Had a question about changing my differential out and to find out if it's a myth.
 

I've got a 92 rs 305. I know it's got a 273 stock gear in it. I've heard that in the v6 model they have a 342 gear stock and was wondering if that's a direct bolt in or is there a better rear axle that's a direct bolt in application.

Re: Had a question about changing my differential out and to find out if it's a myth.
 

Any 3rd or 4th gen rear will bolt right in. The later slightly stronger 10 bolt, with the 7.65" instead of the 7.5", and 28 instead of 26 spline axles, is what you have in your 92. The later 3rd gen V6's had 3.24 gears.

Re: Had a question about changing my differential out and to find out if it's a myth.
 

BTW, what is the myth you are referring to?

Re: Had a question about changing my differential out and to find out if it's a myth.
 

The myth was that the v6 had a better rear end than the v8-gearing wise anyway. So then would it be better to get one from a v6 and change it out to get better assistance with torque from off the line through highway speeds?

Re: Had a question about changing my differential out and to find out if it's a myth.
 

6-cyl cars often came with better gears than V8 cars.

Coupla reasons for that:

A 6-cyl needs ALL THE HELP IT CAN GET to disturb the car however vaguely from a stop, even if it's hard to notice it while it's in progress. Don't wanna get T-boned in an intersection by Grandma with her walker.

A V8, back in those days, needed all the help it could get with artificially inflating the gas mileage "ratings". Even though those AREN'T anything anywhere even dimly remotely near "real world", the law is the law, and it is what it is. So they put those stoooooopid 2 series gears in most of the V8 cars to bogosify the CAFE #s as legally as they could, even though it crippled and nutted the cars. Hey, just make the "IROC" or "screaming chicken" stickers bigger, and people will buy em anyway. Right???

Problem with 6-cyl rears is, the brakes SUCK. They're DRUMS. I wouldn't pay for a rear with that. I wouldn't accept it as a gift. In fact I've paid people to come haul that crap off my property. Which is to say, a drum brake rear has NEGATIVE value.

Gears are CHEEEEEEEEP compared to trying to fix a car that just rear-ended a school bus or something. Don't be penny-wise and pound-foolish.

Re: Had a question about changing my differential out and to find out if it's a myth.
 

What exactly are you looking for in a rear end? Do you just want a better gear ratio, or do you want a limited slip differential and good brakes too? If you are just looking for a gear ratio upgrade then a V6 rear end would be fine. If you want the other stuff too then a brake and differential upgrade can be done on a V6 rear end, or you can find a complete Z28 rear end that has what you want.

Re: Had a question about changing my differential out and to find out if it's a myth.
 

With the '90 - '92 f-body's, a V6 with the T5 got a 3.42 rear ratio. The automatic equipped cars received a 3.23 ratio.

RBob.

Re: Had a question about changing my differential out and to find out if it's a myth.
 

I would like a better gear ratio actually, and a limited slip would be nice too. Are you saying a z28 rear end from the third gen would work just fine also, I guess that has the limited slip and a better ration also. I'll assume it's a caliper brake set up, if so are there change over kits for the parking break and brake lines? Do you know what that ratio is?

Re: Had a question about changing my differential out and to find out if it's a myth.
 

Some Z28s came with 3.42 gears and limited slip. The problem with the 3rd gen rear ends is that the most common LSD was the Auburn. They are not a very good differential. The only other LSD in the 3rd gen was the Governor Lock, which is probably worse than the Auburn. If I had the choice I would find a '90 to '92 rear end with 3.42 gears and put in a Eaton Posi, Eaton Truetrac or a used Torsen.

Re: Had a question about changing my differential out and to find out if it's a myth.
 

Are you saying a 90-92 Z28 then doing the change over?

Re: Had a question about changing my differential out and to find out if it's a myth.
 

Whatever rear end fits your needs with the right gear and the brakes that you want, and then install the LSD of your choice.

Re: Had a question about changing my differential out and to find out if it's a myth.
 

Also, don't forget that when you change rear gears- however you do it- the speedometer will be WRONG. You also need (probably) the drive, and driven gears from the transmission, if possible, to correct the speedo. Or, you can look up at the stickies for guidance.
Good luck!