Reinstalling final drive shaft in 440 final drive. Installed new seal, bearing cups and bearings. Everything seams to fit and the snap ring is installed. The service manual indicates to add shims and tighten up the quill and measure end play and then remove enough shims to pre-load 0.000 to 0.003". End play I assume is the amount of play in the shaft when you pull it in and out as shown in Fig 170-10-21. However, what does the manual mean by pre-load? If I measure 0.010" of end-play, does that mean they want me to remove 0.010" of shims to get 0.000" of preload? Should this then result in no end play?
Now here is where I think I have a problem. Even without shims, I have a measuremeable amount of end play. If I remove all the shims and carefully start to tighten the quill, the shaft will be so tight it will not rotate but I can still move the shaft in and out and measure some end play. So no matter how many shims I remove, I will always have some end play.
Is this normal, or is something not correct? I would think that with no shims, the end play to go to zero before the shaft is so tight it will not rotate.
440 Final Drive Shims
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hunter41mag
- 440 crawler
- Posts: 126
- Joined: Tue Apr 12, 2005 7:11 am
- Location: Eastern Pennsylvania (NE of Allentown)
Re: 440 Final Drive Shims
Hi,
The object is to put more shims in so you end up with end play (only because it is something that we can be easily measure with a dial indicator) and than measure the end play of the shaft. You than subtract whatever your end play is plus the amount of required preload (example: measured .012" end play, subtract the .012" plus the preload spec .003" = .015" of shims to remove to end up with .003" preload). This is the same procedure that we use for setting preload on countershafts for Mack Truck transmissions. When everything is properly preloaded it allways runs true and will not wobble around, also as the component heats up and everything expands it stays under a slight preload. It is also important when anything is running under a preload that an EP lubricant is used (extreme pressure), so make sure that an SAE 90 EP or higher is used. Do not use any SAE 50 or lower as this is not an EP lubricant.
If new bearings are being installed we set to the high side of the preload, if used bearings are installed than we go to the low side of the preload spec.
If you have end play without shims than something is amiss, wrong cups and or bearings?
I just pulled the finals on my 440 and the one side had a makeshift shim under the outer bearing cup. Maybe this had the same problem after some else had rebuilt it? My parts manual only shows shims for the outer diameter of the cover, not under the cup.
Lavoy might be able to give more insight on this.
Don
The object is to put more shims in so you end up with end play (only because it is something that we can be easily measure with a dial indicator) and than measure the end play of the shaft. You than subtract whatever your end play is plus the amount of required preload (example: measured .012" end play, subtract the .012" plus the preload spec .003" = .015" of shims to remove to end up with .003" preload). This is the same procedure that we use for setting preload on countershafts for Mack Truck transmissions. When everything is properly preloaded it allways runs true and will not wobble around, also as the component heats up and everything expands it stays under a slight preload. It is also important when anything is running under a preload that an EP lubricant is used (extreme pressure), so make sure that an SAE 90 EP or higher is used. Do not use any SAE 50 or lower as this is not an EP lubricant.
If new bearings are being installed we set to the high side of the preload, if used bearings are installed than we go to the low side of the preload spec.
If you have end play without shims than something is amiss, wrong cups and or bearings?
I just pulled the finals on my 440 and the one side had a makeshift shim under the outer bearing cup. Maybe this had the same problem after some else had rebuilt it? My parts manual only shows shims for the outer diameter of the cover, not under the cup.
Lavoy might be able to give more insight on this.
Don
jac wrote:Reinstalling final drive shaft in 440 final drive. Installed new seal, bearing cups and bearings. Everything seams to fit and the snap ring is installed. The service manual indicates to add shims and tighten up the quill and measure end play and then remove enough shims to pre-load 0.000 to 0.003". End play I assume is the amount of play in the shaft when you pull it in and out as shown in Fig 170-10-21. However, what does the manual mean by pre-load? If I measure 0.010" of end-play, does that mean they want me to remove 0.010" of shims to get 0.000" of preload? Should this then result in no end play?
Now here is where I think I have a problem. Even without shims, I have a measuremeable amount of end play. If I remove all the shims and carefully start to tighten the quill, the shaft will be so tight it will not rotate but I can still move the shaft in and out and measure some end play. So no matter how many shims I remove, I will always have some end play.
Is this normal, or is something not correct? I would think that with no shims, the end play to go to zero before the shaft is so tight it will not rotate.
Here is what I think is going on. If I drive the inner bearing on all the way, then slide on the drive gear and outer bearing, there is a small gap between the outer bearing and the snap ring. The outer bearing is not tight on the shaft, as such the shaft can move slightly, the amount it moves is equal to the small gap between the outer bearing and the snap ring (0.012"). So, if this is correct I have the following options.
1) spray the shaft to build of the outer bearing seat area
2) use some gap filling Loctite to tighten up the outer bearing
3) do not drive the inner bearing on all the way
4) add a 0.012" shim to take up the end play
5) replace shaft
6) leave the end play alone
Any thoughts on best option.
1) spray the shaft to build of the outer bearing seat area
2) use some gap filling Loctite to tighten up the outer bearing
3) do not drive the inner bearing on all the way
4) add a 0.012" shim to take up the end play
5) replace shaft
6) leave the end play alone
Any thoughts on best option.
