twitchy rear
Thread Starter
Cruising
Joined: Jan 2015
Posts: 13
Likes: 0
From: Martinsburg West Virginia
twitchy rear
I tried a search but I'm probably not using the correct terminology. The rear of my 75 seems to twitch to the right when I accelerate and then when I lift off the throttle the car pulls to the right. What is the most likely problem with the rear suspension? I don't have much experience with independent rear suspension.
Drifting
Joined: Mar 2011
Posts: 1,886
Likes: 9
You need to carefully check the rear suspension. Look for :
sloppy trailing arm bushings, loose or missing trailing arm toe shims, sloppy wheel bearings, worn U joints on the half shafts, loose wheel lug nuts, loose or worn torque control bushings on the nose of the diff., strut rod bushings, etc. Any metal to metal joint that shows a trail of rust is moving relative to the piece next to it. If one of the U joint caps has a rusty edge, or a bolt head somewhere that should be tight, for example, that could be your problem.
Bringing the car back to stock will improve things. Please don't believe those who say you need to reinvent the entire suspension of the car to get it to behave well. You can spend a bunch of money on your car, and it certainly will be different afterward. But it's not so easy to improve it.
Let the flaming begin.
sloppy trailing arm bushings, loose or missing trailing arm toe shims, sloppy wheel bearings, worn U joints on the half shafts, loose wheel lug nuts, loose or worn torque control bushings on the nose of the diff., strut rod bushings, etc. Any metal to metal joint that shows a trail of rust is moving relative to the piece next to it. If one of the U joint caps has a rusty edge, or a bolt head somewhere that should be tight, for example, that could be your problem.
Bringing the car back to stock will improve things. Please don't believe those who say you need to reinvent the entire suspension of the car to get it to behave well. You can spend a bunch of money on your car, and it certainly will be different afterward. But it's not so easy to improve it.
Let the flaming begin.
Safety Car
Joined: Mar 2007
Posts: 3,652
Likes: 49
From: Bridgewater nj
It does sound like trailing arm bushings or hub bearings. Another sign of trailing arm bushing problems is the inside of the rear tires being worn. I have to do my 82 this winter and I'm not looking forward to it.
2026 Loser of the Year
Joined: Sep 2013
Posts: 36,599
Likes: 7,046
From: New Or-leens Loo-z-anna
No flaming here...(it also could be a worn-out "snubber bushing" that holds the front of the differential in alignment)...
remove only one trailing arm and rebuild it.....then drive the car and notice the difference----then you'll have the experience to rebuild the other arm twice as fast as you rebuilt the first arm!
Some members would suggest to remove the complete rear suspension and rebuild everything---that's good advice if you have a bucket of money and lots of spare time!
remove only one trailing arm and rebuild it.....then drive the car and notice the difference----then you'll have the experience to rebuild the other arm twice as fast as you rebuilt the first arm!
Some members would suggest to remove the complete rear suspension and rebuild everything---that's good advice if you have a bucket of money and lots of spare time!
Last edited by doorgunner; Jan 6, 2015 at 09:55 PM.
Melting Slicks
Joined: Feb 2004
Posts: 2,111
Likes: 32
From: Damascus MD
Twitchy Rear
Check all the rubber bushings. Chance are very good that they all need replacing after 40 years if there was no previous work performed.
Before rebuilding everything get a dial gauge and begin checking the actual play in the trailing arm bearings and axles coming out of the differential too. If they are out of spec it may make sense to consider a total rebuild. The differential is likely okay as they have been known to go 300k miles with proper maintenance. Just read of a 66 that went that long.
Whatever you do with the suspension, it will need a 4 wheel alignment when you are finished.
I highly recommend an AIM that will illustrate exactly how the factory assembled everything. A lot of times things were not reassembled properly when previous work was done.
Start with the simpler things as door gunner suggested like the snubber. (No alignment needed there either) Strut arm bushings are one of the simpler items to R&R as well.
