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Tips for rear end rebuild.


Demi_II

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Tomorrrow I start my rebuild of the 7.5. I know I could have done an 8.8 swap, but the down time wasnt feasible right now. I picked up a Detroit true track locker and some 4.10 gears. This is my first attempt at a rear end job. Anyone got any need to knows before I get in way over my head?
 


PetesPonies

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This is far too complicated to give a "few" tips. At the least, you need something to follow and have the appropriate tools and measuring devices. In order to have a differential rebuild last, you have to do it right and be within spec.
 

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You are changing gear ratio?

Do you have an install kit with shims, ring gear bolts, bearings, crush sleeve, pinion seal and new pinion nut?

Do you have a press, bearing pullers, micrometer, dial indicator with magnetic base and inch lbs beam or dial type torque wrenches?
 

Demi_II

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You are changing gear ratio?

Do you have an install kit with shims, ring gear bolts, bearings, crush sleeve, pinion seal and new pinion nut?

Do you have a press, bearing pullers, micrometer, dial indicator with magnetic base and inch lbs beam or dial type torque wrenches?
I have the install kit with all that stuff. So what Im doing is getting the it all put together, and driving it a block to the garage and having them setup the backlash and preload as I dont have and cant afford a dial indicator at the moment.
 

Explorin94

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I have the install kit with all that stuff. So what Im doing is getting the it all put together, and driving it a block to the garage and having them setup the backlash and preload as I dont have and cant afford a dial indicator at the moment.
So you are expecting to put this rearend together and drive it to the local mechanic and have him set up the gear you just installed cause you have no clue what you was doing in the first place?
That is all fine and dandy for you but the guy who is going to set up this gear with all the backlash and pinion depth to specs will have to take this rearend back apart (the same job you just did) to get shims in the right spot and correct thickness'. You may as well take it to him to do as it is going to cost you the same as it would if he initally set it up. It isn't that simple for you to simply install the gear and have him turn some bolts to set this thing up.
If you don't know what you are doing save yourself some money and have someone who knows what they are doing complete it the first time around not the second or third time.
 

Demi_II

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So you are expecting to put this rearend together and drive it to the local mechanic and have him set up the gear you just installed cause you have no clue what you was doing in the first place?
That is all fine and dandy for you but the guy who is going to set up this gear with all the backlash and pinion depth to specs will have to take this rearend back apart (the same job you just did) to get shims in the right spot and correct thickness'. You may as well take it to him to do as it is going to cost you the same as it would if he initally set it up. It isn't that simple for you to simply install the gear and have him turn some bolts to set this thing up.
If you don't know what you are doing save yourself some money and have someone who knows what they are doing complete it the first time around not the second or third time.
Yeah this is my first go at this, and its pretty confusing for a first timer. This was kinda the question I was after, because I wasnt sure if it was possible. I guess Im having trouble visualizing how the backlash is set. Im going to do some more reading and see where I end up.
 

simpler=better

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You can get cheap indicators on craigslist and my HF indicator seems to be pretty decent(checking with feeler gauges)
 

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Seems it would be alot less hassel to switch ourt to the 8.8 than rebuilding. If i understand right it takes half an afternoon to do the switch once you have all the parts together. But whatever floats your boat.
 

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Yeah this is my first go at this, and its pretty confusing for a first timer. This was kinda the question I was after, because I wasnt sure if it was possible. I guess Im having trouble visualizing how the backlash is set. Im going to do some more reading and see where I end up.
The teeth of the gears get thicker as you get toward the base of the tooth. The backlash is actually the space between the teeth of the pinion and the teeth of the ring. Backlash is adjusted by moving the carrier assembly, and ring gear, left or right in the housing, making it sit closer to or farther from the pinion gear, until you get the space between their teeth in a given optimum range. If you are still having trouble visualizing what is being adjusted and how, hold your hands in front of you, fingers spread apart and tips facing each other. Now move your hands together so your fingers go between each other and watch the effect on the visible gap. The orientation is wrong, but the effect is the same.

These clearances are measured in thousandths of an inch, and cannot be judged by feel unless you are very experinced (I do work with a guy who can grab a ring gear, rock it, and consistently tell you what the backlash is to within .001"). This number is also critical because too tight will bind up the gears and make them wear prematurely, then make noise. Too loose and the slapping of the teeth as the space is taken up going from drive to coast and back will tear the assembly to pieces. Whenever you see pictures of a diff with whole teeth stripped off the ring it is usually from excessive backlash. Partial teeth stripped off is from insufficient pinion depth.
 

