D2 sagging equilizer spring

I wouldn't space the mount at the track frame as that is essential to hold the engine down on high torque---i would re arch, add a leaf, or space under the pan

I.ve got a couple of D2's with the same issue. One has had a 1" block of steel welded to the frame under the spring ends which seems to work okay. The other has had an extra leaf put into the main spring.

I prefer the extra leaf in the main spring as it stiffens the spring and help to reduce the amount of nose rise and fall under power.

Not sure how you could space under the pan and the leaf frame sits into a recess and crudely pivots across this pan/recess. The pivoting action is probably why the pans gets cracks in this area.

I pulled mine out and had a heavy truck spring shop re arch it, holds its head up now.
Gary

On mine the end few inches of the bottom spring were worn off, I had a truck spring shop replace the leaf and problem solved

I seem to remember that there were about five different spring groups for D2 5J through 5U. Maybe you want to swap for a good used spring group of a stouter version.

My 5J had one broken leaf. It was a bit of a chore finding the right leaf for the right group, and they don't all interchange one group to another group, but we found it and it sure firmed up the ride under drawbar power as well as when bulldozing.

For those of you that had it re-arched.. did the spring shop know what to do or did you come up with a spec somehow?

For those of you that added a leaf.. do you have any specs on what you added?

I like the idea of stiffening it a bit with an extra leaf. Are there any cons to doing that?

dunno if the specs are that crucial to getting what you want as long as its long enough

If the spring is reset the fella in the spring place should only need the measurments between the track frames and how much you want it to sit
If it has sagged to me it needs extra leaves otherwise it will just sag again but any good spring type should be able give you the right answers

Paul

Hi, MrsMP.
A part of the issue with the D2 and D4 equaliser springs as opposed to truck suspension springs is an equaliser spring is pretty much always under the same load that it was designed to support unless the tractor is moving a load, be it by the drawbar or via a 'dozer blade. when the tractor is under load in the forward direction, the twisting effect of the pinion against the crown wheel will tend to lighten the load on the spring relative to the load itself and for the duration of that load.

What this means is that the spring will slowly change to accommodate that constant load, the weight of the engine, radiator etc., pressing down on it, thereby changing its shape in the direction in which that load is pushing it, in this case, DOWN. The 'TRULY TECKER-NICKEL' term for it is 'sag'. Or, to put it another way, gravity will have its way. Ask ANY older woman about this.

Then again, I have heard it said that there is no such thing as gravity, that instead the Earth SUCKS.

For those who have 'droop-snoot' or 'concorde nose' on their favorite vintage Cat, I would suggest that you check the spring itself to see if there is any upward curve towards the outer ends. IF there is an upward curve toward the outer ends, my own choice would be to have the 'sproing' reset, possibly with a SLIGHT upward curve to the leaves toward the center - downward toward the outer ends - - - or simply dis-assemble the spring, turn each leaf over while keeping it in its same position within the spring pack and re-assemble. Yes, you will likely have to cut off the rivets holding the pack clamps to their respective leaves and re-rivet them on the opposite sides of those leaves. Is that too much to pay for a 'free' spring reset?

Placing blocks on top of the track frames under the outer ends of the spring can cause a whole new problem if it raises the spring too high to be able to get the retainer pins back in. These little jiggers have been known to rear over backwards under load if the spring is not secured to the track frames by those pins.

Just my 0.02.

Hey guys, here's a few things I've learned when dealing with sagging/worn D2 main springs-

There are indeed a number of different mainspring part numbers and design differences throughout the J series and U series (including early and late) models. When substituting another good used mainspring in place of your old one, it's best to have all the parts manuals and serial numbers of your machine as well as the donor machine to ensure you're putting the correct spring in. There are major differences in spring/track frame perch design by the time you get to serial #5U7210 and up.

I scanned a couple of pages out of my 5U1 - 5U13236 parts book to show the main design difference between the earlier D2 mainsprings and the later - but keep in mind that this is not a complete representation of ALL mainsprings from 5J up on through the late model 5U production that started at #5U13237 and up - as always you'd need to consult the parts book for your particular machine - but this is a decent representation of approximately mid-range D2 production when Cat started moving away from the arched leafs and began using flat ones.

This scan is of the earlier style arched mainspring assemblies found in #5U1 - #5U7209, and in fact the 5J D2's had springs designed like this too, although I'm not saying they were identical beacuse parts numbers, leaf counts, leaf thicknesses, etc are all over the board.

