Hey guys. Well, my idiot x-gf totalled my '94, so I am in the process of finising my 350 for the '88 car and am gonna use the LT1 T56 in it. The motor has victor junior heads, solid roller cam, expecting about 450-460 fwhp with it. The rear in my '88 is a 3.27 9-bolt. Has not given me any trouble YET, however, with a T56 those gears are gonna be just junk, the car will bog a lot.

So, I am curious what 9-bolts are like with a set of ET Streets and a Speck stage II clutch. I broke 3 10-bolts in the '94 and am REALLY sick of them. BUT, given the situation I am in now, a 9" is not in my reach as of yet.

So, anyone have any experience running ET Streets or even Drag Radials with a 9-bolt? How do they hold up? What about the strength of the 4.10 gears for a 9-bolt? Even that might be cheaper then building a 9" for now. Any help would be great. I am excited to have a manual in that car again THAT CAN HANDLE POWER, but the 3.27 I am gonna hate, and snapping diffs every week sucks too. Thanks a lot guys!

 

If I remember correctly, gears and all other parts for the 9 bolt's are really expensive. I dont have hard figures, but you may want to check out www.9bolt.com.

Hope this helps a little,

--Dave

 

I already did, it seems like a waste of money to me if its not gonna hold. Even if its iffy, its kind of expensive to take a chance. A 9" would be smarter, then I can go 4.30 gears!!!

 

The 9-bolt is significantly stronger than the 10-bolt. When they first started using them back in '85 it was considered to be on a par with the Dana 44 for strength. Stronger than a 10-bolt, cheaper than a 9".....it's a pretty good compromise.

I've never run slicks on mine, but with the T-56, 3.70 gears, a Spec stage 3 and some thoroughly aggressive driving, I haven't had a problem out of it.

Keep in mind...the whole reason GM imported the 9-bolt from Australia is because they didn't think the 10-bolt would hold up to the higher torque of the TPI engines. Once they realized the 10-bolt would be fine, they stopped spending the extra money to use the stronger 9-bolt rear ('89 was the last year of it.)

 

So what is the least amount of parts I need to get 4.10s. Just the gears or the gears AND the install kit? I am going to be running ET streets and Spec 2

 

You'll need a new crush sleeve, and possibly a couple extra shims for the pinion shaft. I don't know if you can get them seperately or not...if not you'll need to buy the whole install kit just for the sleeve and a shim or 2. It's a good idea to put new pinion and carrier bearings in since you have the diff apart anyway, but the old ones will hold up if your budget can't afford new ones.

 

Ok. Lots of people seem to be trusting 9 bolts! Anyone on here brake one yet?

 

One guy posted a while back about breaking a set of 3.45's (which is a 9-bolt ratio,) but I don't know what kind of power he was making or how many miles were on the rear or anything like that.

 

I've heard they don't like launching any better than the 1.5x range. Only takes a couple of those and they are toast.

Mine has been 1.6x and its still nice and quiet. Of course that's when the car was still running all the stock stuff. Bigger turbo, injectors, exhaust, etc and I can only muster high 1.7s. Pretty soon should be back to the 1.6x or better.

This is with an A4 so M6 clutch dumps might be another story.

 

I've got more than 30 runs with et streets with 1.7x 60 fts and 345 rwhp. No problems besides the pinion nut backing off.

 

I've been running a 9 bolt for 5 years now behind my 500hp/520lbft big block without a single problem. Low 1.7 60 fts. I was orginally running a 3.27 ratio but switched a few years ago to a 3.73.

I do have some used 3.70/3.73 and some 3.9x and some 4.10/4.11 ratios available with a minimum install kit (ie not the full install kit).

Miles
www.9bolt.com

 

That'd be me with my '87 IROC with the LB9 305 TPI, T-5, and 3.45:1 9-bolt rear.

I was cruising home late one night back in Jan. and I downshifted from 4th to 2nd doing about 35-40mph and as soon as I let the clutch out....KABOOOM!!. It had about 102,000 miles on it when it happened, and I'd owned it since it had 77,000.

I took pretty good care of it since I had it, but it sure had a rough life before me, considering when I picked up the car, the previous owner had spun the bearings on the crank and when I replaced it, the oil looked like sludge.

The only thing aftermarket on the car is a stage 2 chip from FastChip, and a Flowmaster 80 series muffler along with a 3" pipe from the cat to the muffler. I always wanted to do more but I was afraid the T-5 wouldn't handle it and didnt want to spend the money to rebuild it first. Go figure, I was always worried about the tranny, and the damn rear ends up breaking.

Anyways, yes parts are EXPENSIVE for 9-bolts. If I remember correctly, when I had it rebuilt, the gears themselves cost $400+. I believe they came from U.S. Gears and they didn't have 3.45s so I went with 3.73s. I always thought the 9-bolt ratio was 3.70s but I guess they've changed since then.

 

3.70 and 3.73 are both valid 9-bolt ratios. 3.70 was the one they used from the factory (albeit very rarely.)

 

Broke my 3:27 borg warner last year. It was a junkyard rear, but I got almost 3 years out of it before it went, running a 91 aluminum head vette L98 with a few mods. Probrobly would not have broke if I hadnt been acting a fool! Backed it out of a friends driveway and dumped clutch while still rolling backwards......left a hell of a set of posi's, but about a mile down the road it sounded like it was gonna explode! Replaced it with another 9 bolt, a 1LE rear from 89' with 3:45 gears. No problems yet after driving a year with new built motor! They just dont like dumping clutches at high RPM! If I remember right, that was a $475.00 burnout!!!

 

Well, my 4.11s in the 10 bolt on my LT1 were houling, I already broke two previous sets, so I knew time was comming. I took it to the track, ran 5 passes, got a 1.8 60-foot best on ET streets launching off 5k, drove home. BUT that was it. Took a bunch of teeth off the crown and pinion gear.