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GM power steering pump shaft sheared


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My wife was driving our 2001 Yukon and was trying to back into a tight spot when the power steering quit. No funny noises, plenty of fluid, belt still on, so she drove the 4 miles home. This is what I found. I'm assuming that the shaft is designed this way to act the same as a shear bolt to prevent a spike in pressure from damaging something that would keep you from driving. If someone knows different, I'd love to hear it. Sure made it easy to get the pulley off

ps shaft 002.JPG

ps shaft 001.JPG

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Most I seen broke were hydro boost trucks and there were using the brakes and steering fully turned .

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I had the same thing happen in an 02 Yukon. Shaft broke and replaced with reman pump. Broke reman shaft almost immediately. Installed reman steering gear box along with another pump and no issue since. Not sure if The pump was defective or the gear box played into it. Frustrating either way.

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10 hours ago, yellowrosefarm said:

My wife was driving our 2001 Yukon and was trying to back into a tight spot when the power steering quit. No funny noises, plenty of fluid, belt still on, so she drove the 4 miles home. This is what I found. I'm assuming that the shaft is designed this way to act the same as a shear bolt to prevent a spike in pressure from damaging something that would keep you from driving. If someone knows different, I'd love to hear it. Sure made it easy to get the pulley off

ps shaft 002.JPG

ps shaft 001.JPG

While aircraft accessories like generators mounted to an engine drive pad have a built-in shear point on the quill shaft to protect the engine if the accessory seizes, I'd be quite impressed if GM did such a thing for their pump. It would seem the relief valve is the only concession likely. Still, it enabled her to drive. PU truck with hydro boost brakes would be hard to steer and stop but doable.

Pretty cool that she's the type to muscle it home! 

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10 hours ago, Ian Beale said:

Engineering by bean counter?

They aren't that intelligent they usually don't know the ship is sinking until their pay check bounces

Purchasing is usually the source of value engineering.

I run into it all the time at work  they find alternative source and just start using it with out the proper testing to make sure it meets the design requirements.

They get the accolades from upper management for saving $5 per unit and the increased warranty costs from the failures is never reconciled.     

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3 hours ago, jeeper61 said:

They aren't that intelligent they usually don't know the ship is sinking until their pay check bounces

Purchasing is usually the source of value engineering.

I run into it all the time at work  they find alternative source and just start using it with out the proper testing to make sure it meets the design requirements.

They get the accolades from upper management for saving $5 per unit and the increased warranty costs from the failures is never reconciled.     

With over 30 years of purchasing experience,  every place I've ever bought parts for assembly required a P-PAP, Purchased Part Approval Process of every part from a new supplier. QA even got involved approving new suppliers before I could ever even order samples from a new source. Engineering had to approve the P-PAP since they owned the part design and material.

    The last three places I worked were ISO certified,  we said we did things so had to be able to prove we did them.  I will agree with your comment that Purchasing is most often the one pushing value engineering.  QA and Engineering resist and drag their feet approving the new source.  Things like "special processes" or material specifications/requirements not listed on the print cause part failure during testing hopefully.

    Last company I worked at had a sister plant in China we originally sent parts to for them to build Our product, one-by-one they they found Chinese sources for them.  Their purchasing group even sent quote packages around to potential Chinese sources they had found. I sent them six parts, all made from a special copper alloy or plain C-360 free machining brass. They were cheaper, about 50% cheaper. My Bosses really started beating on ME to get the cost savings, and have them quote more parts. Part of the P-PAP approval was a chemical analysis, the metal had all kinds of crap in it, things like aluminum, iron, last batch had LEAD, in a potable water contact part. They never even came close to the actual material chemistry.

     I had a potential new supplier about 40 miles from our plant to make huge open die forged blocks of a special stainless steel alloy. We were buying it from a mill 850 miles away. MASSIVE resistance to my new source because they didn't melt and vacuum arc remelt their own steel, they bought certied ingots and forged with their own highly automated equipment. Boss and I flew to Baltimore, toured the current suppliers plant, old antiquated equipment, spec's on our print ignored because they couldn't test for them.  The product line's engineering manager met with the VP of my new source and me, and explained this test. When the VP was told what the test really was He informed the Engineer the current supplier had NEVER met that ultrasonic test requirement on an unmachined billet, and HE wouldn't certify to that spec without machining. He said HE could meet it, and test and certify to it IF He could machine all 4 sides of the billet, He needed 4 smooth sides to reflect the sound waves undistorted.

     I was reassigned to a different dept, had different dragons to slay, but another buyer tells me the other group is in deep trouble, their metal forging supplier is closing up, the shop in Baltimore. Their decrepit old equipment and processes, and the EPA had caught up with them.  One night couple months later I'm down on the recieving dock and I see a dozen BIG shiney smooth surfaced silver stainless steel blocks, no rough sides like tree bark like we used to get, Yep, first shipment from MY new source 40 miles away, BIG enevelop attached to each block, envelope an inch thick, "Ultra-Sonic test documents enclosed".

    The old source couldn't do any machining,  the new source could do all kinds of machining, they filled TWO 20 cubic yard dumpsters with maching chips a DAY at each of their two plants.

   I had one manufacturing engineer that was totally against my supplier,  past history, hated PLAID, don't know why, but I never rubbed his forced supplier change in his face.

   My SON was a QA inspector for a large, actually HUGE construction equipment plant, worked in assembly for 7 years, then 3 years in inspection and QA.  He accepted a Quality Engineer position at a newer smaller but fast growing company a year ago. He was recently promoted to Quality Manager with a nice raise and has 3-4 inspectors working for him. Oh, and just ONE plant and product line to focus on. The company's CEO said his ability to form lines of communication between departments and between members of the same department,  knock down all those "silos" was something He was not aware was needed but wants Son to continue working spreading across all 5-6 of their plants.  SON has told me 100 times in the last year he's asked "Why do you do this that way?" and been told,"Because we've always done it that way."  There was a time that was a good enough answer, now days, further explaination is needed, maybe pull a print with special instructions on it, look at past corrective actions or supplier rejections.

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5 hours ago, DOCTOR EVIL said:

Engineering had to approve the P-PAP since they owned the part design and material.

On products that are made in large quantity and the design is done totally internally there is a chance for better control of manufactured parts from a vendor this should be the case at GM.

When you have lower volume of units and the designs are made from purchased assemblies like motors, limit switches, gear boxes etc. it comes down to quality of the brand you use this is where purchasing can burn you. Sometimes the brand choice is not controllable you can’t get what you want from brand A in your allowed time frame and forced to used brand B so there isn’t time to do life cycle testing to validate the new supplier you have to take their ISO accreditation in faith

IMO ISO standards are just a way for the group of auditing companies to make money from you and it won’t necessarily ensure the vendor has a robust product a lot of times the product works as designed i.e. poorly. 

The ISO accreditation just confirms that the vendor is following their internal procedures which may be lax.

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