I never used an impact to tighten anything as critical as an axle bearing nut. The impact load as radially applied in the same direction of rotation as the bearing. The bearing is doing nothing to accept the load from the impact. It's being applied to the pinion gear and spider gears in the differential, where the mass of the pinion itself is absorbing much of the impact.
I'm not arguing for the use of impact wrenches on axle bearings, but there are cases where they would be appropriate. For example when you have a nut so tight it can not be removed by any normal means. You want to save the axle but the bearing is being replaced anyway. One time we had to use the weight of the car to get a rear axle nut on a 280ZX removed, pry bar between the lug nits, breaker bar on the axle nut itself, then drop the car down on the lift until something moved. Reused the lower control arm and stub axle, replaced the bearing and seal.
Fixed a 1977 Honda Accord when it was a year old. Right wheel took the impact. Drove the strut tower into the unibody hard enough for the windshield to pop out of its weatherstrip, but not break. Even broke the heater housing inside the car. Replaced the strut, everything else was reused, front end aligned AND SOLD IT TO MY FATHER!!!!!!!!!!!!!!!!!!!!!!!! Reinstalled the windshield, repaired the busted heater housing with a torch and an oyster knife.
Only the strut itself was bent. HE DROVE IT ANOTHER 50k miles without any problem with any part in that wheel, NOTHING was replaced in 50 k miles. He traded the car in and they gave him $2800 for the car with 63k miles. When you talk about impact on a bearing, that example takes the cake for me. We did replace the whole right side skirt, from the cowl to the radiator support, but no other suspension component except the strut itself, just the cartridge assembly.
Arguing hypotheticals is an exercise in ludicrous confrontations. POP had retired and worked as a volunteer for the American Cancer Society. They paid him 39 cents a mile and he averaged 39.5 MPG. This was a man who flew B17s home from missions over Germany with almost unbelievable battle damage, bombs dropped through the wing, one near miss from an 88 that left 175 holes in his plane and knocked him out cold in the pilots seat, when a piece of that 88 hit his helmet. It was hi first mission 12/24/43, supposedly a milk run to the French coast where they were building the launch ramps for the V1 buzz bombs. It took 3 planes to make his 30 missions, ending on D-Day 6/6/44.
Ever rolled a car around with no steering gear? They roll good forward, terrible backward, due to the caster in the front end.
I read almost daily, on this forum, about bearing replacements that failed in days. weeks, months after installation. I NEVER had a bearing failure like that and replaced hundreds of bearing from 1969 to 1999 when I retired, every configuration you could imagine. These days the bearings are made as an assembly, back then they were individual bearings with a spacer between them and seals separate. Never had one fail.
