Re: 8.75 diff near-death experience
[Re: 70Drop]
#2580802
11/20/18 10:14 PM
11/20/18 10:14 PM
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Joined: Nov 2003
Posts: 36,041 Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
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It sounds more like it was just a perch failure (kinda rare tho) as opposed to the 8&3/4 being inadequate for your app.
live every 24 hour block of time like it's your last day on earth
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Re: 8.75 diff near-death experience
[Re: 70Drop]
#2580809
11/20/18 10:21 PM
11/20/18 10:21 PM
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Joined: Jan 2003
Posts: 8,028 Tulsa OK
Bad340fish
master
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master
Joined: Jan 2003
Posts: 8,028
Tulsa OK
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Were the welds factory? Mine failed on one side once, didn't break the pinion but put a hell of dent in the floor.
The factory weld had almost zero penetration, its a miracle it lasted the 35years it did before it broke.
68 Barracuda Formula S 340
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Re: 8.75 diff near-death experience
[Re: 70Drop]
#2580812
11/20/18 10:28 PM
11/20/18 10:28 PM
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Joined: Jan 2003
Posts: 8,028 Tulsa OK
Bad340fish
master
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master
Joined: Jan 2003
Posts: 8,028
Tulsa OK
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I will add if you are going to replace the perches replace them with the ones from Calvert Racing or make some gussets to make the stock ones stronger.
68 Barracuda Formula S 340
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Re: 8.75 diff near-death experience
[Re: Bad340fish]
#2580820
11/20/18 10:39 PM
11/20/18 10:39 PM
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Joined: Jan 2005
Posts: 223 California
70Drop
OP
enthusiast
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OP
enthusiast
Joined: Jan 2005
Posts: 223
California
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Were the welds factory? Mine failed on one side once, didn't break the pinion but put a hell of dent in the floor.
The factory weld had almost zero penetration, its a miracle it lasted the 35years it did before it broke. The welds were definitely not factory. The springs were re-located 1.5" inward by the previous owner. I'm guessing they were his welds
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Re: 8.75 diff near-death experience
[Re: 70Drop]
#2580826
11/20/18 10:49 PM
11/20/18 10:49 PM
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Joined: Feb 2005
Posts: 20,185 PA.
pittsburghracer
"Little"John
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"Little"John
Joined: Feb 2005
Posts: 20,185
PA.
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I have a heavy-duty bolt-in sprag and a billet drum, so hopefully the trans. is OK, but I was also worried about the trans.
I will definitely reinforce the perches. I saw the Calvert ones. Other than being kinda expensive, they look like good pieces Take the transmission apart or start saying your Prayers right now.
1970 Duster Edelbrock headed 408 5.984@112.52 422 Indy headed small block 5.982@112.56 mph 9.42@138.27
Livin and lovin life one day at a time
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Re: 8.75 diff near-death experience
[Re: 70Drop]
#2580835
11/20/18 11:07 PM
11/20/18 11:07 PM
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Joined: Aug 2003
Posts: 43,228 Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,228
Bend,OR USA
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Before you decide one way or the other on reusing the current 8 3/4 check the housing for straightness now and then decide My Duster had a bunch of mid to low 10. second runs on it when it bent the heck out of the housing enough to break the ladder bar mounts welds loose from the housing Luckily that happened on the starting line and not going into 3rd gear It may have been bent a little to start with after having it narrowed I have someone help me check the housings by using two carpenter square and measure off of the axle flanges or the rear end bearing ends 14 to 16 inches out from the center of the axle to the front and rear and up and down as much as possible, if it varies more than .125,1/8 inch or more, between the front and rear or top and bottom measurments it is bent more than it should be Let us know what you find and decide to do
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: 8.75 diff near-death experience
[Re: Cab_Burge]
#2580849
11/20/18 11:26 PM
11/20/18 11:26 PM
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Joined: Feb 2005
Posts: 20,185 PA.
pittsburghracer
"Little"John
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"Little"John
Joined: Feb 2005
Posts: 20,185
PA.
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Might want to check the tailshaft for cracks and the tranny mount while you’re under there.
1970 Duster Edelbrock headed 408 5.984@112.52 422 Indy headed small block 5.982@112.56 mph 9.42@138.27
Livin and lovin life one day at a time
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Re: 8.75 diff near-death experience
[Re: pittsburghracer]
#2580851
11/20/18 11:33 PM
11/20/18 11:33 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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We are talking about 12"? (4x3"?) of weld all loaded in shear. That would have to be some pretty crappy weld.
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 diff near-death experience
[Re: 70Drop]
#2580993
11/21/18 11:21 AM
11/21/18 11:21 AM
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Joined: Dec 2006
Posts: 2,115 Byron, NY
W.I.N. Racing
top fuel
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top fuel
Joined: Dec 2006
Posts: 2,115
Byron, NY
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I have a heavy-duty bolt-in sprag and a billet drum, so hopefully the trans. is OK, but I was also worried about the trans.
