4.10 gears...not what I expected.

[Bob Eyres]

Originally Posted by rhipsher

4:10's might make 6th gear useful but I wonder if I would run out of RPM's before reaching top speed with them.
I'm with Pete on this one. If I had $1,500 to burn on performance mods I go with the ones that are actually going to create more HP. Because more HP is just more. And with 3.45 your going to see gains in every way. Launch and top end. Id rather have the overall increase than one or the other.

According to Paul's gear charts the 4.10's give you 174.29@7,000 and 186.74@7,500. So you'd have to raise your rev limiter a bit, but you could get up there with 4.10's.

And as far as getting a better launch with more power, but stock gears, and the same tires....good luck.

Just what can you do on a ZR-1 for $1,500.00 that can give you the performance increase of 4.10 gears? Headers is the only thing I can think of, and that's only if you say good-bye to emissions compliance.

I bow down to Pete for his efforts to find the outer limits of the stock block ZR-1. Somebody's got to do it, and he's done a phenomenal job. The goal is to get into the tens with a stock block 350, and he's knocking on the door. But one look at his great 60ft. times with the 4.10's tells me that the right gear is the answer. My guess is that 4.30's or 4.56's and the right tire would get him there, because then he's using all the revs available. Running a three speed ZR-1 is like trying to do it with your hands tied.

[Bob Eyres]

Originally Posted by mgg

The one thing that no one has brought up is how does the single mass fly wheel affect al of this. I have a 90 ZR-1 with Marc's 510 hp package. I also installed 4:10s a few years ago. With the single mass flywheel getting to the torque curve and Hp sweet spot much more quickly I am curious how this would impact the discussion. Personally I really like the 4:10s. I only drag race once or twice a year. I don't own drag radials so trying to hook the car is just about pointless from a dead stop but it does pretty well from even a first gear roll. I am curious what the opinion is on how a single mass fly wheel would impact this discussion. I can tell that I am thrilled with the result of Marcs 510 package the gears etc. The car now has some "edge " to it and makes it really fun to drive. I know it will take some drag radials to take advantage of the launch but I 1/4 racing was not the biggest priority in purchasing one of these cars.

I've found that the lightweight flywheel improves the performance of the LT5 everywhere but at the launch.
Once you're hooked up and moving though, the light weight unit gives you an advantage throughout the run, by using less horsepower that it takes to spin it.
Bottom line, shorter gears=advantage, lightweight flywheel=advantage, Marc's 510 package=big advantage.

You have the one performance "problem" that we all love to have, traction
If you don't want Drag Radials, check out the thread on the Toyo Proxes 888's. they look like a good alternative, if you don't put a lot of mileage on the car.

[5ABI VT]

I believe many of you are just not understanding what gears do. Please re-read my post about final drive ratios of 3.45 vs 4.10. the ONLY advantage 4.10s gives you is 1st gear. When you go to 2nd the leverage advantage goes to the stock gears while still in first. and it passes back and forth. That is why there is a ET advantage with 4.10s but no MPH difference. IF the 4.10s were making you faster throughout the entire rpm range and through the gears there would be a mph difference but there is none. if you are gaining mph its possibly due to being at a better rpm through the traps where after the traps they would even out again.

Using 6th is not smart. its a .5 ratio. DESIGNED FOR FUEL ECONOMY ONLY. it shares a synchro with reverse so get ready to melt your synchro and destroy your zf if you are using it for acceleration.

I ran almost 118mph with stock gears. headers and a tune and emissions compliant. On 25 series tires pumped to 48 psi if I remember right on 450 lb springs. Set up for 1/4 mile it is not but right at home at high speed.


It is true the LT5 has more rpm but many of you are not realizing what the truth is. GM didn't want to alter rear gears or the zf SO Lotus was asked to build a dohc 32v motor that still had peak power at what.. 5800 ? I could bet something that Lotus was like WTF when gm asked them to do that. Basically they cammed and setup the potential screamer to act just like a wheezing pushrod sbc. if the motor truly needed 4.10 gears, the motor should peak power well higher than what an LT4 does. it would have pushed the hp and torque curver higher and 4.10 gears would have been justifiable because it would bring the torque back in the low end. As it is now on a stock motor I feel 4.10 gears just makes it too torque for a street tire and the increased rpm range isn't really used because of the way the cams are profiled etc.

