I have an '81 that I want to put a fairly strong engine into (700hp or so at the flywheel). I've read and been told that my 4-speed car is supposed to have the bigger half shafts. I've also been told that the aluminum rearend is a weak link but not exactly why. All the blown up rearends I've seen involved an inner failure, generally the posi unit. I have seen a few Ford 9" cases broken when the pinion puked out the support but haven't seen a Corvette rearend torn up this way, at least not one that didn't start with a failed posi unit. The aluminum differential supposedly has the carrier bearing caps "as-cast" rather than fitted. Is it possible to replace these with billet aluminum or steel and beefier bolts/studs? If I'd be throwing good money after bad, is it possible to bolt-up or adapt and earlier differential to the '81 batwing and if so, what needs to change? I don't plan to drag race this car (I have another ride for that), so I don't plan to ever try to plant and stick the tires, so chances are that the rearend won't be hit with a big shock, but I'd rather be safe than sorry. This is more of a "scare hell out of the passenger (and probably myself)" ride, not intended for road or drag racing. I already have the VBP strut rods (heim-ended ones) and plan to replace all the u-joints with solids, but I need to know that the center section will hold up before I spend the money on other things.
Any help or advice you folks care to send my way would be appreciated!

 

Tom's Differentials has what you need at a price.

 

With street tires you will be alright, they spin you save parts, don't even try drag radials, I put over 500ft/lbs of torque thru my stock rear end daily and it holds up. I do have DragVette safetly loops installed just in case.

YOu are right about shocking the rear end, if you do you will leave parts behind in a stock setup. Make sure all your parts are in good condition back there.

 

:comp:

 

63Mako, I've seen the Tom's stuff, would be great if I had that kind of cash to drop or planned to push it that hard. As oily and slick as the streets are locally, I'm not really scared to run Nitto's or MT Drag Radials on the street since they won't hook.
Anybody with differential experience, I'd like to know what it takes to convert to the cast iron diff without breaking the bank. I plan to use a new posi and completely deburr the housing (either way, aluminum or cast iron), upgrade U-joints and caps. Looks like I can get the rebuilt cast iron case from Tom's, polished and with steel cap for about $1000 exchange. Add the correct stub axles and I'll be around $1500. I'll call Tom's and see what they recommend and I'll report it back here.

 

I'm looking to do just the oposite. I want to remove my iron 3.55 rear end and replace with an aluminum 3.55 rear end with aluminum bat wing to save weight. My 350 may grow up to be a 383 some day, but I'm never gonna run drag slicks or anything. I'm in the market for a complete '82 rear end.
Bee Jay

 

Bee Jay, t there's a couple of sellers on fleabay that have good feedback and sell a few of those, reasonably priced IMHO. I talked to Dan at Van Steel this morning and he made what I felt were some sound recommendations to build it as strong as it will take to make me feel comfortable when I decide to stand on the loud pedal. One of my strongest beliefs when it comes to mechanical parts of cars is that if you spend your money to build a performance ride and you cringe when you get on it, you don't have much confidence in your parts and machine work/labor investment - and that's money wasted. I'm trying to put something together that'll be quick thru the quarter and fast on the top end. If it likes to buzz to 7500, that's what it'll get. I think this 3.75" stroke/4.600 bore solid roller engine is going to be a dream mated to my tough 4-speed for a hot street Corvette.

 

I hope your tough 4 speed isn't a Super T 10, I blew 2 of them when I installed my 406ci

 

Actually, it is a ST-10, but it's the nodular iron case and midplate, high nickel gears unit. BW called it a "power brute" and it was an OTC only unit. Hell, if it blows, it'll give me reason to get an OD unit!

 

Think that is the Richmond version. You won't hurt it. They are Bulletproof! Very hard to come by and expensive if you can find them.

 

63mako, I just stumbled onto it on an old internet trading site a few years back. I wasn't even in the market for a tranny but when i checked it out, I just couldn't pass it up at a great price. Tranny guy took it apart and blueprinted it plus added the nodular midplate. As long as something really crazy doesn't happen, it should make it. Dan at Van Steel will get my business, just gotta rattle a few cages and shuffle some parts for the cash and I'll have all I think I'll ever need. Dan really sounds like he's done more than one like mine and his figure is very affordable, plus he comes highly recommended on this site.
What will it be like to cruise at 150 with the engine spinning about 6500, floor it and get pushed back in the seat like a muscle car launch? Anticipation of finding out keeps the fire burning on this project

 

I have a pristine one modified for a 5 bar/rear toe control setup...but shipping will be a problem

 

If you ever think of putting sticky tires on a 700 HP stick shift C3, you'll be breaking a lot of parts.... It's not power that kills parts, it's traction.

If you want to be able to actually hook up without breaking parts at every trip to the track, you need the following:

1) either a solid axle or Tom's 12-bolt IRS + axle & half shaft kit.
2) upgrade the driveshaft to 3" chromoly or carbon fiber driveshaft with 1350 series u-joints (new yokes needed)
3) make sure that your tranny is REALLY strong enough.

There are no shortcuts. This is what you have to do. If you'd be using a automatic transmission with a conservative converter, you could get away with a fairly stock setup, but with a stick shift and traction, you'll be breaking parts every couple of passes at the track...
It took me only a 465 HP engine with a 5-speed to break differentials etc...