[Bill.H]

My '83 446 falls into the range of serial #s with the potential for the broken bolt problem. From reading the FAQ, it appears that the nuts come off, then the bolts come loose, then break. I take it this means the bolts don't break as long as the nuts stay tight?

As my diff has no leaks and no obvious problems with seals or bushings, I'm wondering if I can avoid a complete tear down at this time by simply verifying that the locknuts are still on and then either A. removing and replacing them with the addition of blue Loctite; OR: B. securing them to the bolts with a tackweld.

It appears as if I need to separate the diff from the frame to remove the diff cover. True? In order to do so, is it necessary to remove the lines from the motor (or the factory holding valve) or is there enough flex in those lines to get the cover bolts off? I'm thinking that if I have to remove the lines, I might as well drain the system from them as long as they're open - I plan on doing a fluid change anyway. Will this work or do I have to open the port on the TCV as well?

Sorry if some of these questions are totally obvious, but it's my first time and I like to understand what I'm doing before I start, not spread the job out over a week because I'm missing something. I know I'll need a cover gasket (RTV) and the oil.

 

[99flhr]

Assuming a tractor where the bolts have not failed or loosened, and the bushings /seals are "good"

I wonder if the carrier halves could receive the recommended welding while still in place ? :headscratcher:

 

[Hydriv]

Only you can decide the course of action.

If you intend to keep this tractor and you want to put your mind at ease, then the wise thing to do is preventative maintenance.

There are two things that go wrong with the trans-axle. Broken bolts and leaky seals.

The question is: Why would you address one and not the other? No matter what, you have to remove the complete trans-axle from the tractor. If you order in all new seals, two new axle bushings and buy four new bolts from the local CAT dealer, then you should have everything you need if you buy the 7 quarts of oil at the same time.


Do all of this now and you should never have a problem down the road. This is all covered in the FAQ's,

 

[Bill.H]

There's two things stopping me from just doing it all right now as the FAQ says, Tom: money and experience. Being unemployed, I don't have the money for a lot of parts, but I do have time to "play" a bit; so I prefer to tackle smaller jobs first and get to know this equipment better before I attempt a total tear down.
There's no rush on any seals or bushings, hence no hurry to replace them all. But I do worry about the diff coming apart and that's why I'm asking if there's anything that can be done to prevent that short of a rebuild. If I wasn't worried about the locknuts coming loose, I'd just change the oil and be happy.

 

[Bob MacGregor]

The bolts break just before where the nut is and where the differential pieces mate. I have changed bolts in differentials that had the new style bolts but broken bolts. The bolts broke as I was removing the nuts to replace the bolts. Two on one tractor. Any 400, 4000 series tractor with the 41 tooth high range driven gear is a broken bolt suspect. On the newer 4000 series tractors with a 46 tooth high range driven gear, this gear has threaded bolt holes into which the bolts are installed and the locknuts keep the bolts from unscrewing. The 46 tooth gear is the slower speed high range gearing. In 2000 I was mowing on a hilly area when the final bolt broke in my 1985 448. When the bolts break you have absolutely no control or breaking of the tractor as the brakes stop the transaxle before the differential and when the bolts break half of the differential does what it wants to do. This accident put me in the emergency room. I pushed the tractor onto my trailer and drove myself to the ER. It took lots of effort to clean up the blood from the fabric seat and carpet in my van after I healed up some.
I called Ingersoll and Bill Parkin suggested that I purchase the 46 tooth gearing changes and I did. He faxed me the part numbers and I ordered them from a local Ingersoll dealer. They were pricy!!!! But I liked the slower ground speed in high range and it made plowing snow in high range much easier.
Mad Mackie in CT :thumbsup: :446:

 

[Bob MacGregor]

