Jimmy in NC
Addicted to ArboristSite
Gravely two wheel tractors originally came as a model L. They soon realized some instances required a lower ground speed...so they started making L-I and L-S tractors which are intermediate and slow speed respectively. They did this by changing the ring and pinion which is a worm gear setup. A regular or "high speed" has 8 leads on the worm, an intermediate 6 and slow a 4 lead worm. Of course the change in worms like all gear sets requires a different ring gear. Well slow speed tractors are good for snow blowers and plowing, high speed are good for regular mowing and snow plowing, etc. The down side to a slow tractor is it is slow to the barn and mowing. The original fix was an add on gear reduction wheels. They cut ground speed in half, added weight, and could change the balance point or add ground clearance to a tractor. They did require a bit of work to swap out..once in fall for winter snow blowing and spring for mowing wasn't too bad... but alas people got tired of the greasy, messy job.
Along came the swift-o-matic which is a two speed axle or an L-8 / C-8. This allowed shifting between speeds of an L and LS by moving a lever. Finally high speed to the garden, slow for plowing, then quickly to the barn.
The two speed axle did add complexity to the machine and add another set of wear points. For this reason Gravely continued to make "straight" tractors for many years. If a person only wanted to blow snow they may not want the extra complexity, cost, and hassle. Same token if a person only wanted to mow grass, a high or intermediate speed machine was all they needed.
An L runs 3 & 4 mph at WOT depending on range.
An L-i runs 2 & 3 mph at WOT.
An L-s runs 1 & 2 mph at WOT.
An L-8 runs 1, 2, 3, 4 at WOT.
Now if an L-8 runs all speeds why would I want an Li? An L-i is simple and shifting range changes ground speed AND PTO speed. Running the Li will allow higher PTO speed and not crawling but not jogging ground speed.
Bush hogging I really like an 8. Fast to the job but slow speed working in the woods.
More than you wanted to know huh?
