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Discussion Starter #1
I have a stock Mark aluminum diff now and was wantin to make a tracklok out of it. Plan on picking up an SC diff and was wondering if its worth moving evrything into the Mark diff just to keep it aluminum or just throw in the SC diff and go? Plan on putting in 3.73's as well. Already picked up 3 quarts of 75w90 Royal Purple to avoid the friction modifier additive. Thanks.
 

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You can buy the trac-loks from SCP or summit reasonably. They have come down a good bit in the last couple years. You'll need someone to assemble it for you that has a case spreader. I made my own. I suggest new bearings while you are there, and gears are always a good thing if you don't already have at least a 3.73.
Alan
 

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Discussion Starter #4
Thanks guys, youre already saving me money lol.
 

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Discussion Starter #5
Well upon further searching I tihnk I will do a combination of three if I can. The traclok unit of an SC and the gears of an Explorer put into the mark diff. I saw the thread of the explorer having factory 3.73's however it didnt say what years to get them from. Anyone know? Thanks.
 

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Yeah don't do that, explorer gears were screamers, but they are plentiful.
Buy new frpp gears and be done with it. You are about to find building the diff is more difficult than you think.
Alan
 

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You are about to find building the diff is more difficult than you think.
Alan
Yah, I've read the Ford service manual. I'll put that along with an auto transmission rebuild - best done by an expert.

For which, I am NOT an expert! I just have to follow Pournelle's Law (find someone who knows what s/he is doing, open the wallet, and smile while they help themselves.)

*grumbles* Mean no disrespect, Alan, but you're too far without me putting some coin into shipping (which I just may do!), but we used to have a fantastic transmission shop in town. The owner closed it when he hit 60 and retired ... oh, and the state bought it for the entrance ramp to the Arthur Teague Parkway. Sigh.

RwP
 

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The person who started this thread isn't very far away at all. I went to highschool less than 1/2 hour away from him but I am about 1.5 hours away now. That still wasn't what I was getting at.

Differentials can be a wonderful thing when done correctly. They are not to be taken light hearted as failure can be destructive. What appears to be simple parts assembly really isn't that simple. The chances of the pinion shim being the same are good if you use the one from the original case and it isn't mutilated, but the carrier shims being the same would be a miracle. The caps must be marked and go back on exactly the way they were removed, seal leakage is common. The solution is an OEM seal with the proper seal installer. It is also important to polish the flange on a lathe.

I personally have about $2500 worth of tools for the purpose of changing gears and rebuilding differentials. Some of the tools I had to make myself. It is hard to beat a solid pinion spacer but I find the best ones you just have to make yourself with a lathe and a piece of tubing or the solid pinion spacer kit. The shims never seem to get the number you want for perfection, I find they need to be within about .003 to get a perfect fit and the shims in those kits are .008.
Alan
 

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Having a diff built is basically something to be done by the best in town if thats not good enough the shipping you pay to get a proper unit sent to you is worth it. Its not something many shops deal with as I have learned. There are dedicated diff shops here if that tells you something.
 

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Discussion Starter #10
Advice duely noted DD. I will order some gears instead and just go with the SC unit ang not worry about swapping it into the marks. Im sure the weight difference between the two really wont make any difference. Good lookin out.
 

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rebuilding a diff is not really that hard you make it out to be.

And you don't need 2500 worth of tools to do it.
 

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No rebuilding isn't just put all the shims and spacers where they went, if you go changing things the process changes.
No you don't need $2500 worth of tools to do it, but you need $2500 worth of tools to do it right quickly. The pinion depth gauge I use is expensive, but I don't mind investing in proper tools to do a job if I am going to do the job enough to make it worth it. Yes you can beat the seals in with a hammer, I prefer to use a proper seal installer.
Alan
 

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You've shipped enough - about how much is a loaded diff shipped? Iron for worst case?

Gotta start saving up for that also.

RwP
 

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PostSlut
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who said it was the way you describe?

you might like to spend $2500 on tools for gear changes, but I don't do it for a living.
I borrow the tools I need, and buy what I will reuse from time to time.
 

