Hey guys, I'm looking for some opinions here. I've got a line on a complete 4th gen rear with a Wilwood prop. valve included for $200. The guy says that the guy he bought it from told him it was a 3.44 (assuming the guy meant to say 3.42?) ratio, but I'll need to verify that before purchase obviously. I'm just trying to figure out if it's worth going with the 4th gen rear or if I should just get a powertrax street locker and all new brake components for my 3.73 geared '84 rear end? I'd spend more money that way, but is the 4th gen rear worth getting into? I know it's a direct bolt in swap, but then I've gotta either run different offset rims in the front and rear or run spacers up front. I'm also thinking about getting a set of Zo6 wheels/tires (less than 1k miles on the tires) from the same guy for $1150. 18" rear, 17" front. Anyway, I'm just looking for opinions on if I should do this or not, and if the prices are decent, thanks for any and all input and experiences!!

-Paul

 

I will keep it short and simple.

The 4th gen rear is basically the same as the '89-92 3rd gen rear. It has 28 spline axles and some have rear disc brakes, I think 4th gen has all disc brakes. They are not stronger. But the 4th gen rear is a little wider.

I will say this... if you want to use 4th gen wheels, I would go with the 4th gen rear so no spacers would be required. But if I was going to use 3rd gen or any other aftermarket wheel, I would swap in a used '90-92 (89 was transition year for 26-28 spline axles) rear that is rebuilt with whatever gears and posi you want.

 

200 bucks is a steal for large disk breaks, prop valve, and posi. Sure they are the same as 3rd gen rears but 200 bucks will only get you a used set of gears and a take out posi on your 3rd gen rear. I would buy it. If not you could sell it for much more.

 

The 3.73 rear you have should be a posi/ limited slip rear already if that's what you were looking for. At least the 3.73 rear in my 84 is is a posi. You may need the diff rebuilt. Your TA may be different though.

Here's the rpo's for mine.

GT4 : AXLE REAR, 3.73 RATIO
G80 : AXLE POSITRACTION, LIMITED SLIP
J65 : BRAKE SYSTEM, PWR, FRT & RR DISC

 

Thanks for the input guys, I'm thinking I will probably grab the rearend. I know that the 4th gen rears are the same design, the advantage for me would be the posi and the better rear brakes, cuz my '84 rear discs suck and need to be totally gone through anyway. I'm up in the air on the rims though, especially because he wants over a grand for the wheels/tires and one wheel has a bend on the inside that he says doesn't affect them, but is noticable. As far as my current rear end goes, my car has the "WY6" performance package which was the same as the WS6 just minus the limited slip. So I got the WS6 suspension, L69 engine, 3.73 gears, J65 disc brakes, but no posi I haven't actually pulled the diff cover to check, but I don't believe I have the RPO code for posi, and I know that when I have the car jacked up and spin one wheel the other one spins the other direction. Anyway, I guess since the price is pretty good I'll grab the rearend, just gotta decide on the wheels now.... Thanks again for all the input, keep it coming!

-Paul

 

Should be a posi. If you put it in drive in the air and they both spin it should be limited slip/posi, not a peg leg. Turning one wheel should not effect the other if it is not a posi I don't think.

But hey, if you can get a newer, fresher rear with bigger brakes I'd say go for it. You could go with the 16" formula rims maybe. They should clear the brakes. Just mway stick out some since the 4th gen rear is wider.

 

generally, in my experience if a car doesn't have posi, if you jack it up and spin one wheel the other one will spin the opposite direction, and will still spin even if the car is in park/gear. If, however, it does have posi, both wheels will spin in the same direction, and if the car is in park/gear, you won't be able to turn either wheel at all. In any case you're correct, newer is better I'll probably end up getting this rearend, because the whole rear is 1/2 of the cost of just a Powertrax street locker for my current rearend and the 4th gen unit has stronger axles, better brakes, etc. I'll check on my rearend now though, you've made me want to double check myself hehehe

-Paul

 

Very odd indeed.

 

If you are worried about wheels you can get a complete set of 17x9 take off SS wheels for $800 from SLP. A set of front spacers and you are set.

 

with the car on stands:

if you spin one wheel and the other spins in the same direction it is a limited slip unit.

however if you spin one wheel and the other wheel rotates in the OTHER direction then you have a open carrier.

This is a fact

 

That's what I was saying too...that's the way it's always worked in my experience....

 

dude!! that's a steal! I sell 4th gen rears for $225. buy that bastard

 

I'm pretty sure I'm gonna grab the rear, I just want to verify for sure that it has 3.42 gears, not 3.23s or 2.73's. Does anybody know how to positively ID the 4th gen rears for their ratio without taking the inspection cover off?

 

You can alsways spin the input and watch the axles spin. Just do the math. 3.42 turns on the input for one wheel turn.

 

Yeah, I can certainly do that if worst comes to worst, but the rear is in NJ and I'm in NY, so I was hoping to find a way to positively ID it via codes somewhere on it before I make the trip to NJ, if ya know what I mean

 

what makes swapping to a 4thgen rear worth it is that its cheap..

somtimes you may be getting a gear/posi/axle spline/disc brake upgrade... but mostly what makes it worth it is the price.

i got a rear for free with a TA cover... only thing it needed was brakes since the guy upgraded to a 12bolt... $100 later i had a TA cover braced, 3.42 posi disc 10bolt under the car.

 

Might be a mute point at this time but it seems to me that most early 3.73 rears wear open diff. I've now had 3 of them (I explode a lot of rears, that sounds bad huh?) and they were 84, 84, and 85 I think. All of them open :-(

 

Just a quick comment on the "posi test" of jackin up and turning one tire. If anyone ever runs accros a Zexel torsion differential, you will find that this test doesn't work. It'll look just like an open rear, with the opposite wheel spinning the other direction. Them helical gears do some wierd things .

Patrick

 

Yeah, good point on the Zexel, I'd read that before on here too. I just found out the rearend I was considering has 3.23 gears not 3.42 gears, so I'm really not so sure I wanna go for it right now. I think I'll just wait. I don't NEED a rearend right now, mine's not blown up or anything so I think I'll keep looking. Thanks for all the advice and input though guys!

-Paul

 

um, i have a 97 rear end in my car.... it spins the same direction... so i have posi. do i have an eaton, then? or a zex?

 

I don't think GM put the zexel into anything stock except for the SSR (which is slow as hell i might add.. lol.. drove one last weekend)... so.... you probably don't have a torsion diff (zexel).

Patrick

 

Holy misinformation Batman! The Torsen diff was optional in the 98 F-bodies, and came standard in 99 through 02. Chances are if its an LS1 rear, its got the Torsen diff. You are correct on the "posi test" though. When will people learn to stop that poor shadetree test and do it right... spin the INPUT... aka driveshaft.

flyitlikustolit - The LT1 cars 93-97 got an Auburn posi unit.

 

oh, well.... ****..... that's awesome.