741 case w/3.91 SG?

[*Mopar*]

Is $300 a good price for a 741 case w/3.91 SG? $300 is
including the
shipping to my door.

Thanks in advance,
Stoney

[Dartcustom]

Is it any good? or are you going to rebuild it. The 741 is the smallest pinion of all the 8-3/4's. If the suregrip unit is junk then all your paying $300 for is the pumpkin and used ring and pinion. Probably not worth $300 if thats the case. If it is known good unit then it's worth it.

[ehostler]

I just watched a good clean 3.91 SG in a 489 case go for $310, on ebay. I know where I can get a 4.56 SG in a 489 case for $250 (gears need to be properly setup).

Just rememer that the 741 is not going to accept anywhere near the torque that a 742 or 489 case will. Other than that, I would say that it is a good deal.

[concord997]

ehostler...Darn, just about the time I think I've got it together, I get shot down... REARENDS.. I've heated my engine a bit, cam,302 heads/1.88/1.60 cam and lifters...ETC ETC....now i'm trying to get a SG for my 741 (2.94) and you say the rear isn't strong enough, ....So now I'll be looking for a 489 (2.94) If you have any more info, shoot it my way. The 2.94s are by choice.... Thanks, Don

[sixpackcuda]

I have a 741 case with 3.91's in my 70 Cuda with a 340-6 pack and it handles it fine. The only problem is try finding gears for the 741 case! You won't unless you buy used! The posi unit itself is one of the best as it is rebuildable and can be transfered to any other case.
I'll buy that 4.56 in the 489 for $250 if it's available.
I have an empty 489 case I plan on putting the posi unit from the 741 into with maybe 4.30 gears.

P.S. Have you ever heard of anybody blowing up a 741 case?

[ehostler]

It's not so much blowing up the case. It's snapping the thin shaft on the pinion. If you are running a 4 speed, with alot of torque, you want the 742 or preferably the 489. Because of the way an automatic works, the 741 should survive a little more torque.

From Auto Hobby Digest:

Strength Considerations
-----------------------
Pinions...

The 1-3/8" '741' pinion is the weakest. It is still a capable unit in most moderate power, moderate traction street applications. For high torque applications with high traction tires, the 1-3/4" or 1-7/8" should be considered.

The 1-3/4" '742' has a larger rear pinion bearing yielding greater strength in this area. The 1-3/4" shares yoke mount diameter and mounting nut with the 1-3/8".

The 1-7/8" '489' is supposedly the strongest. Although the stem tapers down along it's length, it appears inherently stronger from a pinion stem perspective and the inherent strength of the fine splines (OEM gears).

For perspective, the 7-1/4" has a 1-3/8" pinion, the 8-1/4 has a 1-5/8" pinion, the 9-1/4" (70s) has a 1-7/8" pinion.

As far as the 4.56 gears in the 489 goes, they are in WV. I have no idea of what the cost of shipping would be. The guy that is selling them is Andy. His email is grimms@peoplepc.com

[Doug Wilson]

There really is no problem getting new gears for the 741. I just bought a set of 3.55s from Randy's - I think the web site is: ring-pinion.com, or maybe randysring-pinion.com

Got them for a 450 HP 340, and Randy's said the 741 will handle that fine.

[concord997]

Thanks GUYS... I don't have a ground pounder, but I do want the rear to hold-up. Now all I have to do is find a S.G.!!! Summit I guess..... Thanks again......Don

[ehostler]

Randy's can set you up with a new SG as well. If you ship them what you have, they will properly assemble everything, as well.

[concord997]

EHOSTLER, thanks, I might have to look into that, Have a good day, Don.

[Doug Wilson]

Randy's is good people - also about the least expensive rear end guys out there.

[*Mopar*]

Thanks to everyone for the replies. I'm going to take the SG. It is the cluch style. Hope it is what I expect.

Stoney

[ehostler]

Originally posted by Doug Wilson
Randy's is good people - also about the least expensive rear end guys out there.

Randy has also been in business for 20 years. That says alot about a rear end shop. He also just opened a new shop in TN, so that he can beter serve both coasts.

[71383bee]

I am running a 3.91 SG in a sure grip case and so far I haven't had any issues with the gears per say.

