I knew this day would eventually come, but I never expected it to be a week and a half before xmas . I have an '87 IROC-Z with the LB9 TPI V8, T-5 tranny, and 9-bolt 3.45:1 posi rear. I was comin home this past fri night after a night out with the guys and 3/4 of the way home, I hear a popping/banging sound and then a constant high-pitched whining (all happening in fractions of a sec) sound after downshifting from 4th to 2nd. I wasn't really gettin on it and after the downshift, the engine was spinning about 3500rpm. I wasnt sure at first what it was, I figured its either the tranny or my rear. I limped home in 5th, not lettin the engine spin more than 1800rpm. Next day, me and my buddy jack her up and disconnect the driveshaft from the rear and manually spin the wheels......sure enough, the rear is clunkin and after about 1-1/2 revolutions of the wheels, the rear seems to bind up cuz the wheels stop dead and you have to exert a little force to get them to continue spinnin and then the pattern repeats. My buddy talked to a friend of his (who's also his mechanic) and the guy said that those 9-bolt aussey rears arent very strong and that 1) if I need gears replaced, I'm probably lookin at $400 just to purchase the gears and 2) I'm probably better off tryin to find a 10-bolt from another 3rd gen (which I'm guessin would be from the '90-'92 model year). I know I'm not the only one that has faced this prob, and I figured a good deal of you out there would have some suggestions for me. So, at this point in time, what are some of my choices?? Any help would be greatly appreciated.

 

The mechanic was right about one thing - the price of the gears.

However, the 9 bolt is substantially stronger than any of the 10 bolts offered from 82-02. If you've already got it, I would stick with it.

You need to pull the cover off and see what broke. Then go from there. And, if the price is too steep for you, look around in the classifieds and junkyards. You probably won't find another 3.45 rear as they are very rare, but the 3.27 are fairly common. They are sold quite often over at www.thirdgen.org , and usually cost less complete than a set of new gears or new posi.

Edit: There are a couple of large Thirdgen specific salvage yards in the CT area. I've seen them post quite often on several different boards. Search around.

 

Marc,
think you could send my pics of you Z(if U could send to
bluepastu@yahoo.com)?
did U use wheel adaptors?

LMK

 

If I got a rear with 3.27's in it, how would it affect my car? Will it make my car a tad slower around town? Just wondering cuz I've asked ppl in the past if I'd notice a difference if I swapped out my 3.45's for 3.73's, and I was told that the 3.45's are a perfect match for my tranny and power characteristics of my 305 TPI.