My rear is gonna be needing some attention pretty soon, and i know where i can get my hands on a 9 bolt for 100 bucks, but the posi is dying, and it only has 3.27 gears. Looking at the parts available from 9bolt.com i can have everything i need to rebuild it with a new posi unit and 3.73 gears for about 800 bucks. Add 150 to have it installed and i have a rear for less than 1000 bucks. now the question is, will it be strong enough to widthstand clutch drops with a Spec stg 3, some stickies, and 400+ hp motor? I'm gonna be looking for high, high 11's with my setup this season.

Reason i ask is i can't see spending 2g's on a 9 inch when i could spend 1000 on a 9 bolt that will get the job done. I know it's not gonna be as strong as a 9 inch, but the question is will it be strong ENOUGH?

thanks for your help/ opinions...

Eric

 

Check out www.9bolt.com. Miles, who is a member of this board and owns the company, has a 427 and he's running a 9 bolt.

 

yeah i've been to 9bolt.com, thats where i got the pricing info from. My main concern is that i will spend all the money on this and then it will break when i put some ET Streets on the back and start cutting some 1.6ish 60' times.

I've also read that if the posi unit is dying you don't have to replace it, it can be shimmed. This would save me a lot of money, but i don't know that anyone around my area has ever done it before.

I know the big block guys are using them but remember one thing, they have autos which are much nicer to rearends. I have a t-56, which shocks the drivetrain a lot more....

Eric

 

ebmiller has got a mailing list going for instructions on how to rebuild a 9 bolt, but I'll be darned if I can find it. I'll check around some more and if I find it, I'll edit this post. Did you ask Miles about a stick shift and a 9 bolt?

 

i was kinda hoping Miles would of chimed in by now but i guess i'm gonna have to PM him... I asked the guy that had the build sheets to email me a copy but i haven't seen them yet... no biggie. I'm most likely gonna go pick up the rear tomorrow so any quick input anyone can give would be great...

Eric

 

Well i bought it. Paid 100 bucks for the rear, the prop valve, the master cylinder, "most" of the brake lines, brand new discs (little rusty from sitting) with new pads and i even snagged the springs

It's a 3.27 posi disc, came out of an 85 trans am. I'm gonna be ordering a set of 3.73s and install kit, along with the shimming kit for the differential sometime here this week. I have to give the folks over at www.9bolt.com a call so i can see EXACTLY what i'm gonna need to do the swap....

Wish me luck with this thing. Oh and for those of you that do gear swaps, do you find it easier to do with the rear out of the car or with it installed? I'm debating whether or not i wanna bring just the rear to the shop to have it setup, or install it as is and give him the whole car....

Eric

 

Eric,

As you noted, slicks and trans brakes are much harder on the rear gear than a foot braked automatic. I personally have been running a 9 bolt for over 4 years behind my 500hp big block (more info on my car is at www.koolmeister.com ) with 1.72-1.75 60fts. I have talked to and sold parts to many people running low 11's/high10's with many 1.6x and some 1.5x short times. I set up my gears with a little more toe pattern and light on the backlash to get as much strength as possible.

The 3.27 ratio is a series 3 so you can go up to a 4.10 ratio. As for shimming the posi, well, you get what you pay for. I am putting together a rebuild kit that will consist of new posi cones, new spring pack, shims, rear cover gasket, instructions. Just adding shims is only a temporary fix. The best solution of course is a new unit because a rebuilt unit will never be quite as good or last as long, but a correctly rebuilt unit will suffice for most street applications.

Another option is mini spool, but this a strip only piece and aftermarket axles are strongly recommended.

We've got more stuff in the works for the 9 bolt and some new stuff for 10 bolts too. Just keep checking www.9bolt.com or www.diffsolutions.com

Miles
Diff Solutions
www.9bolt.com

 

So a posi with your "heavy duty" parts put in it, wouldnt be as good as a used one ???

 

how long will it be until your rebuild package is together and for sale? Any idea on a price for it? I'm not really looking foward to having to spend 400 bucks on a new unit if a properly rebuilt will get the job done.

Eric

 

I sell shims to tighten up the 9-bolt posi unit. it'll be better than new if you shim it tight. a few forum members brought shims from me and loved em. and your spending $10 instead of a new posi unit.

 

Eric, let's see somw shots of that 13xx mile Iroc! I'd like to see that.

Ed

 

lol the 1365 mile iroc is a site for sore eyes right now... It sat in a field for 15 years before i bought it....

heres the old website i posted when i first bought it. It still looks the same, but it starts now... the tranny is shot, and most of the interior wiring is gonna have to be redone, along with brakes and fluids before it even driveable. then we have to paint it and put it together.... Theres a lot of work ahead of us on this one....

http://www.geocities.com/zupmanZ28/85IROC.html

Larry Burd, i'm seding you a PM right now....

Eric

 

Probably in the next month or so. Just waiting for a few things to be finished up.

Miles

 

I really couldn't afford to redo my 9 bolt this winter but i needed a limited slip for getting through the snow. lucky for me i found Larry Burd. His fix works. Granted its not a rebuild. but for the few bucks i spent my posi works better than new.

 

shiming the 9-bolt posi will and can make it BETTER than new. You decide on how tight you want it, not the factory. You want it tight, you put a thicker shim in there. you want it factory spec, use the specs from the service manual.

Even borg warner used shims to make up for manufacturing differences. I have heard of people who found shims when pulling a factory unit apart.

The 9-bolt cones and posi case are a wear item by design. eventually it'll loosen up weather new or rebuilt, and it just needs to be reshimed to make it tight again.

If the cones bottom out, you can machine or"clearance" them to give more wear room. Mark P did his and is very happy with the results.

I owned my 89 formula since new. The posi stopped working at 5000 miles! Then I drove another 50,000 miles until I heard of shimming the unit. I only wish I found out eariler !!!!

 

https://www.thirdgen.org/newdesign/t...tservice.shtml

very informative reading, and it works !!!!

 

larry i sent ya another email this morning regarding payment info and such. let me know as soon as ya can...

Miles i've also sent you a couple emails along with a pm, haven't heard back from ya yet, it's been couple days since i sent the first email.

Eric

 

i think one of the reasons that shimming works so well is that once the cones wear they have more surface area. There is a spiral groove on the friction surface of the cone, and the ridges these spirals create seem to taper to a point ( i have never seen one new) once worn down they become flat. in my case there were ridges and grooves worn in to the cones, i flat filed them down and polished the surface. My cones were bottomed like Larry described, my machinest flaked on my so i was stuck clearancing them with a belt sander and die grinder with a carbide burr. It worked great, the kicker is i didn't have enough shims and was about .010" short on both sides. The unit works better than new. It will leave 2 dead even patch marks and goes around turns really smooth. I am running Royal purple lube and a tube of posi additive ( i didn't know royal purple had it already in there). Buying all new parts may be the "right" way to do it, but for a few bucks in shims i achieved my goal of a working rear. In time i will get a 12 bolt moser, but that will be after this unit is unrepairable.

 

Thanks for the shots Eric. I have seen that car in another post somewhere.....

If you need the GFX, I've got a set on ebay right now and they're dirt cheap!! I guess no one needs GFX...

ID is ebmiller88...

Ed

 

Ed have you sent out the rebuild sheets yet? I put my email in the other post but haven't seen anything. jsut wanna make sure i didn't get skipped

higotoody@hotmail.com

Eric

 

Sent them out last night.

Ed

 

just checked, didn't see anything. What was it titled so i can look out for it?

Eric