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Sorry I don't do the borrowed tools thing, I have lost too many expensive tools to being loaned out. Sounds like you need to borrow a shop because you need a press, How do you intend to clean everything. Does every person want their shop smelling like friction modifier? Need a side bearing puller, if it gets stubborn use a torch to loosen them up. Need a large bearing splitter, a good one is really expensive. I guess you are going to spend a few hours hand sanding the flange? I have a drain table that the oil goes to a bucket underneath and then I clean it up with brake cleaner, not everyone will want that on their bench or floor. Also need a good indicator, flange holder, large torque wrench (250ft-lb). If you aren't going to use a solid pinion spacer you have to crush the sleeve. Have fun with that part, an impact is a bad idea. Every time I see someone use an impact the bearings fail quickly including the once I tried it. Even to use an impact you will need an air supply of 175+ PSI and a very good gun.

Aluminum pumpkins usually cost about $100 to ship. I am shipping one to south dakota today and the estimate from UPS was $128 IIRC.
Alan
 

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who said it was the way you describe?

you might like to spend $2500 on tools for gear changes, but I don't do it for a living.
I borrow the tools I need, and buy what I will reuse from time to time.
We will be looking forward to your write up on how to properly build a differential using little to nothing in tools.
Alan
 

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hold your breath.
Oh come on, go ahead put your time and effort where your mouth is, it will be fun...For us. Besides we all really want to watch you sitting in a cave by the fire rebuilding a differential with a hammer and chisel you crafted yourself! Just watch out for the bears!
Alan
 

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I have to say I don't see why people make rebuilding a diff out to be such a complicated process. I have rebuilt at least 30 diffs, with the only special tools being a press to change the bearings, a dial indicator to check backlash, and the paint to check the tooth pattern. None have ever blown up, and the only one that ever made any noise was the one in the lemons car had a bit of a howl after boiling the gear oil out of it after 10 straight hours of road racing and running 130 down to 40 back to 130 again every 90 seconds. A case spreader is nice to have, especially if you are doing a bunch of them, but you can get it back together with a brass punch and a bench vise, so if you are only looking to rebuild your own diff, it is not necessary. For pinion depth, either reuse the factory shim, or measure the thickness of it so you know what size to use on the new one. Pinion depth shims are case specific, so as long as you match the shim to the case, you should be alright. If for some reason the tooth pattern is too high or too low once you get everything together, then you can take it back apart and adjust it, but unless someone has already been in there and screwed it up, or unless you are using some cheap gearset or somthing, reusing the factory shim will be alright. For the side shims, again, reusing the factory ones in the correct locations should give you a good starting point. Most of the time, you will be lucky and it will come out perfect by putting all the factory shims back in their original locations, but if it doesn't, that will show up in the backlash and tooth pattern, and you can adjust it from there. Having $2500 worth of tools is a good way to make sure that you only have to put the diff together once, but considering a new crush sleeve is about $12, and even if you have to take everything back apart it will take you a couple extra hours, you do always have the option of putting it together and seeing where you are at, and making adjustments accordingly to get it where it needs to be. If you don't feel comfortable doing it, then by all means pay someone else to do it, but if you are comfortable doing other work on your own car, then rebuilding the diff should be no exception.

Edit: Forgot to mention the torque wrench, I guess that does qualify as a special tool, even though I consider it a tool that every car enthusiast should own. As far as crushing the sleeve, chock the diff in a vice, screw in 2 driveshaft bolts, and hold the flange from turning with a prybar while tightening the pinion nut with a breaker bar.
 

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PostSlut
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Oh come on, go ahead put your time and effort where your mouth is, it will be fun...For us. Besides we all really want to watch you sitting in a cave by the fire rebuilding a differential with a hammer and chisel you crafted yourself! Just watch out for the bears!
Alan
No need to do what you are asking........I have the info I need for doing what I do.
I'm not here to please you.
It doesn't take a rocket scientist to find or get the info on rebuilding a diff. like you make it out to be.
I'm happy that you do this for a living, I do it for my enjoyment.

And no bears around here....but I have seen some chupacabra!
 
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