johnnymotz27

I was doing some research on a 3.42 rear upgrade on my 1989 5.7 Iroc. There seems to be so much out there like do i need a spacer or not etc etc. Is there anywhere on the site that lists all parts needed for the swap?? By the way its a 2.77 G80 rear.

thirdgen4me

iTrader: (1)

I would just grab an 87-89 rear out of a V6 camaro or firebird from the junk yard for $75.. Direct bolt in, just put one in my formula a couple weeks ago. You have to grab the speedo gears to.

JamesC

iTrader: (5)

If you have a 10-bolt, you might check the following FAQ for info on gearing and brakes:

https://www.thirdgen.org/forums/tran...-10-bolts.html

JamesC

84 z28

Just grab a thick gear set in 3.42 ratio.

DJP87Z28

Everyone STOP and think for one second...2:77 ratio = BW 9-BOLT 2-series carrier.
Not a lot of things are going to work for this guy unless he gets correct answers.

JamesC

iTrader: (5)

The OP may need to simply double-check what's in his car. While 2.77's are 9-bolt gears, 3.42's belong in a 10-bolt.

Johnny, should your car be a 9-bolt, check the following link:

https://www.thirdgen.org/forums/faq-...now-about.html

JamesC

johnnymotz27

Hey , just was reading through my service manual it shows 2.77 are the borg warner rear which i believe is the 9 bolt. So forget the 3.42 i guess i am really looking for 3.45's correct?

JamesC

iTrader: (5)

Correct. Since parts may be difficult to locate for a 9-bolt, you might consider a 10-bolt replacement with a gear ratio and brakes that meet your approval.

JamesC

johnnymotz27

Thats getting a little more involved than i was hoping......Why weren't the 5.7s standard with the 3.27s? 2.77 does not seem like the best performance option for the top engine Iroc. I know you could order the G92 so why weren't the ordered more often or like i said STANDARD.

johnnymotz27

Good Point

johnnymotz27

Wow it seems i am going to have a hard time finding a 3.45 ring and pinion!!

johnnymotz27

Well got what i hope is a good deal on a 3.27 posi housing and ring and pinion out of a 89 GTA for $275. Ive been looking for a few weeks and it seemed reasonable, he says i will need to replace the bearings though. Now the question is do i wait to try to find 3.45 ring and pinons or go with the 3.27s which would have been stock G92 upgrades????

Dustytrix

iTrader: (3)

You might want to check the splines 26 or 28? You probably have 26 and the 89 could be 28. Anyway something else to look at.

big gear head

Do you know how to set up a ring & pinion set, or will you be taking it to someone else to set it up?

Stephen

iTrader: (12)

9-bolt parts aren't hard to find. Just less places to get them, but that doesn't equal hard.

9bolt.com is the 1st place that comes to mind. To go from a 2.77 to a 3.45, your going to hafta change the carrier too, not just the ring gear & pinion.

johnnymotz27

Dustytrix:I have an 89 and the part came out of an 89 so wouldn't i have 28 also?

big gear head: i absolutely will be having it installed any tips on added pieces i may need?

JamesC

iTrader: (5)

All 9-bolt rears for f-bodies use 28 spline axles.

JamesC

big gear head

Get a good installation kit. This will make it easier for whoever installs it. Get a good quality kit, not a bargan brand. Some that I don't like are Ratech and Richmond. Some of the better kits are DTS, Yukon and Tom's Differentials.

johnnymotz27

Will do thanks!! Any thoughts on if i should hold off on the install until i purchase 3.45s? I assume i will feel a nice difference from 2.77 to 3.27 just wondering if its worth the move to 3.45

Ron U.S.M.C.

I did the 2.73 to 3.42 upgrade.( 10 bolt ) I'm really glad I chose the 3.42's. Any thing less would have been a wast of time and money in my opinion. In your case I say get the 3.45's. Throw a Eaton Posi. in there and be done with it.

big gear head

There is no Eaton Posi available for the 9 bolt. The 3.45 will be nice if you can find one. The 3.27 isn't bad and will be a nice improvement over the 2.77.

Ron U.S.M.C.

No Eaton Posi. for a 9 bolt. Thats a shame. How about a LPW support cover than. Well I looked at LPW"s site and could not find one for a 9 bolt ether. But I did find this = http://www.hawksthirdgenparts.com/ca...entgasket.aspx

johnnymotz27

Thanks for all the help!! I guess it will take a few weeks before i get the 3.27s installed so if i come across a 3.45 ring and pinion before ill go for it.

DeanJ

I also think this would be your easiest and cheapist option. I just recently did this. If you find a manual trans, V6 car in those years it will have a 3:42 gear, autos are, I think have 3;23,but I would double check either one. Pop off the rear cover, takes 5 minutes. Always check before you buy. Dean.