8 3/4 Axle 276 open carrier...what's next? What gears are you running?

[DrewTX]

I purchased a 8 3/4 (742) axle 276 open carrier from a 68 Chrysler 300 axle (same dimensions as the C-body at 61-3/4″) for $180. My 1971 Charger is 63 from drum to drum and I have about an inch of clearance between the tires and the leaf springs. It's really close, so I may have to get a spring relocation kit...1/4" weld on spacers are tempting as I don't need much.
I was thinking of going 323 or 356 gears, so I can still get on the highway. I'm debating using my 276 case, or just buying another one to have a highway and street setup. I'm thinking that even though swaping gears will be possible...maybe just get the right setup. Anyone out there really swapping these often? Next, should I buy a new Eaton, clutch type Sure-Grip "Powr-lok", or used center section? Buying this, new gears and axle shop expenses...this is getting up there in $$$. It seems most center section Sure-Grips with gears are $1000+. I'm starting to think I should have gone with a 9 1/4. UGh....

 

[moes]

ya I run a sure-grip with 3.55 gears, it's a good all around gear to run, the rpms at not to bad on the highway

 

[RT K_line]

3.55s here also runs at 3000 rpm at 72mph. Running a 4200 stall also with a mild 440, you can barely hear the cam lope but still runs mid 12s in the quarter. Last full pass was 12.51. If you are planning more hiway cruzing than 3.23s would work better. Just depends on what your after.

 

[lewtot184]

I have 3.23's in both my cars. I don't think they're interstate friendly.

 

[MOPOWER871]

Running 3:23 with 742 case ,27" drag radials in my 67 GTX the 67"s are limited in the wheel wheel department at 60 mph taching 3,200 rpm. great gear .my stroker 440 makes near 600 foot pounds of torque, car pulls hard. would love to put some 3:73's but don't want to give up my long range highway driving. if you have a taller tire 3:55's would be the choice I.M.O.

 

[747mopar]

I purchased a 8 3/4 (742) axle 276 open carrier from a 68 Chrysler 300 axle (same dimensions as the C-body at 61-3/4″) for $180. My 1971 Charger is 63 from drum to drum and I have about an inch of clearance between the tires and the leaf springs. It's really close, so I may have to get a spring relocation kit...1/4" weld on spacers are tempting as I don't need much.
I was thinking of going 323 or 356 gears, so I can still get on the highway. I'm debating using my 276 case, or just buying another one to have a highway and street setup. I'm thinking that even though swaping gears will be possible...maybe just get the right setup. Anyone out there really swapping these often? Next, should I buy a new Eaton, clutch type Sure-Grip "Powr-lok", or used center section? Buying this, new gears and axle shop expenses...this is getting up there in $$$. It seems most center section Sure-Grips with gears are $1000+. I'm starting to think I should have gone with a 9 1/4. UGh....

I'm running a sure grip with 3:55s but I also have 2 extra gears, don't know that I'd run them if it wasn't for the overdrive though? I drove the car for a year before adding the 6 speed and it drove me nuts screaming down the freeway, I'd likely go with 3:23s.

As for what to buy? If your someone who will build your own it's hard to beat the sure grip but they get expensive otherwise.

 

[6PKRTSE]

I'm running a sure grip with 3:55s but I also have 2 extra gears, don't know that I'd run them if it wasn't for the overdrive though? I drove the car for a year before adding the 6 speed and it drove me nuts screaming down the freeway, I'd likely go with 3:23s.

As for what to buy? If your someone who will build your own it's hard to beat the sure grip but they get expensive otherwise.

I run 4:10's in my Charger on the street (some day overdrive trans). It screams on the freeway. Or someday as I get older I may tame it down abit & throw the 3:55's or even some 3:23's back in it. Hard to believe these were daily driver back in the day. I couldn't imagine going from Cali to Florida with 4:10's but people did it like it was nothing.

 

[beanhead]

Currently I'm running 3.73 gears with a 28 in rear tire, car doesn't really see freeway use... it has for a few short spurts and it was a little much for me above 65mph(freeway traffic flows 75 to 80 around here) Either the 3.23 or the 3.55 is a good choice for multi-purpose driving. Maybe check out one of the online RPM calculators to get a better idea of what your RPM will be at a given speed.. as far as swapping centers back and forth it's way more of a hassle than it's worth in my opinion, unless you really want to run around town in something like a 4.xx gear and only swap the peg-leg in once or twice a year for a long road trip. Your idea to build a good all-around setup and go with it is a good one..

 

[1967coronet]

I have 3:23 gears and 26" dia. rear tires, I think its a pretty good all around ratio.

 

[DrewTX]

Hey, thanks for everyone's great input on this. I found a 489 casting 3:55 Sure Grip used section from a 1971 383 Road Runner. We're negotiating on now. He's at $650, I'm at $500. From another thread, used asking price is usually around $450 so I feel $500 is fair. I see them on ebay, craigslist, etc usually around $850-900. I'm not sure what's up with that. My local axle shop, Fort Worth Differential, will build my 742 case with new 3:55 gears, bearings and Power Lock (Yukon?) for $1200 including axle shaft bearings and seals so I'm not sure why anyone would pay $900 for a center section used.

