BlackenedBird

iTrader: (5)

I have my choice:

A 1987 9-bolt or a 95 Firehawk rear end with a LG Motorports stud girdle on it. Obviously the 95 rear end has better brakes, but who wins in the differential section? Which would be the better choice?

Yes, I know about the width difference & how it affects wheel fitment. In this case, it does not matter. I can deal with either rear end when it comes to the wheels. I already have wheels that will clear the 95 brakes, so that is not a problem, nor is how the wheels will fit in relation to the quarter panels. I just wanna know which rear end is the better choice.

9-bolt has bolt in axles, 10-bolt has c-clip axles. I could do the c-clip eliminator kit, but that isn't exactly cheap & this car is not used for drag racing, so not a lot of high torque launches will be done, if ever. And even then, not on slicks. Just on street tires.

Apeiron

At least if the 10 bolt breaks you can get parts for it.

BlackenedBird

iTrader: (5)

I really hate when people that argument. No, you can't just walk into any Jo-Blow auto parts store & get pieces any day of the week. Sorry, but finding 9-bolt parts are not hard to get, just gotta know where to look.

88fastgta

iTrader: (9)

i just broke my nine bolt rear end with the mods i have now..... i was just driving on the highway and speed up and heard a loud pop.... everything since then the rear was whining and grinding.... when me and a fellow member on here (camaronewbie) took it took alot of teeth were shaved off and lots of tiny metal particles were all over the inside...

BlackenedBird

iTrader: (5)

Well yeah, sounds like you ran it dry & kept driving after it stated making noise. What was the point of your post? It make no sense. All you did was post to show that YOU kept driving it after running it dry. Has more to with the owners lack of upkeep than the rear end. You'd have blown up a Dana 44/Dana 60/Ford 9"/whatever like that.

88fastgta

iTrader: (9)

it wasnt dry at the time that happened.. actually it was full of fluid because i serviced the rear about 1 year prior... i think i would know how to check for leaks in time to fix them.... that happened was about six months ago when i was on the highway i was driving then accelerated hard...then the rear made a huge bang sound then started whining and grinding seconds afterwards.. still full of fluid then. because i pulled over to check it out.. then about 1 month ago i then noticed it sprayed rear end oil all over my undercarraige and muffler and panhard bar... im guessing it busted something in there and caused it to leak dry.... so it wasnt ME running it dry that killed it because i was still driving it all this time making sure to put my finger in the refill plug to make sure there was fluid in there..... i even put in fluid at that last month to make it long enough to swap out to a new rear because it was leaking so badly. which i did... these rears are weak when you put any real power behind them...

subroc

iTrader: (2)

I have a 9 bolt now. Its only marginally stronger than a 10 bolt. Also at this point in time 90 percent of the 9 bolts will need the posi rebuilt. I did mine a year or 2 ago and it is getting close to needing it again. This time i might just fork over the dough and buy new posi cones from 9bolt.com.

As for finding parts for it...that is a legitimate argument. A lot of parts places have the seals listed wrong for the left and right side axles so getting the correct ones for me took me buying one from napa and one from autozone. All the parts from the posi must be gotten from 9bolt.com or used off of ebay. There are no aftermarket posi's available. At least with the 10 bolt you can upgrade to an eaton posi down the road if you choose.

In the end its up to you. They are both weak in their own ways but one of them is already beefed up a bit with that stud girdle. that will save you about 150 right there.

BlackenedBird

iTrader: (5)

If the PHB got wet, it sounds like the front seal went out. That would explain a lot.

I was reading that in the GM Woodward test, the 9-bolt exceeded their tests better than even the Dana 44 that was used in the Firehawks. So if people think the 44 is "the best" or that the 9-bolt is only marginally better than the 10-bolt & the 9-bolt exceeded them in the tests.............

6 yrs now of running my 9-bolt & the only problem I have ever had was the rear cover bolts loosening, leaking at tad & needing tightened then topped off with fluid. I just have the extra 95 Firehawk 10-bolt now & wondered if it was worth it to put it in.

I like the reliability of the bolt-in axles of the 9-bolt vs the c-clips of the 10-bolts. And the 10-bolt bolt-in conversion kit is like $150. I have no plans for slicks or 4000rpm launches at a drag strip, so I see no need to do the c-clip eliminator/bolt-in conversion on a 10-bolt.

My main desire for the 10-bolt is because of the bigger brakes. But I also don't want a c-clip breaking & the axle assembly exiting the car, making it a 3-wheeler. I have considered just selling the stud girdle off the 10-bolt to buy a stud girdle for the 9-bolt.

