Need John deere 755 mfwd front gears

[Need advice]

I have a JD755 in Eastern Canada. A bearing let go in the frond drive and ruined some of the gears. Dealer says some parts are not available to repair. ANY suggestions on sourcing new or used parts? I am new to the forum so bear with me. Thanks

 

[ddbackhoe]

Accurate measurements and patience. Odds are JD bought them from somebody, so you can too. Salvage yards nearby? Worst case scenario, get a decent machine shop to make them for you.

https://www.machinedesign.com/learning-resources/whats-the-difference-between/article/21832142/whats-the-difference-between-spur-helical-bevel-and-worm-gears

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[Jims1025R]

Hello Need Advice, I had a JD650 for 25 years, and loved it. Lost it in a fire. I had one front axle side apart once to change leaking seals so I have an idea about what's going on in there. I also know that machines that old are poorly supported by JD for new parts.

If the gears are "ruined", you're shopping, and this is a good place to ask. That said, how ruined are they? The dealer will resist reinstalling damaged parts, but it is your decision. Sure, if you can replace them, do that, but if it's looking end of life for your tractor if no parts can be found, the gears may not be as ruined as the dealer says. I'd be giving a hard look to either cleaning them up for reuse, or even an attempt at a repair. If teeth are broken right off, yeah, they're ruined, but if teeth or chipped or pitted, they will probably still serve you for a while to come. Reinstalling known damaged parts will mean that it'll be up to you to be much more dedicated to check for deterioration, 'cause it'll happen much faster now. Frequently jack up that wheel and spin it to assure it's not grinding.

As those are miter gears, having one made would be very costly, and probably not worth it. If you cannot clean up and reinstall, or find a replacement at all, the last thing to consider is to remove all the gears from the front end, and run the tractor as a two wheel drive. A poor second choice for sure, but better than walking away from the tractor.

 

[Need advice]

I appreciate the advice. I think plan A will be to give the a dealer a couple 9f days to work on any leads (as it is torn apart on thier shop floor). Plan B is to have them pull what wver gears are needed for it to run free in 2wd.. (at least this will get it moving and home) plan C will to be inspect the gear ls myself and see if I can eithery patch/track down a replacement. .. or have the elusive "one that can't be found" machined. There is a local place that is known for thier machining... I appreciate the links... the gear terminology helps a lot! And Wenger may have what I am looking for... I think it is the crown and pinion pair that is the issue... just not sure which one until I can take a look at it

 

[Jims1025R]

There are two sets of miter gears, upper and lower. Most likely the lower ones damaged if they picked up chunks of broken bearing. There's a vertical driveshaft in each of the steering parts of the "axle" assembly. I would have both left and right driveshafts, and their gears (one at each end) and bearing removed. You sure don't want one side left in, and find yourself with three wheel drive! You may find the dealer reluctant to "modify" your tractor by reassembling with parts omitted. But you can point out that the same tractor was also made as a two wheel drive, with a simple front axle.

Make sure that all of the bearings are either replaced, or at least cleaned out, and that the seals and O rings are replaced. Even though you wont' have driveshafts and gear, you'll still need the front axle to hold oil to keep the wheel bearing lubricated.

Save the old damaged gears, even if they cannot be reused. They would be a pattern for a shop to make new ones (though that's not a small job) and you'll want to be able to make a harness measurement of the teeth, in case they are heat treated, and newly manufactured should also. My guess is that they are not, but make it possible to check. If they are hardened, then it may be appropriate to have the steel analyzed for it's alloy to assure the intended properties, though a shop able to cut such gears would be able to guess that pretty well too. If the gears are not hardened, your choice of steel alloy is more open.

It's also worth inquiring about similar size JD tractors at the junk yards - the 750 for sure, and maybe the 650/655 had common parts, it's worth inquiring. More recent models might too. Manufacturers don't invent new parts, if a part they already make will work!

 

[5030]

Think I'd look for one in salvage like on Tractor House and replace the entire front axle as one piece with one that works.

For some reason, JD likes to forget about older models and sell you a new one instead, the main reason why there are no green tractors here..

 

[Need advice]

It's funny because JD in the US has the parts but not available in Canada. I compared the JD part numbers and they are the same... anyway, now that I have the JD numbers I can search for them specifically. FIRST google search found used parts in the US thanks to ebay. A couple spots have matched pairs. On a side note, can I mix and match new and used gears? Or is that asking for trouble? Are they shimmer or adjustable?

 

[Need advice]

On a side note, in case anyone is interested, once I got the JD part numbers and searched for them specifically I was able to find out that the 755, 770, 790, 855, 856, 870, ... and some of the older mowers all use the drive assembly parts.... this made finding used parts way easier because I was able to search for more models. Lots of 855 parts but few 755.... and they are the same!

 

[Jims1025R]

can I mix and match new and used gears? Or is that asking for trouble?

Generally for this type of application, I would say yes, unless the service manual says not to. Make sure that the older one is free of any damage or pitting. When the front axle is off the ground, the wheels spin very nicely through the drive train, so you can feel how the gears are meshing.