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Allis Chalmers 712H bevel gear box

Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Garden Tractors
Forum Description: A great place to discuss the Simplicity and Allis Chalmers Garden Models
Printed Date: 23 Sep 2023 at 10:27am
Software Version: Web Wiz Forums 11.10 -

Topic: Allis Chalmers 712H bevel gear box
Posted By: ma2022
Subject: Allis Chalmers 712H bevel gear box
Date Posted: 01 Aug 2022 at 4:09pm

I'm new to garden tractors and don't know a lot but have been working on my grandparents Allis Chalmers 712H. I replaced the carburetor and the engine starts and runs great. The driveshaft spins but there doesn't appear to be any output from the bevel gear box. The belts don't spin. Am I right in assuming that the beveled gear box needs to be replaced? 

Posted By: HudCo
Date Posted: 01 Aug 2022 at 10:43pm
is the coupler on the engine good ?

Posted By: Gary
Date Posted: 02 Aug 2022 at 7:16am

I believe some of the belt pulleys or bevel gears are keyed to the shaft.

I'd first check for a failed key.

Start by removing the belt and turning the the belt pulley.


Posted By: Steve in NJ
Date Posted: 02 Aug 2022 at 8:49am
Gary is correct. In lot's of cases, I've found the key in the input shaft of the BGB fails allowing the driveshaft to turn. The problem is sometimes they booger up the imput shaft or does some damage to the keyway where it would lead to pulling the BGB out and getting the keyway/shaft repaired.  HTH

39'RC, 43'WC, 48'B, 49'G, 50'WF, 65 Big 10, 67'B-110, 75'716H, 2-620's, & a Motorhead wife

Posted By: ma2022
Date Posted: 02 Aug 2022 at 11:32pm
Thanks all for the replies. I think the coupler is still good on the engine. That makes a lot of sense about the keys. When I have the chance I will check that. Thanks again for the direction I appreciate it. 

Posted By: Mikez
Date Posted: 03 Aug 2022 at 10:27pm
With it shut off grab the pulleys sticking out each side and see what they feel like. Spin by hand. 
You sure those were spinning when engine was running. The left pto side only the outer part of the clutch will spin unless the lever is engaged. But something should be spinning 

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