Front end frustrations

[David H.]

OK, so putting the front end back together has pretty much frustrated me to near death.
The drivers side seems to have gone relatively well.
I have remounted the cross member to the frame to make it easier to reassemble the passengers side.
However, mr. murphy has struck again.
First it was the lower outer pivot pin and bushings had too much slop.
So, I bought a replacement one and tried again. The nut that is welded to the yoke of the a-arm is pretty much stripped and useless. The welds holding it in are also loose.
Then I find the upper inner pivot bolt wont tighten correctly in the shock tower, so I order a new pivot bolt. The new one is the same as the old one. Wont tighten up. So, I call CC and they send the replacement bushings. Now, logic says that with these two parts in hand, you should not be able to tighten the new bushings onto the new shaft. Right?
Well you can with ease. So, I call CC again and they are checking into it for me. But something here is not right.
So my question is, if there is not enough interference to the shaft in the bushings, is there anything I can do to create more interference so the shaft will tighten correctly? I would prefer to use the bushings that are already in the shock tower as I did with the drivers side.
Open to any suggestions.

Thanks

[William C.]

Re: Front end frustrations

If what you are calling the upper inner pivot bolt is the threaded shaft that goes completely thru the tower, the one that the upper inner bushings rotate on, then the problem is that the shock tower is worn. There are (were) oversize shafts available in the aftermarket "in the day" and some are still available. Try a '54 Chevrolet outfit or someone like "Kanter" who specialize in the eralier passenger cars. I have some for my '62, and I've measured a difference of about .025 in diameter from the smallest to the largest, should be able to find one in that range that will tighten up for you.

[Richard M.]

Re: Front end frustrations

David,

I'm afraid you may need a set of these. They are repair bushings for the shock tower. It is not unusual to have them stripped as I have heard

Zip SU-371

Also, the threaded upper shaft can only go in one way. It has a relief in one end and smaller threads to allow it to be inserted in one direction only. The ST-12 says which way and I think it's from front to rear.(I just did this a few months ago and can't recall). I also believe the thread sizes for the repair bushings are different and have to be put on the correct side of the tower. I've never had to replace them. Hopefully the parts come with info as to which one goes where.

Rich

[John H.]

Re: Front end frustrations

Then I find the upper inner pivot bolt wont tighten correctly in the shock tower, so I order a new pivot bolt. The new one is the same as the old one. Wont tighten up. So, I call CC and they send the replacement bushings. Now, logic says that with these two parts in hand, you should not be able to tighten the new bushings onto the new shaft. Right?
Well you can with ease. So my question is, if there is not enough interference to the shaft in the bushings, is there anything I can do to create more interference so the shaft will tighten correctly? I would prefer to use the bushings that are already in the shock tower as I did with the drivers side.
Open to any suggestions.

Thanks

David -

There should be NO interference between the upper inner and upper outer pivot shafts and the end bushings; that's a threaded connection between the two parts, and they should move freely relative to each other as the control arm moves up and down. The only designed interference is where the inner upper shaft threads into the spring tower (which is why it's so difficult to install it, as the replacement shafts are slightly oversize), and where the end bushings thread into the holes in the control arms (which is why they require so much torque). See cross-sections of the inner upper and outer upper assemblies below.

[David H.]

Re: Front end frustrations

David -

There should be NO interference between the upper inner and upper outer pivot shafts and the end bushings; that's a threaded connection between the two parts, and they should move freely relative to each other as the control arm moves up and down. The only designed interference is where the inner upper shaft threads into the spring tower (which is why it's so difficult to install it, as the replacement shafts are slightly oversize), and where the end bushings thread into the holes in the control arms (which is why they require so much torque). See cross-sections of the inner upper and outer upper assemblies below.

You are correct and I realize and agree with what you are saying. I guess I didnt explain it well enough.
What I am having issues with is the upper inner shaft, (called the pivot shaft) not tightening into the nuts (bushings) in the top of the shock tower. It does go only one way, front to rear, with the slightly smaller diameter end slipping thru the front bushing (nut), then threading into the rear bushing (nut) and at the same time the front bushing (nut). As it starts to thread into these bushings it should become extremely difficult to thread it, (as it did on the drivers side) until there is 1 1/8 inch sticking out of the rear side of the shock tower bushing (nut). In this case I can pretty much thread it in by hand with no wrench involved.
Ok, so that tells me that there is not enough interference between the threads in the bushings (nuts) and the threads on the pivot shaft. Even with a new pivot shaft and new bushings (nuts) in my hands instead of on the car, I dont believe I should be able to thread the new bushings onto the new shaft without great difficulty. Is that true? The bushings are different sizes and will only go on the shaft one way. But both of them thread on easily by hand.

