1977 rear gear swap

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Re: 1977 rear gear swap

Post by Joe73 on Sat Jul 12, 2014 8:22 pm

Ok, I got the measurements for you but forgot to post them.

My stock SS lower arms measure up like this. I have two different measurements for you.

From the end of the insert to the furthest edge of the arm is 4 7/8".

Or from the end of the insert to the metal case of the bushing is 2 1/2". That would be measured inside the arm.

Thats how my stock arms are set up. Close to that ballpark and your good to go.
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Re: 1977 rear gear swap

Post by Dinomyte on Sun Jul 13, 2014 11:59 am

Joe73 - thanks for the information, it's about where I'd put the inserts in the pic I posted. Are the SS control arms different from the stock ones? Do they have any reinforcement? or are they just drilled to accept the insert?

I also got the following comments from a couple of others I know that I'd asked, one of whom is a mechanic millwright who's been a great help with other things.

1. strengthen the LCAs by welding in steel rod in the lip, as the sway bar is so big.
2. move the sway bar further forward so it's in front of the diff, and thus the inserts are in the thicker stronger part of the LCA.

I still don't understand how in front / behind the diff alters handling characteristics, but I can see that it would, and I'd expect it to be really weird behavior in front, but I've seen a number of sway bars located in front of the diff.

I did find this

http://www.ozmpsclub.com/forum/handling-wheels-tyres/5882-suspension-theory-basics.html

on-line that did a great job of explaining how sway bars, springs, shocks and bushings all work together to get a better handling car.

Still confused about placement. Sad
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Re: 1977 rear gear swap

Post by dynchel on Sun Jul 13, 2014 1:49 pm

Mine is mounted on top of the control arms (aftermarket arms combined with arm relocation brackets) and it handles way better than it did mounted underneath.
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Re: 1977 rear gear swap

Post by Joe73 on Sun Jul 13, 2014 2:27 pm

The SS arms aren't any different than normal arms. There isnt any other reinforcement in them. They just have holes for the insert to bolt in.
I dont understand how the "thicker stronger" part of the arm idea. The arm has the same curled lip from bushing to bushing. So an insert would still be in that area.
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Re: 1977 rear gear swap

Post by Dinomyte on Mon Jul 14, 2014 7:55 am

The concern is / was that the sway bar would exert a lot more stress on the old arms. Not to mention that the Impala SS bar is 1" and the stock options on the Chevelle were max 7/8", the force the bar exerts is ^4 so a 7/8 bar, with all other things being equal is significantly less force (if the 7/8" bar is the norm, a 1" bar is 1.7 times as much force). That's a lot of force on something that might not have been designed for it.

Please don't ask me to explain the math, I understood it as I was reading it, and distilled it down to how much more or less force there would be, as I wasn't going to change more than the bar itself.

I still don't understand how placement on the control arm affects handling, but I'm sure it does, and I've seen both in front and behind the diff.

If you take a look on Google for the Impala SS and the location of the rear sway bar, it's in front of the diff, with spacers to drop it down so it clears everything. This fits with all the OE information. All the information I've gotten here is to put the bar as far back as possible, and the bar behind the diff.

I just don't understand why. †Question†it fits in both locations easily, doesn't interfere with anything either.

Can anybody here explain this?

Question 2. What type of material should I use for shims between the insert and the arm? There is too much space between them..

Thanks,
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Re: 1977 rear gear swap

Post by Joe73 on Mon Jul 14, 2014 8:10 am

There was a 15/16" (considered 1") stock bar for G3's. †This is one from a '73 †442. †I've seen one on a Monte as well.

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Re: 1977 rear gear swap

Post by Dinomyte on Mon Jul 14, 2014 8:41 am

I guess the worry about added stress is looking like less and less of an issue. With all else equal the 1" bar is only 29.5% more force than the 15/16" bar. I'm sure there was at least that much extra strength built in.

Now how about some info on how placement of the sway bar affects suspension?
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Re: 1977 rear gear swap

Post by Joe73 on Mon Jul 14, 2014 9:22 am

I agree. I think its been proven that a boxed arm is the best way to go for strength and least amount of flex. But how crazy and expensive does anyone "need" to go?

And another thing (to stir the pot) would be the percent difference in diameters between a front bar and rear bar. Everyone thinks bigger is better. But when the percentages get messed with, you can get bad understeer or oversteer which makes the car handle erratically. Which would be unsafe. Google search for sway bar diameters and how they can adversely affect your vehicle.

