Differential bolts upgrade

[Skipper 1,788]

Hi good folks.

 

So what would possess someone to upgrade diff bolts you might ask. Well, I was driving along on the C195, and I heard a slight ticking sound, and stopped. Then went backwards to turn, and the rear wheels lokked up. could move like a 1/4 rew of the tires, then locked up again in both directions.

 

Opened up the tranny, and found this mess.................

 

 

 

 

 

2 Bolts were sheared off, and the left diff flange had taken a beating. The remaining 2 bolts were loose. The bolts look to be the original grade 8. Luckily no gears were damaged, even though the bolts had been chewed upon a bit.

Also the super thin washes were missing on 3 bolts, and had split, and were deformed on the 4th . That had also a part in the "getting loos" initially, one could speculate.

So, I started looking into why they had broken, and in that search I found that it was/is an issue on D series machines. So with all the added weight and abuse I have stressed this horse with, that's probably also part of the reason why.

 

But, and here goes my rant:

 

What the heck went thru the minds of the numnuts, who figured out to use these exact bolts? That is an engineering blunder of magnitude! Let me explain, before you choke in your Coffey 

 

Take a look at these bolts

 

 

 

The threads are all bashed and worn, and that is caused from the right side diff flange, riding on threads instead of a bolt shoulder. And they sheared right between the right diff flange and the ring gear.

 

Perhaps this explains better.

 

 

The "golden" bold is the correct grade 8, in original length etc. As you can see, the whole right flange is only riding on threads. Next to it is a bolt they could have chosen, but for some reason didn't. More on that later.

 

So when those lock nuts comes a bit loose, and they do under stress it seems, or it is the thin washer that breaks apart, then the ring gear can move a bit, and the result is that the holes are worn slightly oval on the right flange, and the bolt eventually snaps. 

 

Well you say, that can't cause a bolt to break, can it? Well, perhaps/perhaps not, and then again, because that is far from all of that blunder I was talking about. You see, they bored the holes for a 10mm bolt, and put in a 3/8 instead. A 3/8 should be 9.525mm, but these are 9.4, not that that is the deal breaker. But this much to small bolt for the hole, will allow the flanges to turn and scissor cut the bolts ever so slightly, instead of making it a solid joint.

 

 

 

In machine terms, this is as far from a tight fit as you can get! 

 

End of rant................

 

So what to do to make it better?

 

Well, I came up with 2 solutions, that I do believe will be way better.

 

1. The easy on. Just do what WH should have done from the start: Put a M10 bolt in, that fits the hole, and has shoulder all the way thru. That is a good and way tighter fit. I got some 12.9 bolt, that are equivalent to Grade 9, or a tad stronger. About 20% stronger than grade 8, and then add the bigger diameter, that gives 12% more bolt material, that bolt then on its own has about 35% more tensile strength. Then add that it doesn't allow riding on the threads, and a good fit in the hole, I think it is the right way to go. That M10 bolt is too long on the threaded part though, so it need to be cut off, when torqued inn. 12.9 nut, and a lot of locktite should keep this together just fine. This is the solution I think everyone should use in one form or another, and should have been standard from WH. IMO that is. If you do something like this, please remember to check clearance with gears, as big bolt heads may cause the need to grind a bit.

 

 

As you can see, the M10 bolt only leaves a gap of 0.004 inch

 

 

But, as you know, I tend to over do things once in a while, so on to option 2. The HD overkill upgrade. 

 

 

 

Same 12.9 bolts come in a M12, that's just shy of 1/2 inch. And as you can see, it is way more bolt than 3/8 or the M10. This upps the tensile strength of the bolt alone, to 195% of the original.

 

This of cause takes a bit of machining, and as the ring gear is hard as you won't believe, luckily I know a guy

 

I had the diff parts aligned and locked together, and had all 4 holes made in 1 go, so they are now perfectly aligned. Holes were machined by Wire EDM. That happens in a water bath, to keep things cool, so the whole unit came up brown from protective coating and a light surface rust, but only so slight that it could be wiped off with a cloth and some diesel.

 

 

As you can see, we are now down to a tolerance of 0.001 inch. Or in machining terms, a nice tight fit

 

 

So now there is absolutely no wiggle room, and all is 100% tight and as 1 solid piece, even without tightening the nuts.

 

So I cleaned everything up good, and put it all back together. 

 

The bigger heads on the M12 Allen head, were sticking out too far and wide, and would hit the mushroom gear, so I taped it all really well off, to avoid shavings etc. in bad places, and cut them down in size, after I had torqued them to 100nm, or about 75 ft/lbs (that's about 2 times OEM)

 

 

In order to avoid the bolts rotating, and damaging the gears, I made a "MIG LOCK"  

 

 

The other side could be left alone in regards to the clearing gears, so I cut the ends of the bolts, and made another "MIG LOCK" between bolt and nut, in stead of locktite.

