69 Leaf Spring Alignment Issue

[Michael C.]

Sometime ago I "refinished" the rear leaf spring on my 69 (cleaned, repainted and replaced liners). Now I'm trying to install it and attach to my trailing arms (rebuilt by Bairs). I've attach the spring to the differential with the original mount plate and bolts. Per the AIM I torqued those bolts. I've since read posts by Joe Lucia and others not to torqued those bolts at this stage. Who's right?

At this point I saw that the spring link bolt hole in the TA didn't wasn't vertically aligned (front to rear) with the cushion cup hole in the spring. Just to see if the holes would align after raising the spring to installation position, I "completed" installation of the right side. You can see in the attached photos that the spring hole is 1/2" or more to the rear.

Another photo is of the unattached left side. You can see the misalignment exists on that side as well.

I took care to be sure the leaf spring center bolt is in the hole on the bottom of the differential. There doesn't appear to be any latitude here for front to rear movement. The differential wasn't removed.

Should I loosen the mount plate bolts, as well as any other previously torqued bolts? I previously left the camber bolt nuts finger tight. Any other suggestions?
Thanks,
Mike

[Edward J.]

Re: 69 Leaf Spring Alignment Issue

Mike, with the suspension hanging nothing is going to line up, install the cushion bolts put the wheels on, and drop to the ground. Also loosen the plate bolts, and adjust the Chamber bolts close and tighten. Then with car on ground torque the plate bolts. As for the camber adjustment make the wheels about vertical as you can and then get to a alignment shop.

[Michael C.]

Re: 69 Leaf Spring Alignment Issue

Thanks for the reply Edward. I didn't previously mention that the misalignment was so extreme that the link bolt head wouldn't clear the top hole of the TA when the bolt is angled enough to enter the hole in the leaf. I'll try loosening the plate bolts as you suggest and see what happens.

[Larry M.]

Re: 69 Leaf Spring Alignment Issue

NOTHING gets fully tightened or torqued until the weight of the car is on the wheels. NOTHING........

Initially, finger tight or barely snug is fine.

Also nothing on the rear suspension will align properly until the car is at its approximate ride height. You may have to elevate the trailing arm a bit to even get reasonable alignment for initial bolting of the spring. This means lifting the spring end higher as well......which is not convenient.

A little soap and water on the spring rubber end bushings may help in getting everything together properly. I know it was needed for me.

EDIT: Two of the four spring center mounting bolts to the rear cover go into blind holes. Make absolutely sure that the bolts are not to long (or to short) for the blind holes. If to long, they will crack the rear cover when you tighten them. If to short they will strip out. Do not assume that the original bolts are still fine, as the current liners for the spring leaves are different thickness than originals........which changes the bolt insertion into the blind holes.

Way to many bad stories over the years about guys who got this step wrong.

Larry

EDIT 2: When tightening/torqueing the rear suspension bolts with the weight of the car on its wheels, you need to check the design ride height measurement, and if needed, add weight to the rear to adjust this height before final torqueing. The AIM goes thru all this. But unless this is checked and done, rear ride height may not be correct.........and you will be unhappy.

[Michael C.]

Re: 69 Leaf Spring Alignment Issue

Larry, I'll loosen all suspension related components and try again...and employ your soap tip.

Regarding your first edit - maybe my guardian angel was watching over me, but I don't think I had an issue with the length of the original bolts. None stripped out, and no sign of a cracked rear cover (yet). But, how would one determine in advance that the bolt length would be a problem?

Regarding the second edit - I do plan to follow that procedure.

Thanks

[Larry M.]

Re: 69 Leaf Spring Alignment Issue

Various ways to check the bolt length for these blind holes.

One easy way is to get a threaded bolt or piece of all thread rod and screw it up into the blind holes (both) until it bottoms. Finger tight only. Mark the bolt or rod and unscrew. Measure this length.......then subtract about 1/4 inch for some clearance for bolt stretch and for safety margin.

Then measure the length of bolt that sticks up thru the spring mounting plate and subtract the stacked spring height measured at the middle of the spring. See how this length compares to the test bolt/rod. Cut or add length (new bolt) as needed. Remember that the thick lock washer on the four spring mounting bolts is also not compressed when you take this measurement....so that 1/4 inch margin I mentioned above will help to compensate for this also.

There are other ways to do this as well. I actually did it a couple of different ways to double check..........but what I stated above should be sufficient. Other method involved a depth gage and a dial caliper and some calculations on paper.

I actually wound up buying all new bolts for the spring (Paragon reproductions) and cutting them to the needed/correct length as required based on my measurements.

My friend who is restoring a 69 car and I am helping him......we found a cracked rear cover with gear lube pouring out when we went to remove the rear spring for rebuild. Needless to say he wound up with a new replacement rear cover for the car. When all was said and one, we had to replace the rear carrier and rear gear set as well. Bubba was busy the day when he worked on the rear of this car before my friend bought it.

Larry

[Tom E.]

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