88fastgta

iTrader: (9)

either way you still roll the dice.... if the original poster has to ask which one to get its obvious he knows how fragile the units are... either unit is still fragile and bottom line its just a matter of time till it goes if you got a decent motor.... like subroc said the majority of the stock rears that came out of these cars are most likely worn and need rebuilding. auburn units arent even rebuildable... zexel rears which are (99-02 rears) never wear out but they are still weak... if you do any sorta of spirited driving with decent amounts of horespower and torque the factory rears just wont last even with studed girdles.. they are more for looks.. those girdles are beefier than stock but do you really think a cover its going to make alot of difference when you still have those tiny teeth and gears......granted there are people in the tens and elevens with them.. there are also tons of people who popped them with just mild boltons.... i'd say these rears are just as bad as stock 700r4's once you start modding the engine.. ... i already busted my ten bolt from a 4th gen..my next rear will be aftermarket... why spend a ton of money on engine performance but try to skimp out on a decent rear.. i heard this from a wise man once.... " if you put 4000 in an engine count on spending that or more to make the rest of the driveline up to par with the engine" there is just no way around the tiny teeth and gears of they stockers no matter what you throw at it.. buy aftermarket rear and never worry about it again...

Apeiron

That's been tossed around so much in the past 25 years and net not once has anyone ever produced original documentation.

A 9 bolt is decently stronger than a 10 bolt. They're both still stock rears, they can be made to break.

You want bigger brakes, so that means discs? If so, the caliper will retain the axle in the unlikely event that you were to break a C clip.

BlackenedBird

iTrader: (5)

I already have discs, but they are the iron caliper & smaller rotor than the later 9-bolts with PBR calipers & bigger discs.

But yeah, your right. The calipers should hold the axle in, unless the caliper bolts/mounts/ears snap off. Not sure how strong they are in relation to the sideway forces of an axle sliding out. Although they should be strong enough for "Crap!" (pulled straight over) Hadn't thought about the calipers holding them in.

Apeiron

The bolts that hold the caliper backing plate on are the same ones that would be holding the axle retainer on a non-C-clip rear.

BlackenedBird

iTrader: (5)

I haven't seen it on the net, just in the Dec. 84 issue of HPP in my hand right now. No, it isn't "documentation" from GM, but not just net talk either.

88fastgta

iTrader: (9)

im not trying to be mean or a smartass but how can that be if the firehawk was built in 1992 and the ninebolts in 85 or 86... even if that was true everyone would have a ninebolt in thier car right now and there would be a nice aftermarket for the ninebolt rear.... im sorry but i just dont believe it..... i had both rear ends and i can tell you right now they both suck in my experience.. i gernaded both of them... if the nine bolt is soooooo strong then it wouldnt have shredded teeth behind my mildly built motor with l98 heads... people say anything in magazines..... just because its printed doesnt mean its all true....

BlackenedBird

iTrader: (5)

The 9-bolt was an Australian imported item. I have no doubt it was just cheaper (the dollar is the almighty bottom line for GM, not performance) for GM to drop the 9-bolt & just beef up their own 10-bolt they already had.

Not to be a smartass either, but I love your line "just because its printed doesnt mean its all true". You printed your words here, but doesn't make them any truer.

I'm just balancing opinions, which is about all anyone can really expect anymore, most times.

Apeiron

Yeah, that one article is what everyone points to. Even in the text they say that the yet-unreleased 9 bolt is "rumored" to be stronger than a Dana 44, but have absolutely nothing to back it up.

GM's own warranty replacement practices at the time and 25 years of accumulated collective owner experience since then are more telling.

BlackenedBird

iTrader: (5)

I just re-read the article (twice), word for word, start to finish.

It talks about 4 pinions vs the normal 2 pinions. It speaks of true positraction as opposed to the Eaton Locker (which is what was in the 10-bolts at the time of the article, right?)
It speaks of tapered roller bearing & elimination of the c-clip as additional strong points of the design.

NOWHERE is the word "rumored" in there.

7 3/4" Ring & pinion/28 spline axle/4 pinion gears 9-bolt
vs
7 5/8"Ring & pinion/26 spline axle/2 pinion gears 10-bolt

Apeiron

We're comparing it to the Dana 44, not the 10 bolt.

BlackenedBird

iTrader: (5)

And your point is?

