samiam91RS

I bought an upgraded rear end, from out of a 3rd gen, complete with disc brakes, posi, and said he wasnt sure if its a 3.23 or 3.42 but im gonna find out by taking off the plate. also, how can you be assured a rear is a posi? i searched for pictures but found nothing. i think i can figure it out by checkin if only the z28's came with this setup and which gears came in em. but everythings on them, e brake cables and all! pads are still good too. im just waiting for my UMI parts all to get here so i can do EVERYTHING at once. ill have it on a body lift so it should be good. so im checkin if theres any mods ill have to do, or is this going to be smooth sailing swap out since the rear end has all cables and lines? thanks guys, and ill post up all the pictures of my before and after when im done and hopefully ill be

Dale

iTrader: (12)

working on EXACT same thing myself.

91rs with drum...swapping to a 3.23/posi/disc.

Dont forget to change the prop valve and slave cylinder.


Other then that, to me it appears to be a strait swap.

Dale

iTrader: (12)

buahh, saved myself some work.

The master cyl is not different. But the prop valve is.

samiam91RS

honestly I have no idea what a prop valve is, or located. can i just get one from the local parts store? and earlier you said the slave cylinders were different or did you mean the master cylinder? I would probably know what your talking about but until my UMI parts come in its not going on the frame lift. thanks and let me know how it comes along!

84redta

iTrader: (34)

prop valve = proportioning valve/combination valve.

you need a disc/disc set up, you (i'm assuming) have a disc/drum setup of which drums use more or less (can't remember at this point) pressure to operate than drums. People will suggest 89+ 1LE proportioning/combination valves.

number two...didn't know we had a slave cylinder for our brake?! master may be different, you would have to check www.GMpartsdirect.com for that answer.

samiam91RS

yes, i have a disc/drum set up and i have a COMPLETE rear end sittin in my pick up so ill be switchin to disc/disc soon. now, theres a metal line coming from each disc, then combine and lead out to a threaded end, and both ends are together (male, female) ends and after about 3 inches someone just snipped the line off (when they pulled it im assuming) so this is the "prop valve" everyone is talking about? if it is im about to just find a way to join the mother F----RS together instead of all this mayhem! hopefully i lucked out with everything on this rear, and if not i hope it all goes together like peas and carrots. i know theres a slave cylinder for each disc! did you go through this before? im doing searches right now and i think i read one of yours..

84redta

iTrader: (34)

prop valve is underneath the master cylinder/container. It's connected by two brake lines coming out of the master, and has 3 brake lines (two out the bottom and 1 out the back). One goes to the back, running along the body, right past the fuel pump (directly beside the driver side rear shock) is where the body line meets the rubber brake line that connects the line to the axle. At the end of that you will meet a T-splitter, of which those two lines will go into that T-split. Now be aware, they used different ends...when i took my drum axle out in favor of the LS1 rear....my drums were using bubble fittings into the T-split off of the rubber line. The LS1 disk rear lines used a double flare. I had to very simply cut the ends off and create the bubble fitting (big PITA) to make the LS1 disk axle lines work with my drum body-to-axle rubber line.

In summation...your prop valve is that quorky looking thing that is directly below the master cyliner connected by two brake lines from the MC, and three lines going to the rest of the body.

84redta

iTrader: (34)

and yes, i went through this headache with my LS1 rear axle swap. As i mentioned above, i made due with what i had...because i searched 3 stores for a disc version of my body to axle rubber line and noone had them, all they had were drum body to axle lines. So i said F**K it and just made bubble fittings on the two axle lines and put it all together with the proper fittings and all is perfect. After that i found someone with an 89 Formula with the J65:4 wheel disc brakes, and got his proportioning valve. From what i've read...89 uses the same fittings as 88 and older...but i'm not sure what 90 uses if they changed the fittings. Then i've heard 91 and 92 (possibly 90 as well) were all the same. If you are doing searches...check out anything that "ebmiller" has commented on. He's our brake specialist and the guru when it comes to modifications.

