The ones Allis Chalmers did not build

If they did, and they may have, they were all prototypes. If what you are talking about is the cotton picker D17 with 262 that would be different but it's not a D18. From what I understand the D18 was a D19 prototype that had a lower hood line that made it look like the size of a D17 and the sales people thought it would be too hard to sell a souped up D17 with the added price. A souped D17 it was not cause it had the rear end of what was to become the D19. So they raised the hood line up to make it look bigger and justify, in the farmer's mind, the added cost. If the diesel D18 had a turbo I do not know but I'd guess they did. In the end I'm pretty darn sure non were ever sold unless you count what was sold as scrap.

.

Old thread but I'll add a bit:

-They lost a lot of market share by not paying Ferguson for rights to use the three-point for the WD launch or even late years of the WC. It was well proven by Ferguson TE/TO and the Ford N-series by the WD. Trying to engineer around a patent wasted a whole crew of workers, lab time, marketing, and sales efforts plus left customers at risk for proprietary connections. Companies still stumble over this, thinking things like their unique phone charger connector will ensure market dominance when it's the common connector that makes ownership seamless. We had both a WD and a Ferguson TO35 on the farm when I was a kid and I only remember the WD doing sickle bar mower duty because it lacked the three point all the rest of our tractors had. I had the impression the mower was really hard to put on/off that tractor too. I did get to grind the bar teeth quite a few times but never drove the tractor (we had hills and a NF was more than enough dangerous).

-AC spent too much time trying to 'go toe to toe' with the competitor models in every market, advertising how they matched all the competitor tractors in all the markets. Had they focused on the tractor middle-hp-market, no lawn mowers and no tractors over 100hp, they would have been strong enough to continue. 

-Flowing artful curves of the 50s/60s machines gave way to the blocky 70s/80s styling that looks no where near as graceful. My father stopped buying Ford trucks for twenty years until they came out with better styling. It matters for tractors too.

-Large round PTO driven baler would have been a great product to launch.

Look at the production rates of the WC/D/45 and D-15/17/10/21 vs their later number series tractors that pushed for higher hp and ever higher prices and those tractor sales were abysmal. There were, and still are, many family farmers making a go of it, even with day jobs to cover the big bills, that would consider a workhorse tractor for a fair price.

The unhinged monetary expansion and resulting inflation during the 70s/80s made it impossible to continue for too many companies. That was outside of their control and just made making the decisions they executed against an unknowable outcome.

.

  GREAT POSTING!!!

AC 715 Loader Backhoe with Four Wheel Drive with Full Cab, air conditioning and heat.

AC 652, 653 and 655 with wet steer clutches, pedal steering and side dump bucket.

AC/Fiat Allis 345C Series with 4 wheel steering, air conditioning and heat. 

AC Telehandler using an integral frame from an 840 Wheel Loader or 345B.

Continued work on the G2200 engine with a small turbo to use an optional engine on 650

series Crawler, Loader and Dozers. 

~ Orangeman