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Re: 8.75 bracing
[Re: 1980volare]
#2165359
09/30/16 08:17 PM
09/30/16 08:17 PM
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Joined: Aug 2003
Posts: 43,157
Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,157
Bend,OR USA
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and I'm going to reuse my 8.75 35 spline axles. Make sure and reuse those axles on the same side in the new Dana 60, do not swap or change sides on them  I did the same thing as you are planning on my old Duster with Strange 35 spline axles when I swapped them from the 8 3/4 with a Strange 35 Spline spool to the cut down Dana 60 with a Moser 35 spline 3 sereis spool, I had to cut about 3/4 inch off the passenger side axle. I took it to a freind who has steel chop saw and we beveled the ends on his bench grinder when done  BTW I do have several different gear sets of use Dana OEM gears in decent condition that I'm willing to sell if your interested, if so PM me on here 
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: 8.75 bracing
[Re: 1980volare]
#2165517
09/30/16 11:52 PM
09/30/16 11:52 PM
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Joined: Aug 2003
Posts: 43,157
Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,157
Bend,OR USA
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I would slide the rear end into the car and center the pinion yoke in the tranny tunnel and go from there on the axle tube lengths needed to make your old or new wheels fit into your car properly   I think my truck rear end axle tube on the passenger side was 3/4 shorter than the left when I was all done with it BTW, my axles extended past the splines in both spools into the center of the spools  I figure that way didn't hurt anything and I knew I had max spline engagement on both the axles and spool splines
Last edited by Cab_Burge; 09/30/16 11:54 PM.
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: 8.75 bracing
[Re: Monte_Smith]
#2165603
10/01/16 02:10 AM
10/01/16 02:10 AM
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Joined: Oct 2011
Posts: 3,036
bean town ....Ca
WHITEDART
master
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master
Joined: Oct 2011
Posts: 3,036
bean town ....Ca
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You can brace it like a tank and it will NOT fix the inherent weakness of the 8.75. Torque pushes the ring gear away from the pinion when the case flexes. You CAN'T fix that. They break caps because all the debris from the shelled teeth gets in there and it pushes the cap off. So you will spend a lot of time and money trying to fix a problem you can't fix and it will eventually break anyway.
Put a 9" inch in it and forget it yes what he said👍👍👍
In the 8s N/A.with Brett miller W8's
5.07 at 133 at 2700lb
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Re: 8.75 bracing
[Re: 1980volare]
#2165888
10/01/16 02:16 PM
10/01/16 02:16 PM
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Joined: Jan 2004
Posts: 8,250
fredericksburg,va
cudaman1969
master
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master
Joined: Jan 2004
Posts: 8,250
fredericksburg,va
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Next dumb question,
I used drdiff's calculator for tube length with my axles, and subtracted a half inch per side for spool engagement.
Will it hurt anything to have equal length tubes with a truck 60 pinion offset in a factory style chassis? All stock engines with reg engine mounts are moved to the pass side, some quite a bit. 8 3/4 pinion offset is the most, dana is less, reason one tube is longer. The tunnel is also offset to the right. I centered the dana housing in my 64 and didn't have a problem, there is wiggle room to line it up, front to back. No more misalignment than the up and down movement of the drive shaft. I wouldn't cut any axel, unless they touch, since the splines go thru the spool
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Re: 8.75 bracing
[Re: Monte_Smith]
#2166091
10/01/16 08:24 PM
10/01/16 08:24 PM
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Joined: Dec 2006
Posts: 4,647
aotearoa
rebel
master
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master
Joined: Dec 2006
Posts: 4,647
aotearoa
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You can brace it like a tank and it will NOT fix the inherent weakness of the 8.75. Torque pushes the ring gear away from the pinion when the case flexes. You CAN'T fix that. They break caps because all the debris from the shelled teeth gets in there and it pushes the cap off. So you will spend a lot of time and money trying to fix a problem you can't fix and it will eventually break anyway.
Put a 9" inch in it and forget it if you look at the pic i posted earlier we tried to address that very problem. the extra cap on the cap is designed to fit snuggly against the back of the housing so its harder for the caps to deflect & allow the failure as you described. it seemed to have held out ok as since i did this trick the 8 3/4 lived without a failure. i dont use a brake on this car anymore so i'm sure my upgrade with live as long as i'm abusing this car. my other racecar has a 9". too easy & you trip over parts everywhere.
