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REAR SUBFRAME SWAP METHOD

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Old 04-23-2013, 12:33 PM
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Default REAR SUBFRAME SWAP METHOD

i have a 1990 miata with vmax coils, and fm sways.
I also have a rear subframe from a 96 left over from a part out.
My 1990 subframe dont have the extra bracing the 96 has.
Also the allighnment bolts on the 90 are broken and the controll arms are pritty rusted looking.

So what i thinking i will do is clean up all the allighnment bolts on the 96 while its out and swap it into my car.

My question to anyone who has experance here is this.

What is the easyest way to do it...
If i am correct i belive i could unbolt the axles from the diff and leave them atached to the spindles and hub, just unbolt the controll arms from the spindles, unbolt the cross member from the chasis, the coils from inside the trunk, slide the driveshaft from the trans... (dropping the exhaust first of corse) this would allow the rear subframe to come out with the diff, driveshaft, coils,and contrll arms on it. Then i could swap the diff with driveshaft and coils to the other subframe bolt it all back in and re attach the axles.
is this possable? or would i need to do somthing else?
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Old 04-23-2013, 12:45 PM
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Yes. Don't forget brake lines.
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Old 04-23-2013, 12:46 PM
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Unbolt tophats in trunk, unbolt brakeline junction block on RR, remove catback exhaust, unbolt the subframe and take it out in 1 piece. Swap whatever you want while it's off of the car. Clean/paint as desired.
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Old 04-23-2013, 01:06 PM
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I would take the diff out. its a pain to move the subframe + diff + ppf together

Also what you're doing is mostly futile. Just buy new alignment bolts and be done with it. Swapping subframes is more work than it's worth.
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Old 04-23-2013, 01:37 PM
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I left the control arms, diff and half shafts in place. But then again I was after removing the fuel tank. I'm probably leaving out a few steps. My car is a race car so many things have been removed.

Remove exhaust, PPF and driveshaft.
I used a 2x4ft section of 3/4" plywood and my race jack. It takes careful placement of the jack so the subframe was balanced.
Unhook brake line from the junction block.
Then undo the 2 nuts on top of each shock. Then the 6 fasteners on the subframe.
Lower jack slowly. If you see the plywood start to tilt too much. Raise the subframe back up. Refasten and then reposition the jack puck.

Oh yeah and be sure the front/nose of the car is secure. You'll be removing a good part of the weight at the rear of the car. If you put the jackstands in the front too far back.... well use your imagination.
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Old 04-23-2013, 02:13 PM
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Originally Posted by soviet
I would take the diff out. its a pain to move the subframe + diff + ppf together

Also what you're doing is mostly futile. Just buy new alignment bolts and be done with it. Swapping subframes is more work than it's worth.
I also thought of just doing this but i see the overall condition of the second subframe is far superior..less rust, no cracks on rubber bushings ect.

Also it has the brace at the rear of the control arms and the bracing to go from the subframe to the chasis. are you saying that adding those braces has no benifit?
Out so little that it would not be worth putting Ethel in even tho i have them laying around ?
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Old 04-23-2013, 02:43 PM
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That U shaped bar goes from the subframe to the body.
Your car doesn't have the mounts that the later subframe attaches to. When I put a 94 rear subframe in my 90, I welded in a plate with a bolt in it to secure it.
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Old 04-23-2013, 03:32 PM
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Originally Posted by vortexblue
That U shaped bar goes from the subframe to the body.
Your car doesn't have the mounts that the later subframe attaches to. When I put a 94 rear subframe in my 90, I welded in a plate with a bolt in it to secure it.
I understand where the u brace goes...and i understand that my chassis is not taped like the later models fir that brace...i planned to just drill and bolt thrue the body to secure that brace...but your reply sounds like your saying the subframe itself won't bolt up? Please clearify
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Old 04-23-2013, 04:28 PM
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Where that brace bolts up to does not go into the cabin. It's in a very small 'hollow' between the floor and back wall. If you take your seat out, you'll see the angled sheetmetal as the floor transitions to the wall behind the seat.

I found a large nut (3/4"?) and welded it to a plate.
I mounted the brace up and marked where the mount needed to be.
I removed the brace and drilled a hole big enough to get the bolt into the body, then welded the plate to the body.

I'll bet a huge nutsert might do the trick... either way, you cant get to the location from the top side without surgery.

I'll be at the shop this weekend, I can snap a pic then.
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