[Richard M.]

Re: Front end frustrations

David,

I think I understand your question better now........I think you may be experiencing normal behavior....that is if you're not aware that the shaft ends are different diameters........

When the shaft gets installed from front to rear(note originals have a dimple on the tapered end), it has to thread through the front bushing first, then when it gets past the threads, it's free, then threaded into the rear tower bushing. Because the shaft is "stepped" as shown below on the pictorial I just made up, it will be free until it's begins to thread into both bushings. Then it should get very tight, almost impossible to thread in.

I think once you weld in the new tower bushings, the threads will not line up perfectly between the two when the shaft gets inserted, and you will recognize the clearance will decease and be tight.

Also shown is a tool set I made up from the old parts. It works like the J-2958 tool in the ST-12. Tighten the inner nut outwards towards the front to remove......Tighten the old bushing end inwards towards the tower to install. The big lock washer acts as a jamming device to get the torque you need to tighten.

Remember be verrrry careful not to go to far when tightening the shaft. I get close, then measure both ends to get equal protruding lengths. If you go too far you loose the "tighten-up" and strip the threads on the tower bushings, the shaft, or both.

Rich

[David H.]

Re: Front end frustrations

I am quit aware that the shaft ends are different diameters. Believe me, I have studied everything I can get my hands on about this subject. I am getting to know it inside out. The replacement shaft I have from CC will only go into the bushings one direction. It goes in exactly as you described. However, I can thread it all the way in and then some by hand. It has no interference at all with the old bushings.
What I was curious about was if there is any way to affect that interference without replacing the original bushings, or do I have no choice and need to replace them with new ones.
The attachments you included are very benificial as well.
Thanks for your efforts Richard.
I measured my replacement shaft. Tapered end rear, .740 and .750.
Non tapered end .780 and .734.

[Richard M.]

Re: Front end frustrations

Hi David,

Yes I understand you're very familiar because you've been very up close and personal with this. You will become the resident expert on these when you're done!. I guess some of us were just a little confused, me included. I can see exactly what you mean now, so.......

....I do not think you can do anything else with your existing tower bushings to correct the slop. If you try to weld a bead, or even braze some bronze inside to build up the threads, it would compromise safety and could eventually come apart,or make it too tight and damage something. You could weld around the new shafts and permanently attach the shaft to the tower, but to me that would be a "bubba" solution. I couldn't do something like that.

CC needs to verify if what you have is defective or not. Getting someone there that really knows what the issue is, let alone who in the world to talk to at their supplier is going to be difficult. I would be interested to hear what you find out.

Recently when I rebuilt the front suspension on the '59 I'm working on, I'm pretty sure I was playing around with the new shafts I got. I tried threading in each end into different tower busing locations and saw that I got different tensions based on where I threaded them. I have another pristine original complete front crossmember but I'm not in a state to take it apart to investigate right now.

However, again, I truly think what you are seeing is normal with the new tower bushings and new shaft. As I mentioned before when these bushings are installed, even the originals IMO, there's now way to perfectly align them with respect to distance apart and circular thread alignment. I really think that if you put new ones on, becasue they cannot be perfectly aligned to the 360 degree start point threads, along with spread distance alignment, they will tighten up. I cannot believe that the factory that supplied the front crossmembers as an assembly to St. Louis had such fixturing to ensure alignment. Maybe I'm way wrong here, I just don't know for sure. I would replace the bushings if I had your situation. If I did I would somehow try to deliberately ensure the threads are offset to give you "worst case scenario" alignment for the best chance of tightness.

Rich

[Richard M.]

Re: Front end frustrations

...one more thing I would do. Using a caliper measure the ID of the new bushings and measure the new shaft threads at the bushing contact points. Measure the ID of the "bad" tower bushings.

Rich

[David H.]

Re: Front end frustrations

Anyone happen to have access to the correct replacement part number for the upper inner pivot shaft that we are talking about? It would make my search easier.
THanks.

[William C.]

Re: Front end frustrations

David, the replacement GM part was .008 oversize, part number 3693693, group 6.164. As I mentioned to you AFTERMARKET sources may have had other oversizes available.

[David H.]

Re: Front end frustrations

Great! I'm on the trail of one as we speak.
Thanks very much for all your help with this.

[John F.]

Re: Front end frustrations

Pull up Tom Parsons article on the rebuild. You won't be disappointed. He goes step by step with photos.
It is under front end rebuild I think.
John F

[Tom P.]

Re: Front end frustrations

Pull up Tom Parsons article on the rebuild. You won't be disappointed. He goes step by step with photos.
It is under front end rebuild I think.
John F

John,
Thanks. I sent him an email with the link.