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Re: 8.75 bracing
[Re: 1980volare]
#2166343
10/02/16 10:35 AM
10/02/16 10:35 AM
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Joined: Jan 2005
Posts: 2,540
Milwaukee WI
TRENDZ
master
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master
Joined: Jan 2005
Posts: 2,540
Milwaukee WI
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Yep. Anything you can do to keep the caps from spreading away from their intended position will help the durability. It's not the easy way, it doesn't make it bullet proof, but it does make a large difference.
"use it 'till it breaks, replace as needed"
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Re: 8.75 bracing
[Re: dogdays]
#2167171
10/03/16 05:46 PM
10/03/16 05:46 PM
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Joined: Dec 2003
Posts: 22,696
Bitopia
jcc
If you can't dazzle em with diamonds..
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If you can't dazzle em with diamonds..
Joined: Dec 2003
Posts: 22,696
Bitopia
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That pinion deflection idea of the source of the problem, has been tossed around before. It is somewhat supported by the change in the pinion ,in the 489 case, to a larger diameter pinion, albeit with a ID smaller bearing. Just because they made that change does prove that was the problem, nor that it solved the problem. Why that may be the case, when Mopar brought out the Alum case decades later, with the availability of significantly greater computer design assistance, it was based on the previous 742 case, and advertised as being a 10% stronger design, in Alum. Personally I think the ring gear/mounting would have much greater deflection then the pinion anyhow, by design, and nothing to back that up.  Case design of the alum 742 has added/enlarged external ribs, for stiffness? PS Maybe I missed something here, not sure anyone is much concerned about "caps" moving, so much as just failing from overload, and whatever it takes to mitigate that overload.
Last edited by jcc; 10/03/16 06:03 PM.
Reality check, that half the population is smarter then 50% of the people and it's a constantly contested fact.
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Re: 8.75 bracing
[Re: dogdays]
#2167175
10/03/16 05:55 PM
10/03/16 05:55 PM
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Joined: Nov 2004
Posts: 6,890
North Alabama
Monte_Smith
master
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master
Joined: Nov 2004
Posts: 6,890
North Alabama
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I'm going out on a limb here and saying it isn't as much the caps moving as it is the deflection of the pinion shaft and the case which supports the pinion against the ring gear.
In most any gearing system it's the smaller gear, called the pinion, that's most highly stressed.
The 9" has a support bearing or bushing on the other side of the pinion and that maintains the alignment much better. It doesn't seem like much but it makes quite a difference.
One disadvantage of the support is it moves the pinion lower on the ring gear, which eats more power by friction. The support also robs space for a proper limited slip differential. 9" limited slips are kind of one-sided. Of course, spools don't mind at all.
All in all, the advantages outweigh the disadvantages when we move into higher torque loads.
I see that Dr.Diff has a nodular 8 3/4 case for sale. Nodular iron is 50% stiffer than gray cast iron. This will lessen the amount of deflection for a given load. The nodular case should be the first purchase if you're building a stout 8 3/4.
R.
Bingo........The CASE is what flexes, allowing pinion to move away from ring gear. The cap has zero bearing on this. It pushes the cap off when all the tooth debris gets lodged in there and SOMETHING has to give, that's the cap. A better cap may not break, but something else will. I have seen 8.75s with GOOD caps still shell teeth. When it cant break the cap, I have seen them break the pinion clean off or split the case. You get all that junk lodged in between SOMETHING is going to give
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Re: 8.75 bracing
[Re: 1980volare]
#2167197
10/03/16 06:22 PM
10/03/16 06:22 PM
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Joined: Jan 2005
Posts: 2,540
Milwaukee WI
TRENDZ
master
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master
Joined: Jan 2005
Posts: 2,540
Milwaukee WI
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Yes the case flexes. The issue is, it flexes at the caps. The distance between the driver cap and the passenger cap increases. Internally bracing the housing at the backlash setting adjusters GREATLY strengthens the assembly. The rub marks on the braces proved to me the load that the cap takes. A look at the pig, and it is obvious where the case will move given enough force. I personally proved it to myself. When you make a change, and the problem moves elsewhere, you've "fixed" that problem. Now, did it stop the ultimate demise? No. I ended up with a race intended 9". My only reason for posting this over and over is that the actual reason needs to be disclosed.
"use it 'till it breaks, replace as needed"
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Re: 8.75 bracing
[Re: dogdays]
#2167274
10/03/16 08:42 PM
10/03/16 08:42 PM
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Joined: Jul 2004
Posts: 19,317
State of confusion
Thumperdart
I Live Here
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I Live Here
Joined: Jul 2004
Posts: 19,317
State of confusion
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I'm going out on a limb here and saying it isn't as much the caps moving as it is the deflection of the pinion shaft and the case which supports the pinion against the ring gear.
