ken3983

I got a 89 Formula and the rear end pretty much needs an entire kit. HOWEVER, this is a 9 bolt with 3.27 gears. Rare from what I understand. I got the posi rear. Hard to find the gears for this thing (made in Australia IIRC). If I had other choices, what can I put in that will stand up to the 350 tpi? This has the GW6 RPO code option on it.

sofakingdom

iTrader: (1)

Just about anything will "stand up to" a TPI motor, short of egregious abuse, or nitrous.

What EXACTLY is wrong with it that it "needs an entire kit"?

ken3983

well, A buddy of mine took it to his friend who specializes in GM trannys and rear ends and this is the email he got regarding the situation...

" first of all, we checked the rear end. no gear oil in it at all. we filled it and drove it briefly before thinking we better get back to shop. rear end chattering and whining badly now with grease in it. looks like it burned up the diff cone unit. the gear is so sharp you could shave with it. worst news yet it is not the common 7.5 inch gm rear. it is a 9 bolt 7.75 inch rear. so far no luck finding pars. we need differential unit, ring and pinion 3:27 gear ratio, install bearing and shim kit and outer axle bearings and seals. the left side seal is where the axle lube escaped."

sofakingdom

iTrader: (1)

Needs more than a "kit" if you let it run dry.

Best to find a whole rear rather than trying to fix that one. Gears, posi parts, "kit", and labor, will end up well north of $1500. Watch the classifieds on this site.

cardo0

I wish i had a 9 bolt in my 4th gen. Maybe just a little bit stronger than my 10 bolt 7.5" but it eliminates the C-clips, also i hear its a couple inches narrower and bolts right in.

Anyways for parts try 9bolt.com: http://www.9bolt.com/index.html. Also i think Yukon gear has some ring and pinion sets - maybe other parts to. Take a look: https://www.yukongear.com/Default.aspx

Hope this helps ya. All the upgrades are gonna be expensive - unless u can find a GMPP Dana 44 (i think summit used to sell'm too).

ken3983

Well, I'm waiting on the Paypal invoice from 9bolt.com. He has a complete kit with all I need for $660 including shipping. I'm curious though. If I ever had to put an entirely new rear end, what options are available? 10 bolt, 12 bolt, Dana 44? Something that is easier to find parts for than my current rear end.

Damon

There are no factory-style bolt-in upgrades (something you could take out of a different GM car and bolt in under your F-body). On my old G-body Malibu I upgraded to a Grand National rear end (basically a GM 8.5 10 bolt) but there is no such equivalent for a 3rd gen F-body.

You're either dealing with the 9-bolt, modestly downgrading to a much more common 3rd gen F-body 10 bolt (7.625" ring gear) or you're going aftermarket.

Just be aware that aftermarket is pricey and NOT EVERYTHING MAY BOLT RIGHT ON. E-brake cables and factory brake line routing and retention being two that most most people forget about until they've got it bolted up and wonder "where do I attach this??"

In defense of the factory 3rd gen rear ends, they're both tougher than most give them credit for. It's hard launches on sticky tires with a manual transmission that is the fast path to breakage. Automatics are MUCH more gentle on the rear end, short of launching with a line-lock. If you're running on the street with regular tires the "safety valve" is losing traction. Before I got the GN rear (because I now run drag radials) I ran my supercharged 383 Malibu's power to an even WEAKER version of the 10-bolt (7.5" ring gear, stock in G-body Malibus) and it lasted for YEARS like that because if it ever got "leaned on" hard, the tires just spun.

ken3983

Ok...I gotcha. Is it possible to keep the 9 bolt rear end on and replace the ring and pinion with something like 3.70 or lower? In other words, just replace the guts and keep the rest. And replace all other parts accordingly. Spline, differential, etc...

sofakingdom

iTrader: (1)

Yup, you can do that.

$1500 BARE MINIMUM. Assuming you can find the parts.

