fadetoblack

I own a 1990 Formula 305 TBI w/auto-trans. I have obtained a block to begin work on a 383 for it. I have already made plans to swap the transmission to one from Pro-Built. I also know that the stock rear end is not going to support that kind of power. Unfortunately, I do not know anything (other than gear-ratios) about rear-end assemblies. I have read countless threads on this board about rear-ends, but at some point or another they always tend to talk about something that I am unfamiliar with. Basically, I just need to know the most straight-forward way to get a rear-end on the car that is going to work for me. If I can rebuild the stock one ... great ... just tell me what to do. If not, tell me where to buy a new assembly. My only requirements are positive traction, 3.73 ratio, and disc brakes. Thank you to everyone on this board. You have helped me with just about every mod that I have made so far. I'm really counting on you to educate me AGAIN!!!

88Camaro350

Your stock 10 bolt with a good posi-unit and gears will hold up...probably...

Unless you run slicks....if you do its dead.

Cronic3rd

So.. You want a POSI 3.73 rear that will holdup to a healthy 383. The easiest way to do it is to get either a 12bolt or 9" bolt in rear from either Moser, Currie, or Strange. Your stock 10 bolt will require a lot of work to possible be able to hold that much power but no matter how much work you put into it 400ft/lbs + slicks will kill it. A 9bolt is a possibility but they are kinda hard to get ahold of and expensive to repair and impossible to upgrade.

TheGreatJ

9-bolts aren't nearly as worthless as that last post made it sound. Gears and parts are readily available at 9bolt.com, entire rears can be found at most junkyards (try that with a 12-bolt,) and nearly all of them came stock with posi and discs. You'll have to buy your brakes seperately if you go with a 12-bolt or 9", and thats AFTER paying 2 grand for the rear itself. You can get a boneyard 9-bolt and build it with new bearings, gears, and posi for a LOT less (the new posi/gears/install kit from 9bolt.com runs about $900 shipped.)

BIG_MODS

iTrader: (9)

If you are on a budget and don't mind doing some fabrication, get a 8.625" 10 bolt out of a ZR2 S10 (All S10's have a 7.625" axle except the ZR2).

They have disk brakes, and 3.73 or 4.10 gears, and i think they have a locking diff. 8.625" is the same size gear as the 1500 chevy, but this axle has the tube size comparable to the S10 so it isn't a beef cake like the full size truck axle.

The track width is about an inch wider on each side. You'll have to cut the brackets off the axle and weld f-car brackets on. You'll also have to make a provision for a torque arm. I'm planning to just drill blind holes into the housing and fabbing up a bracket to bolt on.

I've been meaning to right up a post to let people know about this cheap alternitive to the 12 bolt. It is very comparable in siize, 8.625 vs a 12 bolt 8.875 so strength should be very close. Should be able to find on from a junk yard for a reasonable price. I've never heard of anyone using this axle but i'm going to try it.

Austin

zman1969

iTrader: (9)

WITH AN AUTO THE 7.5" 10 BOLT AINT TO BAD. GET A GOOD POSI AND YOU ALREADY HAVE THE GOOD 28 SPLINE AXELS IN YOUR REAR .PARTS ARE PLENTIFUL

jdg68

BIG_MODS, the rear you are thinking of is actually an 8.5" ring gear ten bolt (under a few later s-10 types) so there are tons of diffs and gears available for it.

BIG_MODS

iTrader: (9)

No, it is an 8.625" gear. I'm sure of that. But parts from the 8.5 will interchange

From the outside it looks like an 8.5 but the gear is larger. The diff and componets will all interchange. I'm not sure what year they upsized it, but I would guess around 97.

I'm getting closer and closer to building this axle. I just need some time and to use a friend's shop for the machining for the TQ arm welding for the brackets. I have most of the parts. What I need is some extra brackets because I don't want to chop the rear that I have in the car now.

Nozzghoull

The stock rear will hold up for mild street use and everyday driving. If you throw some sticky tires and a aftermarket suspension on her, kiss your rear goodbye! I have a 383 stroker and turned my rearend into a pile of metal chuncks. Get a moser 12 bolt, they make em as a direct bolt in for our cars.

MrDude_1

what it comes down to is this.

if you put the power to the ground... the 10 bolt blows chunks.


the 9 bolt is stronger then the 10 bolt, but with sticky tires and repeated abuse with a good motor.... it too will eventually go.

the 9" and 12bolt can take pretty much anything you throw at it, but it costs alot... so much infact that alot of people pop in several weak rears until they blow instead of spending the cash on them.

you can also get any strong rear axle, and have the proper pieces fabbed onto it..... but that can become a costly way to go if you dont do it yourself....



anyway you look at it, if you want to put your power to the pavement, it costs money.

the other option is to not get traction.... put some sh!tty street tires on the car, and you can spin your 10bolt all day with 500hp.... it doesnt matter if it doesnt hook.

matt shutt

i ahve the same problem with an 84 TA but i want to bolt in a 4th gen rearend cuz my buddies 93 z lauches off the line while im stuck spinning my one tire can i bolt that rearend in or do ineed to change the brackets if any one has tried it email my at m2fasttransam@yahoo thanks alot

Cronic3rd

You don't need a 4th gen rear you need posi. just get 28 spline axels and a take off posi form slp.

matt shutt

not good at rebuilding rears last 1 blew up even after trying to set backlashing for hours plus got a hook up at boneyard i keep hearing they bolt right in but i know e brake cable wont work with disc brakes any ideas