In most any gearing system it's the smaller gear, called the pinion, that's most highly stressed.
The 9" has a support bearing or bushing on the other side of the pinion and that maintains the alignment much better. It doesn't seem like much but it makes quite a difference.
One disadvantage of the support is it moves the pinion lower on the ring gear, which eats more power by friction. The support also robs space for a proper limited slip differential. 9" limited slips are kind of one-sided. Of course, spools don't mind at all.
All in all, the advantages outweigh the disadvantages when we move into higher torque loads.
I see that Dr.Diff has a nodular 8 3/4 case for sale. Nodular iron is 50% stiffer than gray cast iron. This will lessen the amount of deflection for a given load. The nodular case should be the first purchase if you're building a stout 8 3/4.
R.
Been running Dr Diffs nodular iron 8 3/4 w/stout Ford type caps for several months now and all`s well but only 2 passes a 1.37 and a 1.33 60`s so far and a few more soon I hope.............many, many years on the stock 742 in the 9`s and 1.3`s in the 60 and back braced....... 
72 Dart 470 n/a BB stroker street car `THUMPER`...Check me out on FB Dominic Thumper for videos and lots of carb pics......760-900-3895.....
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Re: 8.75 bracing
[Re: Thumperdart]
#2167296
10/03/16 09:01 PM
10/03/16 09:01 PM
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Joined: May 2003
Posts: 1,751
Graham, WA
Polarapete
top fuel
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top fuel
Joined: May 2003
Posts: 1,751
Graham, WA
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It seems to me that you put your Dart on a serious weight loss program and it could be that is one of the reasons your 8.75" still lives...JMHO.
1986 Dodge Ramcharger 440 2wd, Bracket Racer Under Construction
1998 Ram 2500 QuadCab, new daily driver.
2008 Honda Element
2014 Carry-On 7x14 Cargo Trailer
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Re: 8.75 bracing
[Re: Polarapete]
#2167373
10/03/16 10:47 PM
10/03/16 10:47 PM
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Joined: Jul 2004
Posts: 19,317
State of confusion
Thumperdart
I Live Here
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I Live Here
Joined: Jul 2004
Posts: 19,317
State of confusion
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Most of those were at 3200+ lbs. and in the 10`s but the last 7 years have been 9 second passes and several 1.3`s but on Hoosier QTP`s and my last two passes were w/28x10.5 w Mickey slicks getting me the 1.33 60.............Guessing I`m at 3050 or close but still haven't weighed it yet.............
72 Dart 470 n/a BB stroker street car `THUMPER`...Check me out on FB Dominic Thumper for videos and lots of carb pics......760-900-3895.....
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Re: 8.75 bracing
[Re: TRENDZ]
#2167940
10/04/16 07:03 PM
10/04/16 07:03 PM
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Joined: Dec 2003
Posts: 22,696
Bitopia
jcc
If you can't dazzle em with diamonds..
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If you can't dazzle em with diamonds..
Joined: Dec 2003
Posts: 22,696
Bitopia
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Yes the case flexes. The issue is, it flexes at the caps. The distance between the driver cap and the passenger cap increases. Internally bracing the housing at the backlash setting adjusters GREATLY strengthens the assembly. The rub marks on the braces proved to me the load that the cap takes. A look at the pig, and it is obvious where the case will move given enough force. I personally proved it to myself. When you make a change, and the problem moves elsewhere, you've "fixed" that problem. Now, did it stop the ultimate demise? No. I ended up with a race intended 9". My only reason for posting this over and over is that the actual reason needs to be disclosed. I am not clear on what you are observing regarding the caps distance moving apart and internally bracing preventing and reducing that. I can see the carrier moving in the sheet metal housing, likely with both caps leaving a witness mark from the pre load bolts(?), but not sure what internal bracing improves that, or extends cap longevity. I often feel these issues often arise not in the observation, but in the conclusion drawn from them. I agree this road has been traveled many times here, and its still bumpy. Your comment on making a change fixing the problem, needs to be careful, a broken leg can be fixed with an amputation.  . Related also somewhat, the comment often made on this topic, and I can't dispute, and have yet to see/hear conclusive proof of, is caps fail because of broken teeth jamming the gears, and then over stressing the cap(S). I am not clear how one definitely determines that order of failure.
Reality check, that half the population is smarter then 50% of the people and it's a constantly contested fact.
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