Lower Control Arm Failure Update
by Frank Condos
Here is an update on the lower control arm failure alert provided
by Bob Blenkinsop. Marc Trubert recently experienced a lower control
arm failure while maneuvering in his driveway. The ball joints
had been replaced about 80,000 miles back and the two ears were
retained by 5/16 bolts replacing the original hot set rivets.
He reported it had been some time since he checked the bolt torque.
Both ears were broken and showed a classic fatigue failure characteristics.
The ball joint sides were polished from movement against the A-arm.
Marc welded the A-arm in an attempt to be able to move the coach
in position for the tow truck. The old ball joint with the ears
missing was re-attached on the welded tip of the arm. The arm
broke again while maneuvering.
We reviewed the failure with Bob Lamey and confirmed some of the conclusions that have been previously stated, such as:
* The looseness of the ear mounting bolts allows the ears to work within the A-arm resulting in fatigue failures of the ears and/or the arm.
* The critical load is the bonding moment applied under tight turns which explains why there are few on the read reported failures.
* Both the ball joint ears and the clamping friction between the ears and the arm are necessary to distribute the loads since the re-welded arm fitted with the ball joint without ears broke while turning.
* A suggestion of tack welding the bolt head to the A-arm is probably not enough since the ball joint ear holes are oversize (11/32) and if not clamped tight will allow the ball joint to work.
Some suggestions to reduce the likelihood of failure are:
* Do not change the original equipment ball joints unless they are looser than the 118 in specified in the service manual.
* Ream the ear and arm holes to 3/8 in, use 318 bolts (SAE grade 8) and tighten the nuts for maximum clamping torque.
* Check the ear bolts torque as part of the routine service when you grease the ball joints.
* If you're a believer in them, J-B Weld or Loc-Tite can't hurt.
Heavily re-enforced A-arms are reportedly available from Eric's RV in Fresno and Buskirk-Rush in Sandusky, MI. In our opinion, the re-enforced A-arm alone does not eliminate the need for maintaining the proper ear bolts torque, I have personally observed about 6 failed A-arms and know of at least two where the ball joint ears have failed as well. The control arm and ball joint are designed to work together, spreading the bending load over the A-arm end. Discussions at the GMC International Meeting at Myrtle Beach in March concurred with these fixes and added the additional suggestion of tack welding the bolt, nut and ear to the control arm.
I am the unfortunate owner who had the A-arm/ball joint failure reported above. The failed ball joint was a replaced ball joint with 5/16 bolts that had at least 80,000 miles on it. I had not checked the looseness recently- my mistake!!
My thinking is pretty much in tune with that of Frank and Bob. My theory is that the ears break first, then the arm fails. I believe that the primary load on the ball joint is a moment (about a horizontal axis along the coach) created by the wheel offset which is increased when the front wheels are turned left or fight (so the failure while maneuvering). This moment is reacted by the center stud and the two ears of the ball joint creating the primary load path. If the 5/16 bolts become loose, the ears rub against the arm causing them to flex (the ears are angled from each other and wedged in the side lips of the arm), generating a fatigue failure of the ears. When the ears have failed, the only remaining attachment is the center stud that pries the tip of the arm. The tip cannot carry this prying load and fails right at the hole where the center stud is attached.
The above thinking is the result of my failed attempt to make a temporary fix by welding the tip of the arm and simply using the old ball joint with the broken ears. The welded arm tip failed as soon as I turned the wheel for maneuvering. The next step was to use a brand new ball joint with good ears which I installed on the tip of the now cracked arm with 5/16 bolts for the ears and the center stud bolted through the hole at the tip of the arm. That fix (new ball joint with good ears mounted on cracked arm) allowed me to maneuver the coach in the driveway and out to the street so I could position the coach in line with the fiat bed truck for them to pull me on. I was not bold enough to drive the coach on the freeway!!!
To avoid future A-arm problem a reasonable approach is to try to come as close as possible to reproducing the original design of the riveted ball joint. For my repair Bob Lamey used 3/8 bolts instead of 5/16 for the attachment of the ball joint on the replacement arm. This arm was a used part from the junk yard reinforced only on the sides where the ears are attached but with no reinforcement of the lip at the very tip. The holes in the arm after removing the rivets of the replacement arm (no drilling but grinding out the rivet head) were practically at 3/8, so nothing was really changed for the arm. Bob had to ream the holes in the ears to receive the 3/8 bolts. The ears are pretty beefy around the hole so it does not look like much has been lost near the hole. This is the root of the ears which is thin, and this is where it originally failed. We are assuming that the larger hole in the ears does not reduce their strength
(a question mark). The significant advantage of the 3/8 bolt is that they can be torqued to a higher value than for the 5116, greatly increasing the clamping force of the ears on the arm. Therefore the chance of the 3/8 bolts becoming loose is greatly minimized.
