Right, moving on. One thing I forgot to mention in the previous post is that along with optimizing pinion angle via the temporary tractor hitch adjustable arms, this was also a good time to put the axle in such a position that the wheel looks aesthetically pleasing fore-aft wise in the rear wheel well.
Because I like a luxury ride, I opted to use the standard GM full size rubber bushings for the rear control arms. This needs to be pointed out and I'm sure I'll repeat this numerous times, but there are loads of substandard, sometimes dangerous replacement parts being made. Just because it's the lower price doesn't mean it's the same quality. Sometimes even the more expensive parts are made so poorly they are only fit for the rubbish bin.
I have here a collection of brand new good and very substandard bushings. The good ones are the Harris branded ones (sold in Moog boxes) and then there is some no name imitation crapola ones. Now I bought the cheap ones because I needed a temporary set to install for locating the sway bar. That's coming up.
The substandard ones are made with such an indifference to quality the inner sleeve is placed almost willy-nilly with respect to the outer shell. Unlike the Harris ones.
Another topic I wish to cover is metallurgy. Do not use ordinary construction grade steel for anything structural or safety related on a vehicle and here's why. Ordinary construction steel is rated around 50-55 ksi. Most of the frames and suspension parts that are steel used on cars are higher carbon and other elements added for resistivity to cracking from flexing and then it's heat treated.
The metal I'm fabricating the rear control arms is 4130 Chromoly, 3/4 hard (tempered) aircraft certified steel. Chromoly is extremely resistant to cracking from continued flexing. Ordinary steel you buy a chain hardware store or even a steel supplier is not. It will crack.
I fellow car chum of mine is a big Oldsmobile fan and he mentioned some of the Oldsmobile clan bought tubular control arms as upgrades to their classic Oldsmobile's and are having cracks develop. The last thing you want is a crack leading to suspension or brake structural failure at high speeds. I need not elaborate further.
My bushing housings start off from a seemless pipe of 4130.
I inside bore with my cheap little lathe for a friction fit of the GM bushing. I even step the inside for the shoulder.
You can just make out the slight shoulder the GM bushings have.
These are the beginnings of the cup of the upper control arms.
I even bought 4130 TIG welding rod with a similar as welded strength as the steel, which is around 140-150,000 ksi. Much stronger than ordinary low carbon steel. The TIG welding rod flows nicely.
Starting to look like a proper adjustable upper control arm.
Finished products. I powder coated these.
Here is the comparison to the GM original upper arm.
After jigging up the axle in the chassis I rewelded the top mount ears back on the axle housing, I also tacked back in the coil spring perches. I don't have any pictures of the jigging process. But if you can imagine angle iron clamped to the secured rotors then using the frame rails as reference points making sure the axle is centred laterally. The temporary Ford lower control arms hold the pivot point steady and just a final check of the pinion angle was made and everything braced in place. Then I welded the upper ears back on.
Another problem with correcting the pinion angle is the shock brackets are at the wrong angle.
Sliced the brackets and using a long bolt as leverage adjusted the shock brace so the bolt was parallel to the natural position of the shock bolt. Then tack welded back in place.
Some of the follwing pictures you may notice to be out of sequence as I was bouncing around from one part of this elaborate axle installing to another. But for the sake of completion of certain parts I will rearrange them to accommodate that goal.
Rear lower control construction. Again it's all 4130 with the same temper used.
Here's a good example of visual metallurgy as well showing how I arched the ends of the lower control arms.
This is all make shift bits and pieces I had laying around. That lower U shaped piece is 1/2" thick plain Jane steel. Look at how it surrendered to the 1/8" Chromoly sheet I was trying to form. I even use an old proudly made in the USA C-clamp and it was splaying at the force it took to bend that. The round pipe is a spare section of the tubing I used for the bushing housings and that's why it barely distorted, but sprung right back when the pressure was released.
Jigging up the control arms.
Tacking everything in place and checking alignment.