Also, tightening up on sway bars is only as good as the bushing in the front and rear suspension. Then there's a question of spring rates. It could go on and on to "tune" a car to do a specific task.

I say, if you not looking for your car to do a specific task like road racing or slalom, etc. then just smack a stock sized bar in it and go.

I also agree that sway bar placement would be a good discussion. Me personally, I wouldnt mess with what the factory did unless your trying to get the car to do something "extra" that it wasnt designed to do.

Back in the 80's, I removed my rear sway bar (7/8") totally. I also removed my factory front bar (1 1/8") and replaced it with a standard front bar but I spaced the mounting brackets 1 inch off the chassis. WOW the front end was sloppy. Couldnt take a turn without leaning all over the place. But boy did the car hook in a straight line. The spacing allowed the front end to unload easier. And I have drag shocks set at 80/20 in the front as well.
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Re: 1977 rear gear swap

Post by bracketchev1221 on Mon Jul 14, 2014 9:49 am

Dinomyte wrote:I guess the worry about added stress is looking like less and less of an issue. †With all else equal the 1" bar is only 29.5% more force than the 15/16" bar. †I'm sure there was at least that much extra strength built in.

Now how about some info on how placement of the sway bar affects suspension?

Well, lets think about a drag race car that wheelstands. The bars are being used to lift the front of the car off the ground from a point way back in the car. The amount of force being exerted on these bars are huge and they hold up just fine. The sway bar insert in the lower arm strengthens the arm because it prevents the twist in the arm.
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Re: 1977 rear gear swap

Post by dynchel on Mon Jul 14, 2014 11:32 am

" />
Here's where mine is, behind the diff, and tucked up like it was made for it.
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Re: 1977 rear gear swap

Post by Joe73 on Mon Jul 14, 2014 12:28 pm

bracketchev1221 wrote:
Dinomyte wrote:I guess the worry about added stress is looking like less and less of an issue. †With all else equal the 1" bar is only 29.5% more force than the 15/16" bar. †I'm sure there was at least that much extra strength built in.

Now how about some info on how placement of the sway bar affects suspension?

Well, lets think about a drag race car that wheelstands. †The bars are being used to lift the front of the car off the ground from a point way back in the car. †The amount of force being exerted on these bars are huge and they hold up just fine. † The sway bar insert in the lower arm strengthens the arm because it prevents the twist in the arm. †

I agree with that. Strong bars are key. I've dragged my car a ton in the late 80's with no rear sway bar.
I've tried stock arms with aluminum bushings, square tube arms with NO bushings just a sleeve and stock arms with poly bushing with no inserts. My car has been all poly since I found them in the late 80's. Now I find its best to NOT have poly above the diff. It stresses the uppers too much. I think both, a drag car and a street car would benefit from strong arms. But a drag car, properly set up, would have much less twisting (flex) in the bar because the car is fighting to go straight. Of course, unless the drag car has too much squat on the passenger rear tire on launch. Then the arms would be flexing like in a turn. Thats where an air bag in the spring helps.
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Re: 1977 rear gear swap

Post by Dinomyte on Tue Jul 15, 2014 12:34 pm

Placement - I've got this figured out.

The two rear lower control arms and the axle form a triangle if you imagine the control arms extending forward till they touch. So there is only one location that will work for the bar as it's arms are also on the same angle.

I had this whole thing on the floor and the arms were only connected to the axle and nothing up front and could move enough to allow me to locate the bar further forward than I should.

Now to drill the control arms. . .
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Re: 1977 rear gear swap

Post by w451973 on Tue Jul 15, 2014 3:05 pm

The bar with the brackets are only gonna fit the arms in one spot. You cannot move it forward or rearward no matter how hard you try.

What I've done before to locate where to drill was to put the car up on ramps. Take the bar with the brackets bolted to it and fit it into the trailing arms. Mark where the brackets fit. Measue the bracket for the location of the holes. Measue, mark and drill the holes.

As for the bigger bar and force. The 9C1 tyrailing arms are no more heavy duty then our a-body arms. If it was gonna be a problem then GM would have figured it out and corrected it.
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Re: 1977 rear gear swap

Post by chevellelaguna on Tue Jul 15, 2014 7:51 pm

I thought the same thing, there was only maybe 1/4" forward and rearward total movement when I installed my rear sway bar.(from a 75monte Carlo) there was no possible way I could locate it anywhere else in the arm between the bushings. I drove the crap out of my car, NO ONE.... I know... EVER will ride with me. I haven't rolled the car over yet, so the sway bar must be working... Right?


