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Old 06-28-2012, 06:18 PM   #1
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Default do I really need to pay someone to change final drive?

I have the 6 speed and left the stock final drive, I had it on the track and I was shifting all the time so I'm thinking about changing it out. I've never been a fan of short gear boxes and this just cements my stance. never done a rear diff but I replaced a blowed up center diff in my audi. so what can I expect? any reason I cant do this myself? the diff is staying I just need to change the ring a pinion. seems simple enough but obviously I don't want to toast new gears. they are expensive enough as it is and I've already spent my mod budget for the year so i want to keep things thrifty as possible.
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Old 06-28-2012, 06:24 PM   #2
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If you've got the coin, then I'd pay someone. If you have the time, tools, and attention to detail, then I think you would be find doing it yourself. I bought a center section with the 3.6 already installed, and then payed to have the center sections swapped. If you have R&P in hand, then I'd expect to pay a shop anywhere from $700 to $1k to just drop the car off and pick it up when done.
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Old 06-28-2012, 06:27 PM   #3
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R&R of a differential is a writeup on replacing a diff. Includes info on setting the backlash, which is what you need to do to prevent a lot of noise and get the longest life from the gears.

Doesn't appear to be too complicated, just a pain in the a$$.
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Old 06-28-2012, 06:31 PM   #4
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If you don't know what a dial indicator, machinist's blue, or "backlash" is, then you should pay someone.
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Old 06-28-2012, 06:36 PM   #5
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you always cut to the chase. I will read the write up and see whats up. it time for me to learn how to do some of the harder stuff. I'm 35 years old not 12
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Old 06-28-2012, 06:37 PM   #6
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There are only two jobs I have outsourced for my car - ever.

1. Engine rebuild
2. R&P Swap
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Old 06-28-2012, 06:50 PM   #7
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Yea, I think Sav hit it on the head.

If it where me, I would do it myself but I would seriously consider pulling the diff and doing it on a work bench. Its pretty straight forward to pull the pumpkin, and I bet it would make doing the R&P a lot easier.
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Old 06-28-2012, 07:21 PM   #8
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for sure I will pull the pumpkin, I'm just not sure if it is worth doing it myself since I dont own the tools. I'm pretty tight with a shop, perhaps they will loan me the tools over a weekend. I dont plan on doing an event for nearly a month so plenty of time to make arrangements
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Old 06-28-2012, 08:14 PM   #9
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Quote:
Originally Posted by rleete View Post
R&R of a differential is a writeup on replacing a diff. Includes info on setting the backlash, which is what you need to do to prevent a lot of noise and get the longest life from the gears.

Doesn't appear to be too complicated, just a pain in the a$$.
Note that this writeup is only part of the work -- it only covers setting the backlash and the bearing preload, not the pinion depth. If you're just replacing the diff (that is, the torsen bit), then it's all you need to do, but if you're replacing the R&P gears then you need to go further. Grab the "1999-2001 service manual" PDF that's stickied in the "useful saved posts" forum, and go to page 03-14-8 through 03-14-12. Setting the pinion depth calls for about six different SSTs which don't appear to have easily DIYable replacements -- not something I wanted to try.

I just put a 3.6 in my car. Find a reputable local rear end/axle shop (probably from the 4x4 crowd), pull the diff, pull the rear case off (the aluminum bit with the wings and fins), and take carrier with all the gears in it to the axle shop along with your shiny new 3.6 R&P from Mazda. It should cost about $200 to have them install the new gears and set it all up correctly, then you just bolt it back in the car. That's way less than buying the SSTs.

Or if you're lazy you can drive the car in there, hand them the gears and your credit card and spend a grand.

