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Old 02-18-2009, 12:24 AM   #1
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Default Simplest Torsen Swap

If you had two complete cars available, a DD with VLSD and a parts car with a good torsen what would be the quickest, simplest way to swap the differentials? Should I just swap the whole subframe or is it more work than its worth?
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Old 02-18-2009, 12:41 AM   #2
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I don't think swapping the subframe is an option, unless I'm just misunderstanding what you're saying. It's a very strait forward swap. Pull the axles, driveshaft, and diff out of the parts car first. After that you'll have a good idea how long it's going to take you to swap it into the DD and you can either continue or save it for another day. The only pain (that I remember) is messing with getting the diff loose from the PPF. M.net has a nice writeup that will walk you through everything.

Album Index for album 0012: Differential Swap
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Old 02-18-2009, 04:01 AM   #3
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Loosen half shaft nuts on outside of car before putting in air. Put car on jackstands. Pull exhaust, pull driveshaft (4x14mm), unbolt halfshafts (4x14mm per side), unbolt little bolts from mounts (2x12mm each side I believe), support diff, unbolt diff from mounts (one 17mm per side), drop diff, pull half shafts. Reverse to install.
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Old 02-18-2009, 09:49 AM   #4
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If your Torsen has the early two-piece halfshafts, unbolt 'em at the diff first. If not, just leave the shafts in the diff and proceed.

At the wheel hubs, leave the shafts connected to the hubs, and transfer the whole shaft & hub assembly from the old car to the new one by unbolting the hubs from the control arms.

Leave the PPF attached to the diff. Unbolt the PPF from the transmission, and transfer the entire assembly as a whole.
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Old 02-18-2009, 12:35 PM   #5
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Swapping subframes has always been much easier and quicker for me.
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Old 02-18-2009, 01:24 PM   #6
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How are those ways quick for you guys?
Doing it the way I said, I can have a diff out in ~20-25 minutes.... seems like your ways would be much harder and longer.
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Old 02-18-2009, 04:08 PM   #7
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Swapping the subframe is quick and easy. You will need to drop the electrical harness off to the side and disconnect the brake line(and bleed after complete)

I would suggest liquid wrench and cracking all six nuts on each before proceeding.

Tie the drive shaft to the ppf and transfer it all as a unit.
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Old 02-18-2009, 04:45 PM   #8
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Wow, I guess I just never even considered swapping the whole subframe. If it wasn't more work, it certainly seems like it'd be awfully difficult to get everything remounted to the new car.
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Old 02-23-2009, 02:23 AM   #9
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Leave the PPF attached to the diff. Unbolt the PPF from the transmission, and transfer the entire assembly as a whole.
...if you feel like dealing with the 7287389280934 clips that hold the wiring harness to the PPF. There is no benefit to swapping the PPF along with the diff.


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Swapping the subframe is quick and easy. You will need to drop the electrical harness off to the side and disconnect the brake line(and bleed after complete)
This is quite possibly some of the worst advice I've ever seen given on this forum from a senior member. In what world is swapping the subframe, which requires you to fully bleed the brakes and have the car realigned, easier than just dropping a pumpkin to swap a differential? It takes 20 minutes to drop a diff and install a new one. Dropping the subframe is beyond idiotic.
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Old 02-23-2009, 08:49 AM   #10
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This is quite possibly some of the worst advice I've ever seen given on this forum from a senior member. In what world is swapping the subframe, which requires you to fully bleed the brakes and have the car realigned, easier than just dropping a pumpkin to swap a differential? It takes 20 minutes to drop a diff and install a new one. Dropping the subframe is beyond idiotic.

Read the original OP request(complete switch two cars). No alignment required, and don't knock it until you've done it. Takes me all of two hours for both cars parked side by side working alone and I'm an older idiot....
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Old 02-23-2009, 12:35 PM   #11
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I still haven't had a good day to do the swap either. Its windy as hell here in pennsylvania. And I haven't had a good day off work.
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Old 02-23-2009, 03:00 PM   #12
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Read the original OP request(complete switch two cars). No alignment required, and don't knock it until you've done it. Takes me all of two hours for both cars parked side by side working alone and I'm an older idiot....
WRONG!
How is an alignment not required? I would really love this explained.

And by the way, 2 hours is longer than 20 minutes.
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Old 02-23-2009, 03:01 PM   #13
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Read the original OP request(complete switch two cars). No alignment required, and don't knock it until you've done it. Takes me all of two hours for both cars parked side by side working alone and I'm an older idiot....
No alignment required? Are you high? No half-decent repair or race shop would change a subframe in a car without at least checking the alignment. In addition, perhaps you should read the OP; if he's swapping the subframe between two cars, the cars would have to have the exact same alignment beforehand in order to have a hope of not needing one afterwards.

