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B Crank Movement Question

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KenBWisc View Drop Down
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Joined: 15 Sep 2009
Location: Fall Creek, WI
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Post Options Post Options   Thanks (0) Thanks(0)   Quote KenBWisc Quote  Post ReplyReply Direct Link To This Post Topic: B Crank Movement Question
    Posted: 24 Nov 2017 at 4:42pm
Motor is torn down again after a complete overhaul 10 years ago and less than 800 hours. Shop says the crank was moving into the block. I'd appreciate guidance on why this happens and what to check for with the rebuilder so it doesn't happen again. This is my first experience with this shop as the previous rebuilder pasted away. I checked the parts book for a thrust washer but have not found one.
'34 WC #629, '49 G, '49 B, '49 WD, '62 D-19, '38 All Crop 60 and still hunting!
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Dick L View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dick L Quote  Post ReplyReply Direct Link To This Post Posted: 24 Nov 2017 at 4:55pm
When the crankshaft is repaired properly you would have about .0015 clearance between the crankshaft and the crankshaft timing gear on one side of the thrust bearing as shown in the picture below. The Main bearing shell half with the thrust flanges go on the front main bearing cap as shown in the second picture.







The thrust is part of a main bearing set.




Edited by Dick L - 24 Nov 2017 at 5:43pm
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steve(ill) View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote steve(ill) Quote  Post ReplyReply Direct Link To This Post Posted: 24 Nov 2017 at 5:06pm
Ken, I have seen wear on the crank / gear/ or replacement bearings that were slightly less wide.. That results in .030 -.040 end shake . I bought a tractor like that... probably similar to your problem. New bearing did not get clearance down to spec.. I pulled the gear off and cut a small counter bore on the backside of the gear, so the gear went on .025 further ....... I ended up with about .004 inch endshake..

Edited by steve(ill) - 24 Nov 2017 at 5:07pm
Like them all, but love the "B"s.
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CTuckerNWIL View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote CTuckerNWIL Quote  Post ReplyReply Direct Link To This Post Posted: 24 Nov 2017 at 8:13pm
In  my opinion, that thrust bearing is the weak point in these engines. The worst thing you can do for that bearing is hold the clutch in for extended periods of time, while the engine is running.
 Every time you push the clutch in, you are pushing the crankshaft forward into that "half" bearing surface.
http://www.ae-ta.com
Lena 1935 WC12xxx, Willie 1951 CA6xx Dad bought new, 1954WD45 PS, 1960 D17 NF
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Gerald J. View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gerald J. Quote  Post ReplyReply Direct Link To This Post Posted: 24 Nov 2017 at 9:21pm
Should be a topic covered in the AC shop manual.

http://geraldj.networkiowa.com/Trees/Allis-Chalmers-G-B-C-CA-Service.pdf

Gerald J.
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KenBWisc View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote KenBWisc Quote  Post ReplyReply Direct Link To This Post Posted: 25 Nov 2017 at 9:52am
Thank you to each and everyone who responded! Very helpful. This is definitely the place to come for expert guidance!!
'34 WC #629, '49 G, '49 B, '49 WD, '62 D-19, '38 All Crop 60 and still hunting!
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PaulB View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote PaulB Quote  Post ReplyReply Direct Link To This Post Posted: 25 Nov 2017 at 1:14pm
If the shop that reground the crank did a proper job, the front of the crank where the timing gear gets pressed on will be ground off to get the proper clearance when the gear is pressed back on. If the gear had to be altered then the crank shop did not do a proper complete job.  One thing that leads to the trust bearing wearing out is installing a high load pressure plate. When you push the clutch pedal down all the total spring pressure of the pressure plate is against the 1/2 shell that is the trust bearing. 
If it was fun to pull in LOW gear, I could have a John Deere.
Real pullers don't have speed limits.
If you can't make it GO... make it SHINY
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