 

  

 

And there we go, back in place. New gasket, a few new bearings while in there, new seals, and then close it up. 

 

It now runs absolutely perfect, and I can swear that it has been running with the diff all loose and dangly for a while before they snapped, because now it has less rattling sounds, and less play in the diff and so forth. It just goes as it should. Now let's see if this will make it last, of if anything else is up for an upgrade.

 

The sharp eye may notice that the gear on the hydro output seems a little big, and that's right, but that's a soon to come story for another day. 

 

Hope this could help someone out there

 

 

Edited August 13, 2021 by Skipper

[71_Bronco 1,072]

You had me up to the last part, where you welded the bolts to the case, and machined off the female hex key hole. Not sure I would have gone that route, but then again, you may be a little more knowledgeable in this particular area than I.

 

Either way, great write up and build. Glad it's back together and working out 

[Skipper 1,788]

8 minutes ago, 71_Bronco said:

You had me up to the last part, where you welded the bolts to the case, and machined off the female hex key hole. Not sure I would have gone that route, but then again, you may be a little more knowledgeable in this particular area than I.

 

Either way, great write up and build. Glad it's back together and working out 

 

Yeah, I know that's not for everyone. The Allen heads stick out far when in that size, and needed to be trimmed. Could have sourced a HEX head bolt in stead. Doing the spot weld was to make sure the bolt head would not turn and ruin the gears. I could have soaked the holes in Locktite, but in the interest of being able to take it apart again if needed, I chose that option instead. It is only a little tac, and I am convinced it dosn't go deep into the flange, so I took this route, right or wrong. But I know what you mean, I had hesitations too before doing it. So well aware of the risk, I judged that the peace of mind of knowing it wouldn't be able to move was more important to me.

[pacer 3,173]

You lucked out!! Amazing it didnt blow the bottom of the case out, cause that is the usual result. As the gear is turning with a piece of debris between it and the case -- the case loses and the cast iron will give.

 

My D180 did that, and I only had ONE nut loose, really messed the case up.

 

Another comment .... IIRC the earlier D's had 5/16" grade 5 bolts (mine did) and WH fairly early changed them to 3/8", but I think? they were still grade 5. And yours had the 3/8 and was grade 8!! Have seen where a couple guys went to grade 9, that tranny does take on a load!

 

Your 'fix' sure nuf oughta hold up, looks good!

[WHX?? 48,828]

Nice fix Tom and I can see your rant but keep in mind that the designers didn't know that you were gonna do the (excellent) mods to this beast or work it like you have. 

 

Nice the way the tranny can be still attached to the tractor to do this. 

 

I like the tack weld ... can always nip them off with a thin cutoff wheel if ever need be.  

3 hours ago, Skipper said:

Holes were machined by Wire EDM

That's the interesting part I would have thought more of a boring/reaming operation. Didn't know an EDM could do that kind of operation. 

 

Did I miss how the new nuts are locked on? 

 

Excellent write up! 

Edited August 13, 2021 by WHX??

[Ed Kennell 38,224]

16 minutes ago, WHX?? said:

Did I miss how the new nuts are locked on? 

Mig Lock between the bolt and nut.

[WHX?? 48,828]

3 hours ago, Skipper said:

MIG LOCK" between bolt and nut, in stead of locktite.

Ahhh... Yep I missed that 

[Skipper 1,788]

1 hour ago, pacer said:

You lucked out!! Amazing it didnt blow the bottom of the case out, cause that is the usual result. As the gear is turning with a piece of debris between it and the case -- the case loses and the cast iron will give.

 

Yep! for sure. Luckily the tranny is replaceable with any other Eaton 1100 unit, with only difference being the axles that are longer for the large hubs. So those hard to find axles are actually the only thing I'm really scared of loosing. 

[WHX?? 48,828]

1 minute ago, Skipper said:

the large hubs

Was it fun getting them off or did you have them off before? 

What is your method for securing them back on? 

[Skipper 1,788]

Haaagh don't get me going on that. 

 

Securing them again was just to force them on again, and tightening the set bolts. Hope that will hold up, and then time will seize them again. Don't feel like gluing them inn

 

Getting them off was quite a struggle , and that's all in here: 

 

 

 

 

Edited August 13, 2021 by Skipper

[Pullstart 62,910]

Awesome upgrade!  EDM rocks, it doesn’t change hardness of the piece either!  I agree, that in most cases, the black machine bolts in 10mm fashion would have been plenty enough.

[ebinmaine 67,602]

16 hours ago, Skipper said:

What the heck went thru the minds of the numnuts, who figured out to use these exact bolts? That is an engineering blunder of magnitude! Let me explain, before you choke in your Coffey 

Too late....

 

 

Well written mod. 

Thanks!