Big Block Billy

You are right about changing the gears before catastrophic damage occurs.
I'm over here scratching my head, I've got a drive to rebuid, blown up xz upper with steel tower, lower is bone stock generic Bravo and is fine. Usually the problem with the drives is in the uppers. I've seen them with twisted propshafts and broken driveshafts and the lower gears usually were the only good parts in the case.
Does Imco or B-max make better lower gears, or maybe a whole new lower that can take the stress?
Also break in procedure on the drive is important.
Konrad gives you a big red card with break in procedures with every drive.
I have some stock lower gears if you want to play with them, you can have them, I have a machinist neighbor who has a connection with tool and die outfit in China(don't laugh !). Maybe you could make some better quality gears and keep the cost down and sell them when it's all figured out.
There also was some post way back about cryogenicly treating alpha gears, and the difference it made.
I have an xr/xz propshaft , gears, billet carrier, new in box, I will sell it for what, I paid, $550. also have a new XR lower. BBB

tomcei

BBB, I might be interested in the drive parts you have if he's not. I just smoked my xz drive last night and don't know where to turn just yet.
Tom

PatriYacht

Interesting thread Smitty. 8620 sounds like a likely choice for the gears. If you used a carburizing heat treatment, it would raise the surface carbon level while leaving the core softer and tougher. Like you said, there is a chance that the gear will become brittle enough to spit teeth off, but it is an experiment worth trying. I have always thought that S7 tool steel would be a good choice for gears. In the tool and die business, it's known as shock steel or chisle steel. It's used for trim steels in cutting dies. Unfortunatly I dont have the cash laying around for that experiment. Good luck and let us know what happens. Ian

Ratickle

The following is a cut and paste from Sterndrive's website. Looking in the automotive arena, it appears almost all of the high performance stuff like Strange gears are 4340. Mercruiser says they shotpeen their gears, I am assuming this acts as a workhardening for initial strength. Ian, S7 is extremely hard when properly treated and maybe the most used stamping steel in the automotive industry, but what about the side loading a gear has? Would it have to be forged near net and then final machined like on 8620 or machined and then proper heat treat would realign the structural integrity for strength?

"THE GEAR SETS ARE STRONGER AND MACHINED FROM 8620 FORGED STEEL. THE STRONGER TEETH AND HIGHER ALLOY STEEL RESULTS IN A GEAR THAT IS 50% STRONGER THAN ANY OTHER COMPARABLE GEAR SET"

Big Block Billy

P.M. me if you are serious. I don't want to abuse the board for commercial purposes. Thanks, BBB

articfriends

iTrader: (1)

I'm running a aeromotive 11104 eliminator fuel pump with a 1/2 inch pickup with -10 hose from tank. I also use a kenne bell boost a pump voltage booster that turns voltage to pump up to 16 volts under boost. All of the fuel leaving the pump goes thru a large fuel cooler (about 2" dia by 6" long) then extra fuel is bled off thru 2 regulators. The fuel supply is the split off thru 2 -8 hoses to my home made twin rails. The extra fuel bled off thru the base pressure regulator then goes thru a second regulator that raises pressure under boost. The extra fuel that leaves the second regulator is teed in between the supply line from the tank and the inline fuel filter. The fuel experts say it won't work but you have to remember 2 things,the filter and water seperator (in some cases) buffers any pulses to suction side of fuel pump plus when your under boost if your fuel pump is sized close (mine is) there is little or no fuel returning to suction side of filter and pump. This set-up has worked well for me for over 4 years after I tossed all the crap procharger gives you that barely works, I had a essex fuel pump with no voltage booster with this same set-up though when I was making less hp because I didn't need as much fuel,Smitty

articfriends

iTrader: (1)

Ratickle,I build/rebuild rear ends as part of my business,the standard material majority of oem and aftermarket ring and pinion companys use for their standard street and general use gears is 8620 alloy,the pro-series gears are 9310. The funny thing I don't undersatnd is they say the 9310 gears take higher shock loads because they are stronger but are SOFTER and wear faster? I'm no metalurgist by any means so I have no idea what they consist of. I see 4340 shown as a alloy for some of the racing parts for transmissions along with 300m for shafts,Smitty

Ratickle

I was reading about 300M and found this. Will look into both. Am starting to get a headache!!

"Advances in auto racing engine designs and increased engine power have caused an increase in the failure of dog rings, gears, camshafts, input shafts, racks and pinions. The design objective for FerriumŪ C61 was to develop a high
performance secondary-hardening gear and bearing steel with similar surface properties to conventional gear steels such as AISI 9310 and EN36C, but with the added benefits of a ultrahigh-strength core and excellent fracture toughness.
Description
Ferrium C61 is a member of a new class of martensitic secondary-hardening gear and bearing steels that utilize an efficient M2C precipitate strengthening dispersion. Because of the efficiency of this strengthening dispersion, a superior combination of properties can be attained for a given application. Ferrium C61 was designed to provide carburized surface properties (60-62 HRC) similar to conventional gear steels such as AISI 9310 and EN36C with the added benefit of an ultrahigh-strength core along with excellent fracture toughness.
Advantages Ferrium C61 is targeted as a superior alternative to current gear materials in applications where component redesign is not feasible, but elevated core strength is required. Ferrium C61 has surface-wear properties, toughness, and fatigue properties similar to those found in current commercial alloys such as AISI 9310 and EN36C, but it also possesses an ultrahigh-strength core.
If desired, Ferrium C61 can be nitrided to increase the surface hardness to near 70 HRC (1100 HV)."

Ratickle

ArticFriends, Also talk to your guy about nitriding after carburizing. I will also look into it. From what I read, it makes the surface have less friction load than hard chrome plating along with improving surface strength.

"Abstract: This investigation is aimed at improving the fatigue behavior of tank track pins through the use of better processing methods and materials. Five different compositions of steels investigated: SAE 865OH, 4340, 4140, 8620 and 1045. These were subjected to the following treatments: induction hardening, stress shot peening, nitriding and carburizing. All steels except 1045, received final treatment of shot peening. Tension-tension bending fatigue tests were conducted on these pins to determine the S-N curve of each type of steel and the result compared with the data on the regular production tank tack pins obtained in another investigation. Stress shot peened 865OH pins have the highest residual compressive stress of -175 ksi on the surface and demonstrate the best fatigue limit of 198 ksi. The induction hardened, nitrided and carburized 4340, 4140, and 8620 steel pins, which have been shot peened, have a surface hardness range of Rc 58 -62 and shown an equal level of compressive residual stress of about -110 ksi on the surface. Carburized 8620 pins demonstrate the second highest fatigue limit of 175 ksi followed in turn by induction hardened and stress shot peened 4340, induction hardened and nitrided 4140 and carburized 1045 with the lowest fatigue strength."

Ratickle

Finally got together with the guru of metalurgy. He said all gears are currently made with 8620, 4120, etc because the higher the carbon, (20), the more probable the metal will through harden. Due to the extreme pressures put on outdrive gears when entering the water after launch, they actually want the inner metal to be soft and absorb the shock. Much like the damper plate on the flywheel. The pictures looked like linear fracturing of the link between the carburized surface and the softer layer inside. This is usually caused by improper quenching during the heat treat process. He is going to consult with some other specialists in gear design to see if there is anything new in high stress gear metals. He is also checking on nitriding, carburizing, and the best ratio of carbon % in the metal vs carburizing depth. Will keep you informed.