The Stovebolt Site Forums The Shop Area Engine Shop 261 crankshaft excessive end play & clutch judder- need help!

I haven't posted in a long while...got really sick for a long while and am finally getting better.

I have been dealing with clutch judder in my 1950 3600 since the first day it was driven after the restoration. every single time I took off in 1st gear, it chattered and bucked horribly. I have a rebuilt 261 with T5 in it, with an S-10 input shaft and an adapter plate. I have been through three clutches, trying to fix this problem. I laid underneath the truck while my wife held the brakes and slowly engaged the clutch- it wasn't leaf spring wind-up, it wasn't bellhousing or engine mounts- you could see that everything was happening right inside of the cover plate...

I found the bellhousing to be misaligned- runout was .0085 and parallelism was .006" Dave at Vintage Metalworks made me a special T5 adapter that eliminated almost all of the misalignment- it is now .0025 runout & .003" parallelism

While talking to my clutch guy, he mentioned that he had run across a similar issue with a truck with a 235. It had excessive crank endplay (a LOT of end play), which caused the crank to move in one direction during acceleration, and in the other direction when the throw-out bearing was pushed into the cover plate fingers.

I just went and grabbed my flywheel (trans is out right now), and I can move the crank fore-aft with a distinct "clunk-clunk"... it is obviously WAY out. I'll get the dial indicator out and measure this, but it shouldn't be moving like this...

[EDIT]: Crankshaft end play measured 0.014" with dial indicator at the flywheel. Spec is .003 to .009"


Can babbitt be added to #3 bearing halves and then machined to take up this play? We're talking about .009 to .010" increase in the thrust surface (on one side of the bearing or split 1/2 for each side).

I don't know if I have it in me right now to pull this engine and tear it all apart again- Hell, it's going to be a real chore just pulling the pan off and getting everything ready for a new gasket & seals....

I know now that the crank thrust surfaces should have been welded up and re-machined at the machine shop, when the crank was ground undersize. Since it has new main bearings in it, the play will not be due to a worn #3 main bearing thrust face.

Are there #3 main bearings available with an oversize thrust face?? Can a #3 bearing be modified/made to fix my problem? Or am I destined to do pull this engine and do a complete tear-down?

(Also- my 261 does not use the bearing shims) I believe the 235 uses the same main journal bearings, but I am not sure- hoping that someone has had some experience addressing this issue "in situ".

Any help or ideas are greatly appreciated.

Thanks

Dave

I had a similar problem with a racing engine, a small block Chevy- - - -a 400 block with a 350 crankshaft to meet the cubic inch requirements of the track where we raced. We corrected excessive end play by building a fixture to hold a thrust bearing in a lathe, machining the Babbit metal off the rear thrust flange, and building it back up with silver solder. I believe we added .005" or .006" over the thickness of a regular bearing. That modified bearing would last the whole racing season, maybe 1000 laps or so on a 1/4 mile dirt track. That would probably be the equivalent of 100K miles of street use! Silver solder is MUCH more durable than Babbit. If the engine is newer than mid-year 1955, it will have a locator tab on the upper bearing shell at the parting line- - - -that type of bearing can be rolled in and out with the crankshaft in place- - - -no need to do a complete disassembly. Yes, the bearing is the same as a 235. Two #3 main bearing caps from a 235 can be bolted together to serve as a holding fixture, clamped over a piece of aluminum round bar machined to be a heat sink to prevent damage to the main bearing material while applying the silver solder.
Jerry

Hi Jerry,

Thanks for responding. That is exactly the kind of solution I was looking for. .005" would get me within limits. .005" on both sides of the bearing would get me factory new end-play!

I called a bearing babbitting shop today and they said that there are some spray-on performance coatings that are available for babbitted bearings, but he didn't know what kind of thickness you end up with (it sounded as though it might add .001", which wouldn't be worth it).

Trying to find a machine shop these days that would want to take on a one-off project like this is like searching for hens teeth. Nobody has an imagination anymore....

Thanks again Jerry.

I have also heard that some of the older oversize main bearings included an "oversize" thrust bearing surface..... but I don't know if there is any truth to this. I think my main journals are either .020 or .030 under- I'll have to check my part receipts/machine shop invoice.

What undersize is the crankshaft? I can modify a bearing like that, since I have a couple of junk 235s that I can borrow the thrust bearing caps to make a machining fixture. All I'd need would be a correct undersize thrust bearing to start with.
Jerry

PM sent!

I've had clutch-judder problems on customer's cars and my own truck over the years and none of them were caused by excessive end-play. I'm not saying it can't happen, I just haven't seen it. The problems I've encountered were invariably caused by some clutch-related problem or torque-side motor mount.

One time it was a budget reman clutch assy supplied by a budget-minded customer. I charged her for the NAPA clutch and the labor to fix the problem and she's still sore about it 50 years later. On another job I slipped while holding the transmission and let it hang on the clutch disc and bent it. Had to do that job over again. In those days I still thought I could hold a truck transmission up without a jack. Another job went bad because I couldn't get the 10-3/4" 6-cylinder clutch and used an 11" V8 clutch disc. V8 discs have a different number of springs to accommodate the more frequent power pulses. When I put the correct disc in it the problem went away. On another job, the judder had been caused by the rivets that hold the diapharam spring to the cover working loose on one side of the diaphram. Another problem was because the disc was oil soaked. Another time the ball that clutch pivots was loose. On a Dodge dart it was a cracked bell-crank pivot. The list goes on and I'd look elsewhere before tearing into the newly rebuilt engine.

Not that this has any bearing on your situation but I'm sure mine has more than factory spec end-play. It judders slightly after several hours on the freeway. clutches can slip slightly and get hot running in high gear under load if the clamping force is not high enough. For me that's been more of a problem since I switched from 5.13 axle ratio to 4.57. I suspect the original 9-bolt clutch isn't up to the task.

Tommy, it sounds like you have dealt with a full gamut of clutch issues... I find it very interesting that changing the number of clutch disc springs solved a judder problem for you. My judder also gets worse after the truck has been driven a while.

My T5 trans has the S-10/Astro input shaft, and I think those vehicles came in both 4cyl and V6.

I removed my #3 thrust bearing and took measurements. I wish I knew what the new thrust bearing dimensions were... I'm at .014" end play right now, and I am going to fix this. My engine has fewer than 3000 miles on it, and everything still looks nice inside- cylinders, cam lobes, bearings, etc... The end play certainly doesn't feel like much, but there is a definite clunk-clunk when you force the crank forward and aft.

I have tried everything- chaining the engine/trans down to prevent it from rocking, messing with my rear leaf springs, changing clutches- you name it- no change. I think the special adapter plate is going to help, and I had the flywheel resurfaced again, and I am just waiting on my clutch. In the meantime, I am fix the end play issue, just because.