If I ever have the chance and $$ to build a serious LT5 I would build a big bore LT5 to spin the maximum rpm possible (8000-8500?) then and only then would I drop a 4.10 in the back because the cams would be profiled to be efficient at a much higher rpm causing a noticeable reduction in low rpm torque.

Im babbling just bored at work. Gears are very misunderstood. In my opinion it was a trick first started by the drag cars to get off the line faster because that's all it really does.. have a shorter 1st gear.

[XfireZ51]

"It is true the LT5 has more rpm but many of you are not realizing what the truth is. GM didn't want to alter rear gears or the zf SO Lotus was asked to build a dohc 32v motor that still had peak power at what.. 5800 ? I could bet something that Lotus was like WTF when gm asked them to do that. Basically they cammed and setup the potential screamer to act just like a wheezing pushrod sbc."

I'm not sure about a totally stock LT-5, but my ported top end w headers and stock cams(not degreed) peaked at ~6800rpm. Still does now.
I think there's more cam there than air available.

[5ABI VT]

Originally Posted by XfireZ51

"It is true the LT5 has more rpm but many of you are not realizing what the truth is. GM didn't want to alter rear gears or the zf SO Lotus was asked to build a dohc 32v motor that still had peak power at what.. 5800 ? I could bet something that Lotus was like WTF when gm asked them to do that. Basically they cammed and setup the potential screamer to act just like a wheezing pushrod sbc."

I'm not sure about a totally stock LT-5, but my ported top end w headers and stock cams(not degreed) peaked at ~6800rpm. Still does now.
I think there's more cam there than air available.

That is making use of what I feel is the LT5s greatest attribute. RPM =D>

[Bob Eyres]

Originally Posted by 5ABI VT

" the ONLY advantage 4.10s gives you is 1st gear. When you go to 2nd the leverage advantage goes to the stock gears while still in first. and it passes back and forth. That is why there is a ET advantage with 4.10s but no MPH difference."

With all due respect, I think you are defeating your argument in the first paragraph.

Let's establish that we're talking about performance in the quarter mile here, not overall performance in every situation.

You agree that 4.10's have an e.t. advantage in the quarter mile. In a drag race low e.t. wins, end of story.

Once again you mention "mph difference". The only thing that mph in the traps means is that it is an indirect indication of horsepower, of potential.
A car with a mediocre e.t. and a high mph reading in the time traps is a loser. Lots of power, but not set up for the drag strip.

As I see it, the goal in quarter mile gearing setup is to achieve the lowest short time possible (60ft.), then reach the end of the track at the top of the top gear, (4th in most cases).

In our ongoing example, Pete cut his lowest yet 60ft. time with 4.10 gears, but complained that by using fourth gear he reached the end of the track without reaching his desired peak rpm of 7,400. In my opinion, the way to fix that is an even higher gear, 4.30's or 4.56's depending on what tires are available to handle it. The lower the gear, the lower the potential 60ft. time. As long as you can use all of your available rpm at the other end of the track.

BTW, you mentioned that you trapped 118mph. with just headers and a tune. Is that a 375 or 405hp. ZR-1? And what was the actual tire size? thanks.

[Dynomite]

Not discussed so far.......what rpm do you drop the clutch and how fast can you shift (power shift?). If you are spinning your tires in first gear, does it matter what rear end ratio you have?

How does car acceleration vary with how fast you are spinning your tires?

Does traction vary with tire spin?

After you have spun your tires with 4:10s for a bit in first gear you are shifting into a range that is different in every gear with 4:10s as compared to 3:45s (but shifting into the maximum engine power curve zone "rpm vrs hp" each time) requiring you to shift into 4th at the end of the 1/4 mile. So the difference is at the start of the 1/4 mile and near the end of the 1/4 mile only.

Maybe I have it wrong but depends a lot on tires (traction) at least in 1st gear and second gear in a power shift

[5ABI VT]

Originally Posted by Bob Eyres

With all due respect, I think you are defeating your argument in the first paragraph.

Let's establish that we're talking about performance in the quarter mile here, not overall performance in every situation.

