I was looking to buy an 85 Z28 with a 305 TPI (LB9) I was looking and trying to figure out what is the difference between it and a 85 Irocz. both have the same engine, tranny and rearend. Only thing I see on the Irocz's that the Z28 didn't have is foglights, and don't have Iroc-z on the door. The stripes are not the same. So what is the difference, other than looks?

 

It is probably the same difference as the Trans AM and the formala 350 had. which is nothing but looks and the trans am weighs more

 

Suspension...... Sometimes disc brake rears on Irocs that Z's didn't have.

 

In 1985 the only difference between the Z28 & IROC-Z was RPO B4Z (IROC performance package a $700 option) and was it for that year.

 

i'm not sure but that perforamcne package may have included different springs, shocks/struts, sway bars and bushings

i dont really know which of these if not all of these were different from the z28 to the iroc

all i know is that after changing all of these (except springs) it really didnt matter that my car is an iroc, lol

 

The Suspension looks the same, It has the "wonder bar" and it has rear disk brakes.

 

When people say a IROC had Disc brakes & Limited Slip rear remember they were options and you had to pay for them. A lot of Irocs had the base engine and other base equipment, so check what RPO came on the car.

 

for example my iroc came with a drum rear, open diff, and base lg4 305 carb
i do have a wonder bar, i forgot about that

 

Steering box support (AKA wonder bar) is the correct name.
GM added this support to the steering box area to reduce stress caused by the then NEW 16x8 wheels & 245/50/16 tires. Now wonder about that...... Since the IROCs only had this wheel & tire combo they received this support. Now its not a part of any handling package,

 

If the wonder bar was only for the Iroc's that came with 16x8 wheels with 245/50/16 tires. Then why did my 89 Iroc witch came with the standard 15x7 Iroc wheels with 215/65/15 tires have the wonder bar.

All i was wanting to know what was the difference between the Z28 and Iroc-z in 1985

 

I think the over head console z28 had the clock/adjustable reading lights on the overhead headliner,iroc was just dome lamp.

 

If you would read up on the History. You would know that in 1989 15" IROC wheels & tires were standard with the 16" being a $468 option, So the Steering Box support was on the Assembly build sheet for for all IROC models. And In 1989 there were no Z28 Models to compare with.

 

i`m glad that i own a few 91`s an 92`s with the 16" wheels....i don`t have to worry about the wonder bar....i do believe they were factory...how can i get a build sheet for my cars?

 

I want to say that the build sheet is either under the rear seat or on top of the gas tank??? Not sure though.

 

look in the center console