Explorin94

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Yeah this is my first go at this, and its pretty confusing for a first timer. This was kinda the question I was after, because I wasnt sure if it was possible. I guess Im having trouble visualizing how the backlash is set. Im going to do some more reading and see where I end up.
In all honesty you are better off talking to someone who has done this many many times in the past. Then ask him if you can watch how the process is done and occasionally ask questions as to why that certain step was done. But a good teacher will explain his self as to why he just did the step he did. I will admit that when I first set one up for the first time I was a little skeptic not knowing if I did it correctly. I second guessed myself at everything...the pinion depth.....the amount of backlash....the number of shims needed for the carrier and what side that they needed to go on. I have done well over 100 gear setups and still wonder if I missed a step during the install. Like ADSM said there are guys who can set these gears up and not need a dial indicator while doing it. But for your first time you need to have someone there who knows what they are doing so you don't ruin the gear you just bought.
 

Demi_II

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Well I got a dial, pulled the chunk, and found this...




So im fairly sure Im boned. I cannot find bearing caps for a 7.5 anywhere. Are the even interchangeable? Can I pull one from a junker?


The teeth of the gears get thicker as you get toward the base of the tooth. The backlash is actually the space between the teeth of the pinion and the teeth of the ring. Backlash is adjusted by moving the carrier assembly, and ring gear, left or right in the housing, making it sit closer to or farther from the pinion gear, until you get the space between their teeth in a given optimum range. If you are still having trouble visualizing what is being adjusted and how, hold your hands in front of you, fingers spread apart and tips facing each other. Now move your hands together so your fingers go between each other and watch the effect on the visible gap. The orientation is wrong, but the effect is the same.

These clearances are measured in thousandths of an inch, and cannot be judged by feel unless you are very experinced (I do work with a guy who can grab a ring gear, rock it, and consistently tell you what the backlash is to within .001"). This number is also critical because too tight will bind up the gears and make them wear prematurely, then make noise. Too loose and the slapping of the teeth as the space is taken up going from drive to coast and back will tear the assembly to pieces. Whenever you see pictures of a diff with whole teeth stripped off the ring it is usually from excessive backlash. Partial teeth stripped off is from insufficient pinion depth.
Yeah I finally understand now. I found an awesome picture that turned the light bulb on.




Thanks for taking the time to help out a noob guys. I would really like to take it to a shop but Im slap broke now. The diff, kit and gears set me back $800.
 
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simpler=better

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The bad news is, it's busted and need to be fixed. The good news is, your spiders look better than mine :p

Can you return your kit? A whole axle assembly from the junkyard should be well under $800
 

Explorin94

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Wow...that right there is bearing failure. That is why the 7.5 is weak. If you can find an Explorer 8.8 in the junkyard you can expect to pay anywhere from $175-$250 around Central Illinois. You mat also find the correct ratio you need also. I am sorry to see that.
 

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Wow...that right there is bearing failure. That is why the 7.5 is weak. If you can find an Explorer 8.8 in the junkyard you can expect to pay anywhere from $175-$250 around Central Illinois. You mat also find the correct ratio you need also. I am sorry to see that.
Yeah I was on the fence on doing the 8.8 or fixing the 7.5. I need the truck back on the road so I thought this would be faster. I chose poorly. Very poorly. I was hoping to get it done before I have to return from leave, but that isnt gonna happen. Lol. I cant return the kit, gears, or Detroit locker. Im locked into a 7.5. Looks like the next step is grab a 7.5 entire assembly out of the junk yard, put all my new stuff in it and bolt it up. Im sorry if this is a stupid question but are all 7.5s interchangeable? I cant find a lot of information on swapping a ranger 7.5 into a Bronco, probably because no one does. Anyone know where I can find that info? So I made some calls and found a yard with what the guy said was a 7.5 out of a ranger. He wasnt sure the year though. I snapped a picture of the tag, but it doesnt match up with library tag info.



Is this a fit?

They only want $100 for it, but on the other hand I found a 1990 BII 4x4 about an hour away for $200.
 
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