difference between a 742 and a 489?

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moparman111

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Guys not to sounds stupid but whats the differences from one to the other? I know I have read members state that a 489 was better but I am not sure why? Thank you
 
742 - 489 = 253


But really, one of them is stronger.
 
pinion shafts are different sizes i think the 741 is 1 3/8"
742 is 1 3/4"
489 is 1 7/8" but tapered
 
742 also uses shims to set the pinion depth while the 489 uses a crush sleeve, making it a little harder to set the depth! Of course now they have a hard spacer kit available for that!!

I'm partial to the 742 myself, and run them and clutch style SG units! Your preferenceay vary! Geof
 
How much power are you going to put to it?

What gear ratio do you want?

There are more gear sets for the 489 case than a 741

I have 3 741 cases. They were in the small block darts with 340s and held up well. But now try and get a set of 3:91 gears, not available

Had a set of 3.73 put in my 741 case and they whine so bad think they are coming back out and a factory set of 3.55 in a 489 case going in or the factory 3.23 in a 741

Read the 742 case was used in the big block Darts, don't know what else used them but probably b body cars

If you have a choice pick the gear ratio you want in a good quality gear, then a case it will fit in.
 
Surprising how the "lowly" 741 pinion compares to a Ford 9'' pinion.

Wildcat, what brand 3.73 gears did you get? My 3.73 set whines a little bit and my trans guy reset it a few times. Its mostly gone at 2000 miles. They are Liberty gears.
 
fratzog lover said:
Surprising how the "lowly" 741 pinion compares to a Ford 9'' pinion.

Wildcat, what brand 3.73 gears did you get? My 3.73 set whines a little bit and my trans guy reset it a few times. Its mostly gone at 2000 miles. They are Liberty gears.
Click to expand...


Yeah, I thought that the 741's were "black sheep"....
 
440 with roughly 450hp. Its a stout motor as it propelled a steel bodied Duster to 11.80's at 112mph on slicks and 4.10's. Not my car but I heard it run in car before buying it.

I want to run 3.91's if possible. But would settle on 3.73's if I could find a good deal. Its going to be a street bruiser on the weekends, possibly see Mason Dixon from time to time.
 
fratzog lover said:
Surprising how the "lowly" 741 pinion compares to a Ford 9'' pinion.

Wildcat, what brand 3.73 gears did you get? My 3.73 set whines a little bit and my trans guy reset it a few times. Its mostly gone at 2000 miles. They are Liberty gears.
Click to expand...



Been a few years DONT remember the brand, they are noisy, were reset about 1,000 miles ago and didn't change a bit from before or after.

Was told by Rick Allison of A&A transmission that many of the aftermarket gears are not cut right and no matter what you do will whine.

Going with a 450 hp big block think you would want the bigger pinion than in the 741 case, but I'm no expert, that is what the factory did for a stock big block
 
I think US Gear had a street series that was "softer" than their race gears and produced less noise. Thought it was funny they admitted that their gears were noisy.
 
As long as they arent wearing bad pishta, Im not concerned with a little whine. The break in process however is an excercise in restraint! I was a good boy for 400 miles.
 
fratzog lover said:
As long as they arent wearing bad pishta, Im not concerned with a little whine. The break in process however is an excercise in restraint! I was a good boy for 400 miles.
Click to expand...

You're a better man than me, I ran my new gears for a very short time before the tires started slipping, lol. Oops!
 
People still believe the 741's are weak... ???????

The rear pinion bearing size is NOT relevant to the strength of any of the cases, but some writer published something about low HP cars for 741's and people eat that **** up. There are no stress risers on a 741 pinion either, is that important? :) All of them have the same step down to the yoke, guess where every one I've had break take a powder... nothing to do with the rear bearing!

That single article has persuaded thousands of people to spend untold $ on 489/742 units that provides no reasonable benefit. I'll take every one of those cheap, fragile, redheaded step children 741 cases since they are worthless and weak. LOL Might even put one in the next 10.00 car. :)

There is a reason the 9" has a smaller pinion bearing set on it, might be where the bearings are located.
 
My 69 Super Bee came with the 742 case{factory stock} and the only thing that ever broke in it was a set of Zoom 4:56's/ Snapped the pinion gear at the front bearing with a 6 grand jump at the starting line. :) Damn thing would lift the left front about 1 inch off the ground with that hole shot. :-D OH yeah also had 9 inch slicks on it too!

Jim
 

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fratzog lover said:
Surprising how the "lowly" 741 pinion compares to a Ford 9'' pinion.

Wildcat, what brand 3.73 gears did you get? My 3.73 set whines a little bit and my trans guy reset it a few times. Its mostly gone at 2000 miles. They are Liberty gears.
Click to expand...

Because Ford trundles the pinion shaft with 2 bearings instead of one, they can use the "lowly" 1 3/8" pinion shaft! Nothin wrong with a 741 in my eyes!! Geof
 
I pound on my 741 also, and dont have any worries especially on street tires. This urban legend about it being "weak" should be long gone by now.
 
I found some rear axle info that suggests the lowly 741 was used for the Max Wedge,, link supplied,

64 Max Wedge 53-1/4"

Parts Manuals list four different axles for this housing:
2070573 - 741 case w/o SG 30-1/2" overall;
2404003 - 742 case w/o SG 30-1/2" overall;
2070695 - 741 case SG 30-7/16" overall;
2404050 - 742 case SG 30-7/16" overall;

http://www.bigblockdart.com/techpages/875axle.shtml

and I've seen it other places as well..

hope it helps
 
I got so tired of all the discussion, I just tell people the truth, I've got a 657 case in mine. Let them figure it out.
 
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