742? 741?

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oldkimmer said:
............My 11.001 drag car has a 1.34 60 ft....on 12.2x31.25 slicks....4 over 20 years.......with the 741..........kim.........
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Still have the 741 case 3.23 sure grip in my dad's 440 powered Charger going on 25 years.
 
SGBARRACUDA said:
Actually the 9" uses 3 bearings on the pinion. It also has a caged roller bearing on the nose or very end of it. It has to, the front and rear bearing are so close together that it had to use the third bearing to stabelize the pinion.
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thanks for clearing that up. i just knew they were supported on both ends
 
irelandmoss said:
So, bottom line is, look for a 742 because it's more dependable?
Bill
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Bill, If I were you, and if you have the time to put together the optimum center section, I would look for a 742 case, with your choice of gear (probably a 3:91), and a clutch style suregrip unit. Thats the best case scenario IMO. Yes, you can use any case, gear ratio and suregrip and it will be perfectly fine, but if you are not in a hurry, go for the best case scenario. Just my opinion, Geof
 
Thanks for the info. That's exactly what I want to do.
I was talking to a friend that is a mechanic. I told him
I want to go big block, 727 trans and 3:91 gears.
He told me that nobody will touch it with that setup.
Bill
 
irelandmoss said:
Thanks for the info. That's exactly what I want to do.
I was talking to a friend that is a mechanic. I told him
I want to go big block, 727 trans and 3:91 gears.
He told me that nobody will touch it with that setup.
Bill
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To answer your one question about putting the 742 pinion in the 741 case thats not going to work. You can swap just the suregrip cluster from all 3 housings but you need to keep the bearings with the cluster. I personally would look for a 742 or 489 if I was putting a big block in front of it, plenty out there to chose from. To save money now you could use the 741 until you find a better one. Does your 741 have the suregrip in it now? If so then all you have to find is an open 742 or 489 and do the cluster swap.
 
Not sure if it has the sure grip or not. When the weather
breaks here (I'm guessing around July) I'm going to hit some
scrap yards and find the whole rear. It may be a lot easier.
Bill
 
We know the car would be faster with A 7 1/4 even 8 1/4 but we had to go with the rear end that when, people look under the car,
rolleyes.gif
they know what it is. So with all this said we have done A little testing @ the track with the 8 3/4. We started with the 489 center unit. Five passes on the car running 16.41 at it's best. The next unit was A 472 about 1 hour later the car ran 16.37
So the last change we did for the day was the small pinion 471 it and ran A 16.27 this time. All these units running the same gear and oil, run on the same side of the track in the same day, this was alot to do in one day and very hot!! The quick change 8 3/4 makes this possable with jacks stands and battery impacts tools and A helper. For all you gear heads its faster.
grin.gif
 
Mister Twister, the small amount of change E.T. change between the 3 cases could hardly be attributed to the case itself, considering the time it takes to change out a center section, the temp and RH change during that time, and the cooling or heating of the track. Sun, engine temp, trans temp, all play a part in determining that change, and such a small change (less than 2 tenths) to me is not worth the risk of running the smaller unit. I know the 741 is a good unit for most mid-HP applications, and I never downplay the 741, but IMO, the 742 I mentioned above would still be the best unit overall!!! Just my .02, Geof
 
cosgig said:
Mister Twister, the small amount of change E.T. change between the 3 cases could hardly be attributed to the case itself, considering the time it takes to change out a center section, the temp and RH change during that time, and the cooling or heating of the track. Sun, engine temp, trans temp, all play a part in determining that change, and such a small change (less than 2 tenths) to me is not worth the risk of running the smaller unit. I know the 741 is a good unit for most mid-HP applications, and I never downplay the 741, but IMO, the 742 I mentioned above would still be the best unit overall!!! Just my .02, Geof
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Agreed, .14 second e.t. difference is normal variation for most any car given it was done throughout the day. If anything the 742 should have been the slowest because it has the heaviest pinion (1-3/4" the full length vs. a tapered pinion in the 489 case) and largest bearings. Yet in your test the 489 was the slowest. JMO
 
Hello motor heads. This is just the way it came out. Had alot of time on my side that day. Sounds like the 742 will be fine for him!!
 
Yes we did fishy68. Hope to be back out soon. Thanks for the input see you later Don
 
Don, I am more impressed by your tenacity to change the center section 3 times in one day than the results!!! I am also impressed by your forethought to test something that most would not even think to make a difference. As for all your extra time... you obviously do not have a 5 year old!!! Mine seems to soak up all that extra time, but I wouldn't have it any other way!!! Thanks for the test results, now on to the next test!!! What exactly is that going to be???LOL!!! Geof
 
cosgig said:
Mister Twister, the small amount of change E.T. change between the 3 cases could hardly be attributed to the case itself, considering the time it takes to change out a center section, the temp and RH change during that time, and the cooling or heating of the track. Sun, engine temp, trans temp, all play a part in determining that change, and such a small change (less than 2 tenths) to me is not worth the risk of running the smaller unit. I know the 741 is a good unit for most mid-HP applications, and I never downplay the 741, but IMO, the 742 I mentioned above would still be the best unit overall!!! Just my .02, Geof
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I was thinking the same. My car changes that much or more as the temp and wind changes. A different sized pinion shaft ain't going to change anything in quarter mile times.
 
I have a 741 in my 70 Coronet with a built 440. When I was younger I beat the crap out of that thing every time I drove it! Its still fine, just the cone posi crapped out.





Oh wait, I mean sure grip. Better state that before someone rips me a new one.
 
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