building 8 3/4 489 section

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what do you mean with this? Losing teeth on hard launches? Well, I don't let the clutch fly. I Launch with 1500 rpm and release the clutch normally, just a bit quicker as on the street. Sorry, sometimes my english is only good with some beers :)

"Don't be surprised if you shuck some teeth of the r&p on a hard almost dead hook Launch"
 
oh yes, car is heavy. Stock trim, full Interieur. Just the Hemi and the tranny is different. Steel rims ( 15" with 26" tires in the rear )
 
Most of the time when an 8 3/4 breaks it breaks the teeth off the ring gear.

Sorry I didn't realize you weren't in the US. Are you in Germany?
 
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.
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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.
 
ok, so I think to have a significant improvement in ET i Change to richmond 4.86. Even if i have to shift into 4th gear :)
Pro gear? never heard about. Is this not the regular set?.
good tipp with the oil. what viscosity?

justinp61, yes, I am from Germany. But have a trip to PA/MD next month. Will use it for picking some parts. Prices here and shipping is KILLER!
 
just read about the pro gear. Isn't it for race only? I mean it is softer material for hard launches. But i am also travelling with those gears 200 and more miles each direction 5 to 7 times a year to the races. and back. Don't they wear out quickly?
 
Buschi340 said:
just read about the pro gear. Isn't it for race only? I mean it is softer material for hard launches. But i am also travelling with those gears 200 and more miles each direction 5 to 7 times a year to the races. and back. Don't they wear out quickly?
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I ran pro gears in my dana 17 years behind a 4 speed. never wore out, back lash stayed the same.75-90 gear oil is what I used. this was 3400 # car on slicks.
 
I've made many sub 9.70 passes with a 3600lb car with 40 year old case, ring, pinion, bearings. Still 0 issues.
 
I should get to my point here which is pretty obvious that a 4-speed loads and unloads the rear end four times going down the quarter mile pass at RPMs exceeding 4 grand every time including the worst one as you pointed out the starting line. So if you had one that lasted 20 years in an automatic it's one that lasted 80 years in the stick...
 
j par said:
With a 4 speed ?
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Believe me he's hitting his rear harder leaving at 4000 off the brake at 3600# with 1000HP than you with your stick. I think the pogo stick act your car was doing had as much to breaking you rear as anything. That or you had a bad cap.
 
Okay done going back and forth so as my last post on this subject I will say this is my experience with the eight and three quarter rear end at least it just didn't work for me and whatever my car was his doing.
 
I recently replaced the 5.13 gears in my 8.75, broke of 2 ring gears teeth after 30 years of 4 speed street and strip (slicks). the factory service manual does not say to check the diameter of the bore for the carrier bearing races. I noticed slight spinning of the races in the carrier. the outside diameter of the races measured right on at 3.250", the bore measured 3.253". I sanded down the cap faces to get the bores to 3.250". when parts are banging around-they break
 
Still undecided what ratio to get.
Is stepping up to 4:86 a significant change? I know that I have to shift one more but will the extra seconds be covered well? Or should I better start with 4.56? Again, I am now with 6000 rpm in 3rd gear at the traps. 4th gear has a 1:1 ratio.
 
Buschi340 said:
Still undecided what ratio to get.
Is stepping up to 4:86 a significant change? I know that I have to shift one more but will the extra seconds be covered well? Or should I better start with 4.56? Again, I am now with 6000 rpm in 3rd gear at the traps. 4th gear has a 1:1 ratio.
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If you can make 4:86 hook, and you still have another gear left, sound like the way to go to me.
 
If you are driving the car to the track I would recommend a Detroit locker instead of a spool. I love them. I ran 4.86 with a 30 x 12.5 slick. My car is a 65 valiant. So I know its very light. 2850 with me in it. However I run a converter that flashes to 3800 rpm. With a 2.75 first gear ratio. Yes I was buzzing 6200 rpm at end of quarter mile. I run solid lifter motors, so that rpm isn't hateful. My point is the rear will live and give you fourth gear in the quarter. Never ran stick because I mostly bracket race and I never ever saw a stick car consistent enough to make it past 3rd round. But on the street is a different story. Also if you do go the spool route I would recommend harden axles. I have seen 3 times stock axles snap at the starting line with spools.
 
no spool. Was thinking about a true track but they don't have it for 4.86 Ratio?
Limited Slip clutch type will also work fine? It's not wearing out within 5 years or?
 
Spools on the street aren't as bad as people make them out to be. I've been running one for a couple years now on a 95% street driven machine. My buddy just swapped his to a spool as well and he drives that car all over the place. Don't be skeered of a spool and street driving.
 
clinteg said:
Spools on the street aren't as bad as people make them out to be. I've been running one for a couple years now on a 95% street driven machine. My buddy just swapped his to a spool as well and he drives that car all over the place. Don't be skeered of a spool and street driving.
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I agree, I have been running a spool or welded together spider gears on the street for 25 years and never had a Issue.
 
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