Dominic Sorresso

Currently have 3.73's in ZR-1. Due to using 19" wheels, I am looking to bump rear axle ratio. Buy 4.10's or swap differential. Prefer the Dana OEM or Viper gear set.

Paul Workman

Hi, Dom!

Check w/ Suburban Driveline yet? 630-941-7101

They've done some good work for me - new U-joints, balancing the drive shaft, etc.

747 W North Ave, Villa Park (SW corner of North Ave and Westwood-Lincoln Ave. (about 3 blocks from Marc's shop).

Good luck!

Paul.

Dominic Sorresso

Thx Paul. I'll look into that.

Scrrem

Dom,
I heard a while back that the Viper ring and pinion sets were no longer US made, so tread carefully if you are looking at those.
Rich

-=Jeff=-

http://www.justdifferentials.com/D44...4hd-411-oe.htm

Dominic Sorresso

Thanks Jeff. The problem is I keep getting conflicting advice on whether to go from 3.73 to 4.10. I was recently told I would feel little to no difference
that I am also using taller 345/19 tires.

WVZR-1

Taller tires I'd think "reinforces" the thoughts that you need more gear.

-=Jeff=-

I noticed a difference going from a 3.45 to 3.73 then 4.10 on my 89.

so unless you are changing tires/wheels I would think you would notice the difference..

Jagdpanzer

Dom,
I'm running the same 345/19 tires as yours with 4.10 ratio gearing and really like the combination. With the taller 345/19 tire its like running 3.90 gears with 315/17 stock size tires.

WVZR-1

Would a 4.30 build and the 345/19 maybe be a practical thought for maybe some? I didn't do any math with them and I may but the thought occurred to me. What do you actually consider the "rolling/loaded" circumference/diameter of the 345/19? I've never looked at the advertised or actually any of the specs.

Dominic Sorresso

Dave,

Just don't think I want to go that high. But for comparison, the stock
GY Eagles are 25.7" dia. while my Michelin PSS are 27.2". I register about a 4mph@70mph difference between the ODO and my GPS measured speed.
The trans has a stock speedo gear in it. The 3.73s brought the delta a bit closer but GPS still read higher than speedo. So the wheel/tire combo "acts" like a taller gear than stock setup and still does.

Phil,

The 3.90 was supposed to be THE gear for the ZRs.

WVZR-1

This ain't about odometer correction, the gear and tire are performance related, it's they either complement one another or "they don't" - odometer correction is a completely different issue and you can't use "guesstimates" to evaluate. It's all about the "desired final drive"!

Dominic Sorresso

I am not, per se, trying to get the speedo and GPS to agree. We agree that's NOT the point. I am simply using the disparity between the two to indicate that the taller wheels and tires in tandem act as a taller gear hampering performance. So what gear should I install that would put the motor in the same rpm band that you would see when using 3.45 gears and stock tires/wheels?

Phil,

What rpm are u running at when say cruising at 70mph?

Jagdpanzer

I recall around 1900 rpm in 6th gear but I'll confirm for both 5th and 6th gear next time I have it out.
I'm using 13/41 speedo gears which are spot on at 70 mph according to GPS.