--Ian
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Old 06-28-2012, 08:52 PM   #10
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Quote:
Originally Posted by codrus View Post
Note that this writeup is only part of the work -- it only covers setting the backlash and the bearing preload, not the pinion depth. If you're just replacing the diff (that is, the torsen bit), then it's all you need to do, but if you're replacing the R&P gears then you need to go further. Grab the "1999-2001 service manual" PDF that's stickied in the "useful saved posts" forum, and go to page 03-14-8 through 03-14-12. Setting the pinion depth calls for about six different SSTs which don't appear to have easily DIYable replacements -- not something I wanted to try.

I just put a 3.6 in my car. Find a reputable local rear end/axle shop (probably from the 4x4 crowd), pull the diff, pull the rear case off (the aluminum bit with the wings and fins), and take carrier with all the gears in it to the axle shop along with your shiny new 3.6 R&P from Mazda. It should cost about $200 to have them install the new gears and set it all up correctly, then you just bolt it back in the car. That's way less than buying the SSTs.

Or if you're lazy you can drive the car in there, hand them the gears and your credit card and spend a grand.

--Ian
I retract my previous statement. I had no idea so many SST's where necessary. Do what Ian says
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Old 06-28-2012, 09:22 PM   #11
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Phil, I'm sure the Chicago people can hook you up. My friend Jeff (lordrigamus) has everything necessary. We did my swap a few months ago. Everything went perfect. I'm sure something can be worked out. Gives ya an excuse to go out to the suburbs and see what kind of mess my garage is. I can still get to the beer in the fridge.
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Old 06-28-2012, 09:29 PM   #12
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Quote:
Originally Posted by Savington View Post
If you don't know what a dial indicator, machinist's blue, or "backlash" is, then you should pay someone.
lol

I won't touch a rear end...but I'll let Johnwag.
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Old 06-28-2012, 09:34 PM   #13
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Quote:
Originally Posted by hustler View Post
lol

I won't touch a rear end...but I'll let Johnwag.

he a guru? i have had bad luck with 2 different shops here in teh FW...
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Old 06-28-2012, 10:02 PM   #14
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You guys are scaring me. I have this OBX torsen waiting to go in, and it looked like it'd be easy. Now I have my doubts.
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Old 06-29-2012, 12:16 PM   #15
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Quote:
Originally Posted by Savington View Post
If you don't know what a dial indicator, machinist's blue, or "backlash" is, then you should pay someone.
Yes. I know what those are (and have all the tools) and I still will pay someone.

Quote:
Originally Posted by codrus View Post
I just put a 3.6 in my car. Find a reputable local rear end/axle shop (probably from the 4x4 crowd), pull the diff, pull the rear case off (the aluminum bit with the wings and fins), and take carrier with all the gears in it to the axle shop along with your shiny new 3.6 R&P from Mazda. It should cost about $200 to have them install the new gears and set it all up correctly, then you just bolt it back in the car. That's way less than buying the SSTs.
Some of the best advice in this thread, although the local shop here only charges $100 if you have the gears in hand and you pull the R&P prior (which is easy enough). It basically covers their hour labor to get them in and set up.
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Old 06-29-2012, 12:42 PM   #16
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ive done a couple of 3.6 swaps, it not difficult, it just takes time and attention to detail. what savington wrote really
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Old 06-29-2012, 12:58 PM   #17
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I did my R&P in my garage with just a dial indicator. I didn't worry about pinion depth. I did use marking compound to check the wear pattern and it looked OK to me. That was more than 6 years ago.

backlash is tricky without the giant caliper/micrometer. get a piece of steel 10 x 10 and carefully cut it to the minimum and maximum measurements in the manual and you can use it as a go-nogo gauge.
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Old 06-29-2012, 01:22 PM   #18
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Great idea, y8s. Props to you.
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Old 06-29-2012, 01:48 PM   #19
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Ideally, you want to measure and write down everything before you take it apart, on both the old and new R&P. If using a used R&P you want to know how it was in the old housing and set it to at least the specs where it was, if not better. New crush washer and seals.
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Old 06-29-2012, 03:36 PM   #20
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Uh I paid $400 and that included pulling and reistalling diff
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