Mystery bolt

[New Englander]

I pulled the hitch pump out of my 786 and, much to my surprise and disappointment; I found a ½-13 X 1.75 inch grade 8 bolt lying in the case under it! Now I’m perusing the parts book looking for a good candidate. Maybe the last guy dropped it and just couldn’t find it but I really want to make sure. Ideas appreciated.

[rancherman84]

park lock hinge bracket?

[dumbfarmer]

differential?

[Maynard]

park lock hinge bracket?

More than likely.

[farmall666]

WHAT KIND OF MARKING DOES IT HAVE ON THE HEAD? IS IT A IH BOLT? OR W/P BOLT?

[New Englander]

Bolt head marking is WP.

I saw that the differential bolts are in place.

According to the parts book, the parking lock lever support bolts are indeed the correct size. When I get time to get back to the machine, what's the best way to get to that bracket?

[rancherman84]

Bolt head marking is WP.

I saw that the differential bolts are in place.

According to the parts book, the parking lock lever support bolts are indeed the correct size. When I get time to get back to the machine, what's the best way to get to that bracket?

unbolt and remove the parklock cover,flip it over and the bracket is right there.

[OneWelder]

New Englander , how far from Derry are you?

[New Englander]

Mystery solved! Rancherman and Maynard hit it on the head; it was from the park lock bracket.

It turned out that two had fallen out. I found the second one directly below the park gear. From the looks of it , it had a rougher ride to the bottom of the case. A cursory inspection revealed no obvious gear damage.

I will drill the bolt heads and safety wire them in addition to high strength lock-tite.

Thanks for pointing me in the right direction; it saved a lot of time.

[bill1957]

Hey New Englander...

I'm also from New England (Western MA) and also have a 786 with 2200 hrs on the clock. I brought it back to life from junk. If you review my previous posts, you might find some of the same problems you're likely to encounter with your 786. Do you know the history of your machine? Is it open-station?

[New Englander]

Hey New Englander...

I'm also from New England (Western MA) and also have a 786 with 2200 hrs on the clock. I brought it back to life from junk. If you review my previous posts, you might find some of the same problems you're likely to encounter with your 786. Do you know the history of your machine? Is it open-station?

Hi Bill,

Open station, just over 2000 hrs showing, runs excellent but has seen some backyard repairs, things I would never do.

The steering arms apparently were loose on the spindles. It must be very common as undersized arms are available. It was "fixed" by welding them on to the spindles.

The history I was told was that it came from potato farm country in Maine.

I'm putting brakes in it now - they were metal to metal. Funny thing is the parts and service manuals show 6 friction and 7 metal but, the left one at least, had 5 and 6 respectively. There doesn't seem to be room for any more so I'm going to see what the right side has. I got side tracked by finding the loose bolt in the case.

It has good power and my wife liked mowing with it!

[bill1957]

Hey New Englander...

I'm also from New England (Western MA) and also have a 786 with 2200 hrs on the clock. I brought it back to life from junk. If you review my previous posts, you might find some of the same problems you're likely to encounter with your 786. Do you know the history of your machine? Is it open-station?

Hi Bill,

Open station, just over 2000 hrs showing, runs excellent but has seen some backyard repairs, things I would never do.

The steering arms apparently were loose on the spindles. It must be very common as undersized arms are available. It was "fixed" by welding them on to the spindles.

The history I was told was that it came from potato farm country in Maine.

I'm putting brakes in it now - they were metal to metal. Funny thing is the parts and service manuals show 6 friction and 7 metal but, the left one at least, had 5 and 6 respectively. There doesn't seem to be room for any more so I'm going to see what the right side has. I got side tracked by finding the loose bolt in the case.

It has good power and my wife liked mowing with it!

I had to rebuild the front axle and spindles (new bushings, thrust bearings, and...yes...one undersized steering arm-the other is OK). One real Achilles heel is the Bosch injection pump (EP/VA6...CR). The head had seized up on my 786 before I acquired it. Getting the pump rebuilt or finding an exchange unit can be a chore. I ended up at Northeast Diesel in CT. They're an authorized Bosch service station and were able to rebuild. Two things to remember to avoid pump damage: (1) Be vigilant about fuel filter and fuel tank water drain-off, (2) use Stanadyne diesel fuel additive. This improves lubricity of low sulfur diesel fuel. Northeast Diesel recommended the Stanadyne brand.

