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79 Eldorado: Service manual torque spec ball joints may be incorrect

Started by 79 Eldorado, June 16, 2019, 03:51:35 PM

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79 Eldorado

I was changing ball joints today and saw a couple of strange things in the service manual.
1) Lower ball joint stud is larger diameter than the top stud but the torque spec is much higher for the top. It calls for 90ft-lbs upper and 65 ft lbs for the lower.
2) Bolts used to replace the rivets seem to have a lower torque than I expected. I bought Pro-Forged for the top and AC Delco professional for the bottom. They came with different size fasteners and neither gave a value. The service manual calls for 8 ft-lbs. They started to feel about right around 15 ft-lbs.

The suspension is nearly identical to the 2003 S10 4WD and the upper ball joint is the same PN as the '03 RWD Sonoma so I decided to check my S10/Sonoma service manual and it lists the lower ball joint as 79 ft-lbs and the upper steering knuckle to ball joint as 61 ft-lbs. Since the listed lower ball joint torque in the Cadillac manual is so close to the spec for the upper on the Sonoma I suspect GM/Cadillac accidentally reversed the values in the '79 manual. I also checked my '79 Oldsmobile manual and it agrees with the Cadillac values but most of the graphics are exactly the same (Toronado and Eldorado) so I don't view that as a tie-breaker. The Olds manual is an "All series" manual and every other car lists a higher value for the lower.

The rivet replacement bolts (ball joint to control arm) are listed as 17 ft-lbs in the Sonoma manual regardless of position.

I just thought I would mention this for others. Anyone else have a thought on this?

Regards,
Scott

fishnjim

They are probably correct as is, + -.   
The taper pin is what snugs up, you're not stretching the threads, per se, like a normal stud torquing.   aka, interference fit.   Frankly, I rarely use a torque wrench for these.   
Most have a castle nut and cotter, so they just have to be tight enough to get the pin in snug, the cotter in, and the nut then just makes up space and holds it in place so it doesn't slip down under load.   
If you overtighten, you can crack the cast taper hole with the hard taper pin like driving in a wedge.   There's less surface area on a smaller diam taper, so has to pull tighter to hold.     
The hold down bolts, when you replace the riveted kind with the bolt on kind, need to be torqued properly.   There you are "stretching" the bolt to hold tightly.   But those are usually small(grade 8) and fairly low torque - hand tightened.   The cup surface transfers the down force load to the A arm, so the load on those bolts is not great, mostly torque and shear forces.

bcroe

In my 83 manual Toro lists 50 ft-lb upper ball joint,
70 ft-lb lower ball joint.  Bruce Roe

savemy67

Hello Scott,

"2) Bolts used to replace the rivets seem to have a lower torque than I expected. I bought Pro-Forged for the top and AC Delco professional for the bottom. They came with different size fasteners and neither gave a value."

Are there any SAE grade markings on the heads of the bolts?  If so, you can go to one of the engineering or fastener web sites and find out what the torque value should be for the bolts based on the bolt diameter.

Respectfully submitted,

Christopher Winter
Christopher Winter
1967 Sedan DeVille hardtop

chrisntam

There are always errors in the Service Manual.  Generally, the errors get corrected and are noted in the monthly "Cadillac Serviceman" magazine.

I assume they continued the publication for 1979.

I looked for a long time to try to locate the markings on the diff to determine if my car had a controlled diff or not, I could never find the marking.  Upon reading the monthly, I was directed to the correct location.  That's just one example.

I suggest you get that magazine for the year of and a year or two after your car was built, it is very interesting reading.
1970 Deville Convertible 
Dallas, Texas

79 Eldorado

Thanks to all for the replies. I wanted information to be available if anyone else wondered. The "Cadillac Serviceman" Magazine sounds interesting. Bruce's '83 manual numbers seem reasonable. I used 75 ft-lbs on the bottom and moved slightly for the cotter pin. I used my judgement on the top which was around 50 ft-lbs. I would be concerned about breaking something, like Jim mentioned, if the top was set to the original published value.

I think the bolts were grade 5 (at least one set was marked). The Proforged had lock washers and the Delco parts had staked nuts (damaged on one side to act like a lock).

Scott