741,742,489 differences

[cavemanno1]

Hi guys!

I have tried to google it but i just couldn't find the answer for it!What is the difference bettween these three?I know the 741 is the weekest of all and they have a cone type and clutch type 742 with the clutch type being better.I just would like to know if i had a 741 in a 383 4 speed should i get a 724 or 489?Or original 4 speed cars came with 742 or 489?
Don't have a specific car yet so I'm just trying to educate myself over these.

Thanks you!

Peter

[Bronzedodge]

The 741 casting - 1 3/8 pinion.  742 casting - 1 3/4 straight pinion.  Shares a nut and yoke w/ the 741.  The 489 casting - 1 7/8 pinion (tapered).  Some consider it the strongest.   Sure grip types interchange as long as the matching bearings are used.   

[tan top]

 
   what BD said  



the 489 is considered the strongest  , as far as I know  , ! because of the pinion diameter , but  has a crush sleeve to set pinion depth ,   the 742 is the next  strongest / or considered nearly the same as the 489 , but has the more desirable shims to set pinion depth ,
the 471 is considered the weakest ,  imo would have thought it would stand up well to even a 440  making some power , unless its a four speed with slicks    ...    big power & torque  , from a worked 440 & hemi  , with drag strip starts with a four speed  or  auto , and with trans brake  & slicks ,  your be  needing  a Dana .

just for info , the grandnationl chargers / roadrunners   , ran a 8-3/4 rear   , behind  600 horse hemi & a four speed !    

depends how the car is driven / used for , driving style etc etc

[tan top]

info here   

http://www.mymopar.com/Mopar8_75RearEndGuide.htm

[cavemanno1]

Thanks Bronzedodge and Steve!

[John_Kunkel]

the 489 is considered the strongest  , because of the pinion diameter ,

Opinions vary; the larger stem 489 also has a smaller rear bearing and the bearing is what takes the load under hard acceleration.

[tan top]

the 489 is considered the strongest  , because of the pinion diameter ,

Opinions vary; the larger stem 489 also has a smaller rear bearing and the bearing is what takes the load under hard acceleration.

oh  , that's interesting ,  never knew that  !  thanks for sharing the info John !!  appreciated   

[BSB67]

the 489 is considered the strongest  , because of the pinion diameter ,

Opinions vary; the larger stem 489 also has a smaller rear bearing and the bearing is what takes the load under hard acceleration.

Personally, I would take the 742.  The pinion diameter is not the weak link. 

[fy469rtse]

Yep I agree with John and bsb67,  742 the strongest of the 8 3/4. 489 close if you get solid sleeve instead of crush sleeve,
Inner bearing is a slightly weaker point, but if you break this , you should have been running a dana

[tan top]

 interesting stuff  Guys    

have a 742 in the charger  

, for years I had heard  & even read  the 489 was considered the strongest , or the best centre section to have  out out of the three  , only the crush sleeve being the problem ,  & the 742  was the next best thing  


oddly enough I remember a magazine  article in the late 80s  , on the different 8-3/4 centre sections , that mentioned 489 was the strongest , also  said  , you cant fit  2.94  gear set in a 742 centre section , ring gear too big !!  ,  i figured out that this article  might not have been 100% correct    , because i  had a 2.94 & clutch type sure grip , in the 742 , in my charger when i got it  , & still in there now  

 

[John_Kunkel]

When the rear end is under hard acceleration, the pinion tries to screw itself out the front of the housing; this is why the rear pinion bearing size matters, bigger bearing handles bigger load...both lateral and thrust. OTOH, at the same time the head of the pinion is being deflected to the left (severe deflection leads to gear failure) so the size of the pinion stem determines how much it can deflect; so both the bearing size and stem size determine strength.

Too bad Mopar didn't incorporate both the large stem and a large bearing in the same third member.

[tan top]

When the rear end is under hard acceleration, the pinion tries to screw itself out the front of the housing; this is why the rear pinion bearing size matters, bigger bearing handles bigger load...both lateral and thrust. OTOH, at the same time the head of the pinion is being deflected to the left (severe deflection leads to gear failure) so the size of the pinion stem determines how much it can deflect; so both the bearing size and stem size determine strength.

Too bad Mopar didn't incorporate both the large stem and a large bearing in the same third member.

more good info , John , thanks for sharing 

[BSB67]

When the rear end is under hard acceleration, the pinion tries to screw itself out the front of the housing; this is why the rear pinion bearing size matters, bigger bearing handles bigger load...both lateral and thrust. OTOH, at the same time the head of the pinion is being deflected to the left (severe deflection leads to gear failure) so the size of the pinion stem determines how much it can deflect; so both the bearing size and stem size determine strength.

Too bad Mopar didn't incorporate both the large stem and a large bearing in the same third member.

more good info , John , thanks for sharing 

I've broken only one, and been around only a couple of others.  These failures did not seem to be main pinion shaft related.  And people seem to have different reasons for their failures.  Caps, cross shafts, spider gears, small pinions, and the pinion and ring gear.  Some claim it is the housing itself.  My take away from all this is that everything in the unit approaches its failure point at about the same time.

Most seem to agree that the crush sleeve on the 489 is a problem and should be replaced with a solid sleeve.

[tan top]

When the rear end is under hard acceleration, the pinion tries to screw itself out the front of the housing; this is why the rear pinion bearing size matters, bigger bearing handles bigger load...both lateral and thrust. OTOH, at the same time the head of the pinion is being deflected to the left (severe deflection leads to gear failure) so the size of the pinion stem determines how much it can deflect; so both the bearing size and stem size determine strength.

Too bad Mopar didn't incorporate both the large stem and a large bearing in the same third member.

more good info , John , thanks for sharing 

I've broken only one, and been around only a couple of others.  These failures did not seem to be main pinion shaft related.  And people seem to have different reasons for their failures.  Caps, cross shafts, spider gears, small pinions, and the pinion and ring gear.  Some claim it is the housing itself.  My take away from all this is that everything in the unit approaches its failure point at about the same time.

Most seem to agree that the crush sleeve on the 489 is a problem and should be replaced with a solid sleeve.

      more good info  , thanks for sharing 

[c00nhunterjoe]

I ran a stock 489 until it scattered the suregrip cones. Put a 742 in and never broke it. Just kept breaking axles (stick car).

[John_Kunkel]

Most seem to agree that the crush sleeve on the 489 is a problem and should be replaced with a solid sleeve.

I've always been baffled by this assertion; some seem to think there is reliability problem with the crush sleeve and this doesn't make any sense because the sleeve isn't subjected to any real loads in use. However, from an installation standpoint, it's more of a PITA than a problem.

[c00nhunterjoe]

Crush sleeves are only a problem if you dont k ow what you are doing. My diesel made 800 ft lbs of torque going through a stock crush sleeve rear.