As far as slave cylinder...there are wheel cylinders in the drum setup and pistons in the calipers...i've never heard of a salve cylinder in a brake system. I have not read/heard it all so i'm not calling anyone a liar, just saying, i've never heard of such a thing.

samiam91RS

I see what you mean, but Im swapping from a 3rd gen rear to a 3rd gen rear..SOOO, im hoping it will be somewhat the same, if not ill try to find the swappable parts or make something up, maybe check a junk yard for an f body with the rear part(s) that i need. ill search for that name, thanks for the info and i hope this works 1st time around for me.

84redta

iTrader: (34)

shouldn't be a problem, just letting you know that it may be a disc/drum change that they used the different fittings. Just letting you know to be aware of possibilities and to make sure you get all the parts you need before you crawl underneath. Otherwise, swap the proportioning valve and it should be pretty straight foward. Good luck!

samiam91RS

yes the prop valve...i did some search's and it seems like i need an adjustable prop valve since im doing all 4 disc's? from drums becase they need lesser pressure. im hoping the fittings are the same..by the fittings are you referring to the ones that connect to the MC? or the ones underneath the rear itself? yea i wanna have everything i need also b4 i get underneath the lift, if not ill prolly use curse words i never thought existed!

84redta

iTrader: (34)

you can use a GM proportioning vavle from a 82-92 (89+ recommended because it's configured for larger rotors) firebird/camaro with 4 disk brakes (i just got one for $30 shipped) for the cleanest application. By what i mean is the same fittings is that you can literally unbolt the stock disc/drum prop valve that you have on the car right now, and reinstall a disc/disc prop valve with absolutely no modification.

That means you disconnect the 5 connections to the disc/drum prop valve, and re-connect the 5 connections to the disc/disc prop valve. Otherwise you can spend the $100+ for an adjustable prop valve and then you would have to custom plumb that into your rear brake line to the rear axle. Your preference. The adjustable prop valve would give you more control and you can tinker with with how much pressure is going to the rear. Otherwise if you are interested in a stock, simple, with no other modifications, then use a stock GM proportioning valve.

87zjeff

iTrader: (4)

actually, i found out the hard way that they changed the fittings on the lines from the prop valve to the calipers in mid-89. he will need the prop valve from an '89 1/2 up to work with his brake lines.

84redta

iTrader: (34)

alright, as i mentioned way up i heard they made a change somewhere around 90. Seems they made quite a few changes in 89. I guess i got lucky as hell though and picked one up from an 89 4 disc formula and she bolted right in. Then again, can't you get the fitting from a 89 1/2 + car and put it on the brake line of your older car?? Isn't is the same size brake line going to the back, just a different fitting?

I sat there for an hour comparing my 88 disc/drum prop valve to the new 89 disc/disc prop valve i got in the mail...and they look identical outside, and very similar if not identical. My curiosity is that aren't just the springs a different rate (plunger/valves looked different as well). Can't you swap the spring and plunger into a disc/drum prop valve and get the right pressure so that you don't even need to take it off the car??? (sorry if this is hi-jacking your thread, but if you went this route it may prove even easier).

Dale

iTrader: (12)

Doh, yea I meant to put master cyl on that first one. sorry.

I searched and the master cyl is the same between drum and disc. on 91/92 model.

I was told 89'ish is when the thread pitch changed on the prop valve from SAE to metric. I had to order mine from gm.


I had my old axle out tonight in just over 1 hr. After 3hrs the new one is part way in along with some rust control work.

My hardline that goes under the car is partly pinched, so I'm going to have to wait tell the weekend and go to a junkyard to get a replacement.

87zjeff

iTrader: (4)

the lines are the same size. i got lucky(kinda) because i had the motor out when i did mine and just swapped the whole line. i don't know what the internals look like. don't know if they will swap or not. somewhere in one of the threads is discussion of the theory of removing or changing just the spring to increase the line pressure needed but i don't think it ever came to resolution.

Dale

iTrader: (12)

Do you have a link, or know some key words or users involved so I can read this?

samiam91RS

so your saying as long as i have this im good? do you have a part #? please.

oh dont even worry no ones hi jacking anything, its for everyones knowledge i suppose i started something here actually..so your sayin make sure i get a prop valve from an 89+? ill go this route or go to a junk yard and find a 3rd gen with all four discs and if i rip off the prop valve this should work? if so im def gonna do this. another thing im worried about, the lines that connect on the REAR to the disc's are those a perfect match or what? im hoping so since its an identical swap..if anyone knows this q.

oh no its ok! lol. so i def need an 89+ prop valve since i have a 91 correct? thats pretty good timing. whooa how did your hard line get pinched? if i put it on a frame lift will anything bend? just wondering before i do this.

