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720 drive shaft

Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Construction and other equipment
Forum Description: everything else with orange (or yellow) paint
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=69291
Printed Date: 27 Jun 2025 at 3:11pm
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com

Topic: 720 drive shaft

Posted By: Charlie175
Subject: 720 drive shaft
Date Posted: 25 Apr 2013 at 12:45pm

My brothers 720 vibrates in the back and he thinks the driveshaft is bent (It does have a wobble to it). He had replaced the flex coupling when he had it apart, so that should be ok. Any other ideas?

Any other way to remove it without moving the engine?

Any used ones out there? I had heard at one time that other brands (Other than Powermax) might match up as it was a common shaft

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Charlie

'48 B, '51 CA, '56 WD45 '61 D17, '63 D12, '65 D10 , '68 One-Ninety XTD

Replies:

Posted By: aras
Date Posted: 25 Apr 2013 at 2:34pm

I took mine out and straightened it in a press. I was able to remove it after the cover on the middle section is removed on the topside.

The coupler needs to be checked for runnout when installed on the engine

Posted By: Charlie175
Date Posted: 25 Apr 2013 at 2:44pm

Can you explain what you mean by runout?

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Charlie

'48 B, '51 CA, '56 WD45 '61 D17, '63 D12, '65 D10 , '68 One-Ninety XTD

Posted By: aras
Date Posted: 25 Apr 2013 at 3:28pm

The shaft must be concentric to the engine pulley.... I'll see if I can find the service manual

Posted By: RichinWis
Date Posted: 25 Apr 2013 at 4:36pm

Runout is how much wobble the shaft has, in laymans terms if the shaft is bent or tweaked it will wobble

Posted By: DiyDave
Date Posted: 25 Apr 2013 at 5:58pm

Charlie, also check that it was re-assembled correctly. I always mark a shaft, with paint, on each part, and U joint. If the U joints are out of phase, that will vibrate like crazy.

Posted By: Charlie175
Date Posted: 26 Apr 2013 at 7:10am

Thanks for the help!

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Charlie

'48 B, '51 CA, '56 WD45 '61 D17, '63 D12, '65 D10 , '68 One-Ninety XTD