After running a very disappointing 15.6 at the strip on a 300 horse crate motor, I'm convinced my 2:73 gears are what's killing me. My whole rear end (suspension, diff, bushings...) are all original. I'd like to tear into it this winter. The car has a new motor and built tranny, so the rear end is the only weak point.

I've heard all sorts of things about the batwing rear end and aluminum diff, but I'm not sure what to believe. I've heard that there are all kinds of gears available, but I've also heard that there's nothing, so I don't know what to believe.

This car will never run more than 400 horse, and if it does, it'll be far, FAR down the road, so I'm not too concerned with big power tearing the rear end to shreds.

So what's out there, where should I look, and what is anybody else with the batwing doing?

 

you are good to go !!! i would recommend some 355 gears for you that will slip straight into the dana 44 in the 81 if thats your model. yes this diff is weaker then the earlier carriers but it will take abuse up to 450 hp all day long. 355 gears are a happy medium that will give you a good launch and still allow you to cruise at about 3000 rpm at 60 if your running a TH350 . what stall did you choose?

 

when my '82 was stock (Cross-Fire), with the OEM 2.87s, it ran 16.10s in the heat of summer, but following a swap to 3.73s, it ran 15.30s in the cool of November in Taxylvania:
soon, the 700R4 started slippin', and it reverted to inconsistent 15.80s/16.20s, but the anemic gearing of the '81/'82 Corvettes kill their 1/4-mile performance



I believe the Dana-44 IRS is weak, but if you are not putting sticky-streets/slicks on the car, and keeping an automatic behind the motor to cushion the shock, it 'should' survive on OEM-style, rock-hard BFG Radial T/A or Goodyear Eagle GT equivalent.

A Forum-member named 'jamiejamison' (I believe), who rarely posts here, has an '80 with a warmed ZZ4 that he races weekly at Palm Beach International Raceway, towing a small trailer behind him to/from the strip, carrying his slicks & tools:
his car regularly runs 12s, then he drives it home on his street-tires, so he might have some ideas if you contact him
(Red 69 might have his contact info & some pictures)

my '82 now runs very-low 14s/squeaks into the 13s on BFG R-T/A, and I have had no rear-end problems (yet)

 

Good good good. You guys tell me the news I wanted to hear

Just out of curiosity, what's the tallest gear that will fit in a Dana 44? I like the idea of a 3:55, but I could even go a bit taller, as this car doesn't see much in the terms of highway driving, and gas mileage isn't really an issue, as I have another daily driver.

So where can I get a good set of gears for it? How hard is the install, or should this be something I have professionally done?

 

typically, 'taller' gears means higher-mechanically/lower-numerically..... 'deeper' gears means 3.73-4.11-4.56



when I was in the market for my gears in '03, I was told that ZIP Products offered 3.90 or 4.11 gear-sets that fit the original '80-'82 carrier, but when repeated e-mail requests to them went unanswered, I settled for 3.73s (I believe they are Precision Gear) from a place on Long Island that is no-longer in-bidness for $135, including S&H, and I've had no complaints to-date:
I had mine installed by a friend/Corvette-specialist who's owned, restored, & drag-raced several C2/C3, and I think I paid about $400 for his services, including swapping both speedo-gears.

We don't drive our '82 much, and rarely on the Interstate/highways, so I believe I could have gone for 4.11s, simply because I prefer lotsa gear & drag-race the car a few times a year:
with the 3.06:1 First Gear of the 700R4 & 3.73s, I've gone 1.99x in 60' deep-staged, which kills performance.

can't beat the seat-of-the-pants kick from deep-gears!

 

I went from 2.87s to 3.07s and keeping the car streetable, really am happy with the choice. The 700R4 low first gear helps and launches the car as if it was a TH350 with 3.73 gears.

The 80-82 rear has some issues.

1) Aluminum caps are not as stong as steel caps of earlier years. You may be able to get this modified to allow steel caps if your 1/4 launching. I didnt know about this until after I did the job.

2) Soft diffferential cross pin. Designed by GM to minimize noise, therefore is prone to wear. You are almost guaranteed to have wear on this and replacements are becoming scarce I understand. $$

3) Along with soft cross pin are soft side yokes, designed to minimize noise. Good chance these are worn to the point that you'll have mushroomed ends and may not be able to pull them out with firing up an angle grinder and going to town on the ends to try to remove them. This means youll be buying new side yokes as well $$

4) Dana gears sets are out of production so youll be lucky to find a set of NOS from somebody hoarding them or you'll have to go to Richmond or equiv which are prone to noise.


The beefed up alternative is to get an iron rear and set up the halfshafts and trailing arm spindles to mate up to this. $$$$$$

Oh yeah, while your at it, since your torn down this far, you should also get your trailing arms rebuilt, U-joints replaced, and use new service cap screws for the U-joint straps since the originals are probably rounded. Use a 12point 1/4 inch Crafstman deep socket on these originals and prey like hell you dont strip them. The replacements will be 6 point hex head. Hopefully your TA frame bolt is nice and clean or its time to break out the sawzall.

 

I installed a 4.10 ratio rear gear in my 80, so far so good with a 383 stroker approx. 425 horsepower and richmond gear 6-speed trans. I do not plan on any bonzai tire burning starts, but I do have a cast iron 79 or older gear section on standby. I have learned over the years the hard way, if you drive the car normal and do not bang the gears excessively the stock aluminum rearend will hold up ok. But start popping the clutch and banging 2nd and 3rd gear and you will really have some work to do this winter. I snapped an axle on my 73 by simply grabbing 2nd gear hard one day, and that was a lucky break considering what else could have happened.