Link Pins loosen up

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Steve Douglas
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Link Pins loosen up

#1 Post by Steve Douglas » Fri Nov 15, 2019 6:21 pm

My right side link pins wont stay tight, bronze bushings are fairly new, new pinch bolts, wavy washers and nuts. After a 100miles of so the links have started to rattle again, this has been a problem for some time. Any thoughts on a fix?

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Don Gale
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Re: Link Pins loosen up

#2 Post by Don Gale » Fri Nov 15, 2019 7:21 pm

Do you properly back them off just a skosh when adjusting them? Do your new pinch bolts have a shank i.e. the pin groove isn't riding on the pinch bolt threads. Can you rotate the link pins with medium effort after you tighten the pinch bolts? Have you tried fitting the new link pins in the trailing arm without the pinch bolt to see if there is any lateral slop? Can you clamp the trailing arm without the pinch bolt with say a C-clamp to see if it compresses fully? Other than that, perhaps grease has gotten into the trailing arm pinch area or the inside bore has polished itself excessively smooth with wear and it's not snugging tight enough. Try roughing the clamp portion of the pins with some 220 grit and slit a dowel lengthwise to make a small flapper wheel the approx. dia. of the pinch bore and roughen the i.d. to get better "sticktion".
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Steve Douglas
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Re: Link Pins loosen up

#3 Post by Steve Douglas » Fri Nov 15, 2019 7:57 pm

I am guessing the grease and glazed inside of the trailing arm. It has 315,000 on the arms but only about 15,000 on the link pins, I lube the front end twice a year, loosening the links each time. Still has original King Pins and bushings. This summer I had the links all apart, cleaned and polished the shims, greased each one as they went back on. New pinch bolts were hard to find that match the originals, 10mmX 40mm with a 25mm long shoulder, the ones being sold by Wolfsburg West and others have too many threads and are not 8.8 grade. I found some at Partsheaven before they closed. I'll try cleaning and roughen up the inside of the arms and the pins, it is only on the right side, that loosens up and mostly the top one.
Don thank you for your reply

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Don Gale
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Re: Link Pins loosen up

#4 Post by Don Gale » Fri Nov 15, 2019 9:18 pm

8.8 is a little light. You can get 10.9 M10x40 at McMaster-Carr. Up the torque

Edit: I don't have the torque spec handy. The generic torque for an M10 8.8 is 55 ft-lb. Generic torque for an M10 10.9 is 75 ft-lb, which will provide a substantial increase in clamping force on the link pin. Perhaps a little Loctite on the threads (only) or us a nylon lock nut to assure it doesn't loosen. That said, I have never had a problem with one loosening such as yours is doing. An extreme solution would be to use a castellated nut and drill a hole for a cotter pin at the appropriate location.
Last edited by Don Gale on Sat Nov 16, 2019 8:21 am, edited 1 time in total.
1958 1600 Super Sunroof Coupe, "Black A's Matter!"
former 1966 Euro 912 Sunroof
former 1978 Intermeccanica Speedster w/'68 912

Steve Douglas
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Re: Link Pins loosen up

#5 Post by Steve Douglas » Fri Nov 15, 2019 9:32 pm

Don, you are probably right in the 8.8 is standard grade, and 10.9 would be better. The Part number listed is 900.074.060.01 and isn't showing up anywhere. I was browsing thru boxes at parts heaven and found a bag that was marked 356 link pin bolts so i grabbed them, the look like the ones I took out. Hope they will work.

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Re: Link Pins loosen up

#6 Post by Norm Miller » Fri Nov 15, 2019 10:12 pm

Possibly you have turned the pin in the wrong direction.
It will feel tight but it won't stay there, trust me, it's been done before.