Dale

iTrader: (12)

It got pinced because the tube is rusted in the nut.

You can pinch the line if you drop the axle down to soon. Make sure you take the bracket the holds the brake line to the body loose before you drop the axle. You'll see what I'm talkin about when you crawl under the car.

Yes, you need an 89+ J65 prop valve. So far everything else looks like direct swap.


I'll try and snap some pics tonight. But as I said, its already partway back in. I just want to get it off jackstands and back onto the tires tonight. I dont like crawling under a car on stands

84redta

iTrader: (34)

here's a bind...the more i'm reading...the more i'm reading that 91/92 has the same prop valve for disc or drum...so past that i'm not going to be able to comment. I have looked up a 1991 firebird and it still shows disc or no disc. Just to be safe get a 4 wheel disc prop valve.

Dale

iTrader: (12)

ok. It is all bolted in. I could not get my ebrake cables to reach. I have ordered new ones to be here saturday mid day.

Cant wait to drive it

samiam91RS

oohhh im gonna be careful with that then...89+ J65 prop valve huh? do you have a part # for that? or do i have to rip it off another car, if so which ones have this? and thats awesome you have it all bolted in!! tomorrow i get my panhard bar LCA's and LCARB's from UMI, so im sure you can understand why i havent put the rear in yet! lol. im doin mine on sat. your e brake cables didnt work? oh man i hope mines do.. but my rear end came with the full e brake cables so im hopin soooo. and what can we expect with 3.23's from the stock 3.08's? anyone? hope all goes well dale and let us know! soon to be
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yea thats true, im gonna get the 89+ j65 prop valve dale is talkin about. how is your prop valve doin? is it all workin out good?
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OH one more thing redta. you swapped out to a 3.23 what are some of the changes involved? just wondering i havent heard of an example..

Dale

iTrader: (12)

I ordered mine about 3-4 years ago for a drum car to get more rear pressure. I found the part number on this site. But I ordered it from gmpartsdirect. EDIT 10164112 should be it.

My axle came with the ebrake cables as well. But they werent long enough. I'm going to try and drive it around the neighborhood tonight.

2.73/open/disc to 3.23/posi/drum. New springs, and hopefully fixed some of my "clunks" in the drivetrain.

samiam91RS

wait..i dont get it..you ordered your from a drum car? oh man i thought you went from drums to disc's? im going from drums to disc's so do i still need the 89+ J65 prop valve? well i hope mines are long enough if not ill order some also or fab it up. do you have a part num for e brake cables that reach? let me know how it is! hope all that hard work paid off. i just got my UMI susp stuff to tomorrow is the DAY!

samiam91RS

i just checked out this on the web site, its like 60 bucks, so this is what i need for my drum to disc conversion in the rear?
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i just checked out this on the web site, its like 60 bucks, so this is what i need for my drum to disc conversion in the rear?

Dale

iTrader: (12)

I common thing for drum guys to do is install a 4disc prop valve in to put more pressure on the rears for more even breaking. I did that to my old v6, and moved it over to this v8 when I got it.


I drove mine around tonight w/o the ebrake cables in. Quite nice Think I may still have some air in the lines.


ebrakes on order, and should be in noon tommorow.........
Tru-Torque c94264/Bendix c1621

samiam91RS

right, for the time being, im just going to keep the regular one (prop valve) on it. until i can order it up. just to make sure, the four disc prop valve is the part number EDIT 10164112 that you gave me earlier right? from gmpartsdirect..let me know so I can order it please. as far as the air in the lines, did you bleed the brakes? I think over time the air should decrease in the lines from driving...so what overall improvements did you find? better launch? and gears to mph difference? i got my UMI stuff today! so im stoaked and getting ready to do this tomorrow and knock it out in a fulls day work. glad you liked the swap. oh one more thing..what site did you get those part #'s from? for the ebrakes? cant find em when i entered them..

Dale

iTrader: (12)

All part numbers came off here on TGO. The tru-torque is for partsamerica/advanced. I think autozone carrys that brand too.