You agree that 4.10's have an e.t. advantage in the quarter mile. In a drag race low e.t. wins, end of story.

Once again you mention "mph difference". The only thing that mph in the traps means is that it is an indirect indication of horsepower, of potential.
A car with a mediocre e.t. and a high mph reading in the time traps is a loser. Lots of power, but not set up for the drag strip.

As I see it, the goal in quarter mile gearing setup is to achieve the lowest short time possible (60ft.), then reach the end of the track at the top of the top gear, (4th in most cases).

In our ongoing example, Pete cut his lowest yet 60ft. time with 4.10 gears, but complained that by using fourth gear he reached the end of the track without reaching his desired peak rpm of 7,400. In my opinion, the way to fix that is an even higher gear, 4.30's or 4.56's depending on what tires are available to handle it. The lower the gear, the lower the potential 60ft. time. As long as you can use all of your available rpm at the other end of the track.

BTW, you mentioned that you trapped 118mph. with just headers and a tune. Is that a 375 or 405hp. ZR-1? And what was the actual tire size? thanks.

You are correct and i guess Ill clarify that IF you can take advantage of a short first gear with a suspension/tire setup for launch gears can make you 'quicker'. in Petes case i also agree that more gear can shave some more et assuming hes got the setup to launch hard and be at the right rpm to see some mph increase before the traps.

Im not a drag racer and make no secret to voice my opinion on why I don't like it but I think drag racing is about whos quicker not faster. Its just my preference and mph to me is everything. A car can run 10s and go 120 and I can be doing 13s and doing 130mph. ill be happy because if he rolled up beside me on the freeway where I do most my spirited driving I would walk away and ultimately be 'faster'.

I guess all im trying to say is for those who are considering gears.. if you are drag racing and have the suspension setup to hook first gear with an aggressive launch or are looking to optimize the gearing for the 1/4 mile. .. gears are easily justifiable.

I find most people tend to compare gear to gear ie. 3rd gear with stock rear vs 3rd gear with 4.10s. I think that most people fail to consider that the speed range in each gear has been reduced and it would be more fair to compare a 2nd gear with stock rear vs 4.10s in 3rd. That usually makes people think.

My z is a 94. Headers catted to corsa with haibeck chip. tires 315/25/19 on Invos which pretty much grip like all seasons lol.

[Paul Workman]

Originally Posted by 5ABI VT

That is making use of what I feel is the LT5s greatest attribute. RPM =D>

Yup!

That and a relatively flat torque curve!

I've watched the result of the high rpm performance, and others* have noticed too that lots of cars may jump a ZR-1 at the light, but time after time the LT5s will run 'em down on the big end. As Bob G says, "Just about the time (pushrod motors) are getting interesting, you have to shift!" So many times, if the Z lost the 1/4 mile contest, it was gaining and just ran out of track.

Watch what happens at every shift the C5 makes... (I especially like the jubilant "Ha!" when the C5 lunges ahead...followed by the perplexed, "Huh???" as the Z is walking away. And then the reality sinks in: "Your not catchin' him!!")

http://www.youtube.com/watch?v=PzPPEK9Qf3M


And, the numbers seem to agree. Race results from the 1/2 mile shootout in Chicago last spring showed the LT5s - and their decades older technolgy - really took no guff from contemporary pushrod motors. The did really well!

[mike100]

I think most people understand the phenomenon of low gears vs high once you have driven a car with both, but have a hard time explaining it all in words. there are a lot of complex things going on and it isn't just a straight algebraic torque multiplication definition. Mathematically, you want to dwell in the fattest part of the hp curve and spend the least amount of time lugging off the line.

- You can integrate the function (hp curve) and gear the transmission accordingly to drop you back where the engine runs right (more gears or custom ratios in the ZF which don't exist).

-you can gear down the diff to reduce break-away tire spin (tall gears sometimes result in massive runaway burnout speed) and tires deal with wheel slip better if the slip speed isn't too much.

-you can figure out a way to shift faster (automatics and twin-clutch PDK types come to mind)

-or you can put a 400 cubic inch engine in to be able to accelerate harder regardless of gearing.

Obviously the transmission is probably the best place to see gains, but since that isn't available with the ZF, adding power makes sense (not to mention fun).