Ok Ive seen alot of posts of people recommending that people put in a 4th gen rear end in there 3rd gen but I haven't seen any reason why to do this other than you want to switch to disc brakes, your rear end is worn out or broken, or get a different gear ratio, most likley a combination of the above.. getting disc breaks, diff gear ratio, and maybe your old 3rdgen rear end has a problem and its cheaper to put in a used 4th gen than buy an after market 12bolt, and put disc breaks on it.


other info:

4th gen rear ends are 4 inches wider, so your 3rd gen wheels will stick out 2 inches farther than before, or use 4th gen wheels, or buy 2 inch spacers for 3rd gen wheels

What I don't know
Are 4th gen rear ends stronger than 3rd gens?
Can a 4th gen rear end handle 350+ HP?
what modification(s) other than buying an aftermarket 12 bolt or 9 inch rear end would make a 3rd gen/4th gen 10 bolt handle more HP?

 

lets think about this logically...
if a 4th gen rear can put up with the power of MILDly modified LT1s and more importantly LS1s, then they are prime canidates for third gens (especially your LO3TBI motor), but pushing any stock rear past 350-400(rear wheel) horses is a daunting request. this is when we step up to the aftermarket piece. i have had great experiance with Moser 12-bolts.

 

Don't forget about posi as a consideration.

 

nice logic..
here is some more info I know to help you with your logical speculation

I know a few people with Ls1's that have done some bolts on's and have busted there 4th gen 10bolts on hard lauches.

3rd gen Z28's 5.7 tpi's slightly modified have pretty close to the same power as LT1's slightly modified.



Would putting say an eaton posi unit, and aftermarket axles beef up a 3rdgen 10 bolt to handle 350-550 hp?

What on the rear end actually breaks when you bust a rear end on a hard launch with a car that has 350+ hp?

I have looked at Moser 12bolts and would love to have one but were talking 1,600.00+ dollars verses 250-500 for a junkyard 4th gen

If I wanted to completley rebulid a 3rd gen, or 4th gen rear end what all parts would be needed?
posi unit
ring and pinon
new axles
what else?

 

Seems to me the quote above pretty much sums it up. The cheapest way I could get a posi w/disc brakes is to go with a 4th gen rear, unless I get real lucky and find one of the 3rd gen Audburn (sp) rears w/disc brakes.

Why else would someone want to install a rear that is 4" too wide?

BTW....not trying to put anyone's opinion down......just playing devil's advocate.

 

For me I wouldn't mind a 4th gen width rear end so I could run 11 in wide 4th gen spacing wheels on the back without having to use spacers.


but thats apples and oranges, I'm maily trying to find out for sure of 4th gens can handle more HP, but I guess not since modified LS1's can bust there stock rear ends

 

i dont see the problem here... if you are putting out more power then the weak 10 bolt can handle.. get a 12 or 9". 4th gen rears are newwer, better brakes, posi, and probably a tad stronger, but dont quote me on that. Now, does that mean that they will hold 400hp and dont make a sound... no. You can build you 10 bolt stronger as there is an article on the front page of tgo. I would look at that. A TA rear end girdle is a good idea to beef it up along with a stronger carrier and tuffer axles... but if you are aiming for mid 12's or lower... get a 12 bolt or 9inch... You can spend 2200 once or spend 500 over and over to get another 10 bolt. Also, you cut down on buying spacers for teh rear if you want to run 4th gen or vette rims.. I just would like disks right now with 3.42's.

 

i think they are stronger.
i just swapped one in my car an it was about another 45+ heavy than the 3rd gen rear end. i dunno why but that was minus brakes

 

OK, either I read it wrong or you have the sizing issue a little messed up.


With a 3rd gen rear you need spacers to run 4th gen rims BUT
With a 4th gen rear you DON'T need spacers (on the back) to run 4th gen rims.


If you run 3rd gen Rims on a 4th gen rear, each side will stick out ~2 inches further. You can't correct this.


Reasons people go with 4th gen rears is because a lot of times it's as cheap or cheaper to go with them as opposed to a 3rd gen rear, especially if you want discs. Also, 90% of the time they're lower mileage. People don't go with them because they're stronger. They're still just a 10 bolt...same strength as the 91/92 10 bolts.

 

yea.. i ment to point that out, but i kept closing the window... lol.

 

oh sorry I had a typo in my first post, I meant you need spacers with 4th gen wheels if you have a 3rg gen rear. I changed my first post to fix this.

so 4th gen rear ends are 4 inches wider, and there 45lb's heavier.. surley there's a reason for that much more weight, 4 inches of axle tube wouldn't weight that much. maybe there 8 or 8.5 instead of 7.5 or something.... anyone?

 

Ive heard of people running stock 4th gen rears behind highly modified lt1s and what not.

If you dont run slicks youll probably be ok. When you start hooking hard you start breaking stuff.

 

uh the cas also weighted a lil more looked a lil beefer, and maybeanother 5lbs cause of the dif cover. (i had the plate then went to a cast one with stucd gridles.

 

Wyclef....your car is an 89, right?

89's 10 bolts had a different spline count, right?

I'd measure a 91/92 10 bolt's weight and compare it to a 93+

 

i had an 89 slpine 10bolt in my car with drum brakes. the same posi unit was used and the same gears. so no change there. i had 28splines in the 89.

 

Im looking for a 89-92 rear end for mine. I cant find any bone yards around here selling any for less than 300$!!!