[img]http://i802.photobucket.com/albums/yy310/TRNelson/002_zpsudtbb18v.jpg[/img]



Here's a scan now of the flat leaf design which started with #5U7210 and likely carried on at least until the "late" series D2 design change happened starting at #5U13237 (I don't have a parts manual that covers anything after that serial number so I can't verify that).

[img]http://i802.photobucket.com/albums/yy310/TRNelson/003_zpsynoph4eo.jpg[/img]



Now with the differences in spring design there were also differences in the spring perch areas of the track frames, note in the scan below how the earlier style arched mainsprings had their perches sitting right on top of the track frame channel, and the later flat type mainsprings had their perches cut in and recessed down into the sides of the track frame channels. Also note the "#4B9379 plate" pieces that are found in both track frames, they are essentially a replaceable wear surface that the mainsprings sit on, and can become thin over time and also contribute to the "nose down" appearance.

[img]http://i802.photobucket.com/albums/yy310/TRNelson/001_zpszffxbhsq.jpg[/img]



With those differences in mind, always first make sure that you have the correct spring installed in your machine - say, if your serial number indicates that you should have the flat type spring but somebody along the line put the arched type in instead, that would really make the nose sag low to the ground even if the spring was perfectly good. If that isn't the case, next inspect to see that you don't have broken leafs that could be weakening the spring. If that's good, it pays to check the wear out on each end of the spring like SteveA already mentioned - it's not uncommon to see the bottom leaf worn very thin where it sits on the spring perch, and if the spring is worn that thin it's also a good bet that the 4B9379 wear plate I underlined in the scans above is also very worn. If my memory serves me correctly, that wear plate is around 3/8" thick or so, and the mainspring leafs are also close to that same thickness (again, just relying on my memory here) so in theory if both pieces are worn badly you could be having 1/2" to 3/4" worth of wear at the mainspring perch, which would make the nose drop exponentially more by the time you got out that far. I seem to remember when I was renewing the mainspring wear plate on my 5U several years ago that that 3/8" of height difference under the main spring raised the nose about 1 1/2". So severe wear on the mainsprings and perches can cause the nose to drop significantly, enough to be mistaken for just being spring sag.



Also keep in mind that the track frame geometry on a D2 requires a definite mainspring height to keep the undercarriage system operating properly and provide equal weight distribution where it's meant to be. Ideally, you want the weight of the tractor sitting squarely on all four bottom rollers when on level ground. If you've ever looked closely at a D2 from the side, you'll notice that (with the standard diameter front idlers) the idlers are elevated off the ground, as well as the drive sprocket. And since the track frames pivot in front of the drive sprockets, if the main spring ends up being stacked too high it will cause the chassis to "nose up", actually lowering the drive sprocket closer to the ground and decreasing the weight distribution on the lower track rollers. The front track rollers will assume most of the weight, the rear rollers in some cases will lose contact with the rails completely, causing the drive sprocket to become the "heel" of the ground contact which is a very bad thing as it means that shock loads are transmitted through it and into the drive train. See the cartoon below that illustrates what I'm describing - the top picture shows a D2 with the correct spring thickness sitting level with the track frames and distributing it's weight on all four bottom rollers - the idler and sprocket are off the ground. The bottom picture shows what would happen if a later style flat mainspring was installed where an earlier arched one should have been (or far too many leafs are installed) - it puts the nose up too high which causes the pivot shaft to lift the rear of the track frames off of the rails and makes the drive sprocket take part of the weight of the machine.

[img]http://i802.photobucket.com/albums/yy310/TRNelson/D2%20mainspring_zpsio2rvpys.jpg[/img]



My dad bought a 5U that had just this problem, it should've had the arched type mainspring but had a replacement flat type installed instead, which put the nose about 4" higher than it should've been and caused the machine to primarily ride on the front track rollers and drive sprockets only, in fact when I watched it drive by the rear rollers weren't even turning because they were an inch or so off of the rails. It was a heck of a rough riding machine, I have no idea how many years the previous owner ran it that way. It likely would've been just fine with the flat type spring if they would've also put the corresponding track frames on along with it, but that didn't happen. To make a long story short, that's why I don't like to add extra leafs to these springs because you could start to throw off the geometry of the undercarriage. At the end of the day, I personally prefer to find a correct good used spring to replace a worn or sagging one with, or just have new leafs made accordingly. Plus addressing spring perch wear in addition to everything else is good practice also.