Tootie Pang

iTrader: (2)

Just got an 89 IROC Convertible with the auto trans (700R) and looking to upgrade the ring and pinion and rebuild the limited slip. I am thinking 3.73 or even 4.11. It's all stock. Just want a little more "sport".

antman89iroc

I have the same year IROC which was originally 350/auto. It had 2.77 stock and I went with 3.27 and eventually 3.70. I think the 3.27 was a good ratio for everyday. 3.70 is ok with overdrive but I was still revving a little more than I wanted on the highway. ~2500RPM @ 70MPH. I built the motor and swapped to 5 speed and kept the 3.70's. It's ok but in town driving at ~45-50 is a little too fast for 4th gear and too slow for 5th. I am replacing my stock 9 bolt BW rear with a Ford 9" and chose a 3.50 gear. Right in between the previous two.
With a stock engine I would stay a bit conservative. 4.11's may get old if you don't like revving too much. The other issue is that with a lower gear like the 3.70 my 1st gear is pretty much useless and I would upshift more quickly which kind of negated the low gear. A 3.27 was more everyday friendly. One final thought when I went from 3.27 to 3.70 gear my 1/8mile performance didn't change but about 0.05 seconds. It really depend on the overall combination but lower gears can be a pain when the burnout is over lol.

dmccain

iTrader: (2)

I have 3.73s but honestly I may swap them out for a set of 3.23s I have laying around or a set of 3.42s. I cant go through a stoplight without it hitting 2nd gear. With the overdrive it runs 2220 RPM at 60mph which isn't too bad I still get 25 mpg out of the car. Its way peppier than when the car had 2.73s that's for sure. I think if I had my choice to buy some it would be 3.42s though.

big gear head

Which rear end is in the car? Is it the 9 bolt?

Tootie Pang

iTrader: (2)

It's a factory ten bolt. Haven't opened it up yet. Hopefully its a limited slip diff in there otherwise I'm in for some more clams.

Tootie Pang

iTrader: (2)

Wanna get rid of those 3.42s?

I appreciate all the opinions. I am thinking the 3.42s would probably be a nice middle-ground improvement. The only real powers adder I plan do to the stock setup is long tubes, high flow cat and a 150 NOS.

a62belair

I had the stock 2:77's behind my 305, and it was sluggish. I traded for a 9-bolt 3:45, and the difference was night and day! A 10-bolt 3:42 is the same. 2000rpm at 60 with lockup.

big gear head

What gear is in it now? If you have a 3.08 or 2.73 then you will have a 2 series differential. You can't use factory 3.42 gears on a 2 series. There are special after market thick 3.42 gears that are made for the 2 series, but not factory gears.

If you have a LSD then it's probably the Auburn. Don't expect much out of it. They wear out quick when abused and can not be rebuilt. You might be better off if you don't have one, that way you can put something good in it and not have to worry about it.

89rubberburner

Currently switching out my stock 277 for 308. Basically stock 89 formula 350 Tpi. Fresh rebuild with new injectors. Only real performance upgrade is the 3 inch magnaflow exhaust with a set of hooker headers. Seemed to have a lot of zip off the start with the 277 so decided on the 308 as its a daily driver.
Also somehow I got a set of used 308 gears that fit on a 3 series carrier from Glen at 9bolt.

Tootie Pang

iTrader: (2)

So from my RPO I have the G80 and the GU2 which puts me at a 2.73 series II with an Auburn?

I found these:


http://www.jegs.com/i/Richmond-Gear/...791+4294829509

and

http://www.jegs.com/i/Richmond-Gear/...791+4294829509

jmd

iTrader: (4)

I would go 3.42, an OEM 99-02 Torsen, and 28 spline axles if it isn't already.
It will be a great balance for mileage and perf.

Tootie Pang

iTrader: (2)

Thanks sounds great. Trying to keep the spending low. So if I don't need to go with anything but the gears that's good enough for me. I will test the limited slip when I get a chance. It's going to stay stock essentially.

big gear head

Your cheapest way is to use the special after market thick gears that are made for the 2 series. This way you don't have to change anything else. I agree with jmd that the best way to go would be to swap everything for better stuff, but if the money isn't available then go with what you have.

Tootie Pang

iTrader: (2)

Something like this?

98-02 LS1 Camaro SS Trans am WS6 3.42 Rear posi Axle assy 3 CH ABS w/o trac S109

http://www.ebay.com/itm/98-02-LS1-Ca...pYuI4G&vxp=mtr


or Borg warner 9 bolt posi rear disc break axle IROC GTA firebird camaro

https://losangeles.craigslist.org/sf...027811184.html

Ron U.S.M.C.

I went from a 2.73 to a 3.42 and a Eaton Posi. and the difference was night and day. Love the 3.42's.

I highly recommend a "Corvette Servo" up-grade for your transmission.
The firm shifts and that ratio go really nice together.

You can buy the Servo for around $20.00
Here's where I bought mine = https://www.700r4l60e.com/store/prod...&cat=84&page=1

And install it your self like this.
= http://sethirdgen.org/servo.htm

86LG4Bird

iTrader: (1)

Bingo! His entire post.

Tootie Pang

iTrader: (2)

Just following up. I went with the 3:42. Auburn checked out as functional. Love the ratio. I got the Corvette servo. I'll be putting that in this week.

sprojam

3:42 is a great gear if you venture out on the interstate much my 3:73 tack abit high around 3000 rpm at 70/75 mph, but from light to light with a 1800 to 2000 rpm stall is hard to pass up. I stick to the old 2 lane highways better views and more to see.

seanof30306

iTrader: (4)

I think 3.42 is nearly the perfect gear for a street car. You can still cruise comfortably on the highway, yet you'll see a big increase in performance.

Also, on a street car, with street tires, 3.73 and higher can actually hurt your 60' times. Too much wheelspin.

The only thing I'd prefer would be a 12 bolt or a 9" with 3.55s