Difference between 741 and 742?

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70DartMike

70DartMike

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What is the difference between the 741 case and the 742 case in an 8 3/4? A guy I know is willing to sell me his 3.91 gears for a 742 case, but the case I've got in my Dart is a 741. Will they fit?
 
741 case is 1 3/8'' pinion--742 is 1 3/4''--489 case is 1 7/8'' and they are all very durable, and if ur still interesed in gears i have a set of 3.91s in all three cases and a set of 3.55s/489 case, just pm me or call KEN at 4174375352 in sw mo, hope this helps.....
 
you havethe weakest 8.75 case,smallest pinion. still good for a 400 horse car more than that gets iffy.
 
According to DR Diff. {and what ive always thought} the 741 has been unjustly overlooked and if u view above posts{TECH} u will get a clearer understanding about 8 3/4 pigs, the 741 is very stong and is beefier than 9'' frauds, and the only 2 advantages of 9'' is case is beefier[GUSSETED] and plentiful,cheaper. Ive seen 10.80 cars with 741's and live multible seasons, chk out the tech above and compare pinion/bearings even on the almighty danas, 741s 742s 489s all MOPAR all GOOD, alot of things you hear is bs and has no merit just check and reserch it yourself and make ur own conclusion
 
daredevil said:
you havethe weakest 8.75 case,smallest pinion. still good for a 400 horse car more than that gets iffy.
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They can take 400 horse all day. I wonder what kind of power the Max Wedge cars where putting to them back in the day?
 
I had installed 742 gears in my 741 case. It was done in 1991, no issues through 2 trashed tranny's, 3 engines. Best guesstimate of max HP any engine in the car is 450+ HP. Gears are 4.10's.
 
Everyone is twisting my meaning. the 741 is the weakest of the 3 8.75s. now can you in good concience tell him to put 5 or 6 hundred horse in front of it? If he has a choice why not go bigger. How many people you see with dana 60s and a 500 horse 3000 pound car? Overkill is piece of mind. So where would you draw the line on hp in a 741, Just cause dr. diff says it it dont mean anything. He,s trying to sell gear sets for them. Do you expect him to talk trash about them. Aint happening. Hell if 741s are so great I have 3 in the garage you can buy. All I offered was my opinion and i cant comfortably tell him a 741 would take 500 horse. 17 in. slicks and a trans brake could probably find its weakness pretty fast.JMHO
 
Rumble is there any mods to run 742 gears in a 741 case 0r is the pinion bearing the only difference? why did ma make 2 different cases when one would handle both gear sets. I got on my thinking cap so school me.
 
And one last thing. I thought 9in. rears were stronger due to the pinion being supported in the rear also so it wouldnt try to walk off the ring gear. Maybe you experts can tell me why you believe these are not stronger.
 
daredevil said:
And one last thing. I thought 9in. rears were stronger due to the pinion being supported in the rear also so it wouldnt try to walk off the ring gear. Maybe you experts can tell me why you believe these are not stronger.
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Yea the ford 9" has a bearing just inside and up against the pinion gear, some I think call them a snoot bearing. Look at your rear ends in highway tractors, like Rockwell, last I remembered they used the snoot bearing also for strength.

Terry
 
Thank you, I try to think everything Mopar is the best but even I need to face reality. But we still have dana 60s but so do they.
 
wstreetrod said:
Changing to a 742 from a 741 does that change the drive shaft length?
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The chunks all use the same driveshaft length, they have the same physical dimensions on the outside.

The only thing you might encounter is a different u-joint size, or different splines on pinion. I believe there is 3 or 4 different yokes/splines for the 8.75"

If both your 741 and 742 already have the yokes on the pinions, no worries if the u-joints happen to be different, you can pick up what they call a Conversion Joint at the parts store to adapt your driveshaft to the different size on the yoke.
 
rumblefish360 said:
I had installed 742 gears in my 741 case. It was done in 1991, no issues through 2 trashed tranny's, 3 engines. Best guesstimate of max HP any engine in the car is 450+ HP. Gears are 4.10's.
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I did the same thing,just used the bearing and races for the 742 case.My car went 10.40s with it and never broke.I got a dana cheap and put it in.There was no differance in times. Mark
 
daredevil said:
Rumble is there any mods to run 742 gears in a 741 case 0r is the pinion bearing the only difference? why did ma make 2 different cases when one would handle both gear sets. I got on my thinking cap so school me.
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Sorry, IDK the details. It was done over 23 years ago when I couldn't fill the front page of a pamphlet of how to do a tune up properly for your HP vehicle.

dartcuda1 said:
I did the same thing,just used the bearing and races for the 742 case.My car went 10.40s with it and never broke.I got a dana cheap and put it in.There was no differance in times. Mark
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Thanks, I was told what you wrote. We just installed it they said. I had no idea I made a mistake on the part purchase. I was just happy they said it wasn't a big deal to do despite the 742 gears into the 741 case.
 
I once bought a 489 chunk from a guy and when I tore it apart I found it had 741 gears installed in it and there were no mods done so it appears that it may be possible to swap most any set of gears for a 8-3/4 into any case if you use the right bearings.
 
.............I had a 489 case with 742 gears in it......didnt know till i took it apart...the 741 has a collar slipped over the pinion to make it 1 3/4, right from factory..........kim......
 
Wow, now I am confused. You are saying that I can take a pinion / ring gear set for a 742 case and put it in a 741? The spool must be different, and what about the sure grip packs?
 
....yes, it can be done.....same spool same sure drip....personally i'd just get the proper 1s 4 the right case....kim.....
 
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