Another potential nightmare is the shift (range and speed). Mine was as loose as a goose. I did a complete bolts-out restoration and replaced worn parts as needed. Now she shifts pretty well. Spend the money and get factory service and parts manuals for both the engine (D358) and the chassis. Well worth it. You can find them on Flea Bay. I've found I&T manuals to be pretty worthless.

A lot of unsolicited advice...hope this helps.

[Maynard]

Hey New Englander...

I'm also from New England (Western MA) and also have a 786 with 2200 hrs on the clock. I brought it back to life from junk. If you review my previous posts, you might find some of the same problems you're likely to encounter with your 786. Do you know the history of your machine? Is it open-station?

Hi Bill,

Open station, just over 2000 hrs showing, runs excellent but has seen some backyard repairs, things I would never do.

The steering arms apparently were loose on the spindles. It must be very common as undersized arms are available. It was "fixed" by welding them on to the spindles.

The history I was told was that it came from potato farm country in Maine.

I'm putting brakes in it now - they were metal to metal. Funny thing is the parts and service manuals show 6 friction and 7 metal but, the left one at least, had 5 and 6 respectively. There doesn't seem to be room for any more so I'm going to see what the right side has. I got side tracked by finding the loose bolt in the case.

It has good power and my wife liked mowing with it!

7,8 and 986 models used 5 friction and 6 steel plates. 10 and 1486's used 6 friction and 7 steels.

Jim N.

[PopC]

Hey New Englander...

I'm also from New England (Western MA) and also have a 786 with 2200 hrs on the clock. I brought it back to life from junk. If you review my previous posts, you might find some of the same problems you're likely to encounter with your 786. Do you know the history of your machine? Is it open-station?

Anywhere near Otis, in Western Mass??

[New Englander]

Bill,

Range shift arm has been welded to shaft, I don't agree with the method but it is tight!

Jim N.,

Thanks for the brake info. I figured it was something like that as there's absolutely no room for another friction disc and plate.

Jim C.

[New Englander]

New Englander , how far from Derry are you?

Near the seacoast.

[bill1957]

Hey New Englander...

I'm also from New England (Western MA) and also have a 786 with 2200 hrs on the clock. I brought it back to life from junk. If you review my previous posts, you might find some of the same problems you're likely to encounter with your 786. Do you know the history of your machine? Is it open-station?

Anywhere near Otis, in Western Mass??

Probably 60-70 miles North of Otis up against the VT border. Otis is close to the CT border of MA. Small farm of 50+ acres.

[New Englander]

Here's the belt and suspenders fix:

Bolt holes bottom tapped to accommodate a longer bolt, lock-tite, lock washer, and .040 stainless lock wire left over from my days as an aircraft mechanic.

One bolt ha to remain original as a longer one would not clear spring.

Also in the picture is the bolt that had the rough trip to the bottom. I shudder to think what a mess this could have made.

[Maynard]

Here's the belt and suspenders fix:

Bolt holes bottom tapped to accommodate a longer bolt, lock-tite, lock washer, and .040 stainless lock wire left over from my days as an aircraft mechanic.

One bolt ha to remain original as a longer one would not clear spring.

Also in the picture is the bolt that had the rough trip to the bottom. I shudder to think what a mess this could have made.

You shouldn't have used the lock washers there.

Jim N.

[New Englander]

Jim N,

I must respectfully disagree.

In my experience, fasteners are kept in place by stretch or supplemental device. For, instance, we used to measure the bolt stretch for aircraft engine connecting rods, especially radial engine master rods. Big micrometers and long wrenches.

A supplemental device would be a stop nut, lock washer, lock tab, or safety wire.

This particular bracket is positioned with dowels, so there should be, in theory, no shear movement and the bolts could be secured by stretch alone.

:(Obviously, that didn't work.

If there's some other reason that I should not have used a grade 8 washer there, I do want to hear it!

Jim C

[Maynard]

Jim N,

I must respectfully disagree.

In my experience, fasteners are kept in place by stretch or supplemental device. For, instance, we used to measure the bolt stretch for aircraft engine connecting rods, especially radial engine master rods. Big micrometers and long wrenches.

A supplemental device would be a stop nut, lock washer, lock tab, or safety wire.

This particular bracket is positioned with dowels, so there should be, in theory, no shear movement and the bolts could be secured by stretch alone.

:(Obviously, that didn't work.

If there's some other reason that I should not have used a grade 8 washer there, I do want to hear it!

