Is a small pinion 8 3/4 strong enough for a mild 440.

Gunner1

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My car is a 63 polara with a 440. CNC Stealth heads, Isky 292 mega cam, Speed Pro 2355 flat tops, Doug’s D452 headers, MSD 6al and billet dist, Ed RPM intake with a 750 Double pumper. A Built 727 with Manual Valve body and a 3k converter. Just some 275/60/15 street tires. Mostly street but a few times at the strip. I want to add a Sure Grip and some 3.73 or 3.91 gears. I just don’t want to spend the money and then find I should have bought a large pinion punkin from the get go. Oh yeah it has Calvert springs and bars and I’m buying their shocks. Also should I switch from the tapered axles at that time or will they live as long as I don’t put on slicks.
thanks. Bob.
 

1 Wild R/T

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MVB/Calverts it would probably be fine but 489 & 742 cases aren't hard to find... Why take the chance?
 

BeepBeepRR

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Just spent 1500 dollars on a 489 case with a eaton truetrack installed and 3:23 gears. I do have a 489 case and sure grip in the for sale section. It needs to be checked out. But all new parts installed.
 

Lefty71

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If you had a small pinion setup, with the right gears and the traction control you want, I would just run it, period. However, if you have to buy the stuff to get what you want, then I would start with a 742, 489 or aftermarket case.... the reason I say this is purely to preserve the value. I don't think you'll break the 741, but if you put money into it, you'll have a much harder time recouping your cash if you sell compared to the 742 or 489 stuff.
 

33 IMP

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Agree with Lefty.
If you have a 741 in nice shape, run it. I doubt you'll break it with a 440/auto combo. (Sticks, with slicks, are a different matter. Frankly, I wouldn't recommend any 8 3/4 for that scenario).
But if you need to invest in gears and/or a limited slip, it's wise to spend money on a 742/489.
As for pinion strength, see Dr.Diffs discussion on his site. He will also have axles to get rid of the tapered axles, which I definitely WOULD do.
 

33 IMP

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.....and for a quick and dirty traction fix, you could throw a Powertrax Lock-right in your 741 open case. PWR-1240-LR, $455 at summit. You won't have to disturb setup to install it.
 
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khryslerkid

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.....and for a quick and dirty traction fix, you could throw a Powertrax Lock-right in your 741 open case. PWR-1240-LR, $455 at summit. You won't have to disturb setup to install it.

Can you still use the taypered axles with taypered bearings? Still have the ability to preload these bearings?
 

furious70

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Not a power house at all but 25yrs ago I ran a 3.91 741 setup in my 3500lbs Coronet with 8" slicks and 1.88 60' times for many passes and it lived just fine. That pig is now in my fury behind my twin turbo 383.
 

GTX JOHN

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The 741 case is still a good size pinion and plenty strong
enough for you application. the tapered axles worked fine
in my Max wedge car when it was new and never a problem with 10.5 slicks
= but are a pain to work on (I think I still have the tool to remove the axles).

The only real issue to me is a very limited selection of
available gears for the 741 available anymore. I think you can
get 3:73 from Yukon still?
 

khryslerkid

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@Gunner1 Bob you're hard to keep up with!

The '62 - '63 taypered axels are longer in the open rears and shorter in the limited slip rears. About a 1/8". In '64 and newer they were the same length in both rears. It has to do with the type of thrust buttons they used for preloading the bearings.

That's where the conundrum comes into play. You can shorten the original axel when changing to a limited slip and hope you don't shorten them too much. Or you can find a set of axels from a limited slip, '62 - '63. These rears housings from these two years were the narrowest of all the B Bodies.

When trying to figure out what to do with my '62, having an 741 open rear, I spent the extra money for a used 742 and installed a set of 3.23 gears, new bearings and clutches. Then upgraded to the newer backing plates and drums. Bought a set of newer style flanged axles from Dr Diff that are made for this conversion. This way I kept the original narrow housing. Some will say just install a newer rear housing from '65 on up but you'll have a wider housing and have to use a different wheel offset that doesn't look right.

Here's the section in my build thread where I updated my housing. Taking Up New Residence
 

33 IMP

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The 741 case is still a good size pinion and plenty strong
enough for you application. the tapered axles worked fine
in my Max wedge car when it was new and never a problem with 10.5 slicks
= but are a pain to work on (I think I still have the tool to remove the axles).

The only real issue to me is a very limited selection of
available gears for the 741 available anymore. I think you can
get 3:73 from Yukon still?
Summit shows only two ratios for a 741 case, 3.55, and 3.73. Four different manufacturers tho.
 

threewood

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Run it!

I have a 741 housing in my 69 GTX, 3.55 Eaton Trutrac, Mancini billet yoke. M/T Street Slicks. Behind my 727 I've had no issues. Ran a best of 13.1 @ 107mph at 3000ft altitude, 2.0 60ft.
 

Gunner1

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All cool answers guys. Thanks. Now I have some reading to do.
 

Gunner1

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After lots of reading and realistic goals I think I'm gonna stick with my 741 and some sort of a locker. I like the idea of a lunchbox locker just for cost. But I will make that decision when it's time for the rear end. Thanks for all the replies. It truly did help me with making up my mind.
 
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