Nearly completed first pass of welding.
Completed first round of welding and comparing to the original GM lower control arm. I have now installed the cheap set of lower bushings.
This is the reason why, I wanted a rear sway bar. There aren't many option for '71-'76 B and C body GM cars. This particular sway bar was from my old 1991 Caprice Classic I had for 10 years and 300,000 miles. Even on the later full size models the rear sway bar seemed to be an errant option. My particular 1991 Caprice Classic was an unusual car in that someone had a ball ticking all the options available for that car. It came with all the bells and whistles, even leather interior in a Caprice Classic! But it also had the towing package, hence the rear sway bar. So I thought it would be neat if I could adapt it to my convertible.
The problem became readily apparent in that the 91 sway bar was a bit narrow. The '71-'76 full size Chevrolets were the largest (and heaviest) passenger cars Chevrolet ever built. With that they downsized the full size line in '77 and carried that same chassis till '96. It's akin to putting my '73 chassis on a copier and pressing reduce 10%.
I needed to widen the sway bar just a tidge over an inch. I used a 10 ton ram to spread it past spring point to take permanent set without destroying the temper on the bar. It took just about everything that ram could muster too.
Once I had the location of the sway bar I marked the holes on the lower control arms and added a section of pipe vertically for the bolts to grip onto.
Again another piece of smaller 4130 pipe. The bolts are 9/16" grade 8. You can tighten those bolts to your hearts content and you're not crushing that pipe welded into the control arms.
After another round of welding and grinding, then powder coating. Now the good Harris bushings are used and the cheap ones discarded in the bin. These are stout rear control arms. If it wasn't for the soft bushings you could probably use this as a landing gear strut on a Boeing triple 7.
I had to notch the lower control arm mounting brackets on the axle to clear the sway bar under extreme axle positions.
Control arms and rear sway bar done. Well almost. I must concede I do make mistakes and had to remake the cup of the upper control arms. I transposed the width and height of the cup section. Such is life.
Round 2. I didn't smooth out the welds as no one is going to see them from the outside.
I should also note, anytime you weld, or even grind Chromoly or stainless or any material with chromium, you need to either wear a respirator or be in a booth with clean fresh air hitting you and blowing away from the work. Chromium is part of the hexavalent toxic catagories and you do NOT want to be inhaling that. I rolled my welding table into my foldable paint booth. It does have a 2000 CFM blower extracting air to the outside.
Enough of that, back to the propshaft. Now I originally wanted to rid the CV joint by bringing the Cardan joint angles equal and closer to nominal. However since I plan on replacing the aforementioned Turbo 400 with a 4L80E, I will need a longer propshaft made anyway as the 4L80E is about 2 inches shorter than my TH400.
If I can find a way to make the existing propshaft work for now, it saves me the cost of having another propshaft made unnecessarily.
I stumbled over a '69 Lincoln at the U-Pull and Pay and saw it had this. So I cut the end off its propshaft and brought it home along with the Ford companion flange that was on its 9-3/8" axle. Ug, looks like Ford made a mutant variant of the Oldsmobile axle I'm replacing. Or the other way round. Dunno. The companion flange is the same between a 9" and 9-3/8" Ford axle.
My plan was to see if I can use these parts and integrate them onto my GM propshaft and see if the length is close enough.
The extra length works in favour at this end.
Question is will the Ford CV joint end work on the GM CV joint.
Only one way to find out.
Here's my crusty GM CV flange and the Lincolns.
Fits wonderfully. Even the Cardan joints are the same.
I remove the yoke off and temporarily installed the companion flange.
So far so good.
Under worse case axle movement the propshaft is 3/4" of an inch out from nominal. I can live with that as there is plenty of meat of the slip yoke still in the transmission output shaft and tail housing bushing.
So for now till the 4L80E, of which I have procured one to build up, is installed this propshaft will do.
In part V I'll cover the brakes, both hydraulic and parking on the axle and other misc bits I may have missed.