Excavator final drive bearing bore problems.

Mad man marine · Dec 12, 2018

So. This is my first post. Been meaning to join this forum for a while but have been way to busy in the shop. Looks like tons of info in hand. Anyway. On my personal excavator I’m rebuilding the final drive hydraulic travel motor. One of the problems is on one side of the main load bearing ,bearings. The bore is about 3 thou to big so you can just barely spin the bearing race in it by hand. It’s a ntn cr-2256 bearing which is right around 5” od. I’m wondering if I heat up the casting just around that bore if I can then cool it reliatively quick to try and shrink it a touch? I guess my other option is to tig braze a layer inside and then chuck it up on my large face plate and re machine it to spec. Seems like an easy way to mess up an expensive part. I would just buy a used reduction housing but the parts for this 88 John Deere 70d are pretty hard to come by. So that’s pretty much out of the question. Sorry if this isn’t posted in the right area but .... anyway. I wanna say thanks in advance to anyone that chimes in with ideas or info. Thank you Ian Adair.

tdmidget · Dec 12, 2018

Is any of the bearing bore undamaged? You don't have to have a full circle to indicate the center. Indicate the undamaged arc and that should put you over the center of the hole. Sleeve it.

gbent · Dec 12, 2018

Locktite it and forget about it. It will outlive the rest of the machine.

Mad man marine · Dec 12, 2018

Indicating isn’t a problem. Plenty of machined surfaces to get squared away on. I was also reminded a little bit ago of dimpling the surface with a center punch in a ton of places to lift the surface a touch. But loctite sounds like a better option. Just don’t want to have to take it back apart in a month to deal with it again. There is only about a half inch of material around the bearing bore to work with. That was the reason I didn’t jump right to sleeveing it.

Mad man marine · Dec 12, 2018

Have you yourself done this to a bearing with loctite?

john.k · Dec 12, 2018

+ on loctite.....get the strongest bearing mount /green? loctite you can find.......Ive repaired heaps of excavator planetaries,and you have got off very lightly........typically,the whole planetary is destroyed by neglect,and a spare drive assy is often $10k....used......EDIT another option which I have used is to get the bearing race built up with nickle plate,and grind back to the size of the skimmed housing............If you care to fiddle,you could also get the bearing bore built up with electroless nickle.........all this is a lot more work,for a hobby machine..........I admit I'm not familiar with your machine,as JD s were rare here........mostly Cat,Komatsu,Kobelco,Kato,Mitsi .....and of course "Samsung"

R. Dan · Dec 12, 2018

Any chance you could stake that bearing in?

EmGo · Dec 12, 2018

Mad man marine said:
Have you yourself done this to a bearing with loctite?

I've done it a few different times. Not on an excavator but on rolls and some other type of dirt digging stuff. Worked well.

I cleaned the hell out of the bore though and there is also a Loctite primer. Don't know if that is necessary but I wasn't taking any chances.

DDoug · Dec 12, 2018

R. Dan said:
Any chance you could stake that bearing in?

Those leetle divots will easily get wallered right back out.

The loctite acts like a gap filler, sort of a liquid shim stock.

Filling in the whole area, unlike the small surface area of a dimpled piece.

Ziggy2 · Dec 12, 2018

Mad man marine said:
Have you yourself done this to a bearing with loctite?

I did this about 40yrs ago to a IHC 1206, pinion gear bearings to both final drives. Tractor is still going strong with zero problems.

Being that your excavator is relatively small with limited intended use, I doubt if you will have any issues with the bearing getting loose or spinning.

Considering the relatively low rotational speed of the bearing, you could probably get by without doing anything, not that I would recommend that.

m-lud · Dec 12, 2018

If you center punch to raise the surface go light. It doesn't take much. Be symmetrical with your dimples. With loctite as suggested above. I have a NH865 that has a hub I repaired like that and those wheel bearings get beat on by the nature of the machine. 12 years and going.

john.k · Dec 12, 2018

Ive seen loose bearing bores fixed with beer cans.......first make sure the can is very cold,drink the beer,snip the can open,lay across the hole and drive in the bearing.....probably best to have have a spare cold can just in case.

wheels17 · Dec 12, 2018

There is a specific Loctite product for loose bearings. Here's a link to the Loctite page. It's supposed to work to .020 gap. I've used it on something with about 1/100,000 of the load you're seeing, and it worked fine...

