Warlocksirix

Well in the long long road of turning my original 3rd gen into a commendable beast I did a 4th gen swap. Went from the Stock 2.73 limited slip drummed to a 1993 3.42 posi with disk. Did a little paint touch up to make it look nicer and even kept *oddly enough* my bigger sway bar. Replaced all the rubbers with poly during the entire change out. Still have to fabricate the emergency brake lines to work with the 3rd gen hardware, not sure if anyone has tips feel free to pipe in. I did it mainly cause the 4th gen has a meaner gear ratio and it makes these cars look awsome! Never changed out the proportioning valve and it brakes perfectly fine, actually even better now with the disk over drum rear end.

plum92_camaro

You should do the prop valve. drums and discs operate at different pressures. Drums take more pressure to overcome the springs. Discs take less pressure to engage. Running a drum prop valve will cause your rear brakes to engage before the front. Thats what I'm doing for my LS1 brake upgrade with 4thgen rear.

Here's some info
http://gmbrakes.org/gm-brakes/gm-bra...tioning-valve/
http://www.flynbye.com/catalog/i160.html

lowlifepunk

Thats looks pretty good, i plan on doing the swap myself. I bought a rear end but it looks kind of bent. The posi unit looks to be the only salvagable part. But without the housing i cant run axles since they are different spline so my 3rd wont fit in it and the 4th wont fit in the 3rd housing. Im stuck on where to go with it.

TTOP350

iTrader: (8)

I have changed a few drum rears to disc without changing the spring in the prop valve and they work just fine.

MoJoe

iTrader: (5)

You can get 28 spline 3rd gen axles. IIRC, The change from 26 to 28 spline was in 1990.

novaderrik

when i put the '02 disc brake rear end in my 86 this spring, i was getting zero rear brakes with the stock drum brake prop valve spring installed... so i took the spring out and was getting too much rear brake... my solution was to put a Wilwood adjustable prop valve in the rear brake line after the stock prop valve and use that to dial it in... works great now..

Warlocksirix

Thanks for the tips guys. I'll gave to check in on the corvette valve spring. Heard that is the right one to get. Also if i'm correct changing the gears in the rear is what is throwing off my speedo now?

RubberDucky

iTrader: (4)

It was earlier, I think 88. My 89 has 28 spline.

Yes, gear change is going to throw off the speedo.

UltRoadWarrior9

I've read some people have this problem. What's weird is I have an '86 IROC and this summer switched out the stock drum rear diff with one from a 2002 Camaro SS. Has Auburn posi, 3.42 gears and disc brakes.
I've not touched the proportioning valve or master cylinder yet and the rear brakes seem to function pretty well, like TTOP350 mentioned above.
Here's my quote from a thread I started which involved swapping the rear diff, brakes and wheels all at the same time... https://www.thirdgen.org/forums/brak...ette-base.html

WickedBowtie

Hello. I am new here and to forums in general. Just looking for a lite insight on this thread. My question is this. I have an 89 camaro with a 4th gen rearend. Can I fit a 275/60/15 on a stock 3rd gen wheel in there? I know it'll stick out..I'm ok with that as I'm going to change wheels eventually. Thanks in advance for any info.

MoJoe

iTrader: (5)

No.

Stock 16" wheels are 8" wide, which is too narrow for a 275 tire. Besides, at 29" tall AND sticking out about 2 5/8" farther than stock (2" due to axle, and almost 5/8" due to 1/2 of 1 1/4" wider tire), the rear will have to be jacked up like a stink bug to keep from cutting the tires, and/or damaging the body.

WickedBowtie

Ok so what is max I can go with my setup?

MoJoe

iTrader: (5)

If you want the tires (275/60/16 = 29" x 10.8"), you also need the correct wheels ... 16x9-16x10 with 40-55mm offset.

4th gen rear with 0 offset wheels are not a good look, nor good function.

WickedBowtie

I want to run 275/60/15 not a 16..the 15 should be 28 inches tall if I'm not mistaken.

MoJoe

iTrader: (5)

My mistake (15 vs16). Doesn't change my answer significantly.

WickedBowtie

Ok...so what backspacing do I need so wheels don't stick out too far and want some width. Currently has 215/65/15

MoJoe

iTrader: (5)

Don't take my word for it. Research, see what others have done.
Get out a ruler (215/65/15 = 26x8.5") or a block of wood, plastic, anything 1" or whatever size is relevant, and see what a tire 2" taller* and 2" wider** does to clearance.
* 1" above the current tires, 1" below lifts the wheel and whole car.
** 1" to the inside, 1" to the outside".

Then figure out how much offset (versus the probably 0" offset of the car wheel) is needed.

WickedBowtie

By any chance do you know the backspacing on 4th gen wheels?

novaderrik

pretty sure the oem 15" wheels are 7" wide and have a 3.5" backspacing, for a zero offset if that's the language you speak...

so look at the way your wheels fit in the wheelwell, and imagine a 2" taller tire that is about 4" wider centered in the same space in the wheelwell..

a quick google search found me this site that visually shows you the differences in your current and desired new tires and a good description of how it will fit:

http://www.rimsntires.com/specspro.jsp

WickedBowtie

This is the stance i am ok with...i like the old muscle car look....

lowlifepunk

okay so im stuck, i bought a rear from a 94 and planned on using whole unit but the housing is bent, so i planned on just taking the posi unit itself and buying some 28 spline axles and toss it in my 3rd gen housing, where can i get some cheap 28 spline axles? and whats the cheapest way to upgrade to disc so i can get bigger better brakes along with it?

i plan on building the 350 4 bolt my pops gave me over the winter so im trying to do suspension/brakes/etc while i can still drive it before snow/salt this winter.
thanks again for all the help guys

WickedBowtie

It would be cheaper to just buy another used 4th gen rearend. I got mine for 300.

lowlifepunk

thats the problem haha i already bought the rear, but i guess if i can find one for 300 itll be alright i guess, what do i need to put in the 4th gen with discs?

WickedBowtie

It's a direct bolt on. It difference is it's a little wider so your stock wheels will stick out a little. And some say you need the proportioning valve off of a 4th gen so the brakes will equal out. I have not done that yet...I do plan on it eventually.

WickedBowtie

Mine with 4th gen rearend and stock 3rd gen wheels.

lowlifepunk

well mines got 245/45/17 i think it would look good with the offset on them. hopefully a meaner stance. ill have to keep an eye out for a 4th rear, than buy some decent brakes all the way around.

plum92_camaro

I had a situation with my 4th gen rear install that was not exactly bolt it. My rear axle came from an '01 SS with traction control. It had individual brake lines to each rear caliper. Fortunately I have a rear end out of a '99 v6 camaro that I used to own and shelled the spider gears in. I stole the distribution block from that one and bent new lines. THEN, it was bolt in.

Like said above, I would not. Not only is that tire too wide for the wheel but when it sticks out your quarters will hit. I have that size on the back of my 69 camaro. They are too big. I'm going down to a 245/60R15.

You can convert your drum rear end to disc. There is a "how to.." somewhere I've seen where you pull all the drum stuff off, cut off the top of the plate at the bottom of the wheel cylinder holes. drill and tap the four corner tabs remaining to match the back plate of the disc brakes and then they bolt right on. I'm considering this with my factory 3rdgen rear or having the 4thgen axle tubes shortened to 3rdgen specs. Whichever is cheaper considering the 3rdgen rear needs new bearings.

Cheapest way to get 28 spline axles I'd say is at a "you pull it" junkyard.

mikesanto70

What's with the Black Widow Spider in the top pic? Did that big black bitch almost get you?