HammerZR1

Posted the following on the Registry also. Looking for lots of info on this subject.

For those out there that have made the switch from 3:45's to 4:10's, what kind of gas mileage change have you seen?

I'm driving to BG in May from Idaho and don't want to swap the gears right now if I will see a drastic drop in mileage. That could add substantially to the trip cost.

Thanks

95ZR1

The main cost increase will be money spent on rear tires.

For cruising, 4:10's allow me to use 6th gear, so I didn't
see much change in total $$ for fuel.

Rkreigh

typically you'll see 2-3 mpg worse MPG

not too bad in terms of the performance increase

ittlfly

Your rear tires will get a little more "wear" but it is nice to be able to use 6th gear now.

A1990

John, I have driven to BG with my 4.10's and my 3.45's. I had my B&B exhaust for both trips. With the 3.45's I drove in 5th most of the time. I haven't noticed more than 2mpg difference overall and I am sure gas on both trips was about the same.

Now this time will be the first with the 396 so that will be interesting for me too.

ZRWON

Based on my experience with BEAST2's 4:09s, I think on a hwy trip like you'll be doing to BG you'll probably see 24-26 mpg with a lot of time in 6th (75-85 mph) & you'll not need to downshift to 4th or 5th just to pass some one only doing ~55. If you are in heavy traffic or on a lot of hills and curves..a lot of 5th gear your mpg will drop to 21-24 (55-75mph). Remember BEAST2 has been tweaked as a part of JVD's street Skinner Package. Maybe you'll even do better than I get.
Let me know how good my forecast is when I see you in BG.

dallas916

Yeah, a couple of mpg's if you maintain the same speed for very long. When I used to run up to Norcal or Oregon I'd have to keep it at around 80-85 to keep the rpm's at about 2000. With the 4:10's it allowed me to stay around 75 if I wanted the same rpm's and mileage. At 80-85 I did get about 2+ less...but it was sure nice when I wanted to use the peddle without downshifting or going down less than 5th.

I figure 2000 miles @ 2mpg difference cost me around $20. Certainly worth the difference in those gears!

zr1fred

I get about 24-25 @ 75mph. Highly recommend them (4:09's), they make the trip alot more enjoyable, at 2200 rpm your putting out alot more torque. At 75, the 3:45's seem to be almost lugging the engine, especially in the hills. Now if you plan on 100mph..........

xlr8nflorida

I wish I could give you some information but I'm not sure what my mileage is with the 410s or 345s

dallas916

Yeah, at 140 the 4:10's have you running pretty high rpms and kinda loud. I could only stand that for 10-15 minutes at a time. I guess I'd be a ***** in the Silver State events.

ZRWON

Right you are. ..4:09 gearing is NOT desireable for ORR especially in the faster speed classes, even if BB has worked his magic on your ZF tranny. It should be noted that in the 24 Hour Endurance Record accomplishments ZR-1 that Morrison added transmission & rear axle coolers and 3:07 gears replaced the stock 3:45s to accomplish speeds of 190 mph with low rpms for long distances/many hours. ORR is entirely different than a drag race or fastest mile shoot out.

HammerZR1

Thanks for all the replys. I'm puttin' 'em in.

cv67

The motor likes cruising rpm with the 4.09 gear. I doubt youd see much difference at all between the two gears (meaning any negatives). As Fred said the motor isnt lugging.

WydGlydJim

Hmmm.........I must have a little something wrong with mine. 75 MPH with 4:10s I'm only gettin around 20 MPG. Car seems to run well

I noticed the drop after injector replacement.

I look forward to investigating this in May with the experts.

zr1fred

Might have something to do with GETTING to 75 in 6 seconds! Have you checked your plugs for eveness and color?

FU

441 in w/ 4:10 = 24-25 MPG @ 70-75 MPH 10-12 MPG around town.
385 in w/ 4:10 = 22-23 MPG @ 65-70 MPH 14-15 MPG around town.
It's all about the efficency of the combo AND THE TUNE.Both combinations would benefit with less gear esp. the 441.

I'm not light footed either

WydGlydJim

I've checked em before........light gray nothing indicating issue. However I think I was going to change them, and forgot to do it, so I'm sure it could use some new plugs.......I'll try that. I think I was researching that whole flat seat tapered seat thing, and just never did change them.

LT5corsa

He is NOT light footed @ all.....

AtsZR1

I have the 4:10 gears and plan to put them in this spring. What are you guys doing to recalibrate the speedo? I currently have 3:73 gears in the car. Thanks

dallas916

There's a gearset that goes into the present speedo "socket". Unfortunately, to get the gears correct you need to do the inside one, too, which requires removing the tailpiece if I remember right. I think the set runs about $125.