 

[Kern Dog]

Overpriced cars and parts have become more common because it seems that there are some impulsive people walking around with money falling out of their wallets. Greedy sellers see instances like this and want in on the action. Regular guys get priced out. I am an optimist but I think things are getting worse. Have you looked at the asking prices of even rusty 68-70 Chargers lately?

 

[lewtot184]

Hey, thanks for everyone's great input on this. I found a 489 casting 3:55 Sure Grip used section from a 1971 383 Road Runner. We're negotiating on now. He's at $650, I'm at $500. From another thread, used asking price is usually around $450 so I feel $500 is fair. I see them on ebay, craigslist, etc usually around $850-900. I'm not sure what's up with that. My local axle shop, Fort Worth Differential, will build my 742 case with new 3:55 gears, bearings and Power Lock (Yukon?) for $1200 including axle shaft bearings and seals so I'm not sure why anyone would pay $900 for a center section used.

if you can get a total rebuild for the axle assembly for $1200, with new parts, maybe that's not bad vs buying used parts at a lower price you don't know anything about. seems like every time I try to save a buck it costs me two.

 

[DrewTX]

Overpriced cars and parts have become more common because it seems that there are some impulsive people walking around with money falling out of their wallets. Greedy sellers see instances like this and want in on the action. Regular guys get priced out. I am an optimist but I think things are getting worse. Have you looked at the asking prices of even rusty 68-70 Chargers lately?

Good to hear from you Kern Dog. I completely agree with you, and it gets old. I passed on a ragged out 68 Charger driver with a $28k asking price. Funny thing, when I was picking up the 8 3/4 axle out of the 68 Chrysler 300 last week, another guy was there to buy the 440 motor for the very same car I passed on. He got it for $24k,,,,totally nuts.

 

[DrewTX]

I felt like I paid too much for my 71 base model, 40’ horrible paint job from the last guy. It has very little rust and is now a nice and solid daily driver, everything replaced, well under $10k total. It’s no screamer but a nice solid ride. Squint and from a distance, it looks pretty good!

 

[DrewTX]

if you can get a total rebuild for the axle assembly for $1200, with new parts, maybe that's not bad vs buying used parts at a lower price you don't know anything about. seems like every time I try to save a buck it costs me two.

Big thanks for this...you pretty much helped me decide on new. I’m the same... every time I try to save a buck it cost me two. Thanks again!

 

[DrewTX]

Can I get your thoughts on this? Today I found a 489 case locally with 4.56 gears (insanity) that looks super clean at $425. Maybe I go with this and swap out the gears. Do I jump on this? It's crazy clean...almost too clean?? This is the full description: 8 3/4" rear end 489 case 4.56 Sure-grip center section with large yoke. Schafer gear set, Cone-type LSD, spins smooth and free with appropriate backlash; pulled in as run condition.

 

[lewtot184]

Can I get your thoughts on this? Today I found a 489 case locally with 4.56 gears (insanity) that looks super clean at $425. Maybe I go with this and swap out the gears. Do I jump on this? It's crazy clean...almost too clean?? This is the full description: 8 3/4" rear end 489 case 4.56 Sure-grip center section with large yoke. Schafer gear set, Cone-type LSD, spins smooth and free with appropriate backlash; pulled in as run condition. View attachment 588340 View attachment 588341

auburn sure grip with 4.56 gears? chances are the auburn needs work, plus gears, set-up, etc. keep shopping, unless it's real cheap.

 

[DrewTX]

auburn sure grip with 4.56 gears? chances are the auburn needs work, plus gears, set-up, etc. keep shopping, unless it's real cheap.

Thanks for the quick reply on this. It's $425 asking price, add $300 for new gears, $300 labor, and ???? ....then I'm back at $1,000. Once again, trying to save a buck might turn out worse than new. I'm obviously on a low budget...

 

[lewtot184]

Thanks for the quick reply on this. It's $425 asking price, add $300 for new gears, $300 labor, and ???? ....then I'm back at $1,000. Once again, trying to save a buck might turn out worse than new. I'm obviously on a low budget...

if you have to buy a new sure-grip the price will be $1500.

 

[DrewTX]

I completed the 8 3/4 axle swap from a 1968 C body into my 1971 Charger replacing the 8 1/4 open. I used the Dr.Diff spring relocation kit, green bearings with a 3:55 sure grip and it's AWESOME. I took a chance with a used Suregrip that I was told saw very little use- it seems fine. It's a blast to drive in the city and rpms aren't too high on the the freeway. Big thanks to all you guys for your input on this. The only modification was welding in new perches, otherwise bolt it and used the same drive shaft with conversion u-joint. Even the emergency brake cables fit. Getting the pinion angle was a bit challenging, and took me a few times to get it perfect: -2° front, -4° rear for a total of -6°. Thanks KernDog for your feedback on the 11x2 drum brakes. It was the big surprise of this project, as the brakes were pretty scary previuosly. I was not expecting much going from the 8 1/4 axle with 10x2.5 to the 8 3/4 11x2.5. It doesn't sound like much, but the braking difference is huge! This was so worth it. The whole project: 8 3/4 housing, poly bushings, all brake parts, new drums, outer bearings, 3:55 gears center section (used) right at $1000. I have an extra 2:76 center section, if I need a road trip!