GMC Western States

 Tech Center Number 12 - June 1995

In spite of the many times corrective measures and the value of good maintenance has been discussed, recent serious problems call for additional emphasis; so here it is. Two coaches did not make our most recent Roundup at Casa de Fruta as a result of not taking advantage of known and often discussed preventative measures.
Coach # 1: After many successful years with probably good maintenance, had a transmission overflow problem; something that happens once in a while on some transmissions {exact reasons for this event are elusive but the cure is well known). The coach caught fire and burned completely to the ground. There are two places for transmission fluid discharge on the OMC turbo Hydramatic 425 transmission. The first being the relief valve at the front right side on top of the transmission. Unfortunately, close to the exhaust, this can be easily corrected in approximately 45 minutes with $15.00 in materials (see drawing on page two). The second is the dip stick which can also spew fluid on the exhaust, this can be corrected by installing Ken Frey's extended tube and dip stick which has the additional benefit of allowing you to check and fill the transmission from outside the coach. The dip stick is available from Ken Frey Auto repair at 215-536-1246. The total cost of these two improvements, under $100.00, compares favorably with losing a $20,000.00 coach, which has happened many times. Remember to check your transmission fluid level when the engine is HOT, parked on a level surface and idling in park. Checking the level when the engine is cold or not running will give you false readings which can lead to overfilling which will cause fluid overflow when the transmission heats up.
Coach #2: The failure was less dramatic, Bob DeSaussure had the opportunity to inspect the engine after it was torn down because of a broken crank shaft and he noted the following: The present owner purchased the coach in the last two years from the original owner with roughly 42,000 miles on the clock. He has driven it only 10,000 miles since purchasing it. The new owner's greatest contribution to the engine failure was probably a long trip with a heavy tow vehicle and pushing the engine with a "heavy foot". In spite of the relatively low mileage of the engine, the condition of the engine oil and carbon deposits through out was surprising. The residue was like tar, not off, there were pieces of carbon as big as 2-inches square which were covering the oil passages on the intake manifold. If the crank had not broken, the engine would have probably seized sooner or later due to lack of lubrication caused by plugged off passages. The transmission fluid was brown and smelly. Conclusion: very poor maintenance, probably no attention to time or mileage for proper servicing intervals. This occurred before the current owner acquired the coach so the damage was already done by the time he bought it. Surprisingly the engine was strong and smooth running and used one quart of oil every 1,000 miles even though cylinders 1 and 2 were scarred, the timing chain was loose and badly worn. The original water pump was in excellent condition and was used on the new engine. This is testament that a properly maintained engine should give you over 100,000 miles of trouble free service, but "all bets are off' if you do not keep up with the maintenance.
Speaking of maintenance, have you replaced your brake fluid every three years? Have you drained and flushed your radiator and cooling system every two years? Have you serviced and refilled your final drive when recommended in your manual? In discussions at Roundups and during other gatherings, it comes out that many people have not. Don't forget the proper lubrication of the rear axle pins. Replacing a set of pins can cost $1,200.00. Proper maintenance is not only cheaper, but it will also allow you to have a pleasant and safe trip.

Key Quan Description
#1 1 11/2 X 3/8" Rubber Elbow GMC part #25508425 (4pkg) or 5523543 (2pkg)
#2 1 1 - 2" Copper Tubing 3/8" OD
#3 1 1 - 3' 3/8" Marine Fuel Line
#4 1 Standard Overflow Container (Auto Parts House)
#5 1 Plastic Overflow Valve - GMC part #8640496 (10pkg)
#6 4 Stainless Steel Clamps




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