Both tires spin on a burnout. Seems to be willing to spin the tires easier(both). Brakes seem a little more even, and thats still with a partly pinced line. I havent taken it over 30mph yet.

going to try and find hardlines and some nice looking 15" smokys

samiam91RS

hmm well i dont think that i will need new cables it has them already from the beginning to the end and that round cushion on the left side, that prevents it from smushing. well, i got almost everything out! the panhard bar and the LCA's and the sway bar end links, and the coils. i just didnt take the shocks off because the lines would bend (brake lines) and thats my only problem now!! the freaking BOLT that srews into the rubber line connection will NOT COME OFF!!! i twisted it so hard the metal line was turning and that FU--ING bolt will not budge! so i figured i'd go another route, and take that block fitting that bolted on the axle, then splits to a T....so i got one off and i tried to take the other one off but i pretty much ran out of time. the hobby center on base closes at 1700 (5 pm) so i left it over night on the frame lift still. id post some pcitures but dont really know how to on here, is it HTML?

samiam91RS

ok i think i got the pictures on there. well i did get any rear end pics like i said i ran outta time i just threw on the wheels when i was done its pretty much bare in between in the second pic you can see the newer rear almost ready to go in and the other old parts laying on the left. but thats it in a nut shell..

Dale

iTrader: (12)

see, you are having the same problem I had.

I took some map gas to the joint, heated it tell it started to smoke, but not cherry red. Then vise-gripped one end, and 15mm the other end. Twist the hose end, not the tube end.


Then when its apart, keep soaking the hardline with wd40/etc. Mine finally came loose.

samiam91RS

map gas? what the hell is that stuff? man i soaked that stuff with PB blaster, good for nothing! maybe wd would work better, i dunno. well like i said im trying to go an alternative route since i have the lines connected on the rear im putting in. ohh so your saying, dont twist the metal part, but the rubber hose end? im kinda glad they closed i was getting upset and i didnt wanna break something then really F--K myself. thanks for the tip, if anything else comes up tomorrow ill hit cha up. hows your comin along?

ad356

what happens if i use my front disc/ rear drum prop valve with a disc/disc setup? will it work, also is it something that i can change later on?

shermanwizard

iTrader: (2)

What do I need to watch for if I was to replace a 10 bolt differential with a 9 bolt? Would I have to resize the driveshaft or torque arm?

samiam91RS

thats what ive been trying to figure out and from what ive heard, there is different pressure involved between drums and disc brakes...now, for the mean time im keeping mine on until i experience something i shouldnt. but if it works fine, screw it. but im still tempted to get an adjustable prop valve so i can play with the settings and have equal pressure.
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hmmm i dont see a problem..what kind of 10 bolt, out of what? if you did i think all you would need to do is get a U joint i think it called? i know theres also a yoke fitting i dont know if that connects by the torque arm, or by the tranny. some correct me if im wrong..

shermanwizard

iTrader: (2)

I currently have a GM 10 bolt in my Firebird but the previous owner put 4.10 ring and pinion in it. The donor car has the Borg-Warner 9 bolt which has a 3.27. I would leave the 4.10 alone if I never drove outside of the city but it sucks for expressway driving.

grizzlyta44

I guess I'll join the list of people swapping year ends this spring. I am in the proccess of putting in a 9 bolt with 3:23's I am sending it out to have it powder coated before I install it and want to replace all the bearings and seals. my question is I have the axles out and need to get the bearing off, However, the Inner and Outer bearing retainers are preventing this. How can I pull this off? any help would be appreciated.

Dale

iTrader: (12)

Map gas is basically propane in them little bottles. But its a tad hotter.

Since you already took the hose loose on the axle end. Thats why Im saying twist it, so your not taking the chance of twisting your metal line.

