Final drive... rebuild or replace?

[John V]

Howdy, I'm slowly rebuilding my ihi 55j2 excavator. Bought it awhile ago, finally got a new/used isuzu 4jb1 dropped in to replace the 4ja1, and had many of the pin bores line bored and rebushed. One of the last big deals is the left side final drive. Didn't have any plugs on it, therefore no oil. Got the face plate off and of course it's nasty in there (picture attached). The main bearing you can see is missing most of the little polyurethane spacers. There is play in the needle bearings. The planetary gears don't look too bad. The drive still worked before I took it apart. Do any of you have experience rebuilding these things vs just replacing with an off the shelf unit? Suggested source on bearings? The two main bearings look to be nachi 180ba2256. Looks like a son of a to get them out.

finaldriveparts quoted about $2500 for a whole new unit with 2 year warranty.

 

[1693TA]

Has that oil been contaminated with water? By the brown tinge it looks so. If that is the case there may be hidden damage you've not seen yet which could make a reman unit more attractive. I would make the final decision after it were broken down further.

 

[John V]

Managed to wiggle out the big drive gear needles, which made it easy to punch out the main bearing that's missing the plastic spacers. The second main bearing looks fine to me, here's a video of that: https://photos.app.goo.gl/rfyGTDBXnexAE6Wt6 Then again, I'm not sure if these types of "angular contact ball bearings" are supposed to have the play I showed in the video.

The drive gear needle bearings I think are worn out, but I'm not sure if they're supposed to have this play: https://photos.app.goo.gl/b4DcpfS9SeJWZDfC8

 

[1693TA]

I can't honestly answer as no experience with those units. However, I didn't see the inner race wollering around on any of the bearings you worked with. It is the shafting and bearing surfaces that wear out fast when water is introduced. To me, the tapered roller bearings need replaced but that is normal and expected. I consider these to be wear items which should be renewed at rebuild time.

 

[John V]

If anyone has experience reassembling these kind of gearboxes, can you share the order with me? It’s a gearbox with 2 eccentric gear plates that walk around pins that go in the outer rim of the hub. As I try to put the pins back in the hub, eventually it all locks up and gets too tight to adjust the eccentric gear assembly to accept more pins. Curious what order others have put this kind of thing back together in.

 

[hseII]

Howdy, I'm slowly rebuilding my ihi 55j2 excavator. Bought it awhile ago, finally got a new/used isuzu 4jb1 dropped in to replace the 4ja1, and had many of the pin bores line bored and rebushed. One of the last big deals is the left side final drive. Didn't have any plugs on it, therefore no oil. Got the face plate off and of course it's nasty in there (picture attached). The main bearing you can see is missing most of the little polyurethane spacers. There is play in the needle bearings. The planetary gears don't look too bad. The drive still worked before I took it apart. Do any of you have experience rebuilding these things vs just replacing with an off the shelf unit? Suggested source on bearings? The two main bearings look to be nachi 180ba2256. Looks like a son of a to get them out.

finaldriveparts quoted about $2500 for a whole new unit with 2 year warranty.

Please share a photo of the whole machine: I’ve never seen one.


As far as the final, is it still in position?

If it was working, could you fill it with with diesel, & flush it out?
Then see about what’s worn & bring the bearings to a parts house to match up?

Do you have a book on this machine?

 

[John V]

I have a service manual on the machine, unfortunately nothing in it about final drive disassembly. In retrospect, I should have probably done what you said: left it assembly, flushed it with diesel, and ran it until it died. Shortsightedly, I disassembled it. I've got new bearings for it, and obviously it has a much more thorough cleaning.


Here the hub is mounted without any of the internal parts.

This picture shows the pins that get inserted into all of the notches in the hub.

Here is the drive gear assembled. I actually just checked the parts manual and apparently they are different part numbers, which might mean I have them mis-assembled.

Drive gear in the hub

 

[John V]

Drive gear in the hub with the holding flange over it and one of the "reamer bolts" that holds it in place. I had never heard of a reamer bolt. Apparently they're bolts with a machined shoulder, used in situations to take lots of shear force. I galled the crap out of two of them trying to remove it from the hub.

 

[John V]

Here's the parts breakdown of it all.

 

[John V]

So far this is the only video I've found that has a final drive with this design:

In it, he puts the drive gear assembly in place, then inserts the pins 1 by 1, adjusting the drive gears a little to make room. When I try to do this, the gears eventually bind up after I've gotten about 1/3rd of them in.

 

[John V]

Ok fortunately I have some videos during disassembly. There are some witness marks in the video that show I have it assembled slightly differently. I'm going to try taking it apart and reassembly the gear assembly like it was, then see if I can reassemble it all with the pins.

 

[John V]

New video by John Vollrath

photos.app.goo.gl

Alright we’ll that must have been the issue. Super easy to install the pins. Of course I had to destroy some bearings to get the gears apart, but after those come hopefully it’ll all be back together and good again

 

[uffex]

Good day
A word of caution when replacing final drives, often these are built to differing specifications, this can result in crab crawling, best match those which you are using already.
Kind regards
Uffex

 

[John V]

Good day
A word of caution when replacing final drives, often these are built to differing specifications, this can result in crab crawling, best match those which you are using already.
Kind regards
Uffex

I've found a supplier that has a planet gear version of my final drive. I guess that means same gear ratios, but it doesn't use this eccentric drive gear design. Would that be fine to mix-and-match? Also, do you know what they call my current style final drive?

 

[uffex]

Good day John
I would be very cautious mix & match policy may well result in crab crawling, you could adopt a safe approach and make the same change to the remaining side if you come into trouble.
Kind regards
Uffex