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Re: how much hp can a 8.75 differential take?
[Re: 7D9LRE]
#1170536
02/05/12 01:22 PM
02/05/12 01:22 PM
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Joined: Jan 2003
Posts: 4,588
St. John's Newfoundland
440newport
master
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master
Joined: Jan 2003
Posts: 4,588
St. John's Newfoundland
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Yes. spiders were welded, 3.91 out of a 74 4x4 truck. At least I got 4 derbies and 2 wins out of this rearend before it exploded. no sign of sloop or anything getting loose before giving up the ghost. Stock '72 440 out of a New Yorker. It would lay rubber threw 1st and 2nd gear on dry pavement.
I asked because my first thought was that maybe the weld broke sending debris into the ring gear or spiders and side gears, jamming it up and breaking something?
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Re: how much hp can a 8.75 differential take?
[Re: JohnRR]
#1170537
02/05/12 03:01 PM
02/05/12 03:01 PM
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Joined: Jan 2003
Posts: 75,092
A Banana Republic near you.
JohnRR
I Win
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I Win
Joined: Jan 2003
Posts: 75,092
A Banana Republic near you.
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There is another member on here from maine who can tell you 1st hand that they break pretty easy w a 4 speed and a stroker motor. He has broken a couple 3rd members. Broke the pinion rite off. 742 cases.
Whole different story when popping a clutch on a 4 speed than just launching with an automatic. The other thing is a 742 pinion is smaller in diamenter than the 489 which I run. I am not saying they can't break only that mine has held up fine for 16 years and I would choose it over a Ford Or GM rear anytime. Like I said my next choice is a Dana which the other member should have had to start with with a 4 speed.
this is not a knock at you ....
You have a little misconception in your thoughts about what is stronger . The smallest part of a 742 pinion is the area where the outer pinion bearing is , coincidently the 499 and the 741 are also the same size in that same area , the 489 and the 741 use the same outer bearing . If the 742 broke I'd wager that is where it broke so your theory on the 489 being stronger because the pinion is .125 large under the pinion head doesn't hold up.
In my opinion the 742 is the strongest of the 3 , it's inner pinion bearing has rollers that are about twice the length of the 498 , more like that of the dana 60 and it doesn't have a crush sleeve like a 489, yes you can replace it with a solid spacer. When Chrysler made the aluminum center section they chose the 742 pinion even though the 489 has more gear sets available.
The gear teeth are still the weak point .
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Re: how much hp can a 8.75 differential take?
[Re: JohnRR]
#1170539
02/05/12 06:01 PM
02/05/12 06:01 PM
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Joined: Feb 2003
Posts: 1,532
crisfield, maryland 21817
82ramIndy493
pro stock
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pro stock
Joined: Feb 2003
Posts: 1,532
crisfield, maryland 21817
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Quote:
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There is another member on here from maine who can tell you 1st hand that they break pretty easy w a 4 speed and a stroker motor. He has broken a couple 3rd members. Broke the pinion rite off. 742 cases.
Whole different story when popping a clutch on a 4 speed than just launching with an automatic. The other thing is a 742 pinion is smaller in diamenter than the 489 which I run. I am not saying they can't break only that mine has held up fine for 16 years and I would choose it over a Ford Or GM rear anytime. Like I said my next choice is a Dana which the other member should have had to start with with a 4 speed.
this is not a knock at you ....
You have a little misconception in your thoughts about what is stronger . The smallest part of a 742 pinion is the area where the outer pinion bearing is , coincidently the 499 and the 741 are also the same size in that same area , the 489 and the 741 use the same outer bearing . If the 742 broke I'd wager that is where it broke so your theory on the 489 being stronger because the pinion is .125 large under the pinion head doesn't hold up.
In my opinion the 742 is the strongest of the 3 , it's inner pinion bearing has rollers that are about twice the length of the 498 , more like that of the dana 60 and it doesn't have a crush sleeve like a 489, yes you can replace it with a solid spacer. When Chrysler made the aluminum center section they chose the 489 pinion even though the 489 has more gear sets available.
The gear teeth are still the weak point .
I totally understand and was explained to by Hensley Performance about the teeth area being weak especially due to housing flex. My reasoning was not because that one pinion is stronger or weaker than the other only that the person in question running a 4 speed instead of a automatic to me holds to reason why he tears up 8 3/4s. Launching a 4 speed off the line versus an automatic to me would stress the 8 3/4 more and why he has torn 2 or 3 of them up. My preference in this case would be a Dana. I was already told by Hensley that I should consider the Dana for the next rear choice. I am only saying I would rather have a Dana than a Ford or GM part in my Mopar. To each their own.
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Re: how much hp can a 8.75 differential take?
[Re: JohnRR]
#1170540
02/05/12 08:20 PM
02/05/12 08:20 PM
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Joined: Oct 2008
Posts: 131
central,pa
ply64post
member
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member
Joined: Oct 2008
Posts: 131
central,pa
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I was to busy thinking of how not to offend
Wow,have you ever mellowed!! 
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Re: how much hp can a 8.75 differential take?
[Re: JohnRR]
#1170542
02/07/12 07:48 AM
02/07/12 07:48 AM
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Joined: Feb 2005
Posts: 2,709
NJ central
Scamp408
master
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master
Joined: Feb 2005
Posts: 2,709
NJ central
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I was to busy thinking of how not to offend
Wow,have you ever mellowed!!
I have to if I want to be a member of this forum 
I was only helping out I know JohnRR knows his stuff and has helped me many times. 
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Re: how much hp can a 8.75 differential take?
[Re: Scamp408]
#1170543
02/07/12 11:25 AM
02/07/12 11:25 AM
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Joined: Jan 2003
Posts: 75,092
A Banana Republic near you.
JohnRR
I Win
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I Win
Joined: Jan 2003
Posts: 75,092
A Banana Republic near you.
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Quote:
Quote:
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I was to busy thinking of how not to offend
Wow,have you ever mellowed!!
I have to if I want to be a member of this forum
I was only helping out I know JohnRR knows his stuff and has helped me many times.
+
None of this was directed at anyone in general ...
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