So your method takes two hours, requires a re-bleed of the brakes, and a re-alignment. My method takes about 90 minutes (30 per car for swapping the actual pumpkin, plus 30 to swap either uprights or halfshafts), doesn't require you to bleed the brakes, and doesn't require a re-alignment. Easier indeed.
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Old 02-23-2009, 05:27 PM   #14
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Originally Posted by Savington View Post
No alignment required? Are you high? No half-decent repair or race shop would change a subframe in a car without at least checking the alignment. In addition, perhaps you should read the OP; if he's swapping the subframe between two cars, the cars would have to have the exact same alignment beforehand in order to have a hope of not needing one afterwards.

So your method takes two hours, requires a re-bleed of the brakes, and a re-alignment. My method takes about 90 minutes (30 per car for swapping the actual pumpkin, plus 30 to swap either uprights or halfshafts), doesn't require you to bleed the brakes, and doesn't require a re-alignment. Easier indeed.
And a VLSD to Torsen doesn't require that you get the axles out of 4 hubs which may be frozen?

The rears will end up with the same alignment as they had on the donor car. If it is off, you would need the alignment anyway.

Do it your way and enjoy
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Old 02-23-2009, 06:22 PM   #15
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And a VLSD to Torsen doesn't require that you get the axles out of 4 hubs which may be frozen?
Popping the axle nuts takes 2-3 minutes each. If they are frozen, you know quickly (they either pop out with a couple whacks, or they don't). You can then spend the extra 20 minutes I allotted popping the caliper/bracket off, undoing two bolts that DON'T require you to realign the car, and swapping the upright.

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The rears will end up with the same alignment as they had on the donor car.
No, they won't. There is absolutely no way the subframe and bodies are EXACTLY the same. They won't end up with the same alignment for the same reason that fender/hood/door attachments have wiggle room: so you can align them to each individual car.

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Do it your way and enjoy
I will. I've done 4 diffs my way. It's easy as hell and doesn't require unnecessary bullshit like bleeding the brakes again.
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Old 02-23-2009, 07:49 PM   #16
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"My mind is made up, don't confuse me with facts".

We can leave it to the OP to do it they way he likes.

Bleeding brakes is not an insurmountable task; guess you haven't really done it too often. Maybe you should install some speed bleeders to make it easier for you.

The rears I've switched don't have "wiggle room", which the alignment rack has proven several times. But, if they were out, aligning a car is not all that difficult either and it should be checked every once in awhile anyway.

Pressing out the one hub that won't release will be an enjoyable trip and will require a lot more effort in disassembly-reassembly.
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Old 02-23-2009, 09:47 PM   #17
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Quote:
Originally Posted by olderguy View Post
"My mind is made up, don't confuse me with facts".
Well at least you know that your way takes longer.

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Bleeding brakes is not an insurmountable task
No, it's not. But it adds time and makes the swap take longer.

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The rears I've switched don't have "wiggle room", which the alignment rack has proven several times.
The alignment rack has proven that your car and your donor car had the same exact alignment and the same exact dimensions? Astonishing!

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But, if they were out, aligning a car is not all that difficult either and it should be checked every once in awhile anyway.
Again, it adds time and makes the swap longer and more difficult than it has to be. Also makes it cost more because very few people align their own cars.

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Pressing out the one hub that won't release will be an enjoyable trip and will require a lot more effort in disassembly-reassembly.
Alright, out of all the Miatas I have pulled diffs on, there has only been ONE halfshaft that wouldn't come out. The fix was as simple as unbolting the upright. This is still faster than your method by a big margin.


Basically, you are arguing that it can be done your way. And although it can, it is most definitely not easiest or fastest.
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Old 02-23-2009, 09:57 PM   #18
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Originally Posted by olderguy View Post
"My mind is made up, don't confuse me with facts".
"old enough to know, yet young enough to remember"

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Bleeding brakes is not an insurmountable task; guess you haven't really done it too often. Maybe you should install some speed bleeders to make it easier for you.
I have speedbleeders. The only thing easier than bleeding brakes with them is not bleeding brakes at all.

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Originally Posted by olderguy View Post
The rears I've switched don't have "wiggle room", which the alignment rack has proven several times. But, if they were out, aligning a car is not all that difficult either and it should be checked every once in awhile anyway.
Or you could not introduce the possibility of wiggle room and keep your alignment which you've already paid for in time or money by not swapping the subframe.

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Pressing out the one hub that won't release will be an enjoyable trip and will require a lot more effort in disassembly-reassembly.
..or you could just swap the uprights like Joe said. In my experience, the hub either comes out with a couple taps or it doesn't come out at all.

I am not a glutton for punishment, nor do I enjoy wasting money on re-alignments and brake fluid (if you do it by the book, every time you bleed brakes costs around $13 for a fresh can of fluid). I can see absolutely no benefit to swapping subframes, and several serious downsides that will waste both time and effort.
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Old 02-24-2009, 01:29 AM   #19
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+1 on Andrews method. Makes no sense whatever to swap subframes.
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Old 02-24-2009, 01:53 AM   #20
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ive done stock subframes on my car with the stock diff, but never different diffs so i dont kno, but really simple as it is
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