Mine is in and driving. I corrected my speedo today. Still working on adjusting my ebrake properly.

samiam91RS

I finally got it off! i went to town today..got the new one in and everything. so far the new rear is in, and the new coils, and the shocks, torque arm and drive shaft connected and all the brake lines connected (bolted right up) but the e-brake cable tips didnt fit into the connecter. the older ones are a ball type on the ends and the new ones are a cylinder type size. no problem im just going to drill out a wider hole for them to slide in. they did reach however...everything was going fine..until i tried to tighten down two bolts that join the driveshaft to the diff..where that X joint goes in between, and the mother FU--ERS broke off inside!!! so i have one bracket on and one is just screwed beyond recognition. it'll hold but i know its not safe...but that did it, jack stands went flying across the garage, i was pissed. i also go the LCARB's on. all thats left is LCA's and PAN BAR, and bleed the brakes. but i ran outta time again today. post some pics up. also, what do ya think i should do about the bolts broken into the diff connector?

samiam91RS

it ok, i just snapped the metal line on the old one (since the new one had the lines already) and then had better access to get it out, once i droppd the axle. two vice grips got the job done hows it driving? wait speedo? it has to be adjusted with the new rear end?

samiam91RS

some before pics of my progress. as soon as i took the shock bolts off it sat on the stands, then i crawled under and smacked the torque arm and that thing went down! lol. actually rolled off the freaking stands, almost...glad i was outta the way

samiam91RS

racing geek

iTrader: (5)

Broke my rear end today... came home from autocrossing and it was making a howoling (sp?) noise. Got home and looked under the car to see differential fluid dripping to the ground. Since my rear is 2.73 limited slip drum brake rear I'm thinking I'll just swap it for a 3.23/3.42 disk rear with either posi or another LS unit. I have school and work tomorrow so I hope I can use my dad's truck and then we can get a rear end from the junkyard on tuesday. Is there anything specific to look for or avoid? Or should I just have my rear end rebuilt?

84redta

iTrader: (34)

to original question like 10 posts ago, lol. I swapped an 88 open 3.08 to a 99 open 3.08 because i'm in need of this car for the summer and while yes, it would have been more simple to get exactly the rear i wanted now, i felt that not having to play with the speedo gears at this time would be simpler, and once i know that this car is going to be road worthy and worth investing into..then i will upgrade to 99+ 3.42 LSD unit from the Y87 equipped model V6's. Not to mention at the moment i'm a full time college student, i commute 60+ miles per day, and the gas prices of a V8?! forget about it. 3.08 is just like an automatic's 2.73, great for highway mileage. So at the moment it was also more suiting for me to stick with something that will still put a smile on my face while drving, will also put a half way smirk on my face at the pump, lol.

To another question above...i'm not positive about the torque arm...but your drive shaft and u-joint unit should bolt right into a 9-bolt. Like i said, i haven't a clue bout the torque arm, but i do know the lower control arms should bolt right in. To correct your speedo you will just need to change the speedo/VSS gear in your tranny.

To a couple questions above...as far as swapping the prop valve, i managed to find an 89+ for $30 shipped to my door by asking someone on the board, and i have it installed, and the brakes bled. Now if i wasn't stripping and polishing my wheels, and my car wasn't in pieces, i would gladly take her down the road and let you know how it is. I have read damn near all the articles about swapping in a 4th gen rear axle, and when swapping to disks they say that there are different pressures to the disc and drum setup. Thats why drums have thier own individual drum cylinders (to boost pressure back there i assume). Anyways, due to the drum cylinders the pressure being sent to the back is minimal, but with discs you have nothing but a piston to drive in the back, so the pressure from the prop valve is higher. They suggest 89+ due to the fact that in that model year...they switched to bigger rotors...i believe something like 11.5's give or take, i probably am wrong, so as you can probably picture trying to stop an 11.5" (LT1) or 12" (LS1) rear disc application, a prop vavle set for a 11.5" is a more suitable match. (this is all guestimation...so my numbers may be wrong, but this is just for demonstational purposes). I have read people getting by with the drum prop valve and then i've heard of people locking up the rear with the drum (figuring that more pressure is for the drum applications?!) This is why i'm so confused to the application, one place i read drums are less, the next i read they are more. If you are set on sticking with your drum prop vavle, i would suggest an adjustable prop valve for the rear just for minds sake that you can adjust, and even if you get a disc prop valve, you can sill have the peace of mind that you can adjust and tinker with your rear brakes.

