What should I do for a rear end?
 

My current situation is that I have a Borg and Warner 9 bolt rear end. However, the Posi is kinda worn out and the gearing is 2.77. I was wondering what options do I have for a change in gearing. I can think of 3 ways of coming at this, any thoughts/ ideas?

1. Buy a new gear set for the 9 bolt. I've heard these gear sets don't come cheap. Also, I've heard that if you want any gear above 3.08 you need a 3 series carrier, and with a 2.77 it's a 2 series carrier. So a new carrier would be needed? Would this cost so much that it's worth looking at another option?
2. Buy a 10 bolt from a junkyard, and build it with new axles new carrier, and basic mods
3. Buy a Ford 9 inch that's ready to drop in.

It's gonna be a while till this happens since I need to save up, but any input is appreciated. Thanks

Re: What should I do for a rear end?
 

what is the rest of the cars setup? what do you use the car for? how much power does it currently have and what about in the future? hard to recommend something without knowing more details. Also, you said you can save up but what is your budget?

Re: What should I do for a rear end?
 

Tranny is a 700r4. 26 inch tall tires and it's mostly a street car, will see highway. I would comfortably say around 400 to the wheels. And the budget is the cheapest option. Honestly dosent matter to me which one is better, I just like cheap lol

Re: What should I do for a rear end?
 

Cheapest easiest probably find a 4th gen rear seems like those are still out there. All 4th gen Z28s T/A, Formulas had posi and the 6spds usually had better gears.

Re: What should I do for a rear end?
 

Isnt the 4th gen rear end narrower? Also would it just bolt right in?

Re: What should I do for a rear end?
 

4th gen rear is wider; a shade under 1¾" each side. Makes the rear wheels stick out and look real weird and poseur. 4th gen wheels fix that, but then you need spacers on the front, about 1¾" believe it or not, to put on matching wheels.

Bolts right in.

Re: What should I do for a rear end?
 

Any tips of what year rear end to find? I was hoping for a mid 3s gear. And would it hold up to lets say 450whp? Launching at the strip with radial slicks and a stock converter. So its not too hard on the rear end.

Is it that hard to re-gear the stock 9 bolt? I think its in pretty good shape

Re: What should I do for a rear end?
 

Could always upgrade the diff and grab a set of gears. Cheap, not exactly but imo, it would be a bit better than a 10bolt.

9 Bolt Borg Warner Torsen upgrade completed! Thanks keykey! - Third Generation F-Body Message Boards

Re: What should I do for a rear end?
 

is this a real 450 rwhp? or are you just guessing numbers?
also, it is torque that is more of a factor, not horsepower.

Re: What should I do for a rear end?
 

98-02 V8 stick shift car. Likely will be 3.42 or maybe 3.73.

Probably. The cars such a rear would come out of seem to mostly do OK. The stock converter forcing it to launch at only 1700 RPM or thereabouts will largely protect it.

About the same as any other rear. They're all pretty much about the same for the most part. Problems you'll have are, you'll have to come up with a 3 series carrier, since there aren't any 3-series ratio gears for that made to bolt to 2 series carriers, like there are for more common rears; finding all the parts, especially certain seals, is a pain; and if it's a 86, it has the crappy cast-iron brakes. I wouldn't sink money into it, myself. Others may feel differently FWIW.

Re: What should I do for a rear end?
 

No, and I don't think it's pushing that. But I would like to overbuild it just for durability reasons

Re: What should I do for a rear end?
 

Can a 3 series carrier bolt into a 2 series case? Also I never knew about the cast brakes. Makes more sense now, no wonder it does really good burnouts lol

Re: What should I do for a rear end?
 

,

gotcha. I understand overbuilding it. I did the same when i went with my 12 bolt. it got pricey, but thats part of the game.

Re: What should I do for a rear end?
 

Housings are all the same. Any series carrier will bolt into any housing. Of the same make/model of course. So a 10-bolt carrier of ANY series will not bolt into a 9-bolt, or vice-versa; but 9-bolt housings will accept ANY 9-bolt carrier of any "series".

Here's the difference about "series". Pics are POS Auburn carriers from a 7½" 10-bolt but the basic principle applies to EVERY rear of EVERY manufacturer in EVERY year and EVERY car model.

https://www.thirdgen.org/forums/atta...-carriers-2-vs

2 series on the left, 3 on the right. Note how far away from the pinion, i.e. how far toward the bottom of the pic, the ring flange is on each.

The 9-bolt is exactly the same as this (as is the GM 12-bolt, Frod 9", Xler rears of all sorts, etc. etc. etc. ... just basic physics) except different as to the details.

Re: What should I do for a rear end?
 

if you go w/ 4th gen rear, go '99+ when selecting an LS1 rear. the LT1s and '98 (i think) had the auburn diff which is junk. the '99+ Zexel-Torsen is much better. If you care, the LS1 brakes are a tad bigger although the LT1 disc setup is easy to adapt to a 3rd gen drum housing.

you could find a v6 manual 3.8L 4th gen and get an open diff 3 series carrier, believe they had 3.23s? but may be drum brakes. I don't know if any of those came with discs. if they did it would be a budget way to go to get moving.