I say a thirdgen rear is worth about 100 bucks unless it has gears and a good posi unit installed.

 

I got my 92 Drum rear w/ 3.42's from a 95 Z28 AND Spohn LCA Relocation Brackets welded on for only $150

 

i went to a couple guys around me and they all wanted 200-400 depending on the rear end. and then i found the 4th gen rear end i wanted for 500 so i got it. (everything on LI is about 20-40% higher)

 

I'm getting a new rear put in prolly wednesday and monday I will prolly pick it out. I'm still debating, he wants 150 for a thirdgen rear, 250 for any 4th gen rear and prolly around 300 for a 4th gen rear with disc brakes. I right now have a 89 Formula 305 with the crappy beatup 2.73 rear and drums on the back. My rears messed up and has alot of roadnoise so it needs to be swapped before I move to florida in 3 weeks. If I put a 4thg en rear will I need spacers for my 3rd gen formula rims?

 

no, will not need spacers because 4th gen rear-ends are 4" WIDER than 3rd gens. so therefor your wheels(3rd gen) will stick out 2" farther on each side. the answer to this is to buy 4th gen wheels.

 

Does anyone know if the drum brake hardware from a 3rd gen rear will swap over to a 4th gen rear? I know I could find one with the brakes on it, but I can get the 4th gen rear with 14k miles on it for $200. I'd like to know ASAP if this is possible to swap over the brakes. I could at least get the 4th gen stuff in the future.. I'm thinking of mainly for the time being here.

 

yea, it will swap fine... im not 100% on the fittings, but i never heard of any problems... go for it man!! 200 is a good deal!

 

They actually are about the same stength. The 4th gen one Ive got sitting behind the shop is 40 pounds heavyer dont know why either but the casting isnt thicker like people think. The internals are similar except for the ABS ring on the carrier. Thats where we get the extra strength from the brass abs ring, lol
If you can get it cheap enough theres no reason not to get a 4thgen rear, yes they do stick out further but most the 3rdgens running around here have larger rims and tires in the back anyway so you get the same effect for free basicly if you into that look. Warning though If you look for 4th gen rims at bone yards there very expensive. In my neck of the woods they run $100 for plain black steel rims.

 

wow, whata rip off..

 

what about the front tires? if i wanted to go with the 4th gen rear with 4th gen wheels how would that work up front? would the 4th gen wheels fit? would i need spacers up front?

 

yea u would need spacers

 

If you're talking about swapping third gen drums to a 4th gen drum rearend (V6 only), it shoukld work fine. Otherwise, it won't, without the aftermarket bracket kit that one of the vendors here sells. A drum brake rear has a housing end thats basically square, but with a rounded tab sticking up on top. The disc rears don't have this tab, so its not a bolt on swap, at least not with factory parts. So, if you're going to swap a disc rear in a drum car, get the whole thing, you'll save yourself some money in the long run. Speed Automotive sells complete 4th gen rears with brakes for about $300 last time I checked, and thats with shocks and e-brake cables, too.

 

Ok, I have a 4th gen rear lined up for my car with the big LS1 brakes on them. Would it be bad if I just kept my stock rims on there? I realize they'll be 2 inches wider on both sides but is there any real problems with the rear wider than the front? I think it would actually look a little better to have a wider rear than the front. Can anything bad happen with this?

 

Quick question. In what way will putting a 4th gen rear end in a 3rd gen affect your suspension, cornering, and stability? Anyone know?

-Mace

 

does using the spacers and 4th gen wheels on the front cause any added stress on the balljoints and struts? the back cant be that much different than if it were on a 4th gen can it?

 

SSC is correct, 4th gen rearends are NOT stronger, they use basically the same internals. If you buy a 4th gen gear because it can "handle" and LT1 or LS1, you wasted your money.

 

They are exactly the same internals as the later year 3rd gens! In fact, overall they are weaker because the axles are longer and will twist more on launch. The only reason to go with a 4th gen rear is 1) for disk brakes and/or posi 2) you can't afford a 9 bolt, 9 inch or 12 bolt.

Miles

 

I said "basiclly" the same because some came with different Limited Slip carriers and the axles are longer, But the gear set is the same, the bearings are the same, etc...

 

4th gen rear ends appear to be like Fish Stories...the longer time passes the bigger it gets!!

When I swapped my 4th gen rear axle in...the accepted width difference was only 3" wider. I predict in a few years the thing will be 5" wider!!!!

FWIW: I swapped mine for disk brakes, newer posi, and 3 series posi to put 3.42 gears in.

40 lbs heavier could partly be because it is wider...

 

I went with the 4th gen rear so I could run 4th gen wheels without any spacers on the back. My car already had 3.27 posi/disc 9 bolt, just didn't want spacers on the rear.

My new rear is from a 99 SS with 4.10 gears and disc brakes.
This complete rear is really heavy, probably since it has the brakes and the LCA reloaction brackets on it.
I've also heard that the LS1 rears are slightly wider than the LT1 rears.

this is what a bolt on 96 6 speed T/A does to the rear pinion gear,


That is only 3 of the 10 gear sets my brother has broken.

 

after i get the 12bolt/9inch(notsure yet) for the 2002 the 3.42 posi will be going in to the 89

it now has a 3.73 posi but the posi is going and the speedo gear is setup for the 3.42 anyway so sould be good