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rear end/differential question Rate Topic: -----

#1 User is offline   firebird512 

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Posted 26 May 2010 - 01:02 PM

hi i have a 1996 pontiac firebird formula 5.7 and i am thinking about getting a new rear end for my car like the whole differential and axles too either new or used prolly used though for money purposes but i was just wondering how do you take the rear axle and differential off? is it all just one big piece? and do i have to use differential that was on another 1996 pontiac firebird formula or can i get one from other cars too and if so what kinds? thanks for your help like usual and hope to hear some thoughts thanks! have a good day!
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#2 User is offline   firebird512 

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Posted 26 May 2010 - 01:44 PM

and on average how much would it cost to rebuild the stuff inside the pumpkin like the gears and stuff on my car???
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Posted 26 May 2010 - 02:22 PM

The entire rear end will come off as one piece. You'll need to remove the wheels so you can take the brake callipers off. You'll also need to unbolt the driveshaft from the rearend then unbolt the control arms by the wheels. It'll come out in one piece from there.
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#4 User is offline   Injuneer 

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Posted 26 May 2010 - 02:31 PM

The rear axle assembly is removed as a complete unit. I have an online guide to swapping the rear axle assembly out:

http://www.injuneer.com/Strange12.html

Strange 12-bolt full replacement:

http://www.injuneer.com/images/photos/axl09.jpg

First.... why do you want to change it? Do you know what rear axle ratio your 96 has? It either left the factory with a set of 2.73:1 gears (base automatic - RPO option "GU2") or 3.23:1 gears (perfomance rear axle = RPO "GU5"). Look on the build code tag in your glove box for the RPO codes.

Whether you can swap out the rear with the assembly from another 4th Gen - both Camaro and Firebird work - (can not use a 3rd Gen - same weak 7.5/7.625" 10-bolt assemlby, but 3" narrower), depends. First, all V8's have a limited slip differential. V6's do not, unless the car had extra cost option G80. V8 cars all have rear disc brakes. V6 cars do not, unless they have the Y87 package. Then there's the issue of ABS (only) vs cars with ABS + TCS. If your car has only ABS, you need to get a rear axle assembly from a car with only ABS. If your car has ABS + Traction Control, you can only use a rear axle out of another car with ABS + TCS. The wheel speed sensors are different. And, then there's the issue of a rear axle assembly from an LT1 car (93-97) and one from an LS1 car (98-02). The E-brake is different, so you have to pull you 96 E-brake off and use it on a 98-02 rear axle.

Now... again, why do you want to change? If you simply want to change the rear axle ratio for better performance (3.73:1 gears is the usual upgrade for the 4L60E tranny cars), you can get new gears ($200), and install kit ($75-100) and have them installed by an experienced shop ($250-350). Or you can find a rear with the gears you want, but most of them are the 2.73 and 3.23 rears from the cars with the 4L60E, and 3.42 rears from the T56 manual trans cars.

If you are afraid of breaking the stock rear, an automatic without sticky tires will survive some decent HP. If you are looking at going over 400-450HP, and using sticky tires at the track, you are looking at something like the Strange 12-bolt or the Strange S60 complete rear axle assemblies ($2,500-$2,800).
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#5 User is offline   firebird512 

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Posted 26 May 2010 - 02:52 PM

i want to change it because i keep hearing a knocking noise coming from the pumpkin i dont know what to doooooo.....was think maybe just get a whole new one or have it rebuilt i dont know.......maybe you can advise me on what to do..
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#6 User is offline   Injuneer 

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Posted 26 May 2010 - 07:54 PM

When do you here the knocking noise? If its only when you are turning a corner, its possible someone refilled the lube and failed to add the required GM limited slip differential additive.
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#7 User is offline   firebird512 

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Posted 26 May 2010 - 08:25 PM

no its when im driving straight and it knocks up to like 30 mph

i was thinking maybe one of the gears in there is busted i was gonna see if my dad would help me this weekend take the differential cover off and have a look in there and see what we can see....