If this gonna just turn into another thread about "he said/she said" thread, I'm done. You are claiming stuff that isn't. "Even in the text they say that the yet-unreleased 9 bolt is "rumored" to be stronger"...........It is NOT in the text like you said it was.

Apeiron

You're right, I had to go back and read it again myself. I misremembered the wording.

That single article is the only original report in nearly 30 years that suggests that a 7.75" 9 bolt rear with its smaller bearings is stronger than a Dana 44 with an 8.5" ring gear and thick axles with 30 splines as wide as a **** star's thighs. It does this by reporting anecdotal results of the legendary "Woodward Test Schedule". The test itself hardly seems to be scientific, since there don't appear to be any concrete details anywhere as to how it's actually conducted and what determines a pass or fail. Either way, if the magazine article is accurate, GM didn't seem to take any lessons to heart when they used the uncommon, expensive Dana 44 to replace the common, inexpensive stock 9 bolt when it broke under warranty.

Is a 9 bolt stronger than a 10 bolt? Yes.
Is it stronger than a Dana 44? Don't delude yourself.
Is a Dana 44 the best rear-end? No, only the best that GM made available for the platform, even if it wasn't stock.
Would I run a 9 bolt if I had one? Sure.
For a new performance build would I choose a Dana 44 over a 9 bolt if I didn't have either one already? No, I'd use an aftermarket 9" and forget about either of those rare things.

BlackenedBird

iTrader: (5)

Please re-read the message title though. You took it completely off track.

88fastgta

iTrader: (9)

if it was me i would get the firehawk rear.... parts are crazy expensive for the ninebolt and are expensive to repair compared to the 10 bolt

dimented24x7

iTrader: (2)

What are the details of the two? What gears are in each? Hows the posi in the 9-bolt? What condition is the 10-bolt in? Those are the real questions here. Really it comes down to which has better gearing, and how much work, if any, does each one need to make it operational for the long run.

dimented24x7

iTrader: (2)

As long as you dont have to replace the gear set or the posi, repairs are reasonable for a 9-bolt, and parts can still be had. But its hard to say if that will remain that way for the forseeable future.

BlackenedBird

iTrader: (5)

1987 3.27/posi/disc (the smaller disc & iron caliper)
Has been in for the 6 years I have had the car with no problems other than the cover bolts loosening from time to time, needing retightening & topping off of the fluid inside



1995 3.42/posi/disc
Picked up used & zero idea of the posi gear condition other than it was in a parts car that was towed home. I definitely would pull the cover & check inside before installing the 1995 rear end into my car.

My only real desire for the 1995 rear is because of the bigger discs. 12" (11.9") vs 10.7" and "better" calipers. Despite all the stories I have heard about the older iron calipers, mine work fine. Can easily lock up the rear wheels at 55mph. I know that is not the best way to brake or even good, but it does prove that the calipers are clamping unlike others who say that theirs won't stop the rear wheels from spinning even when the car is jacked up off the ground.

patricklav

iTrader: (7)

have you had a chance to try out the Firehawk's rear end? Im looking at different options; between a 10 bolt from a 92 (what i have now) or a rear end from a 98 LS1.

BlackenedBird

iTrader: (5)

I sold it last Saturday, never did look inside.

87SLEEPER

so you sold the 10-bolt and kept the 9 ? I am interested in how this is working for you. I'm gonna need to upgrade my rear to handle 400hp 420tq. There is a used one for sale by me and comes with disc. brakes already. I would be willing to rebuild it properly if I thought it would be more cost effective for my goals than purchasing aftermarket ford or 12 bolt

BlackenedBird

iTrader: (5)

I did sell the 10 & kept the 9 but I don't drag race anyways, track or street. The girdled 10-bolt came with a parts car I bought to part out. After putting one of my wheels on it while it was still under the parts car, I knew it wasn't going under my car. I know about the approx. 2" wider per side/4" total wider width but I wanted to actually see where my aftermarket wheels sat. I pretty much "knew" they would stick out & I was right, but it was even worse than expected. I thought maybe an inch at most. Nope.....Almost 2".

I really only wanted the bigger brakes but if I'm gonna go through the hassle of doing a brake swap I'm gonna go C5 or LS brakes since the LT brakes are no bigger than the late 3rd gen brakes & I already had & sold a 89 GTA rear end with the bigger brakes & PBR calipers.

In summary? The 9-bolt is plenty strong for my application & the 10-bolt woulda just been a downgrade anyways except for bigger brakes & the stud girdle. I'll just get a 9-bolt stud girdle if I ever feel like I really need one. A 9-bolt will hold 400 just fine anyways.