Major differences between ST and SS series?

Does an ST necessarily have a Tecumseh in it? Is the SS an upscale version with instrumentation, etc.? Please flesh this out for me. Thanks!

Only the management staff at Sears really knows the answer to the model naming sceme. The only thing I know for sure are observations that I have made over the years.

The original SS series was an upscale version of the Suburban line. There was a woodgrain (fake) panel on the the dash, a cigarette lighter and hubcaps. These were the "Sears Best" tractors of the day and had Hydro transmissions and standard transmissions.

The ST series started around 1973 and is thought to be a way to designate which tractors had the Tecumseh engines, hence the "T". The SS started using Onan powerplants.

As time went on, the ST designation was used on non-Roper produced units also. The Roper produced models that had the Onan's were called "Twins" during the twlight of their production run.

I'd love to hear more on this....

Thanks for your reply. I think one would have to do a lot of research to have a definitive answer on some of this stuff. It does sound like the SS is indeed an upmarket ST; I particularly get a kick out of the cigarette lighter! One small victory today; I got my 1978 GT18 running ! Purchased as a gamble for $50.00, I diagnosed a couple of safety switches that were a little flaky, and especially a starter that wasn't engaging. I took off the shroud and got the starter to engage reliably, repainted the flywheel and the shroud, and put some known, fresh, gas in a tank that looked "OK". I changed the fuel filter, filled the line with gas, and gave her a crank. Much to my surprise and joy, she fired up and settled down into that quasi-magical Onan boxer sound. So, on to find out what else might be wrong with this thing. I know for sure I've got to disassemble the electric powered 3 point hitch, fix a sticky choke cable, and see if the transmission works. The neat thing about this tractor is it APPEARS to be a low-hour machine. The clutch pedal shows virtually no wear, the trans shift is still fairly tight feeling, and some other things make me think I've got a fairly low hour machine. I know I'm the first one to take off the shroud in 33 years. More to come.