building 8 3/4 489 section

Buschi340 said

do you really think the centersection of a 8 3/4 is so weak? I am having this C/S in the car since 2001 ( bought the car )guess it is in since the car has been built in 1972. was from 72 to 2015 a 3,23 R&P and 4.10 just the last year. No wear, no damages. All what broke is the clutch ( worn out quicky ) and the rear U Joint this July. ( 7290 ).

J Par, i don't think it is the power thru the Manual gear box that made the caps break. Maybe overtorqued, invisible cracks inside thru the years? Scary anyway...

I don't wanna go the DANA way. Super expensive and I can't Change the ratios between the races for Long Autobahn Cruises... :)

Do you think a swap to 4.56 is significant or should i step to the next shorter? Ring and pinion manufacturer are not the same in Quality. Who is the best in your eyes?

will try the calculator from above.

Click to expand...

hi, , we ran 8 3/4 in stick shift duster for years. only broke ring gears at times. they were 8620 material, which is hard. Richmond came out with 9310 pro gears, they are softer, will stand impact better .they offer 4.86 ratio pro gear. we ran 5.13 ratio. they stopped making pro gears in 5.13. had a talk with them about heat treating ring gear to soften it up ,like was done in late 60's in jr stock. was told to heat ring gear in oven at 450 deg for 4 1/2 hours. face down on bottom rack. remove next day. the gear turned a straw color. a file would dig into it. we had old gear and new gear tested on a Rockwell hardness tester, old gear tested 57, new gear tested 58. were able to triple gear life. also, found , use synthetic gear oil. also, do not jack up car and run gears with no load. it lets gears slap, causes stress risers and cracks. only way is to drive them. just things to consider. as for quality, we ran Richmond, now I hear Yukon is a good brand. Yukon makes a 4.86 pro gear. it's for 742 case.