Any of you that have or have had liquid filled rear tires I recommend replacing the differential bolts. My 1985 448 had liquid filled rear tires when I bought it from my son-in-law in Michigan. I was with him several years prior when he had the tires filled at a tractor dealer.
With the ability to quiclky change direction that these tractors have, the bolts get much more shearing force put on them while using filled rear tires.
Over the years there has been discussion as to the rolling inertia that filled tires have as compared to non filled tires. I had to prove this to a friend that was convinced that the liquid in the tires was not an inertial problem. I rolled a filled tire to him and had him stop it by himself and did the same with a non filled tire. The filled tire knocked him down while trying to stop it!!!
Bob MacGregor in CT

 

[Hydriv]

Bill,
The seals and bearings can likely be sourced from a local power transmission wholesaler. They sell all kinds of rubber belts, chains, sprockets, gears, seals, speed reducers and so forth. If you are in or near a big city, then your Yellow Page directory is your best friend.

Welding those bolts may do more harm than good and won’t protect you from the damage you are hoping to avoid. As Bob pointed out, the bolts shear right where the threads stop. Bolts are hardened to a certain tensile strength. Welding can interfere with that strength. Since you have never done this before, I see this as a 3 day job tops. Drain the system and remove the trans-axle. Dismantle it so that the axles and carrier are removed . Pop out the axle seals and the brake shaft seal. Those are identical. You could leave the shifter seal as it rarely leaks. You can check the axles for up/down and side to side play. This is not IN/OUT play. That play has nothing to do with axle bushings. If you do have noticeable play, then those bushings can be driven out with an appropriate socket that is sort of snug to the axle bore. Once you have them out, that same supplier should be able to match them. Take an axle shaft with you to help him out with the true ID.

That would be done on day two along with installation and re-assembly of the trans-axle. Day three would find you putting the trans-axle back under the tractor and refilling the hydraulic system.

You can also contact Brian Hildreth for price and availability of all these items. Part numbers are easily found here on this site.

 

[Billygoat]

What Bob is saying about the filled tires makes sense to me. I remember "back in the day" when racing motocross, it was all about unsprung weight, we weighed tires, tubes, rims and anything else that was below the suspension to get as light as possible. Removing the unsprung weight gave us less inertia to overcome when braking, and less mass to get moving again. Filled tires would seem to have more of a flywheel effect to overcome than lighter unfilled tires thus more stress on drivetrain.

 

[Bill.H]

As Bob pointed out, the bolts shear right where the threads stop.

Aha! Thank you, that clears it up. I had the impression from the FAQ that the nuts coming loose was what caused the bolts to break, and just read Bob's post which made me start to think otherwise. Now I understand even tight ones will break. I hope to have new, filled, tires before next winter so this becomes more of a priority.
I'll get an email off to Brian so that I'll definitely have the correct parts. Now to find a CAT dealer.

Am I better off opening the lines from the motor to the holding valve or the TCV lines at the holding valve? From memory it would be easier to do the latter. Should I drain at the test port first or is that not necessary? I'm asking because I want to include the fluid change at the same time and I don't know if opening the lines will get as much of the old stuff out of the system. It's a lot easier to ask than to redo.

 

[Hydriv]

My advice is this. Do the regular drain procedure first. Then remove the trans-axle. Service it. Install it. Refill the trans-axle and the hydraulic system with the same oil.
Buy 10 quarts and you are covered.


Owners have reported sheared bolts, loose bolts and bolts that have bent into an L-shape that distorted the top cover. What actually happens inside the trans-axle is anyone’s guess. Which came first? The chicken or the egg?

 

[Mr onetwo]

When I do this to my differential I am going to go one better on the bolts.You can get 3/8x5-24 12 point ARP bolts for $1.54 ea plus S&H at Allensfasteners.com These are rated at a true 170,000PSI and will not shear.Much stronger than GR8.The guys at Allens are great :thumbup: to deal with and they do small orders for a reasonable price!

