Best Way to Adjust Upper Trailing Arms - Chevy Impala SS Forum
 
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post #1 of 9 (permalink) Old 08-07-2017, 11:09 AM Thread Starter
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Best Way to Adjust Upper Trailing Arms

I tried searching for this, but came up empty, just talk about products and installation.

I need to bring my upper arms in a bit (reduce extension) because my driveshaft is hitting the tunnel under hard acceleration, but more so on the bigger bumps and dips in the road. Also, the area near the U-joints are barely hitting the frame where the pinion snubber should be (it broke off long time ago and I'll be putting the offset front bumpstop).

Getting under the car, it looks like the best way is to simply remove the arm where it attaches to the frame, and turn it so it reduces. Then repeat the other side. I was hoping to be able to do this with the arms fully installed, but that isn't happening.

Any other ideas or suggestions? I'll be doing this solo.

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post #2 of 9 (permalink) Old 08-07-2017, 12:01 PM
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do you have adjustable upper control arms??

\'96 BBB 383/T-56
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post #3 of 9 (permalink) Old 08-07-2017, 12:34 PM Thread Starter
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Quote:
Originally Posted by BALLSS View Post
do you have adjustable upper control arms??
Of course!
3CFab or C3Fab, whatever they're called. I thought I could simply wrench on them installed with jam nuts loose, but it seems like the end of the arm itself needs to turn, not the "turnbuckle" in the middle of the bolt.

Hopefully I'm wrong and I simply need a ton of leverage.

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Last edited by k gee; 08-07-2017 at 12:41 PM.
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post #4 of 9 (permalink) Old 08-07-2017, 12:59 PM
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Just as you say, when installing my adjustable METCOs (~17 years back) I spied that the threaded shaft spun on the other section which looked all the world like it was only adjustable when disconnected on one side - probably completely removed from the car. The 'jamb nut' served just to retain the pre-adjustment calculated by the manufacturer, so I didn't mess with anything.

IDK much, but the uppers get toyed with ONLY to adjust pinion angle, - sure don't think it's to redesign for dropped driveline interferences. I would cut out the tunnel, install a new snub or even get new coils/shocks before touching the UCAs for that reason.

\'96SS SOB: SSRI, Herter Tune, Tri-Y II, , 3000 Edge, F/HO bars, METCO extendeds with CV MMC, Bilsteins, currently Vredestein Ultrac Sessanta (315/35 rear). Finally, wait for it... LT-4 knock module!
\'96FWB BUW-Butt Ugly White: PCMPerformance tune, HDFA w/ swissed filter, 1/2 SLP s.s. catback with H- and Flow Super 50s, oem opti rebuilt 3 times, SS Bars, METCO LCA, Airlift 1000, Monroe SS, PowerTrax No-Slip, CTS wheels with +1 rubber. Finally, yes again... LT-4 knock module!
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post #5 of 9 (permalink) Old 08-07-2017, 01:10 PM
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Google shows a pic of the 3C Fab adjustable arm...if I see it right there is a nut (assume welded to threaded rod) in the middle of the threaded rod part and nuts on either side I assume you "jam" against the arm once you turn the middle nut to get the desired position of the arm....so it would appear they are "adjustable" without disconnecting either end

IDK since I have never used a adjustable UCA. Mine are stock fixed length Hotchkis

Soooo if yours are this way maybe spray some WD40 on the threads after loosening the 2 jam nuts and see if you can turn the center nut. Maybe a BF wrench is needed

you will change your DL angle by making the pinon nose up or down depending on which way you adjust. With lower springs involved maybe some "modification" to areas of the car in contact is required to ALSO maintain DL angle...

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post #6 of 9 (permalink) Old 08-07-2017, 01:44 PM Thread Starter
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Another problem I'm going to run into is getting the 2.5" exhaust pipe to fit in there and not come in contact with the rear end, or springs, or fuel tank shields, or a combo of these, so I'm trying to bring the entire rear end up towards the front of car while raising/rotating it a bit, because I'm also hoping the spring perches move a tad closer to where they should be so the springs sit somewhat level.

Just didn't want to remove trailing arm if I could help it.

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post #7 of 9 (permalink) Old 08-07-2017, 01:49 PM
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I'm viewing the C3 Fab YouTube and it's showing quote: "left hd./rt. hd/ threaded male adjuster" with 2 jamb nuts - for adjusting on the car. That's different than the METCO anyway.

\'96SS SOB: SSRI, Herter Tune, Tri-Y II, , 3000 Edge, F/HO bars, METCO extendeds with CV MMC, Bilsteins, currently Vredestein Ultrac Sessanta (315/35 rear). Finally, wait for it... LT-4 knock module!
\'96FWB BUW-Butt Ugly White: PCMPerformance tune, HDFA w/ swissed filter, 1/2 SLP s.s. catback with H- and Flow Super 50s, oem opti rebuilt 3 times, SS Bars, METCO LCA, Airlift 1000, Monroe SS, PowerTrax No-Slip, CTS wheels with +1 rubber. Finally, yes again... LT-4 knock module!
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post #8 of 9 (permalink) Old 08-07-2017, 02:06 PM
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Quote:
Originally Posted by k gee View Post
Another problem I'm going to run into is getting the 2.5" exhaust pipe to fit in there and not come in contact with the rear end, or springs, or fuel tank shields, or a combo of these, so I'm trying to bring the entire rear end up towards the front of car while raising/rotating it a bit, because I'm also hoping the spring perches move a tad closer to where they should be so the springs sit somewhat level.

Just didn't want to remove trailing arm if I could help it.
well from what pics I saw and what 96 describes it appears your UCL's can be "adjusted" on the car

..whatever adjustment you make to try and resolve clearance issues will effect DL angle so you would need to add/subtract shims from your rear tranny mount to compensate that...assuming whatever adjustment you do make isn't beyond what adding/subtracting shims can offset

a good muffler shop should be able to "massage" the over-axle pipe to clear any conflicts

Championship Muffler is a shop I use in Simi Valley

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post #9 of 9 (permalink) Old 08-07-2017, 02:20 PM Thread Starter
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Looks like I confirmed the answer with this video from Spohn. Guessing the suspension should not be loaded.


Thanks.

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