You can try and rebuild all you want, but a 10 bolt will always be a 10 bolt. They are good for their basic purpose, but it's controversial about say autocrossing with one. There will people that will tell you how many 10 bolts they have blown up, and others that will swear by them. If you pick one up from the junk yard then it will only be a time bomb till it goes again racing around with it. My suggestion is that if your stuck with a 10 bolt and either can't afford/don't wanna switch to a 9bolt or something else...then i would suggest taking some of the steps to strengthen your 10 bolt given to you in the tech articles off of the home page. Welding the axle tubes, heavy duty gurdle (cover), ect. It may be cheaper and more reliable if you were to rebuild the rear axle that you have now if you havne't done any phyical damage, although i'm no professional so i would get the suggestion of others/a reputable shop. Otherwise look for an 89+ (really 90+) rear axle with the gears that you want. In mid 89 (thus the comment above) they switched to 28 spline axles instead of 26, which is rumored to be stronger. For your purposes this may be another step towards a better axle build.

Any other questions feel free to ask!

samiam91RS

hmm thats weird, i never experienced this. did you just blow a seal? i think the best way to find out is pop the cover open and check it out. yea a 3.23 or a little higher might be better anyways. im in the process of the 3.23 posi with disc swap right now and its goin pretty good. i think its less of a pain to just swap rear ends, and prolly cheaper.

Dale

iTrader: (12)

samiam. Just lower the axle back down and vice grip them bolts out. Run a tap down the hole. Get a new DS-mount kit and put it back up.

Same color car too, with same rims. Just mines a vert.

Also looks like you have a pre-89 axle? Thats not how my calipers look.

I guess I should have took pics of the project. But I didnt feel like getting my greasy paws on my camera.

Depending upon the gears in your 2 axles. Yes you need to re-calibrate your speedo. Since mine is ran thru an OBD2 PCM, it was easy. Yours you will need to change the gear on the back of the VSS in the tranny (if changing gear ratios). Fairly simple.

samiam91RS

what do you mean by new DS mount kit? can i just take that DIFF piece that the bolts broke into off and use the other one i originally took off? or is it just connected to the whole thing? yes thats what ill prolly have to do. sucks though it was a pain in the *** getting it back on with the coils too. but i thin i just might have to do that. oh yea same color and rims huh? lol but my paint i hella faded..oxidized for the most. oh did you have the alumminum calipers? those came with 88+ and 82 - 88 had iron calipers..yea i just had gloves and took them off when i snapped pictures. calibrate my speedo? can you elaborate a little for me please?

Dale

iTrader: (12)

DS= drive shaft. They sell new kits for installing the driveshaft that comes with bolts and the c things.

Yes, I have the aluminum calipers. It came off a 92 formula. I never knew the calipers were one front, one rear on the steel ones.

For you to calibrate your speedo, assuming you changed gears. You have to take your VSS out of the transmission. And change the plastic gear behind it. For me, it was re-program my ecm due to how I wired it.

samiam91RS

well i thought i could just take the tip off the old one (the part that connects to the U joint) but i was wrong, theres a bolt on there but it wont come off. i tried to easy out it, drill it out you name it...i broke bits, got shavings all over me and got no where and had to mount the friggin axle back on and up by myself again, so it was all re work. im just going to have the other bracket welded on. screw it. its not like im ever gonna take that thing off, and if i do, its because im gonna replace it again. so its all good. ah your lucky you have alum calipers! well i dunno what advantage that has besides lesser weight. yea i was like, man i need to flip that side of the rotor, but then came to the conclusion that its just like that. yea, 82-88 are iron calipers. yes i changed gears. so change the plastic gear behind it? with another one? if so what kind to match up with the gears i have now? sounds like the VSS is a bit easier to do. so i got a new gasket, and fluid along with some special additive for the clutches inside cuz i found out today that i have a full posi not a LSD. so gasket swap tomorrow with new fluid, and ill be good to go, brake bleed also. aaand try to get those darn ebrake cables to fit. dale, did the ones that you ordered fit perfectly? mine will reach but just wont fit im going to try to fabricate something up. i put in the LCA's and LCARB's. all thats left is the new adjustable panhard bar and ill be set!

Dale

iTrader: (12)

Yea, my cables seemed to fit just fine, they were 6" longer then what was on it. I dunno if my cables will be the same as yours since you have the other style caliper. Might want to search on here.


Also search on which VSS setup you will need.