John,
What you are having trouble measuring is true end play. Most of what you are feeling is the play of the shaft sliding in the bearings. Picture it this way. If you did not install the snap ring on the end of the pinion shaft, but yet somehow could make sure that there was the correct preload on the bearings, you could still pull the shaft out of the final drive. Even if you did this, the bearings would still be correctly pre-oaded, but the shaft would be gone. For the purpose of pre-load on the bearings, the shaft has not real function but to hold everything in line.
Now, with a shaft like yours, it is not possible to accurately measure pre-load because there is no press fit to the bearings. When installing new pinion shaft bearings, it should be necessary to drive the inner bearing on at least a little bit, but the outer bearing should go fairly hard the whole way. What has happened in your case is that the shaft was not properly pre-loaded at some time in the past, or after years of wear or neglect, all of the pre-load was lost, and an end ply situation developed. Once this happens, eventually the bearings will start to rotate on the shaft, and wear it to the point that there is not press fit left. If you shim under the snap ring, you will most likely be able to measure end play and set the preload on the shaft. With the correct preload, the bearings will be pressed against the pinion gear, and that will try to keep them from spinning on the pinion shaft, but that is not likely enough. Sooner or later they will start to rotate on the pinion shaft again and will wear against the side of the pinion gear and then you are back to square one, except that you will not know it because you will have already assembled in on the crawler and will believe you have no reason to worry.
What you need to do is take the pinion shaft to the same guy that is spraying up your axle and have him do the shaft as well. It will not hurt to cut the splines off and build up for the inside bearing, just make sure he does not come out so far that the pinon gear shoulders on the built up area instead of the side of the bearing. Build up the surface of the outer bearing as well. When done, both bearings will be a press fit, and the gap under the snap ring will not matter because you will not be able to move the shaft in the bearings by hand.
Lavoy
What you are having trouble measuring is true end play. Most of what you are feeling is the play of the shaft sliding in the bearings. Picture it this way. If you did not install the snap ring on the end of the pinion shaft, but yet somehow could make sure that there was the correct preload on the bearings, you could still pull the shaft out of the final drive. Even if you did this, the bearings would still be correctly pre-oaded, but the shaft would be gone. For the purpose of pre-load on the bearings, the shaft has not real function but to hold everything in line.
Now, with a shaft like yours, it is not possible to accurately measure pre-load because there is no press fit to the bearings. When installing new pinion shaft bearings, it should be necessary to drive the inner bearing on at least a little bit, but the outer bearing should go fairly hard the whole way. What has happened in your case is that the shaft was not properly pre-loaded at some time in the past, or after years of wear or neglect, all of the pre-load was lost, and an end ply situation developed. Once this happens, eventually the bearings will start to rotate on the shaft, and wear it to the point that there is not press fit left. If you shim under the snap ring, you will most likely be able to measure end play and set the preload on the shaft. With the correct preload, the bearings will be pressed against the pinion gear, and that will try to keep them from spinning on the pinion shaft, but that is not likely enough. Sooner or later they will start to rotate on the pinion shaft again and will wear against the side of the pinion gear and then you are back to square one, except that you will not know it because you will have already assembled in on the crawler and will believe you have no reason to worry.
What you need to do is take the pinion shaft to the same guy that is spraying up your axle and have him do the shaft as well. It will not hurt to cut the splines off and build up for the inside bearing, just make sure he does not come out so far that the pinon gear shoulders on the built up area instead of the side of the bearing. Build up the surface of the outer bearing as well. When done, both bearings will be a press fit, and the gap under the snap ring will not matter because you will not be able to move the shaft in the bearings by hand.
Lavoy
Thanks for all the replies. I think the inner bearing is pretty tight on the shaft since I had to drive that one on. I believe all the problem is with the outer bearing which is loose and has been spinning against the pinion gear. Any chance a cyanoacrylate ("CA"=industrial super glue) will hold the bearing? For example, Loctite 430 is made for metal bonding and has a bond strength of about 3500 psi. All the adhesive would have to do is maintain the preload, since I do not see much additional lateral loading on this shaft and the bearing is not that loose on the shaft. Calculating the bond area for the bearing (ID= ~1.1" and width ~.45") Area = 3.14 x diameter x width = ~ 1.5 sq. in. With a 3500 psi bond strength, that means it would take about 5250 pounds to move the bearing. Now CA adhesives maintain about 90% of their strength in hydrocarbon solvents (oil) so 5250 x .9 = 4725 pounds, not too bad.
The axle is of course a different story and that is being spray weld.
Spray welding is getting quite expensive.
The axle is of course a different story and that is being spray weld.
Spray welding is getting quite expensive.
Lavoy:
Thanks for the information. I took the shaft to the machinist this morning to see what he will charge to spray weld. If it is too much, I will use the adhesive. It should work fine. Everything is within about 0.002" so this will not require gap filling adhesive. I will use the low viscosity version which is much stronger with a thin bondline.
Thanks for the information. I took the shaft to the machinist this morning to see what he will charge to spray weld. If it is too much, I will use the adhesive. It should work fine. Everything is within about 0.002" so this will not require gap filling adhesive. I will use the low viscosity version which is much stronger with a thin bondline.
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