Jim C

Split lockwashers are known to break (no matter the grade) and are not recommended for use on cast iron parts. A hardened flat washer would have been a better choice. Also. black oxide coating is preferred as it will not loosen as readily in cast as plated bolts will.

Also, what if the fasteners loosened only because someone had the assembly apart and merely failed to properly tighten them? Those bolts don't have a habit of coming loose.

My guess about the source of the bolt was based on that's the only place that size bolt is used that could escape and fall to the bottom of the transmission.

Jim N.

[New Englander]

Hi Jim,

Since both you and rancher responded with the same location, I took it that it's a common problem. Assumptions!

Plated bolts are what I stock. The lube torque value in a casting is 160 Lb/ft. By bottom tapping I was able to get in excess of 2X diameter thread engagement. Lock-tite does not have the lubricity of 30 weight oil but it's close enough - if I remember correctly. The bolt head seat is not wide enough to fit an SAE hardened washer, I tried. I have some AN thin washers (grade 6) that I was tempted to use but I would have had to slightly shorten the bolts to feel comfortable that they wouldn't bottom under torque stretch. In this case, the locks filled the bill for size.

As for split ring washers failing: Yes, I've actually seen grade 8s fail, but generally only when subject to corrosion. I have a differential kicking around the shop that has split ring washers under the multitude of bolts holding the ring gear on and I've worked on plenty of stuff, mostly older, that has lock washers securing cast parts.

I do agree that a properly designed part/torqued bolt does not need lock washers, I.E., loaded in tension or, if in shear, close tolerance or having a multitude of fasteners insuring no movement, or pinned, etc.

If I were to disassemble this part, I would find the washer definitely dug into the casting, slightly into the bolt head. That, coupled with the tension supplied, should keep it from backing out even if the assembly should loosen. I know that's old school.

The bottom line is: It ain't goin nowhere!

Jim C

[PopC]

Hey New Englander...

I'm also from New England (Western MA) and also have a 786 with 2200 hrs on the clock. I brought it back to life from junk. If you review my previous posts, you might find some of the same problems you're likely to encounter with your 786. Do you know the history of your machine? Is it open-station?

Anywhere near Otis, in Western Mass??

Probably 60-70 miles North of Otis up against the VT border. Otis is close to the CT border of MA. Small farm of 50+ acres.

Good to know!

Ray

[Bulldogred]

Here's the belt and suspenders fix:

Bolt holes bottom tapped to accommodate a longer bolt, lock-tite, lock washer, and .040 stainless lock wire left over from my days as an aircraft mechanic.

One bolt ha to remain original as a longer one would not clear spring.

Also in the picture is the bolt that had the rough trip to the bottom. I shudder to think what a mess this could have made.

As an a/c mechanic myself,that safety wire job looks straight out of the 65-9a,and using .040 safety wire to boot.Those bolts will be tight when mother earth reclaims her.

[New Englander]

As an a/c mechanic myself,that safety wire job looks straight out of the 65-9a,and using .040 safety wire to boot.Those bolts will be tight when mother earth reclaims her.

Thanks Red!

I don’t do much aircraft maintenance anymore but I do take the yearly training to keep my Inspection Authorization – a fallback in case my current gig goes away.

Jim N. brings up some valid points and I agree with most.

Let us flash back to A&P School, almost 40 years ago.

In the middle of engines, 101, one student asked why some engines had pal nuts on the cylinder hold downs and some did not. He replied “you don’t need them any more” and produced a bulletin from Pratt & Whitney stating so. He also stated that all the other manufacturers said the same.

Since he was on the subject, he went on to produce a paper from some engineers that said that lock washers did no good either. Those of us who had actual mechanical experience didn’t believe him and it was apparent that he also had doubts. None of us had ever seen a lock washer on a head bolt though or a wing bolt, for that matter.

After reading the paper, some switched to the lock washers are useless camp. I was certainly headed that way. The paper said that once the washer was flattened it was effectively a flat washer; who could argue with that?

The instructor devised an experiment. He produced a dozen new AN bolts and a half dozen locks. We were to screw them into an old engine case and carefully torque them with a dial-type wrench. They were dutifully screwed into an old Wright engine, every other one. The results were telling. The breakaway torque of the washer equipped bolts was marginally higher. More importantly, the washer equipped bolts resisted loosening, showing some torque, for some further degrees of turn whereas the plain bolt resistance fell off as soon as it broke free.

I suppose any loss of torque represents a failure. Certainly very few lock washers are used on aircraft. I remember most being star washers, nothing structural.