Rebuilding front end

[StefanLee]

Ok, so I in the process of tearing down my front end completely. I installed poly bushings a year ago but feel the need to do a more thorough rebuild to make the car feel OK. As it is, the car feels very "light" in the front at speed. It´s not a very pleasant feeling when you feel detached from the ground when you steer... The car also veers to the sides when driving over uneven roads and when crossing ruts in the tarmac (steering rack?)

This leads me to believe I have some play in the front end components, calling for a rebuild.

So, I´ve unbolted all control arms (one of which needed an angle grinder to cut the bolt, since the "bolt from hell" held it in an impossibly strong grip...) and the leaf spring.

What I now have to do is unbolt the front crossmember itself, including the steering rack. So on to my question... Is there somethin VITAL I have to think about when doing this? I can see that the crossmember is fastened with four bolts, and a few smaller ones that hold the radiator.
I figure I´ll just loosen the bolt holding the steering column at the rack, and then everything should just come down, correct?

After that, I´ll have to weld in new tubes holding the upper control arm bolts due to wear. The left is the worst, but I could feel a small amount of play in the right today, so I´ll do that one as well. Time to find a metal shop that does quality welding...

I´m trying to figure out if I have to replace my ball joints. They all feel rock steady without any play when I yank them around by hand. I should be able to feel any wear that calls for replacing, right?

How does the adjustment on the rack work? Perhaps a major culprit in the equation...

I hope these repairs, together with a few new poly bushings for the leaf spring and finally a wheel alignment will do the trick.

Any tips ont he subject?

/Stefan

[opelnut10]

Originally Posted by StefanLee Ok, so I in the process of tearing down my front end completely. I installed poly bushings a year ago but feel the need to do a more thorough rebuild to make the car feel OK. As it is, the car feels very "light" in the front at speed. It´s not a very pleasant feeling when you feel detached from the ground when you steer... The car also veers to the sides when driving over uneven roads and when crossing ruts in the tarmac (steering rack?) This leads me to believe I have some play in the front end components, calling for a rebuild. So, I´ve unbolted all control arms (one of which needed an angle grinder to cut the bolt, since the "bolt from hell" held it in an impossibly strong grip...) and the leaf spring. What I now have to do is unbolt the front crossmember itself, including the steering rack. So on to my question... Is there somethin VITAL I have to think about when doing this? I can see that the crossmember is fastened with four bolts, and a few smaller ones that hold the radiator. I figure I´ll just loosen the bolt holding the steering column at the rack, and then everything should just come down, correct? After that, I´ll have to weld in new tubes holding the upper control arm bolts due to wear. The left is the worst, but I could feel a small amount of play in the right today, so I´ll do that one as well. Time to find a metal shop that does quality welding... I´m trying to figure out if I have to replace my ball joints. They all feel rock steady without any play when I yank them around by hand. I should be able to feel any wear that calls for replacing, right? How does the adjustment on the rack work? Perhaps a major culprit in the equation... I hope these repairs, together with a few new poly bushings for the leaf spring and finally a wheel alignment will do the trick. Any tips ont he subject? /Stefan

The light feeling in the front end is more than likely "caster" the front cross member should have had two tapered shims between it and the sub-frame. The ideal setting is three to five positive with as much as seven if you are going to go fast, the more caster you put in the more stable the feeling will be in the steering. Instead of welding new tubes in you can ream the holes out bigger and drill the control arms for bigger bolts. Adjusting the steering rack requires loosening the jam nut on the pinion and running the adjuster in till you have very little play in the steering then lock it down. If you are working by yourself you will need to disconnect the steering shaft sleeve from the pinion and wiggle it by hand while you are adjusting it. Also while you are there pull the rack boots back fron the big end and clean and grease the teeth on the rack.

[tomking]

Originally Posted by opelnut10 The light feeling in the front end is more than likely "caster" the front cross member should have had two tapered shims between it and the sub-frame. The ideal setting is three to five positive with as much as seven if you are going to go fast, the more caster you put in the more stable the feeling will be in the steering. Instead of welding new tubes in you can ream the holes out bigger and drill the control arms for bigger bolts. Adjusting the steering rack requires loosening the jam nut on the pinion and running the adjuster in till you have very little play in the steering then lock it down. If you are working by yourself you will need to disconnect the steering shaft sleeve from the pinion and wiggle it by hand while you are adjusting it. Also while you are there pull the rack boots back fron the big end and clean and grease the teeth on the rack.

tapered shims??? I dont recall any tapered shims between sub and cross assembly? I do recall spacers, but not tapered??