Last edited by chevellelaguna on Tue Jul 15, 2014 7:53 pm; edited 1 time in total (Reason for editing : Spelling)
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Re: 1977 rear gear swap

Post by dynchel on Tue Jul 15, 2014 8:20 pm

Lol, adding a rear bar does make a difference. †I have a one inch front bar ('73 Monte) and a one inch rear bar ('95 impala) add some urethane bushings and links on the front and you're golden.
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Re: 1977 rear gear swap

Post by chevellelaguna on Tue Jul 15, 2014 9:54 pm

Agree
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Re: 1977 rear gear swap

Post by Dinomyte on Mon Jul 21, 2014 10:08 am

Guess what I learned . . .

the upper control arms have a two different sized bolt holes (the end on the rear, not on the frame), so there's only one way to put bolts in, not to mention the replacement bolts I got as everything was well worn, were just a hair too big to make it through.

So the rear end is in, all the bolts are torqued, and now all that's left is to connect and bleed the break lines, do breaks, check the fluid in the diff. Oh and most importantly, lay a pair of patches. Smile
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Re: 1977 rear gear swap

Post by Joe73 on Mon Jul 21, 2014 10:34 am

Make sure you torque the control arm bolts with weight on the axle as if the car is sitting on the ground. I just leave the axle sitting on jack stands.
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Re: 1977 rear gear swap

Post by Dinomyte on Mon Jul 21, 2014 10:55 am

Joe73 wrote:Make sure you torque the control arm bolts with weight on the axle as if the car is sitting on the ground. I just leave the axle sitting on jack stands.

Thanks, I didn't know that.

Why do you do that?


Last edited by Dinomyte on Mon Jul 21, 2014 11:12 am; edited 1 time in total (Reason for editing : question)
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Re: 1977 rear gear swap

Post by dynchel on Mon Jul 21, 2014 11:18 am

So you don't preload the bushings.. That's a good way to wear them out fast. BTW I believe the torque for all the arms and lower shock bolts is 80 ft lbs.


Last edited by dynchel on Mon Jul 21, 2014 11:20 am; edited 1 time in total (Reason for editing : added specs)
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Re: 1977 rear gear swap

Post by Dinomyte on Mon Jul 21, 2014 11:31 am

dynchel wrote:So you don't preload the bushings.. That's a good way to wear them out fast. BTW I believe the torque for all the arms and lower shock bolts is 80 ft lbs.

So I should back them all off first, and do it all over again, including the shocks?

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Re: 1977 rear gear swap

Post by dynchel on Mon Jul 21, 2014 12:09 pm

Its up to you. I like to torque things to spec...most people don't & don't have any problems.
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Re: 1977 rear gear swap

Post by Dinomyte on Mon Jul 21, 2014 12:56 pm

dynchel wrote:Its up to you. I like to torque things to spec...most people don't & don't have any problems.

I just like to do things right the first time, itís less work that way. Not to mention somebody in the know said 80 Ft/lb for the control arms and 65 Ft/lb for the shock studs.

I'm working with the thought that 80 Ft/lb with no load is a lot more than with load on the bushings, that's why I figured I should back them off. Is that correct or not?
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Re: 1977 rear gear swap

Post by dynchel on Mon Jul 21, 2014 1:03 pm

Correct, you want the weight on them when they are tightened. †Like joe said it can be done with stands under the rear end....that's usually how I do it.
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Re: 1977 rear gear swap

Post by Dinomyte on Sun Jul 27, 2014 7:58 pm

Just came back from a ride in the Malibu. Did about 20 miles, and she's cooling off in the garage. Oh it's nice to get back behind the wheel of that car. I feel like a teenager when I'm driving her.

The rear is in, everything done right, all sounds good, no whining sounds or anything other than exhaust and the usual. I'll role back under it in a couple of days and re-torque everything, or is that unnecessary?

Many thanks to everyone here, especially -

Dynchel, Joe73, Bracketchev1221, Chevellelaguna, the guys at Car Quest (south London),

Some very important bits of advice, that made this project a success, with out any major problems.

My neighbor John, with some specialty tools I needed, my buddy Greg for the machine work, and last but not least my two boys Ryan & Jesse who both helped.

I'll be putting the sway bar in a week or so, I just want to drive her, with and without the bar to get an idea of just how different it is.

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Re: 1977 rear gear swap

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