I will definitely reinforce the perches. I saw the Calvert ones. Other than being kinda expensive, they look like good pieces To Pittsburg's point, Have your sprag checked. The fact that is a bolt in doesn't mean it wasn't stressed. **taken from a well written post by PC-Charger "So what do you need to do to minimize the chance of witnessing first hand one of these explosions? If you read and understood the above, you can see that a simple bolt in sprag/roller clutch will do little to nothing to prevent a roller clutch failure of this type. Rarely is the problem of the outer race turning in the case a factor in a drum explosion. Not to say that a bolt in roller clutch is not a good thing, just that it will not help with this type of failure. The stock and most aftermarket roller clutches for the 727 utilize 12 rollers and springs. The super sprags from A&A and Coan have 16 elements. These units may offer some relief from this type of sprag failure simply because with the added elements there is less room for the legs to bend back far enough to allow the rollers to slip or fall out of place. The 16 element clutches are probably a good idea not only for this reason but also their added holding power" Even if you have a Billet/Steel drum
'01 P1500, Blown/Inj BAE,/Veney ,Bruno/CS2,Dana 60 '01 Dodge 3500 S Cummins Auto, Fresh air kit, 4" Exhaust, '05 Dodge Magnum R/T - Too Much to list '60 Willys CJ5 '01 International LPX - Project,DT466, Allison '64 Plymouth Valiant, Inj 528 Hemi, 2spd
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Re: 8.75 diff near-death experience
[Re: 70Drop]
#2581214
11/21/18 07:05 PM
11/21/18 07:05 PM
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Joined: Jul 2004
Posts: 19,318 State of confusion
Thumperdart
I Live Here
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I Live Here
Joined: Jul 2004
Posts: 19,318
State of confusion
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Thanks for the cautionary information about the trans. I will definitely take it out and have a look inside and for cracks in the tailshaft housing. My sprag is the one referred to as the "Ultimate Sprag" and includes more rollers as was mentioned in the write-up. Hopefully it held.
Back to the diff, I've seen write-ups that say to use a billet cap on the driver's side bearing. The price seems kind of high at $100, but if it gives any insurance against future failure, seems like it would be worth it I didn't have tons of passes on mine when I changed it out a couple of years ago but is was behind a mid 9-second 470 bb at 3100+ lbs and in the 1.33-1.35 60's with stock caps. I went with the nodular from Dr.Diff and it's heavier and has thicker webbing to strengthen it plus forged caps so maybe this will last me another 16+ years.........
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 diff near-death experience
[Re: 70Drop]
#2581276
11/21/18 09:39 PM
11/21/18 09:39 PM
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Joined: Aug 2003
Posts: 43,228 Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,228
Bend,OR USA
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Back to the diff, I've seen write-ups that say to use a billet cap on the driver's side bearing. The price seems kind of high at $100, but if it gives any insurance against future failure, seems like it would be worth it All the OEM 8 3/4 third members are made of cast steel according to what was said at the old Mopar drag race seminars back prior to 1980 so adding a billet steel cap to them is a good deal to do instead of counting on the stock cast steel cap with the adjuster bolt hole in the center of it to hold up to constant drag strip abuse I've used 3rd members with a single steel cap on the drivers side and one with both steel caps on it, neither one of them prevented me from cracking the ring gear teeth at the outer corners though on all of them when you start going fast and pulling 3 to 8 inch wheelies on every run I ended up going to a Dana 60 after breaking a lot of 8 3/4 parts in that car No more problems ever after that
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: 8.75 diff near-death experience
[Re: 70Drop]
#2581314
11/21/18 11:00 PM
11/21/18 11:00 PM
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Joined: Jan 2003
Posts: 20,815 A collage of whims
topside
Too Many Posts
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Too Many Posts
Joined: Jan 2003
Posts: 20,815
A collage of whims
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Me, I'd go to a Dana 60 from Dr. Diff, have the perches braced, and go pound on it for years & years. I'm not a fan of a rearend pitching the car into the wall, flexing & steering the car, or breaking the trans up. Yeah, it's heavier, your perches were the cause of your problems - not the 8.75 - I get all that. But for a little extra money, you won't have to worry about the rearend holding up. Been there done that.
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Re: 8.75 diff near-death experience
[Re: pittsburghracer]
#2581580
11/22/18 04:30 PM
11/22/18 04:30 PM
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Joined: Oct 2004
Posts: 3,097 back in Georgia
dthemi
master
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master
Joined: Oct 2004
Posts: 3,097
back in Georgia
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I have a heavy-duty bolt-in sprag and a billet drum, so hopefully the trans. is OK, but I was also worried about the trans.
I will definitely reinforce the perches. I saw the Calvert ones. Other than being kinda expensive, they look like good pieces Take the transmission apart or start saying your Prayers right now. Every broken rear I've ever had has broken something in the trans...Bess be a check'n dat sir.
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