Bill
Before rebuilding everything get a dial gauge and begin checking the actual play in the trailing arm bearings and axles coming out of the differential too. If they are out of spec it may make sense to consider a total rebuild. The differential is likely okay as they have been known to go 300k miles with proper maintenance. Just read of a 66 that went that long.
Whatever you do with the suspension, it will need a 4 wheel alignment when you are finished.
I highly recommend an AIM that will illustrate exactly how the factory assembled everything. A lot of times things were not reassembled properly when previous work was done.
Start with the simpler things as door gunner suggested like the snubber. (No alignment needed there either) Strut arm bushings are one of the simpler items to R&R as well.
Bill
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
If your engine is essentially 'stock', then your explanation is likely one of those listed previously. If you have beefed up the engine to over 400hp, but you haven't really done anything to stiffen the drivetrain and rear suspension, then the 'twitching' you are experiencing might be expected for your car with WOT from a dead stop.
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Safety Car
Joined: Nov 2008
Posts: 3,720
Likes: 554
From: Seattle Washington
No flaming here...(it also could be a worn-out "snubber bushing" that holds the front of the differential in alignment)...
remove only one trailing arm and rebuild it.....then drive the car and notice the difference----then you'll have the experience to rebuild the other arm twice as fast as you rebuilt the first arm!
Some members would suggest to remove the complete rear suspension and rebuild everything---that's good advice if you have a bucket of money and lots of spare time!
remove only one trailing arm and rebuild it.....then drive the car and notice the difference----then you'll have the experience to rebuild the other arm twice as fast as you rebuilt the first arm!
Some members would suggest to remove the complete rear suspension and rebuild everything---that's good advice if you have a bucket of money and lots of spare time!
Le Mans Master
Joined: Aug 2005
Posts: 6,541
Likes: 1,975
From: Temple Terrace Florida
Trailing arm bushing
I agree with Mike. I really think your problem is either trailing arm bushings or your shims have gone south. Just for fun, check your transmission mount. If you have to replace the bushings, use only rubber and not polly. My polly bushings lasted a few years and broke like glass. After researching polly bushings, I learned that this is not uncommon, especially with side pipe cars. Removing the arms is not a tough job unless the bolts and sleeve(s) are frozen. Good luck. Jerry
Thread Starter
Cruising
Joined: Jan 2015
Posts: 13
Likes: 0
From: Martinsburg West Virginia
update
I looked under the rear end and the previous owner has installed a composite monoleaf. It's possible I may just need a four wheel alignment. My new question is how do I check the trailing arm bushings to see if they need replaced? the pinion snubber bushings look good. I blew my stash buying the car and it's going to be awhile before the wife is okay with me dumping money into it 
I'd like to know for sure it's a bushing problem and not an alignment issue before I tell her I need money. I may wear the pants in the house but she wears the skirt and we all know skirt trumps pants.
I'd like to know for sure it's a bushing problem and not an alignment issue before I tell her I need money. I may wear the pants in the house but she wears the skirt and we all know skirt trumps pants.
Racer
Joined: Sep 2014
Posts: 429
Likes: 29
From: Brooklyn, MI
I looked under the rear end and the previous owner has installed a composite monoleaf. It's possible I may just need a four wheel alignment. My new question is how do I check the trailing arm bushings to see if they need replaced? the pinion snubber bushings look good. I blew my stash buying the car and it's going to be awhile before the wife is okay with me dumping money into it I'd like to know for sure it's a bushing problem and not an alignment issue before I tell her I need money. I may wear the pants in the house but she wears the skirt and we all know skirt trumps pants.
I'd like to know for sure it's a bushing problem and not an alignment issue before I tell her I need money. I may wear the pants in the house but she wears the skirt and we all know skirt trumps pants.
Thread Starter
Cruising
Joined: Jan 2015
Posts: 13
Likes: 0
From: Martinsburg West Virginia
Easy way to check, jack rear of car place on jack stands, grab rear tire and see how much play you have moving it fore and aft then up and down. I was having a similar problem as you and I found my TA arm bushings were shot and so were the side yokes. Also check the condition of all your rubber bushings. Best to have someone do the moving and you watch what moves under the car.