I recently went through the same process. however I won't be making as much power, i hope to have a solid 300RWHP and may end up staying on skinny tires.
initially i bought a 4th gen rear but decided I didn't want the 'modern' offset wheels. i kept the brakes and sold the housing recouping most of my money. I grabbed a '91 2.73 rear, gutted it, and rebuilt it from the ground up using 3.42s and 3-series Trutrack. Its still a drum setup for now, but I have all the Lt1 disc parts in abox.
https://www.thirdgen.org/forums/tran...ild-y5e06.html

Re: What should I do for a rear end?
 

Did you buy a complete 9 inch ford and was it a drop in setup,, i am in Australia and need a drop in setup.

Re: What should I do for a rear end?
 

I actually swapped it with a 10 bolt out of a 94 camaro in the end

Re: What should I do for a rear end?
 

are they wider than the 82 model.

What size are the 94 diffs 8 inch.. 8.5 etc

Re: What should I do for a rear end?
 

A brief search of the entire Interwebz (minus Russia of course) yielded the following result. Amazingly enough, it was on this site, in this very post. :eek:

Applies to ALL 93-2002 as compared to ALL 82-92.

ALL 10-bolt differentials in ALL 82-up F bodies are 7½". Also known as 7-5/8" starting sometime in the late 80s when they started making the ring slightly larger OD. Doesn't matter though, the same gears fit ALL rears of that series, back as far as the late 70s when it was introduced. AFAIK ALL replacement gears that you can buy nowadays are the slightly greater OD.

I don't often use "absolute" kind of words like "all", "never", "every", "none", always", etc.; but in this case it's appropriate.

Re: What should I do for a rear end?
 

:lmao: LOL! Almost spit my drink all over the keyboard

Re: What should I do for a rear end?
 

ALL carriers of any given model of rear will bolt into ALL housings of that model.

OOoooooppppps, there we go with those "absolute" words again... ;)

I guess I'm doing a good job then? :D

Re: What should I do for a rear end?
 

i want a 9 inch ford not a GM diff i have an eaton trutrac now and its ok for 6 cylinder cars.
the 1967 to 1979 diffs in Z/28s were pretty tough,,,,,,,,, the rest 1979 up are 6 cylinder stuff and the borg warners were made here in Australia and shipped to America.
We had them same rear ends in locally made 6 cylinder cars from 1979 up until the late 90,s

Re: What should I do for a rear end?
 

Ive heard from forums that the Aussie Borg Warner 9 Bolt can handle 500 ft/lbs stock. I would personally have to see that to believe it, but maybe it has a element of truth, I have no idea

Re: What should I do for a rear end?
 

We build corvette diffs here too for GM America...... Them Borg Warners were used at Bathurst for 15 years.
Check our Racing out.

The most Potent 351 Ford engine was the Aussie 4V cleveland. they were in our GTHO Falcon and used by De Tomaso to run Le Mans.

My car Doesnt have a Borg Warner Diff,, its the crappy early 82 diff. 26 spline. its a GM diff made in the States somewhere.
they were ok with the 305/350 but a hot engine no way..

Re: What should I do for a rear end?
 

1st gen Camaro/Firebird (67-70) used the 8¼" 10-bolt or the CAR 12-bolt (quite a bit different from the TRUCK 12-bolt).

2nd gen (70½ - 81) used the 8½" 10-bolt, after 72 or so. A MUCH more robust unit than the 8¼", far more different than the ¼" ring gear dia difference would lead one to believe.. Some earlier ones came with 12-bolt also.

3rd & 4th gen came with the 7½" 10-bolt (a severely weenie thing, little stronger than the 8¼", invented in the mid 70s for gas mileage), or the 9-bolt.

GM rear ends are a product of the Saginaw division, based in Saginaw, Michigan, north of Detroit. They had plants in some other places that built that product line.

Borg-Warner is an American company that built the 9-bolt in their plant in Australia. It was still in use, in a slightly (very slightly) evolved form, in the GTO/G8/SS car line, which is a GM Australia platform (Holden).

Cleveland is a city in Ohio, in the US, on Lake Erie. That's where the Frod motor known as "Cleveland" was built. (The other main Frod V8 engine facility back in those years was in Windsor ON, a city immediately across the Detroit River from Detroit, in CA). And yes, the 4V version was A BEAST; my late little brother had one, I know it well; a big block Chevy exhaust manifold will almost GO INTO the exhaust ports on the Cleveland 4-bbl heads, they are so YYYUUUUUUUUJJJJJJE. The Cleveland 2-bbl heads were COMPLETELY different in this area; unlike typical GM motors of that time, where there were relatively slight differences, if any, between a 2-bbl and 4-bbl version of the otherwise same motor, other than the carb flange on top of the intake manifold. Alot of 351C 4V parts are totally incompatible with 351C 2-bbl ones. Exhaust manifolds in particular. ;) I'll save that story for another time.

Re: What should I do for a rear end?
 

I have done a good amount of C3 Corvette IRS Dana-44 Rear Differential swaps into Third-Gen F-Bodies.

If you can find a "good-used" Unit from a Automotive Scrap-Yard for a cheap price...
These Differentials can be modified with cut-off pieces of the original Third-Gen. Differential-Housing (to attach suspension components), and
work quite nicely.

Re: What should I do for a rear end?
 

if your going to put any kind of horse pressure to it i would go with a nine inch quick performance has a very nice set up for third gens .