Michigan permits trucks up to 164,000 pounds on the system. However, different than other states, Michigan requires a lower weight per axle which more evenly distributes the load and reduces wear and tear on roads.
MDOT engineers have thoroughly studied this issue and the result of this research is that heavier trucks do not cause a disproportionate amount of damage as long as the weight is evenly distributed over an appropriate number of axles.
Additionally, trucks over 80,000 pounds make up only less than 5% of all trucks operating on our roads. If Michigan were to reduce it's truck weight laws to 80,000 pounds, more damage to the system may occur because of the need to put more trucks on the road. More trucks on the road raise serious questions concerning safety and traffic congestion.
Several other states are currently looking at Michigan's axle weight laws and are considering adopting similar laws.
Here is some interesting info on the popular gearing choices for a "Michigan Special" from this website: [link]
3.55:1s are for folks who like to change out clutches, power dividers and driveshafts. Startability is the biggest issue. Especially with the dirt haulers and loggers.
Most customers of mine go to 4.11:1 if they are running 500+hp and 1850lb/ft torque. Some pile to pile on highway guys will run 3.90:1. The operations running 450-475hp and 1650lb/ft torque typically use a 4.33:1 with the excavators and operations that mostly run county/state hwys occasionally going to a 4.56:1.
Tractor wheelbases are appx 170" with a set back axle and 179"-190" on the set forward axles. Unless they are runnung a 132" hood at 202" WB.
Transmission: 13, 15(rarely anymore), & 18 Speed. 10 Speeds and 8LLs are only for Straight tri/quad dumps(57k#&70k#) and tri/quad lead trailers at 89k# & 102K# GCVW.
Front Axle: 20,000# Though they can only get about 16,000# on it. Rears: 46,000# for the 160k combo rating Frame: 3/8" single or 10/32" with a 1/4" liner
This looks like it's got more wheels than a train! Where I live, near Washington DC, there are lots of heavy trucks tearing up the roads. Maybe if we had some more "Michigan Specials" our roads wouldn't get worn out so fast.