On the 4.77 & 5.0 gears, the stock case must be machined or ground to provide clearance for the cluster gear. On some 4.0 cluster gears, we have found that the case will need to be relieved due to core shift. You can grind the necessary clearance; however, it is recommended to machine the case for this clearance.
If your not sure about this grinding or the machining process, we now offer a new heavy duty front Toyota housing. Our new Toyota HD housing can be used as a crawler box with stock Toyota gears or with our low gear sets. It can also be used as a new front housing for the lower gear sets listed above. This housing will save you time and money. When installing our low gears into a stock Toyota housing, grinding & machining on the stock case is required. Our housing has been engineered with additional clearance for our gear sets. Thus, hours of grinding & expensive machining labor are eliminated. This housing is made from 356-T6 heat-treated aluminum alloy with an average thickness of .550”. A “stock” housing is die cast aluminum and only has an average wall thickness of .200”.