 

[Bob MacGregor]

Hi Bill H,
Do you have a 1983 446? If you do then the differential housing is not the hydraulic system reservoir and only needs several quarts of gear oil or 15W-40 motor oil of the type that is in the hydraulic system. On a 1983 446 the hydraulic reservoir is a plastic tank under the battery in the steering tower.
When I change differential bolts I like to have the plow installed and I place two jack stands under the tractor frame in the area where the travel control valve is located. I then jack up the rear of the tractor with a hyd floor jack to a point where the wheels are off the floor and raise up the jack stands. I like to have a plow installed to reduce the tipping to the side problem. Remove the wheels, the seat, fuel tank side panels, the fuel tank, drain the housing of gear oil, remove the brake band assy. I drain the fuel tank first and I usually have a new fuel line ready to install. Disconnect the hyd lines from the drive motor, cap them if you can as there will be a lot of hyd oil that willl drain from them The transaxle must be removed from the tractor frame. I do this on a floor jack and roll it out from under the frame. You can put the transaxle on a wooden box or something similar to work on it. The axles need to come out and have C retaining rings and the brake shaft has to be driven out with a punch and hammer. It has a locking ring that is internal to the hole in the housing. There are shims that space the differential into the housing.
Remove the differential and clean the interior of the housing and inspect for damage. I grab the differential assy in a vise and replace the bolts one at a time. There is a torque spec for the nuts, it escapes me at the moment. The replacement bolts from Ingersoll are longer than the original ones and this is OK. Torque them in a cross pattern. Reassemble in the reverse. There is a service manual for the transaxle from Ingersoll.
I may have forgotten something but it really isn't that difficult of a job, but remember that the tractor can tip and fall over if bumped as it isn't very stable and this is why I like to have a plow installed and in the down to the floor position.
Mad Mackie in CT :lol: :fingerscrossed:

 

[Rockdog]

Mr. OneTwo,

Stronger bolt is always good if the bolt alone is the issue. This particular joint requires no relative movement between the gear and differential halves. Any movement and you'll end up with a failure at some point due to shearing at he threads. Going with a bolt with higher tensile strength is great if the bolt alone is the issue. I'm assuming this is the Proof Load of the bolt rather than yield.

You can increase the clamp load between the gear and differential halves by increasing the bolt tension which will require higher torque (everything else being the same - surface preperation and finish). You dont want to mess around and go over the yield load of the bolts though. So if you can get that info for the 170Ksi bolt then great. Otherwise going with the CAT bolts with documented torque specs vs. clamp load information is your safest bet.

The CAT dealer you buy the bolts from can give you the torque specs (standard, high, and low). Go with the High. For a 3/8-16 the high spec is 50 n-m (37 lb-ft) for 33 K-N of clamp load (7400+ lbf). The PPer who mentioned going with the CAT bolts is that by doing so you know they are a good product.

The bolt you buy from ACME is one that a buyer bought from the cheapest bolt manufacturer they could find on the internet and who knows if it meets the 170ksi proof load or not. How are you gonna know?

 

[Billygoat]

Rockdog, The company, ARP, that Mr onetwo was talking about is certainly not "ACME". ARP in one of the leading fastener companies, mostly serving the high performance automotive market. They are a good and reputable company and make great products. They most likely can provide whatever documentation one would require.

 

[Mr onetwo]

Well Rockdog, I don't know where you got ACME from. :wtf: ARP manufactures the highest quality bolts in the world....made in the USof A :usa: Just ask any top fueler what they use to keep their Keith Black Hemi alive with. According to their website technical pages the 3/8" bolts have 170,000/180,000 yeild strength @ 45 ft. lbs. of torque and have a preload (clamping force) value 8622 lbs. I doubt very much that your "cat" dealer can even tell you where their bolts come from or are made. I hope my tone is not misconstrued...just stating facts! :mrgreen:........Something else I wanted to put out for discussion.....what if you put a Heli-coil in the holes of the low range gear, used Red Locktite and then the locknuts on the back side to help hold everything together? Seems like it might work :think:

 

[Hydriv]

I think that the two of you are missing RD's point.

There are two issues at stake here. One is tensile strength and that's were you two are focused and the other is shear load, which is something you do not see in many racing applications. Head bolts, crank bolts etc do not see a "shear" load. And when shear loads are expected to be high, the designer often incorporates some sort of "key" into the castings to take the shear load and just use the bolts to hold the item or items in position.

