Here is a dumb question. I'm doing a ground up resto on my 88 IROC. I want to install gears that can work on the highway and tear it up from a dead stop. I'm not too familiar with gears but I found that my stock 2004 Avalanche with a 5.3 has 3.73 gears. It does great on the highway but not too good from a dead stop. Will I feel the same power out of the IROC if it had 3.73 gears or would would 4.11 gears be better off the stop and still be o.k. on the highway ? With the Avalanche, i'm at about 2200 rpm at 70mph. The IROC has the stock 700r4. Any thoughts or advice on this would be greatly appreciated.

Frank

 

depends on the engine and tranny

3.73 is really nice, 4.10 is overkill unless youre running a really built and high rpm enginethe avalanche doesnt exactly have a high output engine in it lol...

im sure a healthy 305 with the 3.73 can outrun that thing no problem, and i bet even a good 4.3 could too, if not a 3.8 also

i would go with 3.42 unless you have some crazy high rpm built engine

virtually any engine in good condition wil run real strong with this ratio

hell with the factory 3.73 that was in one of my 68 chevy longbed pickups(3800lbs) the 1972 truck 4 bolt 355 engine i put in it with TRW flat tops and unknown camshaft and stock untouched 4416 305 heads and stock manifolds with 2.25" dual exhaust would lift up on the front end quite a bit when taking off, and would pull like crazy for a really long ways and it never got outrun by anything but then i never put it up against anything seriously built for a track or anything like that lol, but it was more than plenty of fun around town, i can tell you that much

so i mean.... 3.73 would be more than plenty, i would stick with 3.42 if you are so worried about the highway, but you have to accept tradeoffs, you cant have everything, but you can get close, in most cases, being faster= more fuel use and more RPM, so... decide what you really want before you begin.. do you want mileage, or do you want speed ? pick one now




good luck

 

WAG but i bet the truck has 3:42s, most of them do that i know of. mine does and i have the 5.3 and to me it pulls great from a stop. 3:73s would be great in your car and i've drove a z28 with 4:11s and it really pulled hard and with OD it wasn't that and on the highway. do you have a 10 bolt in the IROC?

 

most likely you have a 700r4 for a automatic. 1st gear in those is pretty low. I have 3.73's in my car. I love them. 4.11 is an over kill unless you have a manual tranny with a 5 speed.
But remember on the highway, your top speed will drop because of the rpms if you have a 700r4.

 

My IROC has the 700r4, 350TPI and 10 bolt limited slip (factory). Sounds like the 3:73 ratio will work fine. On the Avalanche, my dealership sticker (I purchased the truck new) states my truck has 3:73 gears. Once the warranty runs out, I'd like to do more with the Avalanche (engine bored and stroked) but you guys have helped a ton with info on the gears. I'm going with the 3:73's and strocking the IROC to a 383. Hope it works ... Thanks again.

Frank

 

No, all 88 IROC's with 350 TPI engines came from the factory with the 9-bolt rearend, not a 10-bolt. You could have either a 2.77 ratio or a 3.27 ratio.

 

Im sure the Avalanche has alot taller tire to. That would make a difference