Allis T80 mower problems

Guys, I recently acquired an Allis 80T sickle mower that my wife's grandfather purchased new, we think back in the 70s.

First off, I'm looking for a manual for the mower.

Most importantly I am having a major issue trying to run the mower. I put new section on the mower new guards. The PTO and drive to the rocker box works
great. The issue I'm having is at the sickle bar head. The head is a cast steel piece that bolts through the bar and is connected to the rocker box drive with
a large steel threaded bushing that has a bolt run through it. This bushing and bolt situation is what transfers drive from the PTO and wobble box to the
sickle bar.

When I run the mower one of two things happen -

#1 - The bolt shears off, the sickle bar quits travel and I have to use a left handed drill bit to try and get the sheared bolt out. I am using a grade 8 bolt.
When this happens I usually lose the threaded bushing and have to order a new one, and they are not cheap.

#2 - The cast steal sickle head breaks off and the sickle bar quits travel and I have to order a new sickle head, again not cheap.

I have been unable to mow much more than 20 or 30 feet before everything breaks. I am trying to run the mower behind my Allis D17 in second gear low side idled
up. Everything seems to move and run freely.

The picture included is not my mower, its one I found online.

Any ideas or experience would be greatly appreciated! Thanks in advance!

Photo added

I owned/used an 80T mower on my farm for many years. For a manual I'd check with Sandy Lake Equipment in PA. ..or e-bay has manuals from time to time. I also would also check the AGCO on line parts book and check to see you have all the parts on the sickle head/wobble box. I remember replacing the bearings on the drive assembly under the wobble box as they do wear out... especially if they're not greased regularly. Make sure the bearing are relatively tight and the 'arms' cannot stray enough to hit something. Seems to me that the connection to the sickle bar should be tight to the bar... but the 'round' bushing should be free to move or else you'd get binding... and i vaguely remember a grease fitting somewhere around that area. Make sure the end of the sickle bar doesn't hit parts of the outer shoe .. I suspect you checked/replaced the wear plates and checked the up/down and fore/aft travel of the sickle... However, it's been quite awhile since I owned/used the 80T. Other than that, I really don't have a clue as to what your problem might be.

There's a manual for your mower on ebay. Been many years since I had an Allis mower, but remember something in manual about setting up the drive area. Does sickle move free by hand turning the large pulley?

The drive box turns great and everything moves free as it should when I turn the large belt pulley off the PTO shaft.

I will check the gap between section and ledger plate this evening along with sickle bar slop / travel forward and aft.

Thanks guys for the replies!

Can be several things or a combination.First off are you getting the teeth of the bushing meshed in with the teeth on the knife head? That is very critical and if its not seated right it'll
fly apart just as you described.Second if the hole in the cross arm where the bushing goes is worn and lets the bushing get cockeyed it'll break the knife head or the bolt.Also check to see if the two drive arms that connect to the cross arms are straight and not bent and if you have up and down play in the arms it means the rear bearings are worn and that'll cause problems.I
ran different variations of those mowers for years and can tell you everything about that drive has to be in top shape not to cause problems.What part of the country are you located?

Traditional farmer-

Thanks for the reply. I will try and observe the items you described. I am in SE Kansas.

Let us know what you find out.

You have a very dull sickle in the picture. Either fill the sickle with new chrome sections or sharpen that one. With all the nicks I see in those sections it looks like the sickle is too far gone to sharpen.

He says that's not a picture of his mower he got it online to illustrate,also said he has new sections and guard plates in his original post.

Sorry for the confusion. I meant to comment I've tried running
the mower in 2nd gear / low side so I can throttle up the pro
and get plenty of cut stroke compared to the tractors forward
motion

I'm hoping to get a better look tomorrow in the daylight

I got home late this evening

Tractor needs to run fast enough to have a pto speed of 540 rpm.