David - you asked a question "Did IH over-engineer their products?", and then gave your opinion that they properly engineered their products. I'm a little surprised with your position, especially since I know you are an engineer yourself. I'm assuming you are trying to get the opinions of others so here goes with mine.
It's my position they properly engineered some of their components, but they also under-engineered and over-engineered some. Since you show your Quiet Line 1250, I'll keep my discussion specific to the QL series. I'd be glad to discuss other series models later if you want to get into those. (Some of my comments will apply to almost all models anyway).
I think they under-engineered the ISO-bars for the engine mount assembly. I believe CCC updated the design to a "cradle" style which greatly improves the design function.
Another thing I thought could have been designed "just a little" better is the Ross steering box. This is a sub-assembly they purchased but I think it could have been a little better. I don't know if Ross would have done this for IH, but I think you would agree your "Super Steer Upgrade", which is basically just the addition of a bearing, makes a dramatic improvement to actual steering.
And then there is the transmission/rearend. In and of itself, it's probably the most over-engineered component of the tractor. It's actually my position that the transmission, whether it's Hydro or Manual, is why these tractors are still around today. Even tho the IHCC Service Manual has alot of detail about checking components, etc., for the most part the tranny/rearend just doesn't fail. Ya, there is the occasional shifter fork issue with the manual tranny, or the failure of a relief valve on the Sunstrand pump, but for the most part these things are bullet proof. I believe that if the transmission/rearend failes on almost any other brand of tractor, it's end of life for that unit because it's to costly in time and materials to repair.
However, one thing I could never understand about the IH Hydro tranny/rearend is it not having a drain plug, especially since the manual transmission does. And to add to that, the IH Operators Manual does not have a recommendation for changing the fluid. It only mentions to add as needed. We all know the rearend accumulates moisture which eventually exceeds the absorption capacity of the HyTran fluid. So it really does need to be changed and having a drain plug would certainly facilitate the process. Most of us have experienced the "Big WOOSH" when you crack the gasket seal on the rear cover plate, even just slightly it still makes a little swooosh. Having that drain plug would help even tho I realize you still need to remove the cover plate so you can get all the globs of fluid that have absorbed that moisture.
There are a couple other things with the QL series that are interesting to mention. Why did IH change the front spindle and wheel bearings to 1" from 3/4" half way thru the 4 year production of the QL? I understand the 1" design has better load capacity but did the tractor really need it? And why did IH change the steering wheel at roughly the same time?
I look forward to your position and comments.
Hydro Harry
Old Cubs Never Die