741 Center Section question?

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demon34071

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I have been noticing that you never seem to see any 489 or 742 center sections in the 3.91 suregrips for sale anymore. I have been looking for a while (which is fine) but it posses the question as to why??? Other than the obvious being that is is like the 3.55's being it is a very desirable center section and gear combo. But I do notice that 3.91 suregrips in the 741 center seem to be everywhere.

Was it that the 741's centers where in low HP trucks and the 3.91 / 4.10 gears where used in them the most??

Also what realistically can a 741 handle HP wise: I don't need a long speech about how you wouldn't use one etc, I'm just looking for some technical data on what they are living up to HP in the real world.

Granted we have all been there where we pushed the envelope to far on 35+ year old parts and they failed, but back in the day what could these 741's hold up to.


I know I ran a 741 SG- 456 gear in my drag car for years till I got sweet deal on a 742 456 spool and the housing and pinion held up fine, but the $50 junk yard SG units I was putting in it would only last 2 - 3 days at the track.
 
The 741 was an early unit with a smaller pinion gear. Mine has held up to high 11 sec. 1/4 times, over 450 hp from a 360 backed by a 4spd in a E-body Cuda. While not a fire house of a engine, it has seen use and abuse for the last 20 years.
 
I have heard the same thing over the years. And mine held up great behind a 400HP 340 running low 12's / high 11's for years as well.

I am looking at a 500+ HP 416 stroker motor for a protouring Demon and wondering if a 741 391 SG would hold up in rear?

Car may go down a track a couple times in its life just to get a time ticket, but otherwise its going to be street car with attitude
 
Hummmm, I see. I can not say for sure about the casting number being a good to go number for that power. The 8-3/4 has been seen to hold up behind big block strokers running 9's. IIRC, the 741 is just a hair smaller than the 742 which is a hair smaller than the 489. (Exact sizes escape me right now)

I really do not see a problem, but I also can not say for sure since I have not been there and done that or know for sure of someone that has with that 741 case.
 
...........I've been running a 741 in my drag car for 20+ years............11.001.............with a 1.34 60 foot.......on a 12.2x31.25 tire................kim.............
 
I have a 741 Case SG with 3.55 Gears behind a 410 Stroker 4spd. I dont baby the car at all and it lives. It appears to be the factory unit to me and I have never taken it out. It will not hook out of the hole on the street maybe that is why it lives. Once at a roll in 1st gear at about 15-20 mph it hooks fine and I bang the gears violently, and it lives. When you get something to hook out of the hole that is where it will find the weak spots and eventually something will break leading us to UPGRADE the parts so hopefully it will not happen again.
I did buy a NODULAR 489 Case for my 67 Dart with SG and 3.91 Gears. The NODULAR case is BEEFIER than the factory type 489. When I had it built I asked the guy at the shop to put Studs and Mark Williams Caps on it, he said WHY you don't need it, it is already beefed up, he did put ARP BOLTS to hold the caps though because I bugged him about it. FYI
 
I think the Moparts tech archives has a pretty good info page on all the different rear ends out there. I think it was Dr. Diff that even posted all the info. He compared pinions across all the different manufacturers and explained how even though the different cases all have different pinion diameters they all still had a 90 degree step at some point which would be the weak point. Also there is the common point made that the 741 is still a thicker pinion than the Ford 9". Try this link, it should be the article http://www.moparts.org/Tech/Archive/axle/1.html.
 
Most a-bodies, even into the 70's came with 741's from the factory. It was Mopars way of using up old housing stock. 741's are very underrated.

Being 741's have a straight pinion it requires a spacer for the shims.

Chuck
 
IMO, most of the 3.91 gear sets came in trucks/vans. I find them mostly in trucks/vans. Think how tough it is to find an axle packaged A body car. There just aren't a lot of them out there.

741's can handle 500-550hp as long as they are put together well. The ring gear and drivers side cap is the weak point, NOT, the pinion bearing diameter that gets tossed around.

As far as the SG going away in 2-3 trips to the track, they were likely pretty worn before you got there.
 
"As far as the SG going away in 2-3 trips to the track, they were likely pretty worn before you got there" ---- This didn't surprise me at all, that's what I call racing on a budget.

"Most a-bodies, even into the 70's came with 741's from the factory. It was Mopars way of using up old housing stock. 741's are very underrated" --- This seems to be what I am finding out as well

"741's can handle 500-550hp as long as they are put together well. The ring gear and drivers side cap is the weak point, NOT, the pinion bearing diameter that gets tossed around." --- Isn't this the case though even with 489 & 742 housings, unless put together well they will all fail eventually.

Its seems like where I look 741's will hold up for what I am planning -- And it also seems like everyone agrees that are not for extremely racing (which I am not racing at all) so this isn't applicable to my situation. . . . . okay now the search continues for some 3.91's SG

Thanks All!!!!
 
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