[StefanLee]

Thanks Lloyd for the reply. I haven´t measured caster yet, but will definetly look for those shims when I unbolt the crossmember! That´s exactly the info I was looking for, it´s easy to loose small spacers and such and forget where they were if you don´t know what to look for!

But back to those shims... So the entire crossmember is tilted by using those tapered shims, and thereby setting caster. You say "three to five positive", I assume thats degrees backward tilt, right? Are there different tapered shims then? But then, how do the shock towers line up at the top if the tilt is varied, won´t the shock tower misalign with the inner fender hole?

You mentioned reaming the holes, I have thought about that. Reaming the holes and inner bushings to .5 inches. The problem would then be to find bolts, but I guess it would be possible. If that´s the easier way to do it, I will.

/Stefan

[opelnut10]

Originally Posted by tomking tapered shims??? I dont recall any tapered shims between sub and cross assembly? I do recall spacers, but not tapered??

If you don't tilt the front cross member, the only other way to put more caster in it is to bend the A-Arms. If you don't have tapered shims, use the ones off a Kadett or bend the A-Arms, your choice. You will need a caster gauge to see where you are starting from.

[StefanLee]

How can bending the a-arms give more caster? Sure, the hub assembly will have more "caster" i you will, but the a-arms will still rotate around the same bolts, at the same caster angle. So, in effect, caster should be completely unaffected by twisted a-arms...

That´s my conclusion anyway. Am I wrong?

/Stefan

[opelnut10]

Originally Posted by StefanLee How can bending the a-arms give more caster? Sure, the hub assembly will have more "caster" i you will, but the a-arms will still rotate around the same bolts, at the same caster angle. So, in effect, caster should be completely unaffected by twisted a-arms... That´s my conclusion anyway. Am I wrong? /Stefan

Bending the A-Arm will move the spendal angle which will change the amount of caster. Shimming the cross member will not effect the shock alignment with the Inner fender hole as the shock has a certain amount of movement that you can use to allow fitting the stem in the hole.

[StefanLee]

Okay, so I´ve torn down the front crossmember, and have a few questions about those tapered shims. To be short, there were none.

The PO had put rubber sheet between the crossmember and body, only.

So what do these shims look like? Are there supposed to be any rubber sealant och shim between the crossmember and body?

So, what caster angle did I have? I never measured it beforehand, perhaps that part of the answer to why the car handled a little weird...

/Stefan

[hrcollinsjr]

The factory style caster adjustment is to use various thicknesses of spacer washers, one in front and one in back. There were three thicknesses available but any combination had to add up to the same total in thickness. You could place the thick or thin in the front and the other went to the rear. In some cases two washers were used, both the same thickness, one in front and one to the rear.

If you can't get your caster within specs, then the easiest way is to use a tapered shim between the crossmember and the sub frame to tilt the entire suspension to change the caster.

HTH,

Harold

P.S. The more caster you have the more it wants to go in a straight line, ie. think Chopper motorcycle as an extreme example of positive caster. One other thing the more positive caster you have the greater the steering effort.

[StefanLee]

Ok, let´s see if I get this straight...

So there shouldn´t be any tapered shims between the body and the crossmember. OK.

All caster adjustments should then be made by adding washers of different thicknesses to either side of the the front upper a-arm bolt tube.

If I CAN`T get it within spec by this method, THEN I´d need to use tapered shims on top of the crossmember. But then something would be very wrong, ie twisted body or whatnot...

Correct?

/Stefan

[ungermm]

From my reading of various sources, the shims which look like big washers go on the upper A arm bolt between the A arm and the suspension frame. In most instances, the wider shim (8mm thick) goes in the rear of the suspension frame and the thin shim (3mm thick) goes on the front side.

Jerry

[kwilford]

Originally Posted by opelnut10 ... the front cross member should have had two tapered shims between it and the sub-frame.

IMNSHO, there are no such tapered shims between the suspension cross member and the frame on any GT that I have looked at, only a thick'ish gasket-type material made of some sort of phenolic that isolates the suspension cross member from the frame, and that material is NOT tapered. Castor angle is controlled and set by the number of washers placed in front and behind the upper A-Arm locating tube. And to be clear, you can't simply add to one side, you MUST add to one side and subtract the extra thickness from the other.
HTH

[gvy]

Hi Stefan.