A key of some kind should have been designed into the carrier halves. Large diameter dowel pins could have been used to arrest the rotation of the high and low range gears. Had those minor changes been implemented in 1969, then this broken bolt problem would not occurred.

 

[99flhr]

Considering that the "fix" includes welding the carrier halves together, are the bolts that important?

I`m not advocating using hardware grade "cheese", but do we need Kryptounobtainium ? :headscratcher:

 

[Rockdog]

First of all I dont know how to determine what is the 'best bolt in the world' is. 170Ksi Ultimate Strength (their website states ultimate not yield) vs. 150 ksi minimum - I'll take the 150 ksi minimum based on what I know as fact vs. what I read on an internet marketing website. I'll take the bolts with slightly lower claimed strength because I KNOW its a minimum spec, and they dont need any 'special attention' to put them together.

As a product engineer in the driveline industry for almost twenty years now what I dont like about what I read on ARPs website is that they lubricate their threads during torquing. Big variation when doing this because its is not easily controlled. This reduces the stress due to torque on the bolt itself and increases tension at the same torque. The other thing is that the torque specified is at 75% of yield. Hmmm. Is this due to the variation from lubricating the threads, variation in material properties of bolt, friction coefficient, etc. My recollection over the years has been more inthe 90% range. So when I read that I smell a rat. Just give me a bolt that I can torque to a value without having to follow directions on 'lubricating' the threads or any other voodoo hocus-pocus bs. There's a few other things on that site that are marketing foo foo that can lead someone to believe they are getting more than they are paying for - but they arent.

Not too sure top fuel class drag engines are the best litmus test for realibility. They only have to last 1 or 2 thousand cycles. Now if they lasted 8000 hrs then you've got something.

Dowels between the gears and diff halves wont solve this problem. The pinion gear spider or trunnion works for the diff halves together. Dowels are for alignment during installation and until the joint can be properly locked down with fasterners. In this case it simply appears to be too clamp load holding everything together. Can be solved with existing geometry (same size bolts with higher clamp load - and torque and yield strength if needed - or larger diameter bolts and high torque etc. or drill the assembly out and add bolts). Well actually it IS possible that the addition of dowels could keep the darned thing from moving enough to break the bolts but it would not be an efficient design alternative. The design of these diffs is pretty much consistent with a lot of automotive and truck and tractor diffs. Just not quite strong enough.

Adding nuts on the outboard side as described int eh previous post will actually work against ya. When you torque the nut down the friction will tend to make the bolt turn in the loosenging direction within the gear threads (helicoil?). I just dont see 4 bolts as being enough if you're going to impact the diff when 'shifting'.

 

[Hydriv]

Considering that the "fix" includes welding the carrier halves together, are the bolts that important?

I`m not advocating using hardware grade "cheese", but do we need Kryptounobtainium ? :headscratcher:

Fair question.

Most owners report that the OEM bolts failed right at the spot where the threads met the shank of the bolt and this is due to the threaded portion of the bolt being in the holes of the Low Range gear. Neither gear is pinned or indexed to the carrier. Therefore that weakened, threaded portion is subjected to high shear loading by the gear whenever someone asks the max from the tractor. Picture a 448 with tires loaded with Rimguard and 100 pound cast iron wheel weights as well as tire chains. The owner is in a rush to plow the two feet of snow off his driveway He makes 45 degree passes to push the snow from the middle of the drive to the edge of driveway and beyond. He's running at full throttle and never touches the brake.Instead, he just reverses direction on each passes with the travel lever. The twisting action on the entire carrier goes on for more than an hour.

How many times can you do this before the bolts start to stretch just a tiny amount. And every time they do stretch, that makes it easier for the gear to rock back and forth on the four bolts trying to shear them in half. As I see it, that's the real problem but welding the carrier halves together is still a good move. You do whatever you can to either prevent the problem or at least slow it down.

 

[Billygoat]

Rockdog & Hydrive, point well taken. Was just saying ARP wasn't acme off the wall fasteners. Also thanks for the lesson Rockdog, I'm always willing to listen and learn.