Norm
 

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Re: Link Pins loosen up

#7 Post by Steve Douglas » Sat Nov 16, 2019 12:06 am

Norm I might have done that since the left side stays tight, Ill check it tomorrow

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Al Zim
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Re: Link Pins loosen up

#8 Post by Al Zim » Mon Nov 18, 2019 1:04 pm

Am I to assume that you have 315K miles on the king pins? If so WOW! You have caused a situation by loosening the link pins to grease the car. This does not allow grease to lubricate the king pins nor does it allow the grime and dirt that comes from driving your car to be pushed out of the bearing areas. VERY IMPORTANT! I would also bet money that the lower right trailing arm is bent since that is the wheel that hits the curb the most. If you decide to have the trailing arms checked on the factory tool (P 70) when you remove them from the torsion bars (as you should do to have the ling pin bushings machined to fit the link pins) you will probably find that the bearing area is grooved because the trailing arm only moves a few degrees as it rotates from the top to bottom of its travel. OUCH! It is an expensive proposition to restore the front suspension to factory tolerances. al zim 800.356.2964 www.allzzim.com The metal from the wear on the trailing arm bearings is in the axle tube. Removal of the torsion bars, outer roller bearings and inner phonelitic berarings are a must to insure long life in the future.
 

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Re: Link Pins loosen up

#9 Post by Martin Benade » Mon Nov 18, 2019 5:09 pm

Not every car has a bent right lower control arm. And why would you need to remove it while renewing the link pin bushings? I never needed to do that.

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Re: Link Pins loosen up

#10 Post by Harlan Halsey » Tue Nov 19, 2019 5:30 am

Steve,
1. the link pins are all the same, they all tighten in the same direction, looking at the head. (If you turn them in the loosening direction they will stop but with a whole lot of play. Hard to miss that.)
2. Al is right, no reason to loosen the link pin clamp to do a grease job. Better spend your time wiping up the grease which comes out of the head of the link pin.
3. Link pin pinch bolts do not need a lot of torque, grade 8 bolts are plenty strong. However it is good practice to use bolts with a smooth shank where they bear on the link pin grove. A way to get correct bolts is to measure to see what you need, then buy longer bolts with the correct smooth shank length, and trim them to the correct overall length. Check the McMaster-Carr on line catalogue, grade 10 bolts to start.
4. If your problem persists, or you are sure that maladjustment is not the problem, then AL is probably right. I can get the trailing arms checked for you locally on the factory jig, just let me know.

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Re: Link Pins loosen up

#11 Post by David Jones » Tue Nov 19, 2019 10:02 am

There is one thing to note when greasing the front suspension which includes link and king pin lubrication. The car should be on a jack/off the ground or the weight should be off the front suspension components. This according to the service instructions for both Porsche and VW with king/link pin suspensions. This is the time to rock the wheel top to bottom and side to side to check for any slop or wear in steering, suspension or wheel bearings.
If I had known I would live this long I would have pushed the envelope a little harder.
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Al Zim
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Re: Link Pins loosen up

#12 Post by Al Zim » Tue Nov 19, 2019 10:22 am

Harlan: Checking the trailing arms, the "C" carriers that hold the link pin and measuring the king pin hole in the spindle are easy tasks. Repairing the trailing arms where the outer roller bearing has put groves in the trailing arm, and having to machine and oversized king pin to fit the spindle is a difficult task. In 55+++ years a lot of thing can wear out on your front end. al zim 800.356.2964
 

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Re: Link Pins loosen up

#13 Post by Mark Schumacher » Tue Nov 19, 2019 6:44 pm

I had the loose link pin problem as well.
After exhausting all other possibilities I pulled the parts and sent them to Zims. Turned out to be bent trailing arms.
The solution was a set of unbent trailing arms.

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Re: Link Pins loosen up

#14 Post by Martin Benade » Tue Nov 19, 2019 7:38 pm

Was the clamping eye for the link pin deformed?

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Re: Link Pins loosen up

#15 Post by Steve Douglas » Tue Nov 19, 2019 7:59 pm

To All that replied, thank you. I took both link pins out on the right side, cleaned the grease, from both the pin and inside of the trailing arm, scuffed the area of the pin where the clamp is and also scuffed the inside of the clamping end of the trailing arm. Re assembled and drove 45 miles on the freeway with many expansion joints and potholes (101 south of San Jose), everything seems to be staying tight. I have always done front end lubrication twice a year, and in two stages: first, I loosen the link pins, then pump grease into the C Link fittings, and sometimes spray the link shim areas with Wurth HHS-K Lubricant, then tighten up the link pins and proceed to lube the tie rods ends, the C links/King Pin and the beam zerk fittings. Just this fall I changed the tie rod ends, and steering box after 315,000. Original King pins and two sets of Link pins, (150,000 and 290,000miles) lubrication and regular driving does make a difference.

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