The light steering has everything to do with a negative caster.
I had the same problem in the past , and after measuring I found out that I did not only have a negative caster, but the left and right side were different.
So , while breaking , the car went to one side.

Furthermore the car sometimes followed his own way and the steer could sometimes violently (uncontrolled) pull to one side when turning and breaking.

I searched a way to measure the caster myself and a way to fix the negative caster to a positive caster on both sides of +1.5°

The car steers a bit heavier, but is very good on track. It feels much more secure, no pulling. The steering wheel feels firmer an more stable. A huge difference.

Just have a look here:

http://www.opelgt.com/forums/202621-post18.html

Originally Posted by StefanLee Ok, let´s see if I get this straight... So there shouldn´t be any tapered shims between the body and the crossmember. OK. All caster adjustments should then be made by adding washers of different thicknesses to either side of the the front upper a-arm bolt tube. If I CAN`T get it within spec by this method, THEN I´d need to use tapered shims on top of the crossmember. But then something would be very wrong, ie twisted body or whatnot... Correct? /Stefan

Yes, that is correct.
My car had its caster to far of (may be because I installed shackles???), so I did use some additional tapered shims.



Geert

[hrcollinsjr]

[quote=kwilford;206133]

IMNSHO, there are no such tapered shims between the suspension cross member and the frame on any GT that I have looked at,

That you've looked at. I resorted to this method years ago because I couldn't get enought positive caster using just the washers.

only a thick'ish gasket-type material made of some sort of phenolic that isolates the suspension cross member from the frame, and that material is NOT tapered.

Believe there was an entire thread as to what this material is and where it could be obtained.

Castor angle is controlled and set by the number of washers placed in front and behind the upper A-Arm locating tube. And to be clear, you can't simply add to one side, you MUST add to one side and subtract the extra thickness from the other. HTH

Good point! I implied but did not STATE this.

The available washer thicknesses are:
.12" or 3mm
.24" or 6mm
.36" or 9mm
The 3mm and 9mm will be used or two 6mm washers are used with the total thickness adding up to 12mm.

HTH,

Harold

[StefanLee]

Whoa gvy, I can see from your pictures that these cars arent all square and straight! Time to fab (or borrow) a caster adjustment tool then. Thanks everyone for your help, youve cleared up a great deal for me.

/Stefan

[Gordy]

While it is all torn apart I would opt to replace ALL lowerr and upper ball joints as well as inner and outer tie rods. This way every thing is new when you put it back together and you won't be tearing it apart again in a year to replace parts again. Also if you sand blast the parts and get some chasis saver paint, when you get it all back together it will look like new as well as perform like new and you'll be all set!

[JaredT]

Good info in this thread. I'm thinking of tackling the same thing myself. Not trying to Hijack (or am I?) The only difference is that I was thinking (hoping) I could pull the front end out of a '69 parts car, then rebuilt it over the winter to install into a '71. Would there be any additional "gotchas" involved in that?

[BQS4]

Originally Posted by JaredT Good info in this thread. I'm thinking of tackling the same thing myself. Not trying to Hijack (or am I?) The only difference is that I was thinking (hoping) I could pull the front end out of a '69 parts car, then rebuilt it over the winter to install into a '71. Would there be any additional "gotchas" involved in that?

Nope, it's a direct swap

[Gordy]

Jared, that's exactly what I did last winter. Had everything sanblasted and I painted it with chasis saver paint, got all my new parts together including 75 Manta rotors and calipers, then this spring dropped the whole old unit out and installed the new along with new shocks all around and front and rear sway bars. Loved driving it this summer!

[kwilford]

Originally Posted by JaredT Good info in this thread. I'm thinking of tackling the same thing myself. Not trying to Hijack (or am I?) The only difference is that I was thinking (hoping) I could pull the front end out of a '69 parts car, then rebuilt it over the winter to install into a '71. Would there be any additional "gotchas" involved in that?

A direct swap, yes, but one small item would improve the results. The older lower A-arm bushings had a smaller (actually "thinner wall thickness, same ID") inner sleeve. This was upgraded in 1972 with a thicker-walled sleeve, which caused the rubber in the bushing to be thinner and hence less compliant, and improved the previous tendency for these suspensions to suffer from "highway shimmy". The later bushing is available from OGTS. And an even BETTER thing to do is to buy just the thicker sleeves and replace the OEM bonded rubber busings with polyurethane bushings, at all the busing points, and install zerk grease fittings to allow them to be lubed with Teflon grease.
JM2CW