Im not trying to start anything.......Butt. I really would like to know what is wrong with putting Max HP to an 8" rear? 1. Is it that the components are weak and smaller, or is it the housing that is the problem? 2. Are the Axle Shafts the problem? I can brace the Housing if thats the problem. I want to know why a 9" is the cure and the cure for what..specifically?
8" axles are the same axles that comes with a 9" An 8" will live long on street tires...it's the sticky Mickey's that breaks parts. Street tires are made out of a harder rubber compound than drag race tires.
I have run the 8in with great success and no problems with 375hp 306 and c4 in drag only car. The biggest problem they have is the small rear pinion bearing. As the car launches the pinion trys to climb up the ring gear and the rear pinion support bearing stops it from doing this and rotates the ring gear foward or reverse direction. This really is bad on the 8in if you are using a std. shift trans. 9in carriers have almost twice the size rear pinion and the gear ratio selection is or was more available.
the 8" is a great rear end. yesterday i had someone ask me at work what is the best rear end. my answer was what is the intended use? if you are not drag racing you dont need a 9" the 9"consumes significantly more power than most other car and light truck differentials. i only recommend the 9" for racing applications.
DO a search. A few pics in here of 8's with the caps blown up. Check Joedirt I think he grenaded an 8 inch before the 8.8 swap?? MAybe it was Brant?? Maybe both. LOL. If I was going to race with sticky tires and/or a manual trans I would do an upgrade. For a street car? You should be just fine.
Half the broken 8"s I've seen have been by driver error, by ignoring their wheel hop. I wonder if it would make a difference if guys preloaded their cars. That's how FWD drag racers manage to get their 500-800WHP cars down their track on their tiny OEM differentials. Heck they even run the OEM trannies and they survive 10-8 second 1/4 mile passes!
IIRC the weight difference between the two is 40 lbs, and being that it is additional unsprung weight, it needs to be controlled by the springs and shocks. This all plays into how the car handles. Like others have said ... for a street car with street tires, especially cars like ours that are on the very light end of the weight spectrum, an 8" should live a long time. I have never had a problem with mine, and I have been merciless.... smoke-show burnouts and a lot of bracket racing. I ran a locked 4.62 gear for a long time on the street ... tire chirps around every tight corner ... it puts the axles in a bind each time... not good. This is the axle that came in the car and now has 160K miles on it ... original axles and end bearings. Can't wait to see how the car drives with the new 3:55s.
I have found that in an automatic car without a trans brake, they will last a long time, even in some higher HP applications with drag slicks. Heck I have seen 9" rears come apart with a mild 302 and a clutch. Its all in the setup. If the rear end is set up right ( pinion depth, backlash and suspension mods for the wheel hop) The 8" is a fine rear end and will last you a long time if done properly.
Yeah I blew that poor 8" darn near out the back of the case. Good for a low power car that will never see the shock loads a higher power car will give. The 8.8 has taken everything I've thrown at it I don't ever expect to have a problem with it.