LOCTITE 66

tdmidget · Dec 12, 2018

LOCTITE 66 - Retaining Compound - Loctite

gbent · Dec 12, 2018

Mad man marine said:
Have you yourself done this to a bearing with loctite?

Yes. Far superior to dimpling. The only time I would dimple is if the race might fall out while the locktite is curing.

Bill D · Dec 12, 2018

I would put a few dimples in. Just enough to locate it and center it. then use the loctite. I do not think the loctite by itself would keep the bearing centered while it dries. Make sure the bore depth is flat not angled from wear that might let the bearing be cockeyed.
Bill D.

Mad man marine · Dec 12, 2018

Wooow!! You guys are all awesome. So many responses!! Thank you soo much. Made my day. The bore is suppose to have around a 2-3 thou press fit. The bore is now 2 thou roughly bigger then the bearing race. So I’d say loctite wins the money!! Never even thought. The bore from what I can tell is still perfectly round. So I think this is going to work out great. I gotta say though. The beer can trick sounds interesting. If you could get it to drive in evenly I bet that wouldn’t be a bad fix.
Time for a little back story lol. If you don’t care no biggie. Don’t bother reading the rest. The only reason I even found out about the bearing bore was because the metal face seal o rings broke apart and it started leaking real bad. The lower half of this excavator was from a totally burned out 70d. I got it because it had just had 10 grand worth of tracks,idlers ,sprockets , and rollers put on it a few months before the fire. Got the burned one for 3 grand and drove from Maine to Virginia with a trailer and picked up a 70 John Deere doghouse (engine,cab,all hydraulics ) and put the boom,dipper,and track frame on it. Built two out of one. Which was t easy because the turntable bearings were different. (Ugh). Had to drill and tap all 30 somthin 3/4” bolts out and change the bolt pattern by an 1/8”. Anyway. The fire crispifyed the o rings and the just kinda fell out. Good thing I guess cause it let me find the bad bearing bore before it got real bad. Again. Thanks so much for the help guys.

HuFlungDung · Dec 13, 2018

Mad man marine said:
So. This is my first post. Been meaning to join this forum for a while but have been way to busy in the shop. Looks like tons of info in hand. Anyway. On my personal excavator I’m rebuilding the final drive hydraulic travel motor. One of the problems is on one side of the main load bearing ,bearings. The bore is about 3 thou to big so you can just barely spin the bearing race in it by hand. It’s a ntn cr-2256 bearing which is right around 5” od. I’m wondering if I heat up the casting just around that bore if I can then cool it reliatively quick to try and shrink it a touch? I guess my other option is to tig braze a layer inside and then chuck it up on my large face plate and re machine it to spec. Seems like an easy way to mess up an expensive part. I would just buy a used reduction housing but the parts for this 88 John Deere 70d are pretty hard to come by. So that’s pretty much out of the question. Sorry if this isn’t posted in the right area but .... anyway. I wanna say thanks in advance to anyone that chimes in with ideas or info. Thank you Ian Adair.

Yeah, I had an issue like that with my personal battle tank!

EmGo · Dec 13, 2018

HuFlungDung said:
Yeah, I had an issue like that with my personal battle tank!

Really ? Lee at Edwards Heat Treating has one of those too.

But you know heat treaters. They have strange hobbies.

john.k · Dec 13, 2018

Ive worked on a few burned ones.....the fire sure gets them clean tho,all that gooey oil dirt and sticks gone ,and replaced by bare metal and dust.......they reckon they burn extra hot cause of friction between the lease papers and the insurance policy.

Excavator final drive bearing bore problems.

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