Those things are $$$$$$ to do anything to, and hard as hell to get the parts for besides. In fact one of the parts nobody can seem to find is one of the axle seals... that thing uses 2 different ones, can't recall which one is now forged in the fiery furnaces of Hell by 10,000 yr old gnomes from 90% 23.9 karat nonobtanium alloyed with 10% pure Grade AAA extra-virgin irreplacium; doesn't matter too much when you're trying to "renew" something. Odds are never in your favor. If I was the betting kind, (I'm not, I'm a statistics teacher in my spare time) I would bet that the one you need, the one that wiped out everything else, is the one you can't get.

My advice remains the same. If you ran it dry, you destroyed it; it has no future, no matter how illustrious its past. Time to go looking for a replacement. An identical one, for that matter; but, a replacement. It will cost you A FRACTION of "repairing", let alone "restoring", what you have now.

Ron U.S.M.C.

Here's my complete 10 Bolt rebuild.
It give's some indication as to what cost what.
It does fall under the expensive side but works perfectly for my application.
=
https://www.thirdgen.org/forums/tran...de-photos.html

red rock

iTrader: (2)

Here is a brand new 3 series carrier. http://www.ebay.com/itm/NOS-85-90-Firebird-Trans-Am-GTA-Camaro-IROC-Z28-1LE-positraction-carrier-new-GM-/391162584329?hash=item5b131b5d09&vxp=mtr Maybe I should buy it. Lol

sofakingdom

iTrader: (1)

Maybe so... depending on which gear series it is.

Metalizer

Can someone post a picture of there 9 bolt? I picked one up, took all the brakes off it and cleaned it up to paint.

When putting the caliper brackets back on it didn't seem right. A good picture of how the calipers (aluminum) and brake lines are orientated would be a big help so I can install it back in the car.

I thought I took pictures but that was of the 10 bolt I removed.

ken3983

Well, I lucked up. 9bolt.com had a rebuild kit. It comes with a series 3 posi carrier, 3.27 ring and pinion gears and bearings for $680. All in used (excellent) condition. Should last another 100,00 miles hopefully. Lol. Plus. tacreationsusa.com had a set of 3.27 gears for $65.

cardo0

Congrats! U need to keep us updated on costs and over time again if u can to let us know if it lasts for you. Unless u do an awful lot of racing u should be good.

BTW ive been reading some one in the Parts for Sale section that is selling caliper brackets for the 9 bolt rear. Take a look if u need those: https://www.thirdgen.org/forums/engi...t-pbr-1le.html.

ken3983

Well, I got the parts in from 9bolt.com and they were in excellent shape. So total cost to have the rear end rebuilt was $1460. Drives like a new car, I just gotta find that rattling exhaust sound now. Sounds like the muffler. lol. If it aint one thing its something else

cardo0

Cool news! Glad things worked out for u. Feedback helps us all.

Theres an '86 on local CL im looking at but its an GU8(?) with drum brakes. I think i want to start with a disk brake rear rather than try and upgrade. But i feel safer drag racing w/o "C" clip axles in my stock 10 bolt.

yaj15

iTrader: (3)

I had good results when I used 9bolt.com to rebuild my rear end. I upgraded from 2.77 gears to 3.45's. Made a world of difference in terms of how the car accelerates. I got a 3-series carrier, ring & pinion, a rebuild kit and a t/a cover. Had a local shop install the parts and haven't had any issues. Just remember if you do change the gears you'll have to change your speedometer gears to match your new ring & pinion.

I agree with the other posters, the Borg Warner 9bolt rear is stronger than the 7.5'' 10 bolt rear. With mostly street driving, street tires, and an automatic transmission the rear should last a long time. Tires will go up in smoke long before damage gets done. It's hard launches at the drag strip with sticky tires that make these rear ends blow up.

The other side benefit of keeping a factory rear end is that they require less horsepower to turn than an aftermarket 9'' or 12'' rear end. Don't have to use or make brackets to attach brake lines or sway bars to factory rear ends either.

LiquidBlue

Great thread over here : https://www.thirdgen.org/forums/tran...-10-bolts.html


Interesting, these guys are claiming 2.73 gears are faster in real world race....

http://www.camaroz28.com/forums/lt1-...-3-23-a-59156/