterbolts that there was too much distance between the two. What I've run into now is that it seems maybe the flexplate had to flex too much to reach the converter and now it is warped. I kept hearing a strange noise under there when running and found the flexplate noticeably wobbling. I should've figured this out before when I was trying to install my mini starter and found varying distances from starter gear to flexplate ring gear depending on engine position. So this really sucks. I think I may need to remove the tranny and put shims on the end of the crank before the flexplate. I've never had this happen before when bolting a motor and trans together. Do you guys think it may be due to the aftermarket Eagle crankshaft? Anyhow I really want to get it on the road asap so I can take my boy to the Car Craft Summer Nationals next month in a Chevy, not a Honda... Any ideas or experience on this problem? BTW I did get my shifter (Z-gate) installed.

[James McClure]

DO NOT SHIM ANYTHING!!! There are only a few things that will cause this. Was the flex plate installed when you got the eng? It could have gotten bent in transit. Next, if you installed it did you put it on backwards? Any weights ect. should face the oil pan. Does the converter hub bottom out in the end of the crankshaft like it's supposed to? Clearence between the converter screw bosses and the flywheel should be "0" on the slightly raised areas on the flexplate facing the trans. Your going to have to drop the trans to check things out. With the way you describe this issue I think you should be prepaired to replace the flex plate again. Hope this helps, jim

[old Rusty C10]

depending on the flex plate you have ive seen them come bad from the manufacturer... JMc hit it on the head if it aint in backwards its prolly a defect

[babyJay]

Change it out before it kills someone!

[silvereagle07]

It's on backwards. Do you have any pics of it?

[hillytim69]

Flexplate was not mounted when i got it. Its a cheapie Pioneer FRA-104. Its definitely not on backwards, I checked that out a few times. The raised converter bosses and crank flange face out towards the rear. I will be taking it all apart to inspect. I could post pics but don't know how to post them up on here. I do seem to remember a gap between the converter and flexplate mounting bosses when I installed it so I think when I tightened the bolts it pulled the flexplate towards the converter, distorting it. How do I know for sure if the converter "snout" is seated completely in the crank? I believe it is. The converter looks to spin true but the flexplate is wobbling. Any pointers on how to go about posting pics up on here would be great and I'll take some and update as I go. I will be ordering a better SFI approved flexplate as well. Sucks to have to pull the trans but what can you do...

[LONGHAIR]

If this is a stick to automatic conversion, it is possible that the pilot bearing is not allowing the torque convertor to slide into the crank properly.
If that is indeed the case, the flexplate is probably perminently "flexed" an in bent or even cracked.

[hillytim69]

In this case I also changed engines to a 383 so this is a brand new crank, I should've mentioned that. i will be taking it all apart soon and will report what I find.

[James McClure]

hilly, I think Longhair is on to something. Check for a pilot bearing in the end of the crankshaft. The converter hub should drop into the end of the crank an inch or so. Leave the flex plate off and hold the converter up there and try to slide the hub in. It should disappear into the crank hole. Let us know, jim

[hillytim69]

I was just out looking at it. The flexplates raised T.C. mounting bosses face the rear but the counterweight is on the front twds the engine does that matter? Shouldn't it be on the rear of the flexplate?

[powerdriver 1958]

is the weight touching the converter,just wondering

[hillytim69]

Well its gonna have to wait until the wknd now. Wife found some free clothesline poles on Craigslist so I got to dig them out and bust off some 50 yr old cement instead of working on my truck today...

[James McClure]

Hilly, Read my post above. The weights face forward towards the engine. You have it in right. The only thing left to cause this is the converter not engaging the end of the crank properly. Like longhair said above, look for a pilot bearing in the crank. If it has one, remove it and test fit the converter. The hub on the converter should drop right into the hole and disappear. jim

[hillytim69]

Today before i leave to work i loosened the flexplate to converter bolts. There is around 3mm or .112 inch between the converter mounting bosses and the flexplate mounting bosses when the converter is fully seated in the trans. Otherwise the converter has to pull forward or the flexplate move rearward for the 2 to mate up. the flexplate is warped bad as well. Could the converter be seating too far into the trans or do I have a bad flexplate on there or what the heck?

[LONGHAIR]

The converter should slide back and forth in the free space between "bottomed out" in the transmission and touching the back of the flexplate.....when un-bolted of course.

It still sounds to me like something is stopping the converter from moving foreward far enough....As stated before, I have seen the pilot bearing turn out to be exatly that in more then one case.
I have also seen guys try to use the old flywheel bolts when installing the flexplate....this does not work either. They are too long and will hit the back of the block.

[hillytim69]

Hey Longhair, the converter does slide forward in the free space and touch the flexplate. Maybe this isn't the issue. And the engine is a 383 with a new Eagle crank so i don't think it would've had a pilot bearing. I just thought that the "free space" of 3mm seemed like it was excessive. Again, the converter will move back and forth through this free space area. Perhaps this is OK but the flexplate is really warped nevertheless. I rotated it a little at a time and checked the clearance between the starter gear and the flexplate ring gear and it is pretty bad.UPS delivered my new thicker SFI flexplate from Summit and new ARP T.C. bolts today. The tranny is coming off (dammit!). So do you think my "free space" area of 3mm or slightly less than 1/8" sounds normal? Also I did use stock GM flexplate to crank bolts with the starwashers but they just barely protrude through the crank on the other side. WOw I've been swapping Chevy engines/tranny's since I was 19 and never had this many problems. I hope i only have to move the tranny back a little ways to do the flexplate R&R. We'll see how my Harbor Freight scissor type tranny jack works... Thanks for all the help and I'll keep updating as I go!

[Wrecker55]

Tim, I have the same problem on my LT1 383, was rattling so i knew the sound and tightened up torque conv bolts. fixed it right off, them a few weeks later same thing. So I go to tighten bolts again and notice there bottomed out on torque conv, stock 350 crank bolts were just a smidge to long and I didnt notice. So I got right length bolts installed and same noise, and holes were enlonged, so I figuer it's cracked now and need to replace with new flexplate. Hope this hels you out.....Tim

[CSGAS]

Is your tranny case cracked?

[hillytim69]

I mounted the starter an turned the flexplate/engine by hand while measuring the gap between flexplate and starter gear as i went. I'm getting about .090" on average all the way around with maybe .010-.015 max runout which i can live with. The clearance between ring gear and starter should be .075-.125 per the Skip White ebay ad on this mini starter i have so I think I've got it.

[hillytim69]

I drove it today. the horrible noise under load is gone. I do still have this whistling sound coming from somewhere. Could it be the flexplate making this sound because I have no inspection cover? Other than that it seems good. I guess I'll keep trying to figure it out. Next step will be to run the engine with the torque converter bolts out to see if if goes away. Its not the accessory belt because I tried that already.

[77 350 Shorty Wide]

Does it whistle all the time, driving, standing still at idle? I've owned more than one '77 that whistled when ever you drove it down the road. Always figured it was air running over or through one on the openings in the radiator support. Drove me crazy! One of the trucks was brand new. I installed a tube grille in it and it was slightly worse with it in, but never the less the whistle was there with either grille installed. God Bless, Terry

[hillytim69]

No the whistle is consistent with engine speed. I think I tracked it down to an exhaust leak at a muffler clamp. New flexplate: so far so good. Thanks to everyone who offered help and advice. I'm close to having it on the road.