Backhoe 447 Backhoe 3x20 CUT mounting warning and consideration

[Yourkie]

Thought this might be a heads-up to those who are mounting a 447 backhoe on the 3x20 mid size compacts. This from another forum ssbtractor. It is good to share these expensive mistakes. Hope this is OK.

Original Post:

Wayne xxxxx on Monday, April 20, 2009:

Have a 3320 with a 447 backhoe that was just developed a flexing of the backhoe with the rear axle. Took to dealer to find out that the mounting bolts have broken loose from the rear axle with an estimated cost of $4,000.00. This unit has low hours, 400 & never abused. Has any one else experienced this?

Reply:
Dale G. xxxxxxx

I just did one of those, the same failure except it was the dealer that installed the wrong bolts in the wrong transaxle mounting holes. Look carefully the mechanic at the dealer did not see that there are two different bolt lengths in the backhoe attachment kit and they are only one inch longer so it's really easy to miss those two which have to go into the exact holes on the transaxle housing or you will have the failure that you described. It's hard to understand how I did it in my shop for 600 bucks, no wonder I have a lot of customers, based on the 4k price, geeze that is not that hard of a job.

 

[dfkrug]

I just did one of those, the same failure except it was the dealer that installed the wrong bolts in the wrong transaxle mounting holes.

Got any photos, Dale?

The newer 3x20 series, of which your 3720 is a member, seems to have
replaced the 4x10 of old. Question: does your 3720 use cast aluminum
right and left rear axle housings? My 4300 uses Al, with cast steel or
cast iron center section.

 

[Yourkie]

Sorry Dale no photos. I wasn't involved in either the problem or the fix. I'm also not sure about the aluminum vs cast steel on the 3720 axle housings. I found this potential expensive problem when looking for some info on 447 initial installs and decided to share it. If as the post suggested a dealer screwed up this bh install by using wrong length bolts the mistake should be fairly easy to make for the average user. BTW TBN is the predominant forum I go to if looking for info. on this stuff. Google found the other hit.

 

[Cocre]

According to the Deere 447/448 Operator's Manual, for the 3X20 model the bolt sizes are three M14x135 and three M14x120 per side; just a bit over a half inch difference in length. The three longer bolts go toward the rear and all bolts are torqued to 129 ft/lbs with a warning not to overtighten or to replace the hardened washers with standard ones.

I have considered checking the torque values on mine, perhaps now I will actually do it.