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spline rebuild option

spline rebuild option

spline rebuild option

Hi all.

After experiencing the high cost nature of replacing this casing and gear due to spline wear ,looking for best option to repair or replace splines.I assume keyseating this drive assembly would not be up to the job.This drive assembly is out of a 20 tonne track loader.Any ideas appreciated.Not sure of the maximun torque through this final drive assemble ,however we are looking at a hydrostatically driven assembly with 200 net engine horsepower.
A mate has a few ideas of shrink fitting new splines to the casing and gear ,sounds good ,still looking for options and or opinions.

{jpeg} of gear in position onto casing.


RE: spline rebuild option

The high-res photo was very nice. Thanks for that.

I'm assuming you wish to refurbish the 39T internal spline. If this spline has substantial wear, the only way I can think of to salvage the part would be to re-machine the bore to accept an insert with splines on the ID and OD. But from the photo it appears that there is limited material around the existing spline for rework, so you'll have to give some thought about this approach.

If you decide to rework the part for a splined insert, you'll need to make sure the reworked spline provides the proper fit and positioning for the mating shaft. Looking at the photo it's hard to determine exactly what type of fit your spline has, except that there seems to be clearance at the external tooth tips and the internal tooth roots. If the spline joint does not need to provide precise radial positioning then there is probably no need to shrink fit the repair insert. If the repair insert is made from a more durable material than the existing spline teeth used, then the repair insert should provide better service life.

Lastly, I hope you'll take a careful look at the full cost involved to rework these parts. Besides the cost of the precision machining operations required for producing the new splines, you must also consider that many of the parts may not be suitable for salvage if the internal gear teeth are worn or damaged.

Hope that helps.

RE: spline rebuild option

Hi Terry

Appreciate the help mate .
I wish to refurbish both internal and external splines.Cost of new parts around $10,000,00 .
You're right ,the internal spline has only 13mm of material from internal spline tip to threaded hole edge making it seem difficult,i wonder at that thickness whether it will behave strength.
The spline does not need to be located precisely ,it could have some difference as a planetary set up slips inside the 72 tooth gear,some give and take is possible.
All material is flame hardened ,and yes those splines have clearance at root and tip.
I wonder if key seating could be used either with existing splines or splines machined off .

RE: spline rebuild option


Can you post pictures of the individual parts? For example, in your last post you mentioned "13mm of material from internal spline tip to threaded hole edge", but it isn't clear to me from the picture where the threaded hole edge is.

If you could also provide additional details such as spline dimensions, material/heat treat of both components, operating loads, cycles, lube conditions, etc., I could give you more specific suggestions on what I think would be the most cost-effective way to rework/recondition these parts.

Best regards,

RE: spline rebuild option


You sound like an Aussie ;)
Where abouts are you located?
I'm setup in NSW near Newcastle.

I must be going blind but that 39 teeth spline looks to me to be in pretty good shape.
Is the one in the image the actual one that you intend on re-claiming?
You have several options to consider but you'd need to post some rough sketches showing the layout and the amount of clearance either side of the hub before I could come up with a plan of attack for you.

Ron Volmershausen
Brunkerville Engineering
Newcastle Australia

RE: spline rebuild option

tbuelna ,hi mate

This picture shows with a white marker the edge of a threaded hole and the very small white markered arrow shows to the tip of a spline. It has 13 mm of material across this distance.not much to play with.
The lubrication is gear oil 80/90 weight .This gear (hub) is flame hardened material


This inner spline may be cast steel.Link and spline heights are 6mm.The diameter of thise spline is 170mm

Gear cutter

i am in west australia.these splines have movement ,the machine is 30 years old so...anyway this movement is eating the spline material away as the planetaries run the loader forward and reverse it grinds them up even more.The oil is full of glitter,bearing are pitted because of it..

Gear hub ,spline {width} inner spline is 65mm

Thanks for the help hope it makes sense,had a machinsit look at this all,he kinda thought it looked too hard to be bothered with it,but down here my options are limited...

RE: spline rebuild option

The above is the casing with the inner spline showing its over all height


the above is the inner spline damage as close as i could take a pic without blurring

RE: spline rebuild option

Hi Les,

Great photos, thanks.
From what I can see; the spline on the planetary hub looks like it could be re-bushed. It could be a welded, or scotch-keyed sleeve, or a flanged sleeve bolted to one of the faces of the hub. The flange could be offset into the hub to help reduce the overall length. I like the idea of the later as you could easily replace the hub in future.
It looks like we might be able re-cut the shaft which will undersize it but the new hub would be made to fit.
Failing that, a new shaft could me easily made for a lot less than the figures you've been quoted.


Ron Volmershausen
Brunkerville Engineering
Newcastle Australia

RE: spline rebuild option

hi Gear cutter

Thanks mate

RE: spline rebuild option


Thanks for the additional photos. From what I can see of the condition of the existing spline flanks, I don't think they can be salvaged. If the surface damage was modest (ie. .002" or .003" deep max), you might have been able to refurbish the flank surfaces by applying thin dense chrome plating and carefully regrinding them.

What I would suggest is to completely remove the existing spline teeth on both components, machine a new smaller diameter external spline on the shaft, machine a new larger diameter internal spline in the hub bore, and machine an insert that mates with the new splines. I have attached a sketch showing the approach. The black profile is the existing spline, the yellow profile is the reworked internal hub spline, the blue profile is the new insert, and the green profile is the reworked external shaft spline. In the sketch I also showed the reworked splines using a reduced profile (smaller DP and higher tooth count) to save space in the radial direction.

The only issue I see is hardening of the reworked shaft and hub splines. Both components have close tolerance features like bearing journals or gear teeth that would be adversely affected by further heat treatment, so hardening the new spline flank surfaces with a heat treatment does not seem like a practical option. The only thing I could suggest is some sort of hard surface coating like plating or PVD.

Hope that helps.

RE: spline rebuild option



Many thanks for the input,great model of the rework.yeah the spline has a gut full of slack between the splines measured with a dial indicator.

Looks like you put a bit a work into it ,we all like a challenge ,though as you say it looks like a tough fix because of the extra heat treating.
The hard coatings is something i need to be looking into ,that's interesting,i have not heard of that before now.It's not my area though.
Thanks again tbuelna

Gear cutter has decided to take a closer look at the whole thing .I tried a local machining shop about a fix up,they decided the work wasn't for them.
They tend to make and repairs shafts etc,this sort of work is not what they can do.

RE: spline rebuild option


I am always happy to help someone like you that provides detailed and timely feedback. And don't worry, the sketch I provided only took a few minutes to produce.

Please tell gearcutter to post updates on his efforts. Good luck to you.

RE: spline rebuild option


Will do ,it may help someone else out in the process.

stay tuned .

RE: spline rebuild option

I am no expert on rebuilding splines etc. - but I did see at my local machine shop (oddly enough also in Newcastle) that they fill in the damaged splines with weld and then remachine them.

RE: spline rebuild option

Hi BigClive

i am no expert ,that sounds great but i would assume it would cause distortion because of the high heat generated..But who knows ,like i said i dunno if the end result would be as bad as i think.

There are 2 bearing journals close to the splines so..

RE: spline rebuild option

The best option would be to weld and then remachine again but keep in mind what material you use for welding as you need to machine later as well.

Hope that helps

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