I was thinking about going the cheap way and get a rear from a junkyard. Has anyone done this, how much do they go for and would it be hard to find one w/ 3:73 gears to fit my car?

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'86 IROC
T-TOPS, TINTED WINDOWS, BRAKE LIGHT BLACKOUTS
GM GOODWRENCH 350
EDELBROCK TES HEADERS
FLOWMASTER
EDELBROCK 600CFM CARB.
KN AIRFILTER
ACCEL HEI DISTRIBUTOR
2:73 GEARS
Rebuilt 700R4, with manual valve body
B&M Megashifter
Soon to be installed
Exhaust Cut-Out
"There is nothing more addicting than speed"

 

I got 3.73 posi out of a u-pull it junkyard for $35, but obviously I got really lucky
If you want 3.73s they may be hard to find, it took me a year of looking before finally stumbling on the one I got. I'd say a normal price for one is about $180-300 from what I've seen.

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'84 Z28 LG4 T-5
'92 Z28 wheels
153,000 miles
Front& rear suspension rebuild using MOOG parts
350 and WC coming in summer 2001
'70 nova 307, th350, all stock, 40,000 mi almost like new

 

I bought a 3.23 geared 10 bolt out of an '88 Iroc for $200 about 2 years ago. That was complete including the disk brakes.

Sparks a flyin'

 

I bought my 3.73/posi/disc rear axle, out of an '84 T/A (engine code "G", manual trans) for $150. I talked the yard into letting me pop off the rear cover... I verified the 3.73 ratio, and checked the magnet & fluid for busted metal- the gears were good!

Then I spend an additional $450 rebuilding the axle (bearings/paint/brake calipers & hardware) and changing my rear drum setup to take the rear discs. I'll have to spend another $250 to buy the service bulletin parts to "fix" the poor design of the 82-88 rear disc brake calipers.

In hindsight, I should've just bought $200 gears, the $100 SLP posi, and paid someone $200 to install 'em. Oh well; I got discs and bragging rights out of the deal!

If you find a 2.5l 4-cylinder F-body in the junkyard, check it's axle out! Those guys had 3.73/open/drum axles, and the gears/axles are the same strength as the V8's got.

'83-'85 was the years of the 3.73's behind V8's. The "Camaro H.O." (stamped on rear bumper) had a 3.73/open/drum axle, too. If you find an '84 T/A or Z28, with engine code "G" (think "Gold") and a manual trans, you've found the 3.73/posi/disc.

Mid-80's (85-88) 2.8 V6's got a 3.42/open/drum rear axle- same strength as the V8's. If your 3.73 search is killing you, check out the 3.42 option.

'82-'83 rear brake systems used SAE fittings on the brake lines, not metric. All '84-current f-bodies used metric. You'd either have to find adapters, or put your '86's brakes onto the '82-'83 axle.

Rear disc brake axles can't hold rear drums, and vice-versa, without machine work.


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-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.f-body.net/mailbag/3rd/3rd_mailbag.html message boards
---Think your car could be pic of the week? Visit http://www.f-body.net for details!

 

Where can I buy a posi for $100 the SLP you mentioned.

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'86 IROC
T-TOPS, TINTED WINDOWS, BRAKE LIGHT BLACKOUTS
GM GOODWRENCH 350
EDELBROCK TES HEADERS
FLOWMASTER
EDELBROCK 600CFM CARB.
KN AIRFILTER
ACCEL HEI DISTRIBUTOR
2:73 GEARS
Rebuilt 700R4, with manual valve body
B&M Megashifter
Soon to be installed
Exhaust Cut-Out
"There is nothing more addicting than speed"

 

http://www.slponline.com/view_produc...TNUMBER=64501T