i got my project 87' iroc-z.
LB9,with the 700R4 and 2.73's in the rear.
car is completely stock,exhaust will be getting done soon,and that's probably it for a little time being.

i'm looking for off the line speed,and not worried about top speed,and highway driving. 90 percent of the car's driving will be city driving.

i know that with the 4.11's, the quarter mile time will be effected.

what is your opinion on switching out these 2.73's for 4.11's? think i'd be better off with 3.73's? is anything needed to be done to the differential,besides the gears?

 

Good tires You'll be getting alot more wheelspin with those gears. I was going to do the install myself, but setting up the clearance/backlash etc... Seems to be better left to a tranny shop unless you have experiance with that kinda thing.

 

oh,i know i'd be getting alot of tire spin. but i can live with that.

 

My opinion is the 3.73's are a bit much. I would rather see you with those than the 4.11's. Just my .02

 

can save yourself time and money big time if you just yank a stock 3.42 or 3.73 axle from under a donor third gen f body, they are dime a dozen then all you need is a posi and youre done unless you break the axle somehow



good luck

 

dime a dozen....?? i can't find one, 3.42 or 3.73, but i am seeing a nice 4.11... got to get away from the 9 bolt 2.77... any one... help!!

 

i went from 2.73 open to 3.73 posi and i must say it was the best thing i did to the car other than buying the car lol she runs abit higher rpm but the tires spin (275/60/15) alot easier and she likes to get down the track faster and hooks alot better out of the hole....if you want tire eating gears and no speed go 4.11 but want alttle speed go 3.73....plus if you go 4.11 and hook to well you might kill the rear alot faster

 

I think the IROC's come with some type of posi unit in them. If not, order one when you get your rear gears. You'll love having both tires spin. Only problem I have with going to the steeper gears (either set) with your rear end is the cut of the gear. When you order your parts you will end up having to order gears for a series 2 carrier. What that means is your running gears from a 3 series on a 2 series carrier (your open or posi unit in the car). In order to do that they have to change the cut of the gear and you get a thinner built ring and pinion. I've run 3 sets of 3.73's in my car and sheared every set. I don't think that finding a housing with 3.40's or 3.70's is that easy but if you can find one with some type of 3 series carrier you can still get the beefier ring and pinion. You'll love the upgrade but it sucks when you blow up your new rear axle. Also, consider any kind of modifications to your lca brackets, rear girdle, torque arm modifications, etc. now so that you can eliminate any wheel hop and take the shock off the rear axle.

M

 

I've ran with every gear from 3.08, 3.23, 3.42, 3.73, and 4.10. All at times with different torque converters. The 4.10 gear is fun and not bad as long as highway driving isn't in the thoughts. My S10 (same trans, same tire height) has a 3.73 gear with a Torsen diff. I had a 3.08 in there. The 3.73 gear made the performance considerably better and highway driving is fine if I keep it to 60-65mph. Over that gas milage takes big dive and the engine just doesn't need to rev that hard for that long without alot of load on it. I'll make it back to the track soon with it, but figure it was about a .5 gain so far. With my older 2.8L S10 I gained .4 when I would change from the 3.42 gear to the 4.10 gear. My Sonoma GT picked up only just over .1 going from the 3.42 gear to the 4.10, but my shift points needed to be re-adjusted and it was very cold causing tire spin. I have other examples, but you get the idea. I'd recomend going with a 3.73 gear if you mostly do highway driving and 3.42 gear if you do a mix of both. The 4.10 gear is fun for a weekend toy, but gets tiring on a daily driver. You can get a ring an pinion made for your carrier if you already have a posi. I'd also recomend getting a governer recalibration kit for the trans as your shift points will end up being off with the gear change.

 

I have the 4.10s and switched from 2.73. My advice is go with the 3.42s. I have power from take off and loose it very fast.

I will be switching to 3.42 within the next week or to.

BTW: I am at 6.5 miles per gallon and a slightly bolt on mod 305.

 

look for a rearend out of a stickshift thirdgen they have 3.42"s