[Dart]

Isn't the 489 case the one that has the crush collar? From what I remember the 742 case is the better unit.

[pishta]

I had a 340/727 Herbert stage 2 cammed motor that had tons of torque with 11 inch tires, and it took me 6 months to shred a 7 1/4 rear end. This was in a light car and I took the teeth off the pinion, it didnt snap. If you got the 741 in a heavy car, then
worry.

[dirty dan]

the 489 in my opinion is the better unit.
If you have a real heavy car with an 8 3/4 open face behind a fresh factory 440 ,don`t enter any burnout contests.
If you do you may find your self limping home at 10mph .
Hearing many pops ,bumps,snaps,grinds,crunchand all the other sounds that make the hair stand up on the back of your neck.
That would be the sound ofwhat use to be spider gears.
This delema happens in any of the cases .But the 489 has alarger dia pinion gear then the rest. I always figure bigger is better. Except for 3 things bills,trouble and femails.
Opps there goes my opinion again.

[*Mopar*]

Again, thanks for all the replys. I never told ya'll what it would be going in. It will be going in my 66 300 w 440. It has 235-70 15's in the front and 255-70 15's(about 29" tall) in the back. Yes the 3.91's are a little Low but it's not my daily driver. And, I plan on doing an overdrive in the furture.

Thanks,
Stoney

[sixpackcuda]

Ouch, that's a big car! What center section is in it now? All my B bodies I ever owned that had a big block,which were all of them, had a posi in it. It may have a posi that just needs a rebuild!?

[ehostler]

I had a '70 Challenger with a 7¼ open rear. The prior owner had upgraded the engine from a 318 to a 383 and backed it up with a Hemi 4 speed. I put in a very heavy McLeod clutch and a Hurst Vertigate shifter. I stripped the pinion gear and shattered the spider gears after about 15 minutes of test & tune.

Nothing the Dana 60, that replaced it, couldn't fix

[and00542]

Okay, the 741 is usually a 7 1/4" unit that is non-sure-grip, right?
Can it be anything else? What else falls in the 741 family?

Now, the 489 is usually a 8 3/4" unit that is sure-grip, right?
Can it be anything else? What else falls in the 489 family?

[sixpackcuda]

No the 741 is a 8 3/4 unit. The 741, 742 & 489 are all 8 3/4 and will go into any 8 3/4 banjo. They can all be posi or open end! Confused yet!!

[Doug Wilson]

The 741 is an 8 3/4 axle and is often Sure Grip.

The 742 is an 8 3/4 rear end, also often Sure Grip.

The 489 is an 8 3/4, and is often not Sure Grip.

The best of the bunch, from a strength stand point, is the 742.

The only way to determine whether the axle is Sure Grip or not, is to either turn one of the wheels with the car on jackstands to see if they both rotate in the same direction, or take the pumpkin out and inspect it to see if it has the Sure Grip parts.

[and00542]

Now that I sorta know what a 741, 742, & 489 are, please explain this:

What's the difference between a 741 & 742?
Sure grip is when both rear wheels turn in the same direction?
What family would a 7 1/4 axle be under?

[sixpackcuda]

The numbers refer to the ring gear size.
Ex: 8 3/4 has a ring gear size of 8.75"
A 7 1/4 has a ring gear size 7.25" Etc.
7 1/4's were mostly found under A bodies and didn't have the removable pumpkin. Not to desirable.

Here is some more:

http://www.houstonmopars.org/rears.html

[Doug Wilson]

Someone did a real good explanation of the differences on this forum in the last week or so. Try the search feature.

Of the 3 - 8 3/4 axles, the 742 is strongest, the 741 is weakest and the 489 is the middleist (that's a new word!!).

Sure grip is both wheels turning in the same direction, when they are up on jackstands.

A 7 1/4 is in the 7 1/4 axle family.

I sense that there is some underlying question here - how about asking it???

[Doug Wilson]

When I was picking a pumpkin for the HELLFISH, I called Randy's. The price on a 741 Sure Grip complete and assembled was about $700. The price for a 742 or 489 case was about $950. I went for the 741 behind a 340 - 400+ HP and Torque Flite. If the car had been a stick, I'd have used a 742, and considered the extra money well spent.