Well, it?s been almost a year since I?ve posted on the Disco Web forum. I have to wonder if it has something to do with the change of seasons or some other weird phenomenon.
First of all I would like to thank those who have tried our product and those who have attested to our successes and to those who have attested to our committment to customer service when we have been, initially, less than successful.
I will be brief in my posting (for me anyway) and try to address the three basic issues I see in this string. They are; our universal joints, center ball failures and vibrations. Please take the time to read through this posting and see if you?re interested in a free trip to our shop.
I learned a long time ago that you cannot judge a universal joint strictly by appearance as one person seems to have done by stating our universal joints are "crap." Our universal joints are, more or less, a reverse engineered Spicer universal joint with the grease fitting relocated for ease of service and increased strength.
Without a metallurgical analysis and thorough testing for surface and through hardness testing, it is near impossible to distinguish inferior product from that of good quality. I have had this testing performed on our universal joints and have the documentation to prove it. I have also had destructive testing done and our universal joint has proven to be stronger than the common 5-153X, 1310 series universal joint that most other companies use. Our seals are exactly the same as the Spicier universal joint in every respect other than the color. These seals are designed to purge out old grease and contaminates when greasing.
We complete the assembly of all our CV socket flanges with the installation of the centering ball. We had used a well known manufacturer of this ball kit for many years with very good success. It has been within the last six months or so that we began to notice an inordinate amount of premature failures for reasons that cannot be explained by any reason other than a defective product. I believe our long time supplier had done something with either materials or manufacturing processes that caused this. It did not take long before I sought and found another manufacturer which could supply the highest quality seat I need. It is unfortunate for me and those customers who received defective product, that this particular problem needed to manifest itself in the field. We are having very good success with the part as supplied from the new manufacturer.
I am very confident in our balancing equipment and procedures along with the repeatability of the balancing. I know of no other drive shaft shop that maintains our strict procedures in this regard. Yes, I occasionally receive complaints about vibration issues that did not exist with the stock drive shaft. It is only on a rare occasion that this proves to be a balance issue. In these infrequent instances, I have to acknowledge that bot man an machine make errors.
If the root cause of the vibration issues were a problem with our equipment or procedures, I would expect this to happen with nearly all the drive shafts we produce. I have one customer who has purchased 70 Land Rover drive shafts in the last year (thanks Will). I really don?t recall if there were more than a couple people who claimed to have a vibration after installing our drive shaft. I do recall one customer of his who did complain. For him, we paid the return freight and issued a refund.
So why do some vibrate and others do not? I can only theorize since I do not work on any vehicles in our shop. The following are excerpts from an E-mail I sent to the customer mentioned in the previous paragraph: .....Where the vibration seems to be throttle position sensitive I would lean towards a torsional vibration as a result of geometry problem. If this were strictly an imbalance the problem should get worse (to a point) with higher speeds and the throttle position would have no bearing as the drive shaft is spinning at the same speed (RPM) at a given vehicle speed regardless of transmission gearing or throttle position....Sometimes the factory original drive shaft runs smooth but our drive shaft does not. I believe there may be a couple of reasons for this. Primarily the additional mass/weight of our drive shaft is a factor. It is a simple matter of physics that dictates force cannot be generated without mass. Less mass equals less force/vibration. Couple this with the inherent play in a ball bearing like used in the front out-put of the transfer case or even a slightly worn bearing and or a loose out-put flange, our drive shaft will have more vibration than would a lighter, stock drive shaft....
Our drive shafts are built to be the strongest which is practically possible. The slip yoke itself wheigs nearly six ounces more than a comparable cast iron yoke. Our CV center housing and CV socket flange are made from heavier steel components also. Couple this with the heavy wall tube we use in our drive shafts it wouldn?t surprise me if our drive shaft weighed a couple pounds more than our competitors and substantially more than a factory drive shaft.
I would be pretty certain I could overcome most of these infrequent vibration problems by building a lighter drive shaft. But then I risk getting "beat up" for building a weak drive shaft. It is a "Catch 22" for me. Rest assured, I have NEVER selected a component based on cost over quality.
We build well over 10,000 drive shaft per year with very few problems. I must accept that occasionally we will have a problem. I fell pretty good about things when I think about our success ratio being better than NASA though. I try to look at the problems we do have as opportunity disguised as obstacles and work towards resolution for the betterment of all.
I would like to use this opportunity to put this "bad balance" question to bed once and for all. I would like to extend an invitation to someone from this site to come out and visit us, witness our build and balance procedure then truthfully tell everyone what you?ve seen. I am willing to pay round trip air fare (coach) from any major airport in the continental US. I will also provide two nights hotel accommodations in Salt Lake City or Ogden, Utah, a steak and lobster dinner at one of Ogden finest restaurants and give $100.00 allowance for car rental. Heck, we?ll even build a drive shaft for you while you?re here and give it to you free of charge.
The qualifications for this are; you must have been a member of discoweb.org for more than one year and have contributed regular postings in a professional manner. If you would like to take me up on this please contact me at my E-mail address of
tom@tomscds.com
Tom Wood.
PS.
One person had a question about greasing the center pivot point. From my web site
WWW.4XSHAFT.COM and this particular link;
http://www.4xshaft.com/maintenance.html you will find a photo of the servicing and a reference to the tool needed. You amy also find my "essay" on grease usefull from this link;
http://www.4xshaft.com/Grease.html