Of course it remains imperative to check the looseness of the bolts at regular time intervals.
A last point, if everything I have said above is true, when looking for cracks, it is at the ears that we should also look not just at the arm. However it may not be very practical to do such a check since you most likely would have to remove the ball joint for inspection.
Remember: What you do to your coach is your responsibility. Nobody else is responsible!
Fuel Tank Modification
by Chuck Garton
This modification is intended to increase the amount of fuel
that can be drawn from the tanks. It consists of:
1. Removing the two fuel tanks from the coach
2. Removing the fuel level sending unit from each tank
3. Removing the sock filter from the end of each fuel pickup tube
4. Bending the pickup tube to place the end closer to the tank bottom.
A good time to do the work is when the tanks have been removed to replace the fuel hoses. With the sending units removed, inspect the inside of the tanks to verify the interior is clean and rust free. If there is rust or contamination in the tanks they should be taken to a professional for evaluation. When re-installing the sending units use a new "O" ring seal.
I bent the pickup tubes so that they were within one half inch of the tank bottom and installed in line fuel filters in each line near the tanks. This is necessary since the sock filters are removed. With alcohol in today's gas, water condensation in the tanks is not the problem it was once.
On my way to the Hope Rally, I put 512 miles on one fill up and bought 56 gallons when I finally got to a station, so-it does increase the range a bit.
Remember-. What you do to your coach is your responsibility. Nobody else is responsible!
Parts and services for the GMC
The following represents a list of places where the Western Staters can go for help. This is particularly useful in time of breakdown on the road when far away from home. Not all theses places are for emergency repairs. Some are just for parts, supplies and equipment. This list is in no way exhaustive. If you know of any other places you would like to add to the list or you have an update, please send us the information.
There is no endorsement of any of these places by Western States.
BEST WEST RV
Glendale(Phoenix), AZ (602)934-5295
AJ-USA (CASPRO CO.)
San Diego, CA (619)452-8999
After market suspension and steering upgrades,
transmissions, engine and accessories.
CINNABAR ENGINEERING INC.
(650)948-8664 - Technical Assistance
(800)720-2227 - Parts (from MI)
CUSTOM INSTRUMENT PANELS
Gardena, CA (800)462-7635, (310)515-4974
Custom dash panels with instruments.
Sierra Madre, CA (818)355-7753
Frank Sullivan Digi Panels and Doug Thorley Headers.
GMC RV CENTER CO.
Industry, CA (818)961-0790
Coronado, CA (619)435-3300
Front wheel bearings.
(909)983-7872, (909)982-7747 (shop)
Complete service and engine rebuilding.
San Raphael, CA (415)456-1904
Full mechanical services.
ONAN CONTROL BOARD
Orange, CA (714)633-4731
RAGUSSA PATTERN SHOP INC.
Santa Ana, CA (949)261-5898
Custom GMC parts: Welcome step, transmission cover, ladder, and more.
STARBUCK TRUCK REFINISHING
Fullerton, CA (714)879-6140
Custom exterior painting (Imeron).
El Cajon, CA (619)442-9100
Interior and exterior renovation and supplies by Sy Gregorlch
T.C. CUSTOM CAMPER
West Pittsburgh, CA (510)458-5800
Complete service of the GMC.
Longmont, CO (303)530-4995
Custom engine, transmission, water pump.
ALEX SIRUM AUTO
Okeechobee, FL (941)763-1121
Full parts and service, hard to find parts.
GOLBY MOTOR CORP.
Orlando, FL (407)859-9000
Parts, service and renovation.
Jacksonville, FL (904)381-6209
SOUTHLAND MOTORHOME CENTER
Buford, GA (770)271-7502
GMC parts and service since 1973.
Sandusky, M! (800)715-1133
Sales, service, parts and restoration.
CINNABAR ENGINEERING INC.
(800)720-2227 (parts - GM licensed)
(650)948-8664 (technical assistance from CA)
(810)648-2444 (service, sales and renovation)
Northfield, MN (507)663-7266
GATEWAY MOTORHOME CO.
Saint Louis, MO (800)654-0374
GMC Parts Man
OSBURN'S RV SERVICE
Albuquerque, NM (505)821-0543
Complete service of GMC's since 1973.
Novelty, OH (440)423-0809
After market suspension and steering upgrades, transmissions, engine and accessories.
FRY'S MOTORHOME SERVICE
Beaver Creek, OR (503)632-6953
BAXTER'S AUTO SERVICE
Genesse, PA (814)228-3338
KEN K. FREY AUTO REPAIR
Quakertown PA (215)536-1246
Total GMC service center.
DeMONTRON AUTOMOTIVE GROUP
Houston TX, (713)872-7200
KEN THOMA'S PARTS AND SERVICE
Fredericksburg, TX (210)997-3690
Front wheel bearings and hubs.