rear subframe mounts won't budge
#31
Intermediate
I used a lift table to pull the rear end. I pulled mine to get at the fuel and brake lines (see my brake line thread, which I need to update.) I cleaned up and coated the rear cradle while out (See my rust abatement **** thread).
I'm still working on shimming a torsen for my rear diff so the rear end is not yet back in. I don't anticipate any problems getting it back in place. I used the same method multiple times without issue for a Cobra IRS I adapted for my Fox Mustang.
The lift table is pretty simple, I'll post some photos when I re-mount the rear end.
#33
Driver School Candidate
#34
After 4 years and an upgraded air tool arsenal, I tackled it again and finally succeeded! It took several hours of chiseling with various bits, resulting in this much mayhem to get the subframe mounts busted loose:
I slathered the subframe studs up with anti-seize to help prevent that from happening with the Supra mounts, but they slid on so easily, with a bit of wiggle room even, that I think it's just that some of the SC mounts were made undersized. Even once freed up, I still had to use the air hammer the entire way to force them off the studs. Rust alone doesn't explain how insanely tight they were.
[Edit: There was no rust to speak of on the subframe studs. Maybe a tiny little flash rust -- just enough to be worth a light sanding -- but they were nice and smooth. It wasn't metal bonding to metal like theorized.]
To anyone else facing the same challenge, the trick is to attack them from the front side, working the air chisel in between the mount's metal collar and the subframe's rear face. Once you start getting a little bite, angle the hammer so the chisel starts pushing rearward. You'll smell burning rubber as it eats through the metal's cover, and it takes a lot of working into the collar at different angles before it'll budge. I used a long stroke air hammer, but a short stroke might be worth a try due to limited depth at the necessary angles.
No amount of attacking it from the rear side will accomplish anything, IMO. That's where previous efforts failed. If they don't slide off easily, they're basically like a compression fitting and all hitting it from the rear does is tighten it more.
I probably only hit 60-70 ft-lbs on the 8x 12mm bolts (subframe mounts to body)...still skeptical that those little bolts can take 80 ft-lbs without snapping, even with new ones. Any time I'm straining that much, things are either about to break or just broke. I added new Deeza sway bar end links while I was at it (bought those 4+ years ago when first tackling it), and boy were they tough to work into place. I guess that's why the stock end links tend to be bent in the middle...
I slathered the subframe studs up with anti-seize to help prevent that from happening with the Supra mounts, but they slid on so easily, with a bit of wiggle room even, that I think it's just that some of the SC mounts were made undersized. Even once freed up, I still had to use the air hammer the entire way to force them off the studs. Rust alone doesn't explain how insanely tight they were.
[Edit: There was no rust to speak of on the subframe studs. Maybe a tiny little flash rust -- just enough to be worth a light sanding -- but they were nice and smooth. It wasn't metal bonding to metal like theorized.]
To anyone else facing the same challenge, the trick is to attack them from the front side, working the air chisel in between the mount's metal collar and the subframe's rear face. Once you start getting a little bite, angle the hammer so the chisel starts pushing rearward. You'll smell burning rubber as it eats through the metal's cover, and it takes a lot of working into the collar at different angles before it'll budge. I used a long stroke air hammer, but a short stroke might be worth a try due to limited depth at the necessary angles.
No amount of attacking it from the rear side will accomplish anything, IMO. That's where previous efforts failed. If they don't slide off easily, they're basically like a compression fitting and all hitting it from the rear does is tighten it more.
I probably only hit 60-70 ft-lbs on the 8x 12mm bolts (subframe mounts to body)...still skeptical that those little bolts can take 80 ft-lbs without snapping, even with new ones. Any time I'm straining that much, things are either about to break or just broke. I added new Deeza sway bar end links while I was at it (bought those 4+ years ago when first tackling it), and boy were they tough to work into place. I guess that's why the stock end links tend to be bent in the middle...
Last edited by t2d2; 08-09-21 at 09:43 PM.
#35
Advanced
What a nightmare, glad you accomplished your gold of replacing those bushings. But it makes you feel real good that you won.
#36
Definitely a relief, but I won't know until later today when taking it for a drive if it makes me feel good. I was too spent after 6+ hours of working on it yesterday to do anything more than roll it forward a couple feet so I could close the garage door. (Car doesn't fit in the tiny '50s garage, but backed up into the opening is my best, safest, flattest work space.)
#37
BTW, I should point out in the above picture, that much damage to the mounts was done with a dull chisel bit. I tried a sharp one for creating a gap between the mount and subframe, but didn't want to gouge the subframe or stud. I used the dull one as basically a bludgeoning tool, and the metal itself gave out long before friction released its hold. That should give you a good idea how pointless it is to try prying them off if they don't slide off easily.
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Bimmerbill (08-09-21)
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