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Some 7.5 and gear questions


holyford86

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I just recently discovered that my ring&pinion gears are pretty well thrashed in my 7.5 (chunks missing) I dont have the coin to spring for a replacement set of gears and the ratio I have is extremely hard to find used (4.10). I found one set of gears in an aerostar with an LS axle. I would prefer to swap the gears to my housing because I want to keep the locking diff I have. How much of a pain in the ass is it to swap these gears somewhat properly so I can get a decent amount of life out of them? What do I need to reuse? I am going to replace the bearings when I do it.
 


Natedog

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That is alot of work...it has to be all set up again from scratch. You may as well just pay for a gear set, bearings seals and professional setup. Or if you're really lucky find a complete rear axle that isn't trashed and has same gears. Is you'rs 4x4?
 
holyford86

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The axle I have has 4.10 gears. they are extremely hard to find around here, the deepest ratio readily available is 3.73 If I could find a ranger axle with 4.10 gears I would swap it in but I cant so this leaves me to find something else. I am getting the gears installed professionaly and I am buying a complete install kit which should come with all new seals and such. All I was asking about is the feasability of re-using factory gears because the professional installation is already going to eat up atleast 400 bucks of money I don't have.
 

MAKG

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Yes, reusing factory gears in good condition is a very reasonable alternative. Make sure there is no pitting on the gear faces, or they aren't in good condition, will be noisy, and won't last.

Do make sure you have a matched set -- that the ring and pinion both come from the same donor.

You can also reuse bearings in good condition. You MAY need new carrier shims (but I doubt it), and you probably will need a new pinion shim and crush washer. These are cheap. Do replace the axle and pinion seals; it's foolish not to. Note that donor bearings may not be removable without damage; if your original bearings are trashed (a possibility given the chips in the ring gear), you may need to buy new ones.

Take a good look at your axleshafts; if there is ANY hint of pitting under the axle bearings, get GOOD (not pitted) replacements from the same model truck as yours (gear ratio doesn't matter) and replace both the axle bearings.
 
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Hahnsb2

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I'd run it till it blows up, at least if you have another form of transportation from the downtime it will cause if/when it blows. There have been a few people that have driven 7.5s with chunks missing for quite a while. My old axle that was under my rig appeared to have came from a junkyard (yellow paint pen markings) and was submerged under water resuting in a distinct line of rust on the bottom half of the diff inside and pitting the ring gear pretty badly, I put 15-20,000 miles on it before throwing my 4.10 axle under it and it looked exactly same as when I first opened it up and didn't make any noise...
 
holyford86

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the truck is my one and only vehicle so blowing it up isn't an option. Im assuming that when I swap the gears out I will need to st my pinion depth and such just like putting in new gears correct? Will I still need to break in the gears like new ones or would it be a install and go type of thing?
 

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Breaking in gears is not a big deal. Basically, take it easy and only drive short distances for the first few runs, and change the gear oil after 100 miles or so.

They can't be truly pre-broken-in as you will install the gears in slightly different orientations to where they were in the donor truck.

Yes, you will need to set pinion depth and backlash just like new gears.
 
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