So assuming, each company can measure and properly use a lathe, there's no reason that the 90$ solid diff set (http://cgi.ebay.com/ebaymotors/ws/eB...m=370403521215) would be any different than the 180$ (http://splparts.com/store/product-info.php?pid37.html)

Right?

The Ebay guy has 100% feedback and 38xxx transactions. Seems like easy decision.

 

This is a copy of our first generation diff bushings. I am going to appeal to customers to support innovation and USA made products, and purchase our original bushings, but even discounting that, there are some things to consider:

1. How certain can you be that the material is really T6061? If you purchase that amount of T6061 in the USA, without machining, that would be $30-$50 alone. It is not the first time a Chinese factory substitutes a cheaper material in order to meet lower costs. It is the reason why we do not send our drawings off to be produced overseas.

2. We measured the subframe and designed our bushings. The other company measured our bushings, not the subframe, so they do not have the original dimensions, just the dimensions of that specific sample. Our bushings are machined to 1/1000" tolerance, so their base dimensions could be off by 1/1000". Add to that their manufacturing tolerance (which I am certain is alot more than 0.001"), and you end up with a bushing that could be off by several thousandth's of an inch (ie. "tolerance stackup"). For a press fit, a few thousandth's of an inch is the difference between a bushing that is too tight (may crack the subframe) or too loose (bushing would not stay on subframe).

3. Those bushings are not anodized, and bare aluminum bushing against bare aluminum on the subframe will cause galling.

4. Tech support. I designed the bushings, I know what dimensions they are supposed to be, how they are supposed to fit and different methods of installing the bushings. We have a phone number you can call and talk to me if you run into a problem.

5. Over time, we gathered feedback from our customers about the bushings and made revisions to our dimensions and design for better fit on the bushings and better usability on the tool. Nissan subframes are made with a certain tolerance as well, and we have found that our original dimensions are a little too tight, so we adjusted accordingly. The bushing kit we sell now fits better and is easier to install.

 

Another point - 6061 ain't all that. It's a common weldable aluminum alloy that machines OK. 2024 and 7075 are much stronger machinable aluminum alloys. They machine much easier, hold a better finish, and are dimensionally more stable then 6061. When I see someone advertising a machined part as 6061 I tend to think they don't understand aluminum alloys.

Now... for a diff bushings, 6061 is just fine and its cheaper then 2024 or 7075. 3003 would work just fine also. Hell, Nylon 6/6 works well as a diff bushing material and its a no point mod in most time trial series.

BTW... I would buy the SPL parts.

 

I am not certain Nylon 6/6 would take the pressure exerted by the single stud on the rear diff cover on that small area of the bushing. It would have to be a 2 piece design, with a metal piece in the center to distribute the load, which would make it more expensive to produce...

6061 is a certainly a very common grade of aluminum used here in the USA, but it does also certify a certain standard of metallurgy, manufacturing, and mechanical property. There are worse grades of aluminum out there...

2024 and 7075 have great mechanical properties, but suffers from galvanic corrosion, and so I only use them where I really need their higher strength...