Rear control arms for '73 LeSabre

Hello all,

1973 LeSabre with 455 swap (originally a 350 car). I'm having a problem where when I am on the gas a little I go straight, but when I let off the gas I have to make a slight steering correction. Get back on the gas and move the steering back to straight... I'm assuming this is an issue in the rear control arms. When I get under the car the bushings feel like they aren't moving to my hands with a good hard twist and pull on the arms, uppers and lowers. What am I missing? Bolts not tight enough (they are tight)? The control arms are stock, don't seem to be rotted out - they look and feel solid.

Anyone else have (or solve) this problem?

I was looking at replacing the rear control arms altogether, but in looking around (checked out the UMI site) there are no listings for the '73. Are they the same as a '70? They do list arms for a '70 B-body. I can take measurements...

Am I looking at the right solution targeting the rear control arms? The front end is pretty tight. I don't see any play in the ball joints or steering components. I can't say that the issue started with the engine swap, that was done many years ago.

Thanks!
-Derek

 

I guess my question is how to tell if the bushings are worn. They don't seem to be worn, but then again I can't see what it's doing under load.

Is it worth using poly bushings over rubber?
Thanks,
-Derek

 

The front end is tight. I did just replace an idler arm, but the way it's changing with on and off the throttle makes it feel like it's from the rear. The 455 does make a lot more power than stock, so I'm leaning towards just going for the poly bushings in the back anyway.

I'd be surprised if the front shocks would affect the steering related to the throttle like I feel. They are old, but not leaking and it's not overly bouncy. The front control arm bushings were all replaced with poly a few years ago.

Thanks,
-Derek

 

Interesting side note - on Energy Suspension it says the rear control arm bushings need to reuse the original outer metal shells. That sounds like a pain! Anybody have any tips for that job? Or is it not as bad as it sounds?

 

Did you check the engine- and transmission mounts?

 

I Agree with Erik. Before jumping to conclusions you should check ALL engine and trans mounts . Then ALL suspension front and rear. After 43 years the bushings and everything else have seen their useful life.

 

The engine and transmission mounts are new. The front suspension is tight. The control arm bushings were replaced with poly about 20 years ago and they still seem tight, not exactly sure how to check them. There is no ball joint or steering play. There is a very slight wheel bearing movement on the pass. side, I will check in there and clean and repack the bearings, will see if that makes any difference.

The change is very slight, and it's from light-cruise to decel and back that it changes. We aren't talking about heavy throttle, that's not making anything change from cruise.

Thanks all for the ideas so far. I've had this car for 25 years and this is something I just noticed starting about 3 years ago when I pulled it out of a 10 year slumber... It never drove like that before, always tracked straight all the time. Like I said, it's a very subtle but annoying shift in the steering wheel.

 

And what about the steering column coupler, did you also replace it?

 

Meaning the 'rag joint'? I was just looking at it this weekend and the steering wheel and shaft definitely turn the input to the box without any obvious play. I replaced that probably 20 years ago and it hasn't had a lot of miles since then. I also replaced the steering box a few years ago and it doesn't have any slop.

All this adds up to my reasoning that it must be rear control arm bushings or something in the back... I'm surprised how many people are telling me to look at the front again... I am looking!

The only thing I'll probably do in the front that hasn't been done recently is the shocks. They feel good while driving, but they also seem to be wet with oil near the bottom (could be from the engine compartment), but I'll do that too. I've never considered that shocks could possibly affect the steering on a flat car.

When I say 'decel' I don't mean the car is nose diving or that anyone is hitting the brakes - this is light throttle and cruising, not heavy loads. I'm talking about pretty much holding speed, but you crest a slight hill and let off the throttle, then back on again when it flattens out, or just following along with traffic or whatever, but you have to make slight shifts in the steering to keep going straight.

Thanks everyone for all the ideas, I'll definitely report back when I figure this out.

 

I'll try to describe it a different way - I could say this like "The back end of the car shifts a little to the right on positive throttle and a little to the left on light decel." If you mash the gas (wheee!) it changes about the same amount.

 

One more easy check:
Drive shaft play, or differential ring and pinion play.

 

sounds good, I'll check that while it's up. The U-joints were all done not that many miles ago. The driveshaft is one of the long ones for large cars and has the double u-joint "CV" joint in the back.

 

In my mind, I'm almost willing to bet, without a doubt is the rear control arm bushings. It's just been noticed since it has sat for a period of time & the bushings have deteriorated a bit more over time & then you also added MORE POWER!!!!

 

My 72 does the exact same thing. Seems to be dog tracking slightly upon slight acceleration. Front seems to go to left and rear shifts to right. Pulled it in the shop and put it on the hoist to find rear bushings are shot and one bolt on lower arm has not been tightened for a long time and has since rusted. I'm going to replace them with UMI performance upper and lower arms with polyurethane bushings.

hope this helps

 

How do you check for bad bushings? Is it just a visual check?

-Bob C.

 

Not to stir up a great debate between Rubber and Poly bushings BUT :: The Poly bushings have no give. It gives a hard ride. I know a few people that went with the poly bushings and are sorry they did.

The Rubber bushings will take a little flex and that is what is needed instead of "LOCKING " everything together.

Larry is right about boxing the original arms. That and new rubber bushings and you will swear its a brand new car.

Try not to overcomplicate a simple operation. Poly bushings have a place but I don't believe its in a normal Street car.