This post has been edited by firebird512: 26 May 2010 - 08:58 PM

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#8 User is offline   firebird512 

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Posted 27 May 2010 - 01:30 PM

are the gears in the differential known to break under heavy acceleration? my car is all stock by the way and i have ABS and traction control
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#9 User is offline   Injuneer 

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Posted 27 May 2010 - 01:32 PM

The stock 10-bolt rear is pretty weak. The ring gear is only 7.5-7.625". The ring gear will break. A4's are more forgiving than the M6 cars. The rear axle assembly was originally designed for the 4-cylinder S-10 pickup. Its crazy GM put it under a heavy passenger car with a high torque engine.
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#10 User is offline   firebird512 

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Posted 27 May 2010 - 01:44 PM

ok i will keep you posted fred once i take a look inside the differential this weekend and let you know what i see. thanks for your help! you are very knowledgeable about these cars! http://www.firebirdnation.com/forums/public/style_emoticons/default/;%29.gif
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#11 User is offline   firebird512 

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Posted 27 May 2010 - 02:56 PM

what are some things i should inspect on the rear end for the knocking noise so far i was going to inspect the u joint that connects the drive shaft to the differential, then i was gonna take the differential cover off and inspect the gears inside, and i also heard of someone having a similar problem and he found out it was just the caliper sticking how likely do you think that is to happen? because sometimes my ABS light comes on and then other times it wont so almost seems like theres an intermitten problem with the brakes possibly so i might check that too. just wondering if theres any other parts of the rear end you can think of for me to inspect this weekend. thanks for your thoughts!!! have good day/night.
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#12 User is offline   1997ws6 

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Posted 27 May 2010 - 08:37 PM

Ian,

Have you jacked up the car and spun the tires around yet? You might be able to figure it out without tearing apart the differential if it's something else. Please remember to use jack stands.
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#13 User is offline   firebird512 

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Posted 27 May 2010 - 09:19 PM

hey kevin, yea i had a shop spin the wheels for me and no noise i dont think, i will check this weekend though and make sure for myself but it seems to only make the knocking noise under acceleration usually not when coasting and sometimes when i brake i hear like a sorta grinding noise

This post has been edited by firebird512: 27 May 2010 - 09:20 PM

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#14 User is offline   firebird512 

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Posted 29 May 2010 - 05:15 PM

ok so i just got done working on my car, this is what i found out, i inspected for play in the driveshaft theres was no play. then with the car up on jackstands i spun the back wheels and i didnt really hear any noise some little clunks but my dad said that was normal then i took the differential cover off and inspected the ring and pinion and the spider gears they all look to be in good shape no metal shavings and no chipped teeth. so i put the differential cover back on and filled the differential with mobil 1 synethetic gear oil it was 75w-90. it seems to help the knocking noise a little bit i didnt drive it around too much im going to drive it around some more and mix it together better. but the only other things that i could think of that would cause the knocking noise consistent with the wheel spin and the grinding noise when im braking towards the very end when im coming to a stop and im pressing hard on the brake is maybe the wheel bearings or axle bearings but i would think those would make more of a whinning noise. if you guys got any other thoughts on what it could be that would be great! anyways thanks for any help i get, and take care and have great day/night!

This post has been edited by firebird512: 29 May 2010 - 05:24 PM

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#15 User is offline   slackerr26 

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Posted 29 May 2010 - 07:48 PM

did you also put in the limited slip additive made by GM?
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#16 User is offline   firebird512 

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Posted 29 May 2010 - 09:00 PM

what limited slip additive are you referring to? this mobile 1 stuff is for limited slip/posi-traction cars

This post has been edited by firebird512: 29 May 2010 - 09:01 PM

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#17 User is offline   slackerr26 

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Posted 30 May 2010 - 02:30 AM

http://www.shop.spee...t-additive.aspx
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#18 User is offline   firebird512 

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Posted 30 May 2010 - 04:37 AM

how important is it to use that stuff?
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#19 User is offline   slackerr26 

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Posted 30 May 2010 - 08:24 AM

you have to. otherwise it will still make grinding noises
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#20 User is offline   firebird512 

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Posted 30 May 2010 - 10:17 AM

can i pick that stuff up some where by my house or is it something that can only be bought online? and how do i apply it do i just pour it in the filler hole or do i take the cover off and put it on the clutch plates?

i was starting to think maybe a bad wheel bearing or something

